Search for contact interactions in �þ�� events in pp collisions at ffiffiffi s p ¼ 7 TeV S. Chatrchyan et al.* (CMS Collaboration) (Received 18 December 2012; published 1 February 2013) Results are reported from a search for the effects of contact interactions using events with a high-mass, oppositely charged muon pair. The events are collected in proton-proton collisions at ffiffiffi s p ¼ 7 TeV using the Compact Muon Solenoid detector at the Large Hadron Collider. The data sample corresponds to an integrated luminosity of 5:3 fb�1. The observed dimuon mass spectrum is consistent with that expected from the standard model. The data are interpreted in the context of a quark- and muon-compositeness model with a left-handed isoscalar current and an energy scale parameter �. The 95% confidence level lower limit on � is 9.5 TeV under the assumption of destructive interference between the standard model and contact-interaction amplitudes. For constructive interference, the limit is 13.1 TeV. These limits are comparable to the most stringent ones reported to date. DOI: 10.1103/PhysRevD.87.032001 PACS numbers: 12.60.Rc, 13.85.Qk I. INTRODUCTION The existence of three families of quarks and leptons might be explained if these particles are composed of more fundamental constituents. In order to confine the constitu- ents (often referred to as ‘‘preons’’ [1,2]) and to account for the properties of quarks and leptons, a new strong gauge interaction, metacolor, is introduced. Below a given inter- action energy scale �, the effect of the metacolor interac- tion is to bind the preons into metacolor-singlet states. For parton-parton center-of-mass energy less than�, the meta- color force will manifest itself in the form of a flavor- diagonal contact interaction (CI) [3,4]. In the case where both quarks and leptons share common constituents, the Lagrangian density for a CI leading to dimuon final states can be written as Lql ¼ ðg20=�2Þf�LLð �qL��qLÞð ��L���LÞ þ �LRð �qL��qLÞð ��R���RÞ þ �RLð �uR��uRÞð ��L���LÞ þ �RLð �dR��dRÞð ��L���LÞ þ �RRð �uR��uRÞð ��R���RÞ þ �RRð �dR��dRÞð ��R���RÞg; (1) where qL ¼ ðu; dÞL is a left-handed quark doublet, uR and dR are right-handed quark singlets, and�L and�R are left- and right-handed muons. By convention, g20=4� ¼ 1. The parameter� characterizes the compositeness energy scale. The parameters �ij allow for differences in magnitude and phase among the individual terms. Lower limits on � are set separately for each term with �ij taken, by convention, to have a magnitude of 1. The dimuons from the subprocesses for standard model (SM) Drell-Yan (DY) [5] production and from CI produc- tion can have the same helicity state. In this case, the scattering amplitudes are summed, resulting in an interfer- ence term in the cross section for pp ! Xþ�þ��, as illustrated schematically in Fig. 1. The differential cross section corresponding to the com- bination of a single term in Eq. (1) with DY production can be written as d�CI=DY dM�� ¼ d�DY dM�� � �ij I �2 þ �2 ij C �4 ; (2) where M�� is the invariant dimuon mass, I is due to interference, and C is purely due to the CI. Note that �ij ¼ þ1 corresponds to destructive interference and �ij ¼ �1 to constructive interference. The processes contributing to the cross section in Eq. (2) are denoted collectively by ‘‘CI/DY.’’ The difference d�CI=DY=dM�� � d�DY=dM�� is the signal we are searching for in this paper. The contact-interaction model used for this analysis is the left-left isoscalar model (LLIM) [4], which corresponds to a left-handed current interaction described by the first FIG. 1. Schematic representation of the addition of DY (left diagram) and CI (right diagram) amplitudes, for common helicity states, contributing to the total cross section for pp ! X þ�þ��. *Full author list given at the end of the article. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distri- bution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. PHYSICAL REVIEW D 87, 032001 (2013) 1550-7998=2013=87(3)=032001(19) 032001-1 � 2013 CERN, for the CMS Collaboration http://dx.doi.org/10.1103/PhysRevD.87.032001 http://creativecommons.org/licenses/by/3.0/ term of Lql in Eq. (1). The LLIM is the conventional benchmark for CI in the dilepton channel. For this analysis, all initial-state quarks are assumed to be composite. Previous searches for CI in the dijet and dilepton chan- nels have all resulted in limits on the compositeness scale �. Searches have been reported from experiments at LEP [6–10], HERA [11,12], the Tevatron [13–18], and recently from the ATLAS [19–22] and CMS [23–25] experiments at the LHC. The best limits in the LLIM dimuon channel are �> 9:6 TeV for destructive interference and �> 12:9 TeV for constructive interference, at the 95% confi- dence level (CL) [22]. In this paper, we report a search for CI in the dilepton channel produced in pp collisions at ffiffiffi s p ¼ 7 TeV using the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The data sample corresponds to an integrated luminosity of 5:3 fb�1. II. PREDICTIONS OF THE LEFT-LEFT ISOSCALAR MODEL The basic features of the LLIM dimuon mass spectra are demonstrated with a generator-level simulation using PYTHIA [26], with appropriate kinematic selection criteria that approximate the acceptance of the detector. Figures 2(a) and 2(b) show the LLIM dimuon mass spectra for different values of � for destructive and constructive interference, respectively. The curves illustrate that with increasing mass the CI leads to a less steeply falling yield relative to DY production, with the effect steadily increas- ing with decreasing �. For a given value of �, the event yield is seen to be larger for constructive interference compared to the destructive case, with the relative differ- ence increasing with �. For the results presented in this paper, the analysis is limited to a dimuon mass range from 200 to 2000 GeV=c2. The lower mass is sufficiently above the Z peak so that a deviation from DY production would be observable. The highest dimuon mass observed is between 1300 and 1400 GeV=c2 and, for the values of � where the limits are set, less than one event is expected for dimuon masses above 2000 GeV=c2. In order to limit the mass range in which the detector acceptance has to be evaluated, we therefore choose an upper mass cutoff of 2000 GeV=c2. To optimize the limit on�, a minimummassMmin �� is varied between the lower and upper mass values, as described in Sec. VI. III. CMS DETECTOR The central feature of the CMS apparatus is a super- conducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the field volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter, and a brass-scintillator had- ron calorimeter. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke. Extensive forward calorimetry complements the coverage provided by the barrel and endcap detectors. A detailed description of the CMS detector can be found in Ref. [27]. The tracker and muon detector are important subsystems for this measurement. The tracker measures charged par- ticle trajectories within the range j�j< 2:5, where pseu- dorapidity � ¼ � ln½tanð�=2Þ�, and polar angle � is measured from the beam axis. The tracker provides a transverse momentum (pT) resolution of about 1% at a few tens of GeV=c to 10% at several hundred GeV=c [28], where pT is the component of momentum in the plane )2 (GeV/cµµM 500 1000 1500 2000 2500 3000 )2 E ve nt s/ (3 0 G eV /c 1 10 210 310 410 510 = 3 TeVΛ = 5 TeVΛ = 7 TeVΛ = 9 TeVΛ = 13 TeVΛ DY destructive interference left-left isoscalar model PYTHIA simulation (a) )2 (GeV/cµµM 500 1000 1500 2000 2500 3000 )2 E ve nt s/ (3 0 G eV /c 1 10 210 310 410 510 = 3 TeVΛ = 5 TeVΛ = 7 TeVΛ = 9 TeVΛ = 13 TeVΛ DY constructive interference left-left isoscalar model PYTHIA simulation (b) FIG. 2 (color online). Simulated dimuon mass spectra using the left-left isoscalar model for different values of � for (a) destructive interference and (b) constructive interference. The events are generated using the PYTHIA Monte Carlo program with kinematic selection requirements that approximate the acceptance of the detector. As � increases, the effects of the CI are reduced, and the event yield approaches that for DY production. The model predictions are shown over the full mass range, although the model is not valid as M��c 2 approaches �. The integrated luminosity corresponds to 63 fb�1. S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-2 perpendicular to the beam axis. Tracker elements include about 1400 silicon pixel modules, located close to the beamline, and about 15 000 silicon microstrip modules, which surround the pixel system. Tracker detectors are arranged in both barrel and endcap geometries. The muon detector comprises a combination of drift tubes and resistive plate chambers in the barrel region and a combination of cathode strip chambers and resistive plate chambers in the endcap regions. Muons can be recon- structed in the range j�j< 2:4. For the trigger path used in this analysis, the first level (L1) selects events with a muon candidate based on a subset of information from the muon detector. The trigger muon is required to have j�j< 2:1 and pT above a thresh- old that was raised to 40 GeV=c by the end of the data- taking period. This cut has little effect on the acceptance for muon pairs with masses above 200 GeV=c2. The small effect is included in the simulation. The high level trigger (HLT) refines the L1 selection using the full information from both the tracker and muon systems. IV. EVENT SELECTION CRITERIA This analysis uses the same event selection as the search for new heavy resonances in the dimuon channel, discussed in Ref. [29]. Each muon track is required to have a signal (‘‘hit’’) in at least one pixel layer, hits in at least nine strip layers, and hits in at least two muon detector stations. Both muons are required to have pT > 45 GeV=c. To reduce the cosmic ray background, the transverse impact parameter of the muon with respect to the beamspot is required to be less than 0.2 cm. In order to suppress muons coming from hadronic decays, a tracker-based isolation requirement is imposed such that the sum of pT of all tracks, excluding the muon and within a cone surrounding the muon, is less than 10% of the pT of the muon. The cone is defined by the condition�R ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffið��Þ2 þ ð��Þ2p ¼ 0:3, where � is the azimuthal angle of a track, and the differ- ences �� and �� are determined with respect to the muon’s direction. The two muons are required to have opposite charge and to be consistent with originating from a common vertex. To suppress cosmic ray muons that are in time with the collision event, the angle between the two muons must be smaller than �� 0:02 radians. At least one of the reconstructed muons must be matched (within �R< 0:2 and �pT=pT < 1) to the HLT muon candidate. If an event has more than two muons passing the above requirements, then the two highest-pT muons are selected, and the event is retained only if these muons are oppositely charged. Only three such events are observed with selected dimuon mass above 200 GeV=c2, and in all three cases, the dimuon mass is less than 300 GeV=c2. Thus, events with multiple dimuon candidates play essentially no role in the analysis. V. SIMULATION OF SM AND CI DIMUON PRODUCTION This section describes the method used to simulate the mass distribution from the CI/DY process of Eq. (2), including the leading-order (LO) contributions from DY and CI amplitudes, their interference, the effects of next-to- leading-order (NLO) QCD and QED corrections, and the response of the detector. The predicted number of CI/DY events is the product of the generated number of CI/DY events, a QCD K-factor, a QED K-factor, and a factor denoted as ‘‘acceptance times migration’’ (A�M). The factor A�M is determined from the detector simulation of DYevents, as explained below in Sec. VB. The simulation of background due to non-DY SM processes is also described. A. Event samples with detector simulation A summary of the event samples used for simulation of the detector response to various physics processes is pre- sented in Table I. The event generators used are PYTHIA, with the CTEQ6.6M implementation [30] of parton distri- bution functions (PDF), POWHEG [31–33], and MADGRAPH5 [34]. The detector simulation is based on GEANT4 [35]. B. Detector acceptance times mass migration To simplify the analysis, we use the detector simulation for DYevents to determine the detector response for CI/DY events, which have a behavior similar to that for DYevents for the large values of � of interest in this analysis. For a given value of Mmin �� , the product of acceptance times migration (A�M) is given by the ratio of the number of DY events reconstructed with mass above Mmin �� to the number of DY events generated with mass above Mmin �� . Some of the reconstructed events have been generated with mass below Mmin �� because of the smearing due to the mass reconstruction, which has a resolution of 6.5% at masses around 1000 GeV=c2, rising to 12% at 2000 GeV=c2. The dependence of A�M on Mmin �� is plotted in Fig. 3 and values are given in Table II. The increase of A�M at lower mass is due to the increase in acceptance, while at higher mass, it is dominated by the growth in mass reso- lution. Since the cross section falls steeply with mass, events tend to migrate from lower to higher mass over a range determined by the mass resolution. To validate that the A�M factor based on DY produc- tion is applicable to CI/DY production, we compare event yields predicted using the A�M factor with those pre- dicted using a simulation of CI/DY production. The study is performed for the cases of constructive interference with � ¼ 5 and 10 TeV, which represent a wide range of possible CI/DY cross sections. The results differ by at most 3%, consistent with the statistical precision of the study. The systematic uncertainty in A�M is conserva- tively assigned this value. SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-3 1. Event pileup During the course of the 2011 data-taking period, the luminosity increased with time, resulting in an increasing ‘‘event pileup,’’ the occurrence of multiple pp interactions recorded by the detector as a single event. The dependence of reconstruction efficiency on event pileup is studied by weighting simulated events so that the distribution of the number of reconstructed primary vertices per event matches that in data. The reconstruction efficiency is found to be insensitive to the variations in event pileup encoun- tered during the data-taking period. C. Higher-order strong and electromagnetic corrections Since we use the leading-order generator PYTHIA to simulate the CI/DY production, we must determine a QCD K-factor which takes into account higher-order initial-state diagrams. Under the assumption that the QCD K-factor is the same for DY and CI/DY events, we determine the QCD K-factor as the ratio of DY events generated using the next-to-leading-order generator MC@NLO [36] to those generated using PYTHIA. The MC@NLO generator is used with the same PDF set as used with PYTHIA. The resulting QCD K-factor as a func- tion of Mmin �� is given in Table II. The large sizes of the simulated event samples result in statistical uncertainties of less than 0.5%. The systematic uncertainty is assigned the value 3%, the size of the correction [37] between next-to- next-to-leading-order (NNLO) and NLO DY cross sec- tions. For SM processes other than DY production, the QCD K-factor is found, independent of dimuon mass, from the ratio of the cross section determined using MC@NLO to the cross section determined from PYTHIA. The effect of higher-order electromagnetic processes on CI/DY production is quantified by a mass-dependent QED K-factor determined using the HORACE generator [38]. The values of the QED K-factor, as a function ofMmin �� , are given in Table II. The systematic uncertainty is assigned as the size of the correction, jðQEDK-factorÞ � 1j, since the effect of higher-order QED corrections on the new physics of CI is unknown. D. Non-DY SM backgrounds Using the samples of simulated events listed in Table I, event yields are predicted for various non-DY SM back- ground processes, as shown in Table III. The yields are given as a function of Mmin �� , and they are scaled to the integrated luminosity of the data, 5:28� 0:12 fb�1 [39]. TABLE I. Description of event samples with detector simulation. The cross section � and integrated luminosity L are given for each sample generated. Process Generator Number of events �ðpbÞ Lðpb�1Þ Order Z=�� ! ��, M�� � 120 GeV=c2 PYTHIA 5:45� 104 7:90� 100 6:91� 103 LO Z=�� ! ��, M�� � 200 GeV=c2 PYTHIA 5:50� 104 9:70� 10�1 5:67� 104 LO Z=�� ! ��, M�� � 500 GeV=c2 PYTHIA 5:50� 104 2:70� 10�2 2:04� 106 LO Z=�� ! ��, M�� � 800 GeV=c2 PYTHIA 5:50� 104 3:10� 10�3 1:77� 107 LO Z=�� ! ��, M�� � 1000 GeV=c2 PYTHIA 5:50� 104 9:70� 10�4 5:67� 107 LO Z=�� ! �� PYTHIA 2:03� 106 1:30� 103 1:56� 103 LO t�t MADGRAPH 2:40� 106 1:57� 102 1:54� 105 NLO tW POWHEG 7:95� 105 7:90� 100 1:01� 105 NLO �tW POWHEG 8:02� 105 7:90� 100 1:02� 105 NLO WW PYTHIA 4:23� 106 4:30� 101 9:83� 104 LO WZ PYTHIA 4:27� 106 1:80� 101 2:37� 105 LO ZZ PYTHIA 4:19� 106 5:90� 100 7:10� 105 LO W þ jets MADGRAPH 2:43� 107 3:10� 104 7:82� 102 NLO multijet, � (pT > 15 GeV=c) PYTHIA 1:08� 106 8:47� 104 1:28� 102 LO )2 (GeV/cmin µµM 200 400 600 800 1000 1200 1400 1600 A cc ep ta nc e x M ig ra tio n 0.8 0.85 0.9 0.95 CMS simulation FIG. 3 (color online). Acceptance times migration, A�M, versus Mmin ��. Corresponding values and uncertainties are given in Table II. The error bars indicate statistical uncertainties based on simulation of the DY process. The systematic uncertainty is 3%, as explained in the text. The increase of A�M at lower mass is due to the increase in acceptance, while at higher mass, it is dominated by the growth in mass resolution. Since the cross section falls steeply with mass, events tend to migrate from lower to higher mass over a range determined by the mass resolution. S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-4 For comparison, the expected yields are also shown for DY events. The relevant backgrounds, in decreasing order of importance, are t�t, diboson ðWW=WZ=ZZÞ, W (including W þ jets and tW), and Z ! �� production. The back- ground from multijet events is studied using both the simulation sample listed in Table I and control samples from data, as reported in Ref. [29]. The results of either method indicate that no multijet background events are expected for Mmin �� > 200 GeV=c2. For Mmin �� > 1000 GeV=c2 the fractional statistical uncertainty in the non-DY background is large, but the absolute yield is much smaller than that for DY background. E. Predicted event yields Using the methods described above, the sum of the event yields for the CI/DY process and the non-DY SM back- grounds, for the integrated luminosity of the data sample, are predicted as a function of Mmin �� and �. The predicted event yields for destructive and constructive interference are given in Tables IV and V. For destructive interference, there is a region of the Mmin �� �� parameter space where the predicted number of events is less than for SM production. This ‘‘reduced- yield’’ region is indicated in Table IV. The region of parameter space, Mmin �� > 600 GeV=c2 and � � 12 TeV, where our expected limit is most stringent [see Fig. 5(a)], lies outside the reduced-yield region. For constructive interference, the predicted number of events is always larger than for SM production. VI. EXPECTED AND OBSERVED LOWER LIMITS ON � A. Dimuon mass distribution from data The observed numbers of events versus Mmin �� are given in Table IV. The observed distribution ofM�� is plotted in Fig. 4 along with the expected distributions from the SM and for CI/DY plus non-DY SM processes, for three illus- trative values of �. The data are consistent with the pre- dictions from the SM, dominated by DY production. B. Limit-setting procedure Since the data are consistent with the SM, we set lower limits on � in the context of the LLIM. The expected and observed 95% CL lower limits on � are determined using the CLS modified-frequentist procedure described in [40,41], taking the profile likelihood ratio as a test statistic [42]. The expected mean number of events for a signal TABLE II. Multiplicative factors used in the prediction of the expected number of events from the CI/DY process. The un- certainties shown are statistical. The systematic uncertainty is 3% for A�M and 3% for the QCD K-factor, as explained in the text. The uncertainty in the QED K-factor is dominated by the systematic uncertainty that is assigned as the size of the correc- tion, jðQEDK� factorÞ � 1j, to allow for systematic uncertainty in the generator. Mmin �� (GeV=c2) A�M QCD K-factor QED K-factor 200 0:80� 0:01 1:303� 0:005 1.01 300 0:82� 0:01 1:308� 0:005 0.99 400 0:83� 0:01 1:299� 0:005 0.97 500 0:86� 0:02 1:305� 0:005 0.95 600 0:86� 0:01 1:299� 0:005 0.94 700 0:87� 0:01 1:298� 0:005 0.92 800 0:88� 0:01 1:288� 0:005 0.91 900 0:89� 0:01 1:280� 0:004 0.90 1000 0:89� 0:01 1:278� 0:004 0.89 1100 0:89� 0:01 1:275� 0:004 0.88 1200 0:91� 0:01 1:268� 0:004 0.88 1300 0:92� 0:01 1:262� 0:004 0.87 1400 0:94� 0:01 1:260� 0:004 0.87 1500 0:97� 0:01 1:261� 0:004 0.86 TABLE III. Expected event yields for DY and non-DY SM backgrounds. The uncertainties shown are statistical. A systematic uncertainty of 2.2% arises from the determination of integrated luminosity [39]. Mmin �� (GeV=c2) DY t�t Diboson W þ Jets & tW Z ! �� Sum non-DY 200 3630� 18 454� 3 123:0� 2 47:90� 1:35 6:96� 4:14 632:3� 5:9 300 870:6� 8:8 104� 2 38:6� 1:2 12:82� 0:70 0 155:9� 2:1 400 301:6� 5:1 26:0� 0:8 12:7� 0:7 3:32� 0:35 0 42:0� 1:1 500 123:8� 3:3 8:19� 0:46 5:07� 0:41 1:02� 0:20 0 14:3� 0:6 600 55:31� 0:19 2:92� 0:27 2:42� 0:28 0:29� 0:11 0 5:63� 0:41 700 27:35� 0:13 1:12� 0:17 0:86� 0:16 0:07� 0:05 0 2:06� 0:24 800 14:23� 0:10 0:34� 0:09 0:51� 0:12 0:07� 0:05 0 0:92� 0:16 900 7:72� 0:07 0:05� 0:03 0:25� 0:08 0:07� 0:05 0 0:36� 0:10 1000 4:32� 0:05 0:05� 0:03 0:10� 0:05 0:07� 0:05 0 0:21� 0:08 1100 2:46� 0:04 0:05� 0:03 0:09� 0:05 0:07� 0:05 0 0:20� 0:08 1200 1:48� 0:03 0 0:01� 0:01 0:07� 0:05 0 0:08� 0:05 1300 0:91� 0:02 0 0:01� 0:01 0:07� 0:05 0 0:08� 0:05 1400 0:56� 0:02 0 0:01� 0:01 0:07� 0:05 0 0:08� 0:05 1500 0:33� 0:02 0 0 0:07� 0:05 0 0:07� 0:05 SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-5 TABLE V. Observed and expected number of events as in Table IV. Here CI/DY predictions are for constructive interference. Shown with bold-italic font is the expected event yield corresponding to the value of � closest to the observed 95% CL lower limit on � of 13.1 TeV (12.9 TeV expected) for Mmin �� selected to be 800 GeV=c2. Mmin �� (GeV=c2) 400 500 600 700 800 900 1000 1100 1200 1300 1400 Source Number of events Data 338 141 57 28 14 13 8 3 2 1 0 SM MC � (TeV) MC 343.6 138.1 60.9 29.4 15.2 8.1 4.5 2.7 1.6 1.0 0.6 18 359.2 147.7 67.8 34.1 18.7 10.6 6.4 4.0 2.5 1.6 1.1 17 358.9 149.3 69.1 35.1 19.3 11.1 6.7 4.3 2.7 1.8 1.2 16 365.2 153.7 70.3 36.1 20.2 11.7 7.2 4.6 3.0 2.0 1.3 15 365.6 156.3 71.9 37.2 20.9 12.3 7.6 4.9 3.1 2.1 1.4 14 368.5 154.9 74.6 39.1 22.4 13.3 8.4 5.5 3.6 2.4 1.7 13 377.8 164.4 77.9 41.7 24.2 14.7 9.4 6.3 4.2 2.9 2.0 12 379.2 170.5 82.5 45.2 26.9 16.7 11.0 7.4 5.0 3.5 2.4 11 388.9 174.6 88.6 49.9 30.4 19.3 12.9 8.8 6.1 4.2 3.0 10 406.0 184.5 97.9 57.1 36.0 23.7 16.2 11.3 7.9 5.6 4.0 9 440.3 214.8 113.2 68.8 44.8 30.3 21.2 15.0 10.7 7.7 5.5 8 470.0 237.1 138.2 87.7 59.6 41.6 29.9 21.8 15.7 11.4 8.1 7 563.9 307.3 181.0 120.4 86.7 62.1 44.8 31.5 23.3 16.9 12.3 6 696.8 415.0 269.2 187.3 136.9 101.7 75.3 57.4 41.8 30.7 23.2 5 1007 675.0 467.8 345.8 268.0 202.3 153.3 116.9 87.3 64.6 47.0 4 1839 1346 997.4 765.1 586.6 451.1 349.6 266.8 200.3 147.8 109.5 3 4800 3762 2861 2251 1754 1358 1041 791.0 597.1 453.6 338.5 TABLE IV. Observed and expected number of events for illustrative values of Mmin �� . The expected yields are shown for SM production and for the sum of CI/DY production (for destructive interference and for a given �) and non-DY SM backgrounds. For each column ofMmin �� , the expected yield for CI=DYþ non-DY SM production that is just above that expected for SM production is in bold font. Entries above the bold ones correspond to values of � for which the expected yield is less than that for SM production, because of the destructive interference term in the cross section. As discussed in Sec. VI C, the best expected limit is obtained for Mmin �� ¼ 1100 GeV=c2. For this choice, the expected event yield, in bold-italic font, corresponds to the value of � closest to the observed 95% CL lower limit on � of 9.5 TeV (9.7 TeV expected). Mmin �� (GeV=c2) 500 600 700 800 900 1000 1100 1200 1300 1400 1500 Source Number of events Data 141 57 28 14 13 8 3 2 1 0 0 SM MC � (TeV) MC 138.1 60.9 29.4 15.2 8.1 4.5 2.7 1.6 1.0 0.6 0.4 18 134.2 58.0 27.9 14.3 7.7 4.3 2.6 1.5 1.0 0.6 0.4 17 134.5 57.9 27.7 14.4 7.8 4.4 2.6 1.6 1.0 0.6 0.4 16 134.9 58.0 27.8 14.5 7.8 4.5 2.7 1.6 1.0 0.7 0.5 15 135.6 58.3 28.1 14.7 8.0 4.7 2.9 1.7 1.1 0.8 0.5 14 133.7 58.3 28.3 15.0 8.4 5.0 3.1 1.9 1.3 0.9 0.6 13 134.1 59.3 29.1 15.7 8.9 5.4 3.5 2.2 1.5 1.0 0.7 12 138.6 60.1 30.2 16.7 9.8 6.1 4.1 2.7 1.9 1.3 0.9 11 135.7 62.5 32.1 18.4 11.2 7.3 5.0 3.5 2.4 1.7 1.2 10 141.1 66.7 35.7 21.2 13.6 9.2 6.6 4.6 3.3 2.4 1.7 9 148.5 73.8 42.4 27.1 18.3 13.1 9.5 6.9 5.0 3.7 2.6 8 164.7 88.1 54.4 36.8 26.2 19.3 14.3 10.6 7.8 5.8 4.1 7 198.1 117.5 79.4 57.6 43.3 31.6 24.0 17.5 13.1 9.0 6.2 6 278.1 182.3 131.7 100.1 76.7 57.9 45.1 33.0 22.6 16.9 11.3 5 469.2 338.7 261.7 204.4 158.6 123.2 96.7 74.6 56.8 41.5 29.2 4 1025 784.1 620.1 494.2 384.3 302.6 232.8 174.6 127.2 94.5 68.5 3 3199 2517 2012 1599 1242 975.7 744.7 575.4 437.7 320.1 231.4 S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-6 from CI is the difference of the number of CI/DY events expected for a given �, and the number of DY events. The expected mean number of background events is the sum of events from the DY process and the non-DY SM back- grounds. The observed and expected numbers of events are given in Tables IV and V. Systematic uncertainties in the predicted signal and background event yields are estimated from a variety of sources and included as nuisance parameters in the limit-setting procedure. Significant sources of systematic uncertainty are given in Table VI. The uncertainty in the integrated luminosity is described in Ref. [39]. The uncer- tainty in the CI/DY acceptance is explained in Sec. VB. The uncertainties in the prediction of backgrounds depend on the value of Mmin �� . These uncertainties are given in Table VI for the values of Mmin �� chosen for limits on � with destructive and constructive interference. The PDF uncertainty in the expected yield of DYevents is evaluated using the PDF4LHC procedure [43]. The uncertainties in the QED and QCD K-factors are explained in Sec. VC. The uncertainty from non-DY backgrounds is due to the statistical uncertainty associated with the simulated event samples. The systematic uncertainties which decrease the limit on � by the largest amounts are the uncertainties on the PDF and QED K-factor. When both these uncertainties are set to zero, the limit for destructive interference is increased by 0.4% and the limit for constructive interfer- ence is increased by 3.0%. Thus, the systematic uncertain- ties degrade the limits by only small amounts. We considered possible systematic uncertainties in mod- eling the detector response by comparing kinematic dis- tributions between data and simulation of DY and non-DY SM processes. There are no differences in these distribu- tions that could lead to significant systematic uncertainties through their effect on selection efficiency and mass resolution. C. Results for limits on � The observed and expected lower limits on� at 95% CL as a function of Mmin �� for destructive and constructive interference are shown in Figs. 5(a) and 5(b). The value of Mmin �� , chosen to maximize the expected sensitivity, is 1100 GeV=c2 for destructive interference, and 800 GeV=c2 for constructive interference. The observed (expected) limit is 9.5 TeV (9.7 TeV) for destructive )2 (GeV/cµµM 200 400 600 800 1000 1200 1400 1600 1800 2000 )2 E ve nt s/ (2 0 G eV /c -410 -310 -210 -110 1 10 210 310 410 -1 = 7 TeV, 5.3 fbsCMS, data = 8 TeV (const.)Λ = 8 TeV (destr.)Λ = 10 TeV (const.)Λ = 10 TeV (destr.)Λ = 12 TeV (const.)Λ = 12 TeV (destr.)Λ DY tt tW diboson ττ→Z W+Jets FIG. 4 (color online). Observed spectrum of M�� and predic- tions for SM and CI/DY plus non-DY SM production. Predictions are shown for three illustrative values of �, for constructive and destructive interference. The error bars for data are 68% Poisson confidence intervals. )2 (GeV/cmin µµM 500 1000 1500 500 1000 1500 (T eV ) Λ 95 % C L 3 4 5 6 7 8 9 10 11 12 expected limit σ1±expected limit σ2±expected limit observed limit best expected limit -1= 7 TeV, 5.3 fbsCMS, destructive interference(a) )2 (GeV/cmin µµM (T eV ) Λ 95 % C L 4 6 8 10 12 14 16 18 expected limit σ1±expected limit σ2±expected limit observed limit best expected limit -1= 7 TeV, 5.3 fbsCMS, constructive interference(b) FIG. 5 (color online). Observed and expected limits as a function of Mmin �� for (a) destructive interference and (b) constructive interference. The value of Mmin �� , chosen to maximize the expected sensitivity, is 1100 GeV=c2 for destruc- tive interference and 800 GeV=c2 for constructive interference. The observed (expected) limit is 9.5 TeV (9.7 TeV) for destruc- tive interference and 13.1 TeV (12.9 TeV) for constructive interference. The observed limit at the value chosen for Mmin �� is indicated with a red plus sign. The variations in the observed limits lie almost entirely within the 1-� bands, consistent with statistical fluctuations. SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-7 interference and 13.1 TeV (12.9 TeV) for constructive interference. The variations in the observed limits lie almost entirely within the 1-� (standard deviation) uncer- tainty bands in the expected limits, consistent with statis- tical fluctuations. The number of expected events corresponding to the observed limits on � are shown in Tables IV and V. VI. SUMMARY The CMS detector is used to measure the invariant mass distribution of �þ�� pairs produced in pp collisions at a center-of-mass energy of 7 TeV, based on an integrated luminosity of 5:3 fb�1. The invariant mass distribution in the range 200 to 2000 GeV=c2 is found to be consistent with standard model sources of dimuons, which are domi- nated by Drell-Yan production. The data are interpreted in the context of a quark- and muon-compositeness model with a left-handed isoscalar current and an energy scale parameter�. The 95% confidence level lower limit on� is 9.5 TeV under the assumption of destructive interference between the standard model and contact-interaction ampli- tudes. For constructive interference, the limit is 13.1 TeV. These limits are comparable to the most stringent ones reported to date. ACKNOWLEDGMENTS We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative staffs at CERN and at other CMS institutes for their contributions to the suc- cess of the CMS effort. In addition, we gratefully acknowl- edge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effec- tively the computing infrastructure essential to our analy- ses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MEYS (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie programme and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) of Czech Republic; the Council of Science and Industrial Research, India; the Compagnia di San Paolo (Torino); and the HOMING PLUS programme of Foundation for Polish Science, cofinanced by European Union, Regional Development Fund. [1] J. C. Pati, A. Salam, and J. Strathdee, Phys. Lett. 59B, 265 (1975). [2] J. C. Pati, A. Salam, and J. Strathdee, Report No. IC/75/ 139, addendum (Int. Centre Theor. Phys., 1975). [3] E. Eichten, K. Lane, and M. Peskin, Phys. Rev. Lett. 50, 811 (1983). [4] E. Eichten, I. Hinchlie, K. Lane, and C. Quigg, Rev. Mod. Phys. 56, 579 (1984). [5] S. D. Drell and T.M. Yan, Phys. Rev. Lett. 25, 316 (1970). [6] S. Schael et al. (ALEPH Collaboration), Eur. Phys. J. C 49, 411 (2007). TABLE VI. Systematic uncertainties affecting the limit on �, evaluated for the values of Mmin �� that provide the best expected limits for constructive and destructive interference. Uncertainty (%) Source Constructive Destructive Integrated luminosity 2.2 2.2 Acceptance times migration (A�M) 3.0 3.0 PDF 13.0 16.0 QED K-factor 9.0 11.8 QCD K-factor 3.0 3.0 DY MC statistics 1.2 1.6 Non-DY backgrounds 1.1 2.9 S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-8 http://dx.doi.org/10.1016/0370-2693(75)90042-8 http://dx.doi.org/10.1016/0370-2693(75)90042-8 http://dx.doi.org/10.1103/PhysRevLett.50.811 http://dx.doi.org/10.1103/PhysRevLett.50.811 http://dx.doi.org/10.1103/RevModPhys.56.579 http://dx.doi.org/10.1103/RevModPhys.56.579 http://dx.doi.org/10.1103/PhysRevLett.25.316 http://dx.doi.org/10.1103/PhysRevLett.25.316 http://dx.doi.org/10.1140/epjc/s10052-006-0156-8 http://dx.doi.org/10.1140/epjc/s10052-006-0156-8 [7] J. Abdallah et al. (DELPHI Collaboration), Eur. Phys. J. C 45, 589 (2006). [8] M. Acciarri et al. (L3 Collaboration), Phys. Lett. B 489, 81 (2000). [9] K. Ackerstaff et al. (OPAL Collaboration), Phys. Lett. B 391, 221 (1997). [10] G. Abbiendi et al. (OPAL Collaboration), Eur. Phys. J. C 33, 173 (2004). [11] F. D. Aaron et al. (H1 Collaboration), Phys. Lett. B 705, 52 (2011). [12] S. Chekanov et al. (ZEUS Collaboration), Phys. Lett. B 591, 23 (2004). [13] F. Abe et al. (CDF Collaboration), Phys. Rev. Lett. 68, 1463 (1992). [14] F. Abe et al. (CDF Collaboration), Phys. Rev. Lett. 79, 2198 (1997). [15] T. Affolder et al. (CDF Collaboration), Phys. Rev. Lett. 87, 231803 (2001). [16] A. Abulencia et al. (CDF Collaboration), Phys. Rev. Lett. 96, 211801 (2006). [17] B. Abbott et al. (D0 Collaboration), Phys. Rev. Lett. 82, 4769 (1999). [18] V.M. Abazov et al. (D0 Collaboration), Phys. Rev. Lett. 103, 191803 (2009). [19] ATLAS Collaboration, Phys. Lett. B 694, 327 (2011). [20] ATLAS Collaboration, Phys. Rev. D 84, 011101 (2011). [21] ATLAS Collaboration, Phys. Lett. B 712, 40 (2012). [22] ATLAS Collaboration, arXiv:1211.1150v1. [23] CMS Collaboration, Phys. Rev. Lett. 105, 262001 (2010). [24] CMS Collaboration, J. High Energy Phys. 05 (2012) 055. [25] CMS Collaboration, arXiv:1210.0867 [Phys. Lett. B (to be published)]. [26] T. Sjöstrand, S. Mrenna, and P. Z. Skand, J. High Energy Phys. 05 (2006) 026. [27] CMS Collaboration, JINST 3, S08004 (2008). [28] CMS Collaboration, JINST, 7, P10002 (2012). [29] CMS Collaboration, Phys. Lett. B 714, 158 (2012). [30] P.M. Nadolsky, H.-L. Lai, Q.-H. Cao, J. Huston, J. Pumplin, D. Stump, W.-K. Tung, and C.-P. Yuan, Phys. Rev. D 78, 013004 (2008). [31] P. Nason, J. High Energy Phys. 11 (2004) 040. [32] S. Frixione, P. Nason, and C. Oleari, J. High Energy Phys. 11 (2007) 070. [33] S. Alioli, P. Nason, C. Oleari, and E. Re, J. High Energy Phys. 07 (2008) 060. [34] J. Alwall, M. Herquet, F. Maltoni, O. Mattelaer, and T. Stelzer, J. High Energy Phys. 06 (2011) 128. [35] S. Agostinelli et al. (GEANT4 Collaboration), Nucl. Instrum. Methods Phys. Res., Sect. A 506, 250 (2003). [36] S. Frixione and B. R. Webber, J. High Energy Phys. 06 (2002) 029. [37] G. Balossini, G. Montagna, C.M. Carloni Calame, M. Moretti, M. Treccani, O. Nicrosini, F. Piccinini, and A. Vicini, Acta Phys. Pol. B 39, 1675 (2008). [38] C.M. Carloni Calame, G. Montagna, O. Nicrosini, and A. Vicini, J. High Energy Phys. 10 (2007) 109. [39] CMS Collaboration, CMS Physics Analysis Summary Report No. CMS-PAS-SMP-12-008 (2012). [40] A. L. Read, J. Phys. G 28, 2693 (2002). [41] T. Junk, Nucl. Instrum. Methods Phys. Res., Sect. A 434, 435 (1999). [42] T. Junk, CDF Report No. CDF/DOC/STATISTICS/ PUBLIC/8128 (2007). [43] M. Botje et al., arXiv:1101.0538. S. Chatrchyan,1 V. Khachatryan,1 A.M. Sirunyan,1 A. Tumasyan,1 W. Adam,2 E. Aguilo,2 T. Bergauer,2 M. Dragicevic,2 J. Erö,2 C. Fabjan,2,b M. Friedl,2 R. Frühwirth,2,b V.M. Ghete,2 J. Hammer,2 N. Hörmann,2 J. Hrubec,2 M. Jeitler,2,b W. Kiesenhofer,2 V. Knünz,2 M. Krammer,2,b I. Krätschmer,2 D. Liko,2 I. Mikulec,2 M. Pernicka,2,a B. Rahbaran,2 C. Rohringer,2 H. Rohringer,2 R. Schöfbeck,2 J. Strauss,2 A. Taurok,2 W. Waltenberger,2 G. Walzel,2 E. Widl,2 C.-E. Wulz,2,b V. Mossolov,3 N. Shumeiko,3 J. Suarez Gonzalez,3 M. Bansal,4 S. Bansal,4 T. Cornelis,4 E. A. De Wolf,4 X. Janssen,4 S. Luyckx,4 L. Mucibello,4 S. Ochesanu,4 B. Roland,4 R. Rougny,4 M. Selvaggi,4 Z. Staykova,4 H. Van Haevermaet,4 P. Van Mechelen,4 N. Van Remortel,4 A. Van Spilbeeck,4 F. Blekman,5 S. Blyweert,5 J. D’Hondt,5 R. Gonzalez Suarez,5 A. Kalogeropoulos,5 M. Maes,5 A. Olbrechts,5 W. Van Doninck,5 P. Van Mulders,5 G. P. Van Onsem,5 I. Villella,5 B. Clerbaux,6 G. De Lentdecker,6 V. Dero,6 A. P. R. Gay,6 T. Hreus,6 A. Léonard,6 P. E. Marage,6 A. Mohammadi,6 T. Reis,6 L. Thomas,6 G. Vander Marcken,6 C. Vander Velde,6 P. Vanlaer,6 J. Wang,6 V. Adler,7 K. Beernaert,7 A. Cimmino,7 S. Costantini,7 G. Garcia,7 M. Grunewald,7 B. Klein,7 J. Lellouch,7 A. Marinov,7 J. Mccartin,7 A.A. Ocampo Rios,7 D. Ryckbosch,7 N. Strobbe,7 F. Thyssen,7 M. Tytgat,7 P. Verwilligen,7 S. Walsh,7 E. Yazgan,7 N. Zaganidis,7 S. Basegmez,8 G. Bruno,8 R. Castello,8 L. Ceard,8 C. Delaere,8 T. du Pree,8 D. Favart,8 L. Forthomme,8 A. Giammanco,8,c J. Hollar,8 V. Lemaitre,8 J. Liao,8 O. Militaru,8 C. Nuttens,8 D. Pagano,8 A. Pin,8 K. Piotrzkowski,8 N. Schul,8 J.M. Vizan Garcia,8 N. Beliy,9 T. Caebergs,9 E. Daubie,9 G. H. Hammad,9 G.A. Alves,10 M. Correa Martins Junior,10 D. De Jesus Damiao,10 T. Martins,10 M. E. Pol,10 M.H.G. Souza,10 W. L. Aldá Júnior,11 W. Carvalho,11 A. Custódio,11 E.M. Da Costa,11 C. De Oliveira Martins,11 S. Fonseca De Souza,11 D. Matos Figueiredo,11 L. Mundim,11 H. Nogima,11 V. Oguri,11 W. L. Prado Da Silva,11 A. Santoro,11 L. Soares Jorge,11 A. Sznajder,11 T. S. Anjos,12b C. A. Bernardes,12b F. A. Dias,12a,d T. R. Fernandez Perez Tomei,12a E.M. Gregores,12b C. Lagana,12a F. Marinho,12a P. G. Mercadante,12b S. F. Novaes,12a Sandra S. Padula,12a V. Genchev,13,e P. Iaydjiev,13,e S. Piperov,13 M. Rodozov,13 S. Stoykova,13 G. Sultanov,13 V. Tcholakov,13 R. Trayanov,13 M. Vutova,13 A. Dimitrov,14 SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-9 http://dx.doi.org/http://dx.doi.org/10.1140/epjc/s2005-02461-0 http://dx.doi.org/http://dx.doi.org/10.1140/epjc/s2005-02461-0 http://dx.doi.org/10.1016/S0370-2693(00)00887-X http://dx.doi.org/10.1016/S0370-2693(00)00887-X http://dx.doi.org/10.1016/S0370-2693(97)81627-9 http://dx.doi.org/10.1016/S0370-2693(97)81627-9 http://dx.doi.org/10.1140/epjc/s2004-01595-9 http://dx.doi.org/10.1140/epjc/s2004-01595-9 http://dx.doi.org/10.1016/j.physletb.2011.09.109 http://dx.doi.org/10.1016/j.physletb.2011.09.109 http://dx.doi.org/10.1016/j.physletb.2004.03.081 http://dx.doi.org/10.1016/j.physletb.2004.03.081 http://dx.doi.org/10.1103/PhysRevLett.68.1463 http://dx.doi.org/10.1103/PhysRevLett.68.1463 http://dx.doi.org/10.1103/PhysRevLett.79.2198 http://dx.doi.org/10.1103/PhysRevLett.79.2198 http://dx.doi.org/10.1103/PhysRevLett.87.231803 http://dx.doi.org/10.1103/PhysRevLett.87.231803 http://dx.doi.org/10.1103/PhysRevLett.96.211801 http://dx.doi.org/10.1103/PhysRevLett.96.211801 http://dx.doi.org/10.1103/PhysRevLett.82.4769 http://dx.doi.org/10.1103/PhysRevLett.82.4769 http://dx.doi.org/10.1103/PhysRevLett.103.191803 http://dx.doi.org/10.1103/PhysRevLett.103.191803 http://dx.doi.org/10.1016/j.physletb.2010.10.021 http://dx.doi.org/10.1103/PhysRevD.84.011101 http://dx.doi.org/10.1016/j.physletb.2012.04.026 http://arXiv.org/abs/1211.1150v1 http://dx.doi.org/10.1103/PhysRevLett.105.262001 http://dx.doi.org/10.1007/JHEP05(2012)055 http://arXiv.org/abs/1210.0867 http://dx.doi.org/10.1088/1126-6708/2006/05/026 http://dx.doi.org/10.1088/1126-6708/2006/05/026 http://dx.doi.org/10.1088/1748-0221/3/08/S08004 http://dx.doi.org/10.1088/1748-0221/7/10/P10002 http://dx.doi.org/10.1016/j.physletb.2012.06.051 http://dx.doi.org/10.1103/PhysRevD.78.013004 http://dx.doi.org/10.1103/PhysRevD.78.013004 http://dx.doi.org/10.1088/1126-6708/2004/11/040 http://dx.doi.org/10.1088/1126-6708/2007/11/070 http://dx.doi.org/10.1088/1126-6708/2007/11/070 http://dx.doi.org/10.1088/1126-6708/2008/07/060 http://dx.doi.org/10.1088/1126-6708/2008/07/060 http://dx.doi.org/10.1007/JHEP06(2011)128 http://dx.doi.org/10.1016/S0168-9002(03)01368-8 http://dx.doi.org/10.1016/S0168-9002(03)01368-8 http://dx.doi.org/10.1088/1126-6708/2002/06/029 http://dx.doi.org/10.1088/1126-6708/2002/06/029 http://dx.doi.org/10.1088/1126-6708/2007/10/109 http://dx.doi.org/10.1088/0954-3899/28/10/313 http://dx.doi.org/10.1016/S0168-9002(99)00498-2 http://dx.doi.org/10.1016/S0168-9002(99)00498-2 http://arXiv.org/abs/1101.0538 R. Hadjiiska,14 V. Kozhuharov,14 L. Litov,14 B. Pavlov,14 P. Petkov,14 J. G. Bian,15 G.M. Chen,15 H. S. Chen,15 C.H. Jiang,15 D. Liang,15 S. Liang,15 X. Meng,15 J. Tao,15 J. Wang,15 X. Wang,15 Z. Wang,15 H. Xiao,15 M. Xu,15 J. Zang,15 Z. Zhang,15 C. Asawatangtrakuldee,16 Y. Ban,16 S. Guo,16 Y. Guo,16 W. Li,16 S. Liu,16 Y. Mao,16 S. J. Qian,16 H. Teng,16 D. Wang,16 L. Zhang,16 B. Zhu,16 W. Zou,16 C. Avila,17 J. P. Gomez,17 B. Gomez Moreno,17 A. F. Osorio Oliveros,17 J. C. Sanabria,17 N. Godinovic,18 D. Lelas,18 R. Plestina,18,f D. Polic,18 I. Puljak,18,e Z. Antunovic,19 M. Kovac,19 V. Brigljevic,20 S. Duric,20 K. Kadija,20 J. Luetic,20 S. Morovic,20 A. Attikis,21 M. Galanti,21 G. Mavromanolakis,21 J. Mousa,21 C. Nicolaou,21 F. Ptochos,21 P. A. Razis,21 M. Finger,22 M. Finger, Jr.,22 Y. Assran,23,g S. Elgammal,23,h A. Ellithi Kamel,23,i M.A. Mahmoud,23,j A. Radi,23,k,l M. Kadastik,24 M. Müntel,24 M. Raidal,24 L. Rebane,24 A. Tiko,24 P. Eerola,25 G. Fedi,25 M. Voutilainen,25 J. Härkönen,26 A. Heikkinen,26 V. Karimäki,26 R. Kinnunen,26 M. J. Kortelainen,26 T. Lampén,26 K. Lassila-Perini,26 S. Lehti,26 T. Lindén,26 P. Luukka,26 T. Mäenpää,26 T. Peltola,26 E. Tuominen,26 J. Tuominiemi,26 E. Tuovinen,26 D. Ungaro,26 L. Wendland,26 K. Banzuzi,27 A. Karjalainen,27 A. Korpela,27 T. Tuuva,27 M. Besancon,28 S. Choudhury,28 M. Dejardin,28 D. Denegri,28 B. Fabbro,28 J. L. Faure,28 F. Ferri,28 S. Ganjour,28 A. Givernaud,28 P. Gras,28 G. Hamel de Monchenault,28 P. Jarry,28 E. Locci,28 J. Malcles,28 L. Millischer,28 A. Nayak,28 J. Rander,28 A. Rosowsky,28 I. Shreyber,28 M. Titov,28 S. Baffioni,29 F. Beaudette,29 L. Benhabib,29 L. Bianchini,29 M. Bluj,29,m C. Broutin,29 P. Busson,29 C. Charlot,29 N. Daci,29 T. Dahms,29 L. Dobrzynski,29 R. Granier de Cassagnac,29 M. Haguenauer,29 P. Miné,29 C. Mironov,29 I. N. Naranjo,29 M. Nguyen,29 C. Ochando,29 P. Paganini,29 D. Sabes,29 R. Salerno,29 Y. Sirois,29 C. Veelken,29 A. Zabi,29 J.-L. Agram,30,n J. Andrea,30 D. Bloch,30 D. Bodin,30 J.-M. Brom,30 M. Cardaci,30 E. C. Chabert,30 C. Collard,30 E. Conte,30,n F. Drouhin,30,n C. Ferro,30 J.-C. Fontaine,30,n D. Gelé,30 U. Goerlach,30 P. Juillot,30 A.-C. Le Bihan,30 P. Van Hove,30 F. Fassi,31 D. Mercier,31 S. Beauceron,32 N. Beaupere,32 O. Bondu,32 G. Boudoul,32 J. Chasserat,32 R. Chierici,32,e D. Contardo,32 P. Depasse,32 H. El Mamouni,32 J. Fay,32 S. Gascon,32 M. Gouzevitch,32 B. Ille,32 T. Kurca,32 M. Lethuillier,32 L. Mirabito,32 S. Perries,32 V. Sordini,32 Y. Tschudi,32 P. Verdier,32 S. Viret,32 Z. Tsamalaidze,33,o G. Anagnostou,34 S. Beranek,34 M. Edelhoff,34 L. Feld,34 N. Heracleous,34 O. Hindrichs,34 R. Jussen,34 K. Klein,34 J. Merz,34 A. Ostapchuk,34 A. Perieanu,34 F. Raupach,34 J. Sammet,34 S. Schael,34 D. Sprenger,34 H. Weber,34 B. Wittmer,34 V. Zhukov,34,p M. Ata,35 J. Caudron,35 E. Dietz-Laursonn,35 D. Duchardt,35 M. Erdmann,35 R. Fischer,35 A. Güth,35 T. Hebbeker,35 C. Heidemann,35 K. Hoepfner,35 D. Klingebiel,35 P. Kreuzer,35 C. Magass,35 M. Merschmeyer,35 A. Meyer,35 M. Olschewski,35 P. Papacz,35 H. Pieta,35 H. Reithler,35 S. A. Schmitz,35 L. Sonnenschein,35 J. Steggemann,35 D. Teyssier,35 M. Weber,35 M. Bontenackels,36 V. Cherepanov,36 Y. Erdogan,36 G. Flügge,36 H. Geenen,36 M. Geisler,36 W. Haj Ahmad,36 F. Hoehle,36 B. Kargoll,36 T. Kress,36 Y. Kuessel,36 A. Nowack,36 L. Perchalla,36 O. Pooth,36 P. Sauerland,36 A. Stahl,36 M. Aldaya Martin,37 J. Behr,37 W. Behrenhoff,37 U. Behrens,37 M. Bergholz,37,q A. Bethani,37 K. Borras,37 A. Burgmeier,37 A. Cakir,37 L. Calligaris,37 A. Campbell,37 E. Castro,37 F. Costanza,37 D. Dammann,37 C. Diez Pardos,37 G. Eckerlin,37 D. Eckstein,37 G. Flucke,37 A. Geiser,37 I. Glushkov,37 P. Gunnellini,37 S. Habib,37 J. Hauk,37 G. Hellwig,37 H. Jung,37 M. Kasemann,37 P. Katsas,37 C. Kleinwort,37 H. Kluge,37 A. Knutsson,37 M. Krämer,37 D. Krücker,37 E. Kuznetsova,37 W. Lange,37 W. Lohmann,37,q B. Lutz,37 R. Mankel,37 I. Marfin,37 M. Marienfeld,37 I.-A. Melzer-Pellmann,37 A. B. Meyer,37 J. Mnich,37 A. Mussgiller,37 S. Naumann-Emme,37 J. Olzem,37 H. Perrey,37 A. Petrukhin,37 D. Pitzl,37 A. Raspereza,37 P.M. Ribeiro Cipriano,37 C. Riedl,37 E. Ron,37 M. Rosin,37 J. Salfeld-Nebgen,37 R. Schmidt,37,q T. Schoerner-Sadenius,37 N. Sen,37 A. Spiridonov,37 M. Stein,37 R. Walsh,37 C. Wissing,37 C. Autermann,38 V. Blobel,38 J. Draeger,38 H. Enderle,38 J. Erfle,38 U. Gebbert,38 M. Görner,38 T. Hermanns,38 R. S. Höing,38 K. Kaschube,38 G. Kaussen,38 H. Kirschenmann,38 R. Klanner,38 J. Lange,38 B. Mura,38 F. Nowak,38 T. Peiffer,38 N. Pietsch,38 D. Rathjens,38 C. Sander,38 H. Schettler,38 P. Schleper,38 E. Schlieckau,38 A. Schmidt,38 M. Schröder,38 T. Schum,38 M. Seidel,38 V. Sola,38 H. Stadie,38 G. Steinbrück,38 J. Thomsen,38 L. Vanelderen,38 C. Barth,39 J. Berger,39 C. Böser,39 T. Chwalek,39 W. De Boer,39 A. Descroix,39 A. Dierlamm,39 M. Feindt,39 M. Guthoff,39,e C. Hackstein,39 F. Hartmann,39 T. Hauth,39,e M. Heinrich,39 H. Held,39 K.H. Hoffmann,39 S. Honc,39 I. Katkov,39,p J. R. Komaragiri,39 P. Lobelle Pardo,39 D. Martschei,39 S. Mueller,39 Th. Müller,39 M. Niegel,39 A. Nürnberg,39 O. Oberst,39 A. Oehler,39 J. Ott,39 G. Quast,39 K. Rabbertz,39 F. Ratnikov,39 N. Ratnikova,39 S. Röcker,39 A. Scheurer,39 F.-P. Schilling,39 G. Schott,39 H. J. Simonis,39 F.M. Stober,39 D. Troendle,39 R. Ulrich,39 J. Wagner-Kuhr,39 S. Wayand,39 T. Weiler,39 M. Zeise,39 G. Daskalakis,40 T. Geralis,40 S. Kesisoglou,40 A. Kyriakis,40 D. Loukas,40 I. Manolakos,40 A. Markou,40 C. Markou,40 C. Mavrommatis,40 E. Ntomari,40 L. Gouskos,41 T. J. Mertzimekis,41 A. Panagiotou,41 N. Saoulidou,41 I. Evangelou,42 C. Foudas,42 P. Kokkas,42 S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-10 N. Manthos,42 I. Papadopoulos,42 V. Patras,42 G. Bencze,43 C. Hajdu,43 P. Hidas,43 D. Horvath,43,r F. Sikler,43 V. Veszpremi,43 G. Vesztergombi,43,s N. Beni,44 S. Czellar,44 J. Molnar,44 J. Palinkas,44 Z. Szillasi,44 J. Karancsi,45 P. Raics,45 Z. L. Trocsanyi,45 B. Ujvari,45 S. B. Beri,46 V. Bhatnagar,46 N. Dhingra,46 R. Gupta,46 M. Kaur,46 M. Z. Mehta,46 N. Nishu,46 L. K. Saini,46 A. Sharma,46 J. B. Singh,46 Ashok Kumar,47 Arun Kumar,47 S. Ahuja,47 A. Bhardwaj,47 B. C. Choudhary,47 S. Malhotra,47 M. Naimuddin,47 K. Ranjan,47 V. Sharma,47 R. K. Shivpuri,47 S. Banerjee,48 S. Bhattacharya,48 S. Dutta,48 B. Gomber,48 Sa. Jain,48 Sh. Jain,48 R. Khurana,48 S. Sarkar,48 M. Sharan,48 A. Abdulsalam,49 R. K. Choudhury,49 D. Dutta,49 S. Kailas,49 V. Kumar,49 P. Mehta,49 A.K. Mohanty,49,e L.M. Pant,49 P. Shukla,49 T. Aziz,50 S. Ganguly,50 M. Guchait,50,t M. Maity,50,u G. Majumder,50 K. Mazumdar,50 G. B. Mohanty,50 B. Parida,50 K. Sudhakar,50 N. Wickramage,50 S. Banerjee,51 S. Dugad,51 H. Arfaei,52 H. Bakhshiansohi,52,v S.M. Etesami,52,w A. Fahim,52,v M. Hashemi,52 H. Hesari,52 A. Jafari,52,v M. Khakzad,52 M. Mohammadi Najafabadi,52 S. Paktinat Mehdiabadi,52 B. Safarzadeh,52,x M. Zeinali,52,w M. Abbrescia,53a,53b L. Barbone,53a,53b C. Calabria,53a,53b,e S. S. Chhibra,53a,53b A. Colaleo,53a D. Creanza,53a,53c N. De Filippis,53a,53c,e M. De Palma,53a,53b L. Fiore,53a G. Iaselli,53a,53c L. Lusito,53a,53b G. Maggi,53a,53c M. Maggi,53a B. Marangelli,53a,53b S. My,53a,53c S. Nuzzo,53a,53b N. Pacifico,53a,53b A. Pompili,53a,53b G. Pugliese,53a,53c G. Selvaggi,53a,53b L. Silvestris,53a G. Singh,53a,53b R. Venditti,53a G. Zito,53a G. Abbiendi,54a A. C. Benvenuti,54a D. Bonacorsi,54a,54b S. Braibant-Giacomelli,54a,54b L. Brigliadori,54a,54b P. Capiluppi,54a,54b A. Castro,54a,54b F. R. Cavallo,54a M. Cuffiani,54a,54b G.M. Dallavalle,54a F. Fabbri,54a A. Fanfani,54a,54b D. Fasanella,54a,54b,e P. Giacomelli,54a C. Grandi,54a L. Guiducci,54a,54b S. Marcellini,54a G. Masetti,54a M. Meneghelli,54a,54b,e A. Montanari,54a F. L. Navarria,54a,54b F. Odorici,54a A. Perrotta,54a F. Primavera,54a,54b A.M. Rossi,54a,54b T. Rovelli,54a,54b G. P. Siroli,54a,54b R. Travaglini,54a,54b S. Albergo,55a,55b G. Cappello,55a,55b M. Chiorboli,55a,55b S. Costa,55a,55b R. Potenza,55a,55b A. Tricomi,55a,55b C. Tuve,55a,55b G. Barbagli,56a V. Ciulli,56a,56b C. Civinini,56a R. D’Alessandro,56a,56b E. Focardi,56a,56b S. Frosali,56a,56b E. Gallo,56a S. Gonzi,56a,56b M. Meschini,56a S. Paoletti,56a G. Sguazzoni,56a A. Tropiano,56a L. Benussi,57 S. Bianco,57 S. Colafranceschi,57,y F. Fabbri,57 D. Piccolo,57 P. Fabbricatore,58a R. Musenich,58a S. Tosi,58a,58b A. Benaglia,59a,59b,e F. De Guio,59a,59b L. Di Matteo,59a,59b,e S. Fiorendi,59a,59b S. Gennai,59a,e A. Ghezzi,59a,59b S. Malvezzi,59a R. A. Manzoni,59a,59b A. Martelli,59a,59b A. Massironi,59a,59b,e D. Menasce,59a L. Moroni,59a M. Paganoni,59a,59b D. Pedrini,59a S. Ragazzi,59a,59b N. Redaelli,59a S. Sala,59a T. Tabarelli de Fatis,59a,59b S. Buontempo,60a C. A. Carrillo Montoya,60a N. Cavallo,60a,60c A. De Cosa,60a,60b,e O. Dogangun,60a,60b F. Fabozzi,60a,60c A.O.M. Iorio,60a,60b L. Lista,60a S. Meola,60a,60d,z M. Merola,60a P. Paolucci,60a,e P. Azzi,61a N. Bacchetta,61a,e D. Bisello,61a,61b A. Branca,61a,61b,e R. Carlin,61a,61b P. Checchia,61a F. Gasparini,61a,61b U. Gasparini,61a,61b A. Gozzelino,61a K. Kanishchev,61a,61c S. Lacaprara,61a I. Lazzizzera,61a,61c M. Margoni,61a,61b A. T. Meneguzzo,61a,61b J. Pazzini,61a N. Pozzobon,61a,61b P. Ronchese,61a,61b F. Simonetto,61a,61b E. Torassa,61a M. Tosi,61a,61b,e A. Triossi,61a S. Vanini,61a,61b S. Ventura,61a P. Zotto,61a,61b M. Gabusi,62a,62b S. P. Ratti,62a,62b C. Riccardi,62a,62b P. Torre,62a,62b P. Vitulo,62a,62b M. Biasini,63a,63b G.M. Bilei,63a L. Fanò,63a,63b P. Lariccia,63a,63b A. Lucaroni,63a,63b,e G. Mantovani,63a,63b M. Menichelli,63a A. Nappi,63a,63b,a F. Romeo,63a,63b A. Saha,63a A. Santocchia,63a,63b A. Spiezia,63a,63b S. Taroni,63a,63b P. Azzurri,64a,64c G. Bagliesi,64a J. Bernardini,64a T. Boccali,64a G. Broccolo,64a,64c R. Castaldi,64a R. T. D’Agnolo,64a,64c R. Dell’Orso,64a F. Fiori,64a,64b,e L. Foà,64a,64c A. Giassi,64a A. Kraan,64a F. Ligabue,64a,64c T. Lomtadze,64a L. Martini,64a,aa A. Messineo,64a,64b F. Palla,64a A. Rizzi,64a,64b A. T. Serban,64a,bb P. Spagnolo,64a P. Squillacioti,64a,e R. Tenchini,64a G. Tonelli,64a,64b,e A. Venturi,64a P. G. Verdini,64a L. Barone,65a,65b F. Cavallari,65a D. Del Re,65a,65b M. Diemoz,65a C. Fanelli,65a,65b M. Grassi,65a,65b,e E. Longo,65a,65b P. Meridiani,65a,e F. Micheli,65a,65b S. Nourbakhsh,65a,65b G. Organtini,65a,65b R. Paramatti,65a S. Rahatlou,65a,65b M. Sigamani,65a L. Soffi,65a,65b N. Amapane,66a,66b R. Arcidiacono,66a,66c S. Argiro,66a,66b M. Arneodo,66a,66c C. Biino,66a N. Cartiglia,66a M. Costa,66a,66b N. Demaria,66a C. Mariotti,66a,e S. Maselli,66a E. Migliore,66a,66b V. Monaco,66a,66b M. Musich,66a,e M.M. Obertino,66a,66c N. Pastrone,66a M. Pelliccioni,66a A. Potenza,66a,66b A. Romero,66a,66b M. Ruspa,66a,66c R. Sacchi,66a,66b A. Solano,66a,66b A. Staiano,66a A. Vilela Pereira,66a S. Belforte,67a V. Candelise,67a,67b F. Cossutti,67a G. Della Ricca,67a,67b B. Gobbo,67a M. Marone,67a,67b,e D. Montanino,67a,67b,e A. Penzo,67a A. Schizzi,67a,67b S. G. Heo,68 T. Y. Kim,68 S. K. Nam,68 S. Chang,69 D.H. Kim,69 G.N. Kim,69 D. J. Kong,69 H. Park,69 S. R. Ro,69 D. C. Son,69 T. Son,69 J. Y. Kim,70 Zero J. Kim,70 S. Song,70 S. Choi,71 D. Gyun,71 B. Hong,71 M. Jo,71 H. Kim,71 T. J. Kim,71 K. S. Lee,71 D.H. Moon,71 S. K. Park,71 M. Choi,72 J. H. Kim,72 C. Park,72 I. C. Park,72 S. Park,72 G. Ryu,72 Y. Cho,73 Y. Choi,73 Y.K. Choi,73 J. Goh,73 M. S. Kim,73 E. Kwon,73 B. Lee,73 J. Lee,73 S. Lee,73 H. Seo,73 I. Yu,73 M. J. Bilinskas,74 I. Grigelionis,74 M. Janulis,74 A. Juodagalvis,74 SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-11 H. Castilla-Valdez,75 E. De La Cruz-Burelo,75 I. Heredia-de La Cruz,75 R. Lopez-Fernandez,75 R. Magaña Villalba,75 J. Martı́nez-Ortega,75 A. Sanchez-Hernandez,75 L.M. Villasenor-Cendejas,75 S. Carrillo Moreno,76 F. Vazquez Valencia,76 H. A. Salazar Ibarguen,77 E. Casimiro Linares,78 A. Morelos Pineda,78 M.A. Reyes-Santos,78 D. Krofcheck,79 A. J. Bell,80 P. H. Butler,80 R. Doesburg,80 S. Reucroft,80 H. Silverwood,80 M. Ahmad,81 M.H. Ansari,81 M. I. Asghar,81 H. R. Hoorani,81 S. Khalid,81 W.A. Khan,81 T. Khurshid,81 S. Qazi,81 M.A. Shah,81 M. Shoaib,81 H. Bialkowska,82 B. Boimska,82 T. Frueboes,82 R. Gokieli,82 M. Górski,82 M. Kazana,82 K. Nawrocki,82 K. Romanowska-Rybinska,82 M. Szleper,82 G. Wrochna,82 P. Zalewski,82 G. Brona,83 K. Bunkowski,83 M. Cwiok,83 W. Dominik,83 K. Doroba,83 A. Kalinowski,83 M. Konecki,83 J. Krolikowski,83 N. Almeida,84 P. Bargassa,84 A. David,84 P. Faccioli,84 P. G. Ferreira Parracho,84 M. Gallinaro,84 J. Seixas,84 J. Varela,84 P. Vischia,84 I. Belotelov,85 P. Bunin,85 I. Golutvin,85 I. Gorbunov,85 A. Kamenev,85 V. Karjavin,85 G. Kozlov,85 A. Lanev,85 A. Malakhov,85 P. Moisenz,85 V. Palichik,85 V. Perelygin,85 M. Savina,85 S. Shmatov,85 V. Smirnov,85 A. Volodko,85 A. Zarubin,85 S. Evstyukhin,86 V. Golovtsov,86 Y. Ivanov,86 V. Kim,86 P. Levchenko,86 V. Murzin,86 V. Oreshkin,86 I. Smirnov,86 V. Sulimov,86 L. Uvarov,86 S. Vavilov,86 A. Vorobyev,86 An. Vorobyev,86 Yu. Andreev,87 A. Dermenev,87 S. Gninenko,87 N. Golubev,87 M. Kirsanov,87 N. Krasnikov,87 V. Matveev,87 A. Pashenkov,87 D. Tlisov,87 A. Toropin,87 V. Epshteyn,88 M. Erofeeva,88 V. Gavrilov,88 M. Kossov,88 N. Lychkovskaya,88 V. Popov,88 G. Safronov,88 S. Semenov,88 V. Stolin,88 E. Vlasov,88 A. Zhokin,88 A. Belyaev,89 E. Boos,89 V. Bunichev,89 M. Dubinin,89,d L. Dudko,89 A. Ershov,89 A. Gribushin,89 V. Klyukhin,89 O. Kodolova,89 I. Lokhtin,89 A. Markina,89 S. Obraztsov,89 M. Perfilov,89 A. Popov,89 L. Sarycheva,89,a V. Savrin,89 A. Snigirev,89 V. Andreev,90 M. Azarkin,90 I. Dremin,90 M. Kirakosyan,90 A. Leonidov,90 G. Mesyats,90 S. V. Rusakov,90 A. Vinogradov,90 I. Azhgirey,91 I. Bayshev,91 S. Bitioukov,91 V. Grishin,91,e V. Kachanov,91 D. Konstantinov,91 A. Korablev,91 V. Krychkine,91 V. Petrov,91 R. Ryutin,91 A. Sobol,91 L. Tourtchanovitch,91 S. Troshin,91 N. Tyurin,91 A. Uzunian,91 A. Volkov,91 P. Adzic,92,cc M. Djordjevic,92 M. Ekmedzic,92 D. Krpic,92,cc J. Milosevic,92 M. Aguilar-Benitez,93 J. Alcaraz Maestre,93 P. Arce,93 C. Battilana,93 E. Calvo,93 M. Cerrada,93 M. Chamizo Llatas,93 N. Colino,93 B. De La Cruz,93 A. Delgado Peris,93 D. Domı́nguez Vázquez,93 C. Fernandez Bedoya,93 J. P. Fernández Ramos,93 A. Ferrando,93 J. Flix,93 M. C. Fouz,93 P. Garcia-Abia,93 O. Gonzalez Lopez,93 S. Goy Lopez,93 J.M. Hernandez,93 M. I. Josa,93 G. Merino,93 J. Puerta Pelayo,93 A. Quintario Olmeda,93 I. Redondo,93 L. Romero,93 J. Santaolalla,93 M. S. Soares,93 C. Willmott,93 C. Albajar,94 G. Codispoti,94 J. F. de Trocóniz,94 H. Brun,95 J. Cuevas,95 J. Fernandez Menendez,95 S. Folgueras,95 I. Gonzalez Caballero,95 L. Lloret Iglesias,95 J. Piedra Gomez,95 J. A. Brochero Cifuentes,96 I. J. Cabrillo,96 A. Calderon,96 S. H. Chuang,96 J. Duarte Campderros,96 M. Felcini,96,dd M. Fernandez,96 G. Gomez,96 J. Gonzalez Sanchez,96 A. Graziano,96 C. Jorda,96 A. Lopez Virto,96 J. Marco,96 R. Marco,96 C. Martinez Rivero,96 F. Matorras,96 F. J. Munoz Sanchez,96 T. Rodrigo,96 A. Y. Rodrı́guez-Marrero,96 A. Ruiz-Jimeno,96 L. Scodellaro,96 M. Sobron Sanudo,96 I. Vila,96 R. Vilar Cortabitarte,96 D. Abbaneo,97 E. Auffray,97 G. Auzinger,97 P. Baillon,97 A. H. Ball,97 D. Barney,97 J. F. Benitez,97 C. Bernet,97,f G. Bianchi,97 P. Bloch,97 A. Bocci,97 A. Bonato,97 C. Botta,97 H. Breuker,97 T. Camporesi,97 G. Cerminara,97 T. Christiansen,97 J. A. Coarasa Perez,97 D. D’Enterria,97 A. Dabrowski,97 A. De Roeck,97 S. Di Guida,97 M. Dobson,97 N. Dupont-Sagorin,97 A. Elliott-Peisert,97 B. Frisch,97 W. Funk,97 G. Georgiou,97 M. Giffels,97 D. Gigi,97 K. Gill,97 D. Giordano,97 M. Giunta,97 F. Glege,97 R. Gomez-Reino Garrido,97 P. Govoni,97 S. Gowdy,97 R. Guida,97 M. Hansen,97 P. Harris,97 C. Hartl,97 J. Harvey,97 B. Hegner,97 A. Hinzmann,97 V. Innocente,97 P. Janot,97 K. Kaadze,97 E. Karavakis,97 K. Kousouris,97 P. Lecoq,97 Y.-J. Lee,97 P. Lenzi,97 C. Lourenço,97 T. Mäki,97 M. Malberti,97 L. Malgeri,97 M. Mannelli,97 L. Masetti,97 F. Meijers,97 S. Mersi,97 E. Meschi,97 R. Moser,97 M.U. Mozer,97 M. Mulders,97 P. Musella,97 E. Nesvold,97 T. Orimoto,97 L. Orsini,97 E. Palencia Cortezon,97 E. Perez,97 L. Perrozzi,97 A. Petrilli,97 A. Pfeiffer,97 M. Pierini,97 M. Pimiä,97 D. Piparo,97 G. Polese,97 L. Quertenmont,97 A. Racz,97 W. Reece,97 J. Rodrigues Antunes,97 G. Rolandi,97,ee C. Rovelli,97,ff M. Rovere,97 H. Sakulin,97 F. Santanastasio,97 C. Schäfer,97 C. Schwick,97 I. Segoni,97 S. Sekmen,97 A. Sharma,97 P. Siegrist,97 P. Silva,97 M. Simon,97 P. Sphicas,97,gg D. Spiga,97 A. Tsirou,97 G. I. Veres,97,s J. R. Vlimant,97 H. K. Wöhri,97 S. D. Worm,97,hh W.D. Zeuner,97 W. Bertl,98 K. Deiters,98 W. Erdmann,98 K. Gabathuler,98 R. Horisberger,98 Q. Ingram,98 H. C. Kaestli,98 S. König,98 D. Kotlinski,98 U. Langenegger,98 F. Meier,98 D. Renker,98 T. Rohe,98 J. Sibille,98,ii L. Bäni,99 P. Bortignon,99 M.A. Buchmann,99 B. Casal,99 N. Chanon,99 A. Deisher,99 G. Dissertori,99 M. Dittmar,99 M. Donegà,99 M. Dünser,99 J. Eugster,99 K. Freudenreich,99 C. Grab,99 D. Hits,99 P. Lecomte,99 W. Lustermann,99 A. C. Marini,99 P. Martinez Ruiz del Arbol,99 N. Mohr,99 F. Moortgat,99 C. Nägeli,99,jj P. Nef,99 F. Nessi-Tedaldi,99 F. Pandolfi,99 L. Pape,99 F. Pauss,99 M. Peruzzi,99 F. J. Ronga,99 M. Rossini,99 L. Sala,99 S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-12 A.K. Sanchez,99 A. Starodumov,99,kk B. Stieger,99 M. Takahashi,99 L. Tauscher,99,a A. Thea,99 K. Theofilatos,99 D. Treille,99 C. Urscheler,99 R. Wallny,99 H. A. Weber,99 L. Wehrli,99 C. Amsler,100 V. Chiochia,100 S. De Visscher,100 C. Favaro,100 M. Ivova Rikova,100 B. Millan Mejias,100 P. Otiougova,100 P. Robmann,100 H. Snoek,100 S. Tupputi,100 M. Verzetti,100 Y. H. Chang,101 K.H. Chen,101 C.M. Kuo,101 S.W. Li,101 W. Lin,101 Z. K. Liu,101 Y. J. Lu,101 D. Mekterovic,101 A. P. Singh,101 R. Volpe,101 S. S. Yu,101 P. Bartalini,102 P. Chang,102 Y.H. Chang,102 Y.W. Chang,102 Y. Chao,102 K. F. Chen,102 C. Dietz,102 U. Grundler,102 W.-S. Hou,102 Y. Hsiung,102 K. Y. Kao,102 Y. J. Lei,102 R.-S. Lu,102 D. Majumder,102 E. Petrakou,102 X. Shi,102 J. G. Shiu,102 Y.M. Tzeng,102 X. Wan,102 M. Wang,102 A. Adiguzel,103 M.N. Bakirci,103,ll S. Cerci,103,mm C. Dozen,103 I. Dumanoglu,103 E. Eskut,103 S. Girgis,103 G. Gokbulut,103 E. Gurpinar,103 I. Hos,103 E. E. Kangal,103 T. Karaman,103 G. Karapinar,103,nn A. Kayis Topaksu,103 G. Onengut,103 K. Ozdemir,103 S. Ozturk,103,oo A. Polatoz,103 K. Sogut,103,pp D. Sunar Cerci,103,mm B. Tali,103,mm H. Topakli,103,ll L. N. Vergili,103 M. Vergili,103 I. V. Akin,104 T. Aliev,104 B. Bilin,104 S. Bilmis,104 M. Deniz,104 H. Gamsizkan,104 A.M. Guler,104 K. Ocalan,104 A. Ozpineci,104 M. Serin,104 R. Sever,104 U. E. Surat,104 M. Yalvac,104 E. Yildirim,104 M. Zeyrek,104 E. Gülmez,105 B. Isildak,105,qq M. Kaya,105,rr O. Kaya,105,rr S. Ozkorucuklu,105,ss N. Sonmez,105,tt K. Cankocak,106 L. Levchuk,107 F. Bostock,108 J. J. Brooke,108 E. Clement,108 D. Cussans,108 H. Flacher,108 R. Frazier,108 J. Goldstein,108 M. Grimes,108 G. P. Heath,108 H. F. Heath,108 L. Kreczko,108 S. Metson,108 D.M. Newbold,108,hh K. Nirunpong,108 A. Poll,108 S. Senkin,108 V. J. Smith,108 T. Williams,108 L. Basso,109,uu K.W. Bell,109 A. Belyaev,109,uu C. Brew,109 R.M. Brown,109 D. J. A. Cockerill,109 J. A. Coughlan,109 K. Harder,109 S. Harper,109 J. Jackson,109 B.W. Kennedy,109 E. Olaiya,109 D. Petyt,109 B. C. Radburn-Smith,109 C. H. Shepherd-Themistocleous,109 I. R. Tomalin,109 W. J. Womersley,109 R. Bainbridge,110 G. Ball,110 R. Beuselinck,110 O. Buchmuller,110 D. Colling,110 N. Cripps,110 M. Cutajar,110 P. Dauncey,110 G. Davies,110 M. Della Negra,110 W. Ferguson,110 J. Fulcher,110 D. Futyan,110 A. Gilbert,110 A. Guneratne Bryer,110 G. Hall,110 Z. Hatherell,110 J. Hays,110 G. Iles,110 M. Jarvis,110 G. Karapostoli,110 L. Lyons,110 A.-M. Magnan,110 J. Marrouche,110 B. Mathias,110 R. Nandi,110 J. Nash,110 A. Nikitenko,110,kk A. Papageorgiou,110 J. Pela,110,e M. Pesaresi,110 K. Petridis,110 M. Pioppi,110,vv D.M. Raymond,110 S. Rogerson,110 A. Rose,110 M. J. Ryan,110 C. Seez,110 P. Sharp,110,a A. Sparrow,110 M. Stoye,110 A. Tapper,110 M. Vazquez Acosta,110 T. Virdee,110 S. Wakefield,110 N. Wardle,110 T. Whyntie,110 M. Chadwick,111 J. E. Cole,111 P. R. Hobson,111 A. Khan,111 P. Kyberd,111 D. Leggat,111 D. Leslie,111 W. Martin,111 I. D. Reid,111 P. Symonds,111 L. Teodorescu,111 M. Turner,111 K. Hatakeyama,112 H. Liu,112 T. Scarborough,112 O. Charaf,113 C. Henderson,113 P. Rumerio,113 A. Avetisyan,114 T. Bose,114 C. Fantasia,114 A. Heister,114 J. St. John,114 P. Lawson,114 D. Lazic,114 J. Rohlf,114 D. Sperka,114 L. Sulak,114 J. Alimena,115 S. Bhattacharya,115 D. Cutts,115 A. Ferapontov,115 U. Heintz,115 S. Jabeen,115 G. Kukartsev,115 E. Laird,115 G. Landsberg,115 M. Luk,115 M. Narain,115 D. Nguyen,115 M. Segala,115 T. Sinthuprasith,115 T. Speer,115 K.V. Tsang,115 R. Breedon,116 G. Breto,116 M. Calderon De La Barca Sanchez,116 S. Chauhan,116 M. Chertok,116 J. Conway,116 R. Conway,116 P. T. Cox,116 J. Dolen,116 R. Erbacher,116 M. Gardner,116 R. Houtz,116 W. Ko,116 A. Kopecky,116 R. Lander,116 T. Miceli,116 D. Pellett,116 F. Ricci-Tam,116 B. Rutherford,116 M. Searle,116 J. Smith,116 M. Squires,116 M. Tripathi,116 R. Vasquez Sierra,116 V. Andreev,117 D. Cline,117 R. Cousins,117 J. Duris,117 S. Erhan,117 P. Everaerts,117 C. Farrell,117 J. Hauser,117 M. Ignatenko,117 C. Jarvis,117 C. Plager,117 G. Rakness,117 P. Schlein,117,a P. Traczyk,117 V. Valuev,117 M. Weber,117 J. Babb,118 R. Clare,118 M. E. Dinardo,118 J. Ellison,118 J.W. Gary,118 F. Giordano,118 G. Hanson,118 G.Y. Jeng,118,ww H. Liu,118 O. R. Long,118 A. Luthra,118 H. Nguyen,118 S. Paramesvaran,118 J. Sturdy,118 S. Sumowidagdo,118 R. Wilken,118 S. Wimpenny,118 W. Andrews,119 J. G. Branson,119 G. B. Cerati,119 S. Cittolin,119 D. Evans,119 F. Golf,119 A. Holzner,119 R. Kelley,119 M. Lebourgeois,119 J. Letts,119 I. Macneill,119 B. Mangano,119 S. Padhi,119 C. Palmer,119 G. Petrucciani,119 M. Pieri,119 M. Sani,119 V. Sharma,119 S. Simon,119 E. Sudano,119 M. Tadel,119 Y. Tu,119 A. Vartak,119 S. Wasserbaech,119,xx F. Würthwein,119 A. Yagil,119 J. Yoo,119 D. Barge,120 R. Bellan,120 C. Campagnari,120 M. D’Alfonso,120 T. Danielson,120 K. Flowers,120 P. Geffert,120 J. Incandela,120 C. Justus,120 P. Kalavase,120 S. A. Koay,120 D. Kovalskyi,120 V. Krutelyov,120 S. Lowette,120 N. Mccoll,120 V. Pavlunin,120 F. Rebassoo,120 J. Ribnik,120 J. Richman,120 R. Rossin,120 D. Stuart,120 W. To,120 C. West,120 A. Apresyan,121 A. Bornheim,121 Y. Chen,121 E. Di Marco,121 J. Duarte,121 M. Gataullin,121 Y. Ma,121 A. Mott,121 H. B. Newman,121 C. Rogan,121 M. Spiropulu,121 V. Timciuc,121 J. Veverka,121 R. Wilkinson,121 S. Xie,121 Y. Yang,121 R. Y. Zhu,121 B. Akgun,122 V. Azzolini,122 A. Calamba,122 R. Carroll,122 T. Ferguson,122 Y. Iiyama,122 D.W. Jang,122 Y. F. Liu,122 M. Paulini,122 H. Vogel,122 I. Vorobiev,122 J. P. Cumalat,123 B. R. Drell,123 C. J. Edelmaier,123 W. T. Ford,123 A. Gaz,123 B. Heyburn,123 E. Luiggi Lopez,123 J. G. Smith,123 K. Stenson,123 SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-13 K.A. Ulmer,123 S. R. Wagner,123 J. Alexander,124 A. Chatterjee,124 N. Eggert,124 L. K. Gibbons,124 B. Heltsley,124 A. Khukhunaishvili,124 B. Kreis,124 N. Mirman,124 G. Nicolas Kaufman,124 J. R. Patterson,124 A. Ryd,124 E. Salvati,124 W. Sun,124 W.D. Teo,124 J. Thom,124 J. Thompson,124 J. Tucker,124 J. Vaughan,124 Y. Weng,124 L. Winstrom,124 P. Wittich,124 D. Winn,125 S. Abdullin,126 M. Albrow,126 J. Anderson,126 L. A. T. Bauerdick,126 A. Beretvas,126 J. Berryhill,126 P. C. Bhat,126 I. Bloch,126 K. Burkett,126 J. N. Butler,126 V. Chetluru,126 H.W.K. Cheung,126 F. Chlebana,126 V.D. Elvira,126 I. Fisk,126 J. Freeman,126 Y. Gao,126 D. Green,126 O. Gutsche,126 J. Hanlon,126 R.M. Harris,126 J. Hirschauer,126 B. Hooberman,126 S. Jindariani,126 M. Johnson,126 U. Joshi,126 B. Kilminster,126 B. Klima,126 S. Kunori,126 S. Kwan,126 C. Leonidopoulos,126 J. Linacre,126 D. Lincoln,126 R. Lipton,126 J. Lykken,126 K. Maeshima,126 J.M. Marraffino,126 S. Maruyama,126 D. Mason,126 P. McBride,126 K. Mishra,126 S. Mrenna,126 Y. Musienko,126,yy C. Newman-Holmes,126 V. O’Dell,126 O. Prokofyev,126 E. Sexton-Kennedy,126 S. Sharma,126 W. J. Spalding,126 L. Spiegel,126 P. Tan,126 L. Taylor,126 S. Tkaczyk,126 N. V. Tran,126 L. Uplegger,126 E.W. Vaandering,126 R. Vidal,126 J. Whitmore,126 W. Wu,126 F. Yang,126 F. Yumiceva,126 J. C. Yun,126 D. Acosta,127 P. Avery,127 D. Bourilkov,127 M. Chen,127 T. Cheng,127 S. Das,127 M. De Gruttola,127 G. P. Di Giovanni,127 D. Dobur,127 A. Drozdetskiy,127 R.D. Field,127 M. Fisher,127 Y. Fu,127 I. K. Furic,127 J. Gartner,127 J. Hugon,127 B. Kim,127 J. Konigsberg,127 A. Korytov,127 A. Kropivnitskaya,127 T. Kypreos,127 J. F. Low,127 K. Matchev,127 P. Milenovic,127,zz G. Mitselmakher,127 L. Muniz,127 R. Remington,127 A. Rinkevicius,127 P. Sellers,127 N. Skhirtladze,127 M. Snowball,127 J. Yelton,127 M. Zakaria,127 V. Gaultney,128 S. Hewamanage,128 L.M. Lebolo,128 S. Linn,128 P. Markowitz,128 G. Martinez,128 J. L. Rodriguez,128 T. Adams,129 A. Askew,129 J. Bochenek,129 J. Chen,129 B. Diamond,129 S. V. Gleyzer,129 J. Haas,129 S. Hagopian,129 V. Hagopian,129 M. Jenkins,129 K. F. Johnson,129 H. Prosper,129 V. Veeraraghavan,129 M. Weinberg,129 M.M. Baarmand,130 B. Dorney,130 M. Hohlmann,130 H. Kalakhety,130 I. Vodopiyanov,130 M.R. Adams,131 I.M. Anghel,131 L. Apanasevich,131 Y. Bai,131 V. E. Bazterra,131 R. R. Betts,131 I. Bucinskaite,131 J. Callner,131 R. Cavanaugh,131 C. Dragoiu,131 O. Evdokimov,131 L. Gauthier,131 C. E. Gerber,131 D. J. Hofman,131 S. Khalatyan,131 F. Lacroix,131 M. Malek,131 C. O’Brien,131 C. Silkworth,131 D. Strom,131 N. Varelas,131 U. Akgun,132 E. A. Albayrak,132 B. Bilki,132,aaa W. Clarida,132 F. Duru,132 S. Griffiths,132 J.-P. Merlo,132 H. Mermerkaya,132,bbb A. Mestvirishvili,132 A. Moeller,132 J. Nachtman,132 C. R. Newsom,132 E. Norbeck,132 Y. Onel,132 F. Ozok,132 S. Sen,132 E. Tiras,132 J. Wetzel,132 T. Yetkin,132 K. Yi,132 B. A. Barnett,133 B. Blumenfeld,133 S. Bolognesi,133 D. Fehling,133 G. Giurgiu,133 A. V. Gritsan,133 Z. J. Guo,133 G. Hu,133 P. Maksimovic,133 S. Rappoccio,133 M. Swartz,133 A. Whitbeck,133 P. Baringer,134 A. Bean,134 G. Benelli,134 O. Grachov,134 R. P. Kenny Iii,134 M. Murray,134 D. Noonan,134 S. Sanders,134 R. Stringer,134 G. Tinti,134 J. S. Wood,134 V. Zhukova,134 A. F. Barfuss,135 T. Bolton,135 I. Chakaberia,135 A. Ivanov,135 S. Khalil,135 M. Makouski,135 Y. Maravin,135 S. Shrestha,135 I. Svintradze,135 J. Gronberg,136 D. Lange,136 D. Wright,136 A. Baden,137 M. Boutemeur,137 B. Calvert,137 S. C. Eno,137 J. A. Gomez,137 N. J. Hadley,137 R.G. Kellogg,137 M. Kirn,137 T. Kolberg,137 Y. Lu,137 M. Marionneau,137 A. C. Mignerey,137 K. Pedro,137 A. Peterman,137 A. Skuja,137 J. Temple,137 M.B. Tonjes,137 S. C. Tonwar,137 E. Twedt,137 A. Apyan,138 G. Bauer,138 J. Bendavid,138 W. Busza,138 E. Butz,138 I. A. Cali,138 M. Chan,138 V. Dutta,138 G. Gomez Ceballos,138 M. Goncharov,138 K.A. Hahn,138 Y. Kim,138 M. Klute,138 K. Krajczar,138,ccc W. Li,138 P. D. Luckey,138 T. Ma,138 S. Nahn,138 C. Paus,138 D. Ralph,138 C. Roland,138 G. Roland,138 M. Rudolph,138 G. S. F. Stephans,138 F. Stöckli,138 K. Sumorok,138 K. Sung,138 D. Velicanu,138 E. A.Wenger,138 R.Wolf,138 B.Wyslouch,138 M. Yang,138 Y. Yilmaz,138 A. S. Yoon,138 M. Zanetti,138 S. I. Cooper,139 B. Dahmes,139 A. De Benedetti,139 G. Franzoni,139 A. Gude,139 S. C. Kao,139 K. Klapoetke,139 Y. Kubota,139 J. Mans,139 N. Pastika,139 R. Rusack,139 M. Sasseville,139 A. Singovsky,139 N. Tambe,139 J. Turkewitz,139 L.M. Cremaldi,140 R. Kroeger,140 L. Perera,140 R. Rahmat,140 D.A. Sanders,140 E. Avdeeva,141 K. Bloom,141 S. Bose,141 J. Butt,141 D. R. Claes,141 A. Dominguez,141 M. Eads,141 J. Keller,141 I. Kravchenko,141 J. Lazo-Flores,141 H. Malbouisson,141 S. Malik,141 G. R. Snow,141 U. Baur,142 A. Godshalk,142 I. Iashvili,142 S. Jain,142 A. Kharchilava,142 A. Kumar,142 S. P. Shipkowski,142 K. Smith,142 G. Alverson,143 E. Barberis,143 D. Baumgartel,143 M. Chasco,143 J. Haley,143 D. Nash,143 D. Trocino,143 D. Wood,143 J. Zhang,143 A. Anastassov,144 A. Kubik,144 N. Mucia,144 N. Odell,144 R. A. Ofierzynski,144 B. Pollack,144 A. Pozdnyakov,144 M. Schmitt,144 S. Stoynev,144 M. Velasco,144 S. Won,144 L. Antonelli,145 D. Berry,145 A. Brinkerhoff,145 M. Hildreth,145 C. Jessop,145 D. J. Karmgard,145 J. Kolb,145 K. Lannon,145 W. Luo,145 S. Lynch,145 N. Marinelli,145 D.M. Morse,145 T. Pearson,145 M. Planer,145 R. Ruchti,145 J. Slaunwhite,145 N. Valls,145 M. Wayne,145 M. Wolf,145 B. Bylsma,146 L. S. Durkin,146 C. Hill,146 R. Hughes,146 R. Hughes,146 K. Kotov,146 T. Y. Ling,146 D. Puigh,146 M. Rodenburg,146 S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-14 C. Vuosalo,146 G. Williams,146 B. L. Winer,146 N. Adam,147 E. Berry,147 P. Elmer,147 D. Gerbaudo,147 V. Halyo,147 P. Hebda,147 J. Hegeman,147 A. Hunt,147 P. Jindal,147 D. Lopes Pegna,147 P. Lujan,147 D. Marlow,147 T. Medvedeva,147 M. Mooney,147 J. Olsen,147 P. Piroué,147 X. Quan,147 A. Raval,147 B. Safdi,147 H. Saka,147 D. Stickland,147 C. Tully,147 J. S. Werner,147 A. Zuranski,147 J. G. Acosta,148 E. Brownson,148 X. T. Huang,148 A. Lopez,148 H. Mendez,148 S. Oliveros,148 J. E. Ramirez Vargas,148 A. Zatserklyaniy,148 E. Alagoz,149 V. E. Barnes,149 D. Benedetti,149 G. Bolla,149 D. Bortoletto,149 M. De Mattia,149 A. Everett,149 Z. Hu,149 M. Jones,149 O. Koybasi,149 M. Kress,149 A. T. Laasanen,149 N. Leonardo,149 V. Maroussov,149 P. Merkel,149 D.H. Miller,149 N. Neumeister,149 I. Shipsey,149 D. Silvers,149 A. Svyatkovskiy,149 M. Vidal Marono,149 H.D. Yoo,149 J. Zablocki,149 Y. Zheng,149 S. Guragain,150 N. Parashar,150 A. Adair,151 C. Boulahouache,151 K.M. Ecklund,151 F. J.M. Geurts,151 B. P. Padley,151 R. Redjimi,151 J. Roberts,151 J. Zabel,151 B. Betchart,152 A. Bodek,152 Y. S. Chung,152 R. Covarelli,152 P. de Barbaro,152 R. Demina,152 Y. Eshaq,152 A. Garcia-Bellido,152 P. Goldenzweig,152 J. Han,152 A. Harel,152 D. C. Miner,152 D. Vishnevskiy,152 M. Zielinski,152 A. Bhatti,153 R. Ciesielski,153 L. Demortier,153 K. Goulianos,153 G. Lungu,153 S. Malik,153 C. Mesropian,153 S. Arora,154 A. Barker,154 J. P. Chou,154 C. Contreras-Campana,154 E. Contreras-Campana,154 D. Duggan,154 D. Ferencek,154 Y. Gershtein,154 R. Gray,154 E. Halkiadakis,154 D. Hidas,154 A. Lath,154 S. Panwalkar,154 M. Park,154 R. Patel,154 V. Rekovic,154 J. Robles,154 K. Rose,154 S. Salur,154 S. Schnetzer,154 C. Seitz,154 S. Somalwar,154 R. Stone,154 S. Thomas,154 G. Cerizza,155 M. Hollingsworth,155 S. Spanier,155 Z. C. Yang,155 A. York,155 R. Eusebi,156 W. Flanagan,156 J. Gilmore,156 T. Kamon,156,ddd V. Khotilovich,156 R. Montalvo,156 I. Osipenkov,156 Y. Pakhotin,156 A. Perloff,156 J. Roe,156 A. Safonov,156 T. Sakuma,156 S. Sengupta,156 I. Suarez,156 A. Tatarinov,156 D. Toback,156 N. Akchurin,157 J. Damgov,157 P. R. Dudero,157 C. Jeong,157 K. Kovitanggoon,157 S.W. Lee,157 T. Libeiro,157 Y. Roh,157 I. Volobouev,157 E. Appelt,158 A. G. Delannoy,158 C. Florez,158 S. Greene,158 A. Gurrola,158 W. Johns,158 C. Johnston,158 P. Kurt,158 C. Maguire,158 A. Melo,158 M. Sharma,158 P. Sheldon,158 B. Snook,158 S. Tuo,158 J. Velkovska,158 M.W. Arenton,159 M. Balazs,159 S. Boutle,159 B. Cox,159 B. Francis,159 J. Goodell,159 R. Hirosky,159 A. Ledovskoy,159 C. Lin,159 C. Neu,159 J. Wood,159 R. Yohay,159 S. Gollapinni,160 R. Harr,160 P. E. Karchin,160 C. Kottachchi Kankanamge Don,160 P. Lamichhane,160 C. Milstène,160 A. Sakharov,160 M. Anderson,161 M. Bachtis,161 D.A. Belknap,161 L. Borrello,161 D. Carlsmith,161 M. Cepeda,161 S. Dasu,161 E. Friis,161 L. Gray,161 K. S. Grogg,161 M. Grothe,161 R. Hall-Wilton,161 M. Herndon,161 A. Hervé,161 P. Klabbers,161 J. Klukas,161 A. Lanaro,161 C. Lazaridis,161 J. Leonard,161 R. Loveless,161 A. Mohapatra,161 I. Ojalvo,161 F. Palmonari,161 G.A. Pierro,161 I. Ross,161 A. Savin,161 W.H. Smith,161 and J. Swanson161 (CMS Collaboration) 1Yerevan Physics Institute, Yerevan, Armenia 2Institut für Hochenergiephysik der OeAW, Wien, Austria 3National Centre for Particle and High Energy Physics, Minsk, Belarus 4Universiteit Antwerpen, Antwerpen, Belgium 5Vrije Universiteit Brussel, Brussel, Belgium 6Université Libre de Bruxelles, Bruxelles, Belgium 7Ghent University, Ghent, Belgium 8Université Catholique de Louvain, Louvain-la-Neuve, Belgium 9Université de Mons, Mons, Belgium 10Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil 11Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil 12aUniversidade Estadual Paulista, São Paulo, Brazil 12bUniversidade Federal do ABC, São Paulo, Brazil 13Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria 14University of Sofia, Sofia, Bulgaria 15Institute of High Energy Physics, Beijing, China 16State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China 17Universidad de Los Andes, Bogota, Colombia 18Technical University of Split, Split, Croatia 19University of Split, Split, Croatia 20Institute Rudjer Boskovic, Zagreb, Croatia 21University of Cyprus, Nicosia, Cyprus 22Charles University, Prague, Czech Republic SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-15 23Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt 24National Institute of Chemical Physics and Biophysics, Tallinn, Estonia 25Department of Physics, University of Helsinki, Helsinki, Finland 26Helsinki Institute of Physics, Helsinki, Finland 27Lappeenranta University of Technology, Lappeenranta, Finland 28DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France 29Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France 30Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute-Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France 31Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France 32Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucléaire de Lyon, Villeurbanne, France 33Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia 34RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany 35RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany 36RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany 37Deutsches Elektronen-Synchrotron, Hamburg, Germany 38University of Hamburg, Hamburg, Germany 39Institut für Experimentelle Kernphysik, Karlsruhe, Germany 40Institute of Nuclear Physics ‘‘Demokritos,’’ Aghia Paraskevi, Greece 41University of Athens, Athens, Greece 42University of Ioánnina, Ioánnina, Greece 43KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary 44Institute of Nuclear Research ATOMKI, Debrecen, Hungary 45University of Debrecen, Debrecen, Hungary 46Panjab University, Chandigarh, India 47University of Delhi, Delhi, India 48Saha Institute of Nuclear Physics, Kolkata, India 49Bhabha Atomic Research Centre, Mumbai, India 50Tata Institute of Fundamental Research-EHEP, Mumbai, India 51Tata Institute of Fundamental Research-HECR, Mumbai, India 52Institute for Research in Fundamental Sciences (IPM), Tehran, Iran 53aINFN Sezione di Bari, Bari, Italy 53bUniversità di Bari, Bari, Italy 53cPolitecnico di Bari, Bari, Italy 54aINFN Sezione di Bologna, Bologna, Italy 54bUniversità di Bologna, Bologna, Italy 55aINFN Sezione di Catania, Catania, Italy 55bUniversità di Catania, Catania, Italy 56aINFN Sezione di Firenze, Firenze, Italy 56bUniversità di Firenze, Firenze, Italy 57INFN Laboratori Nazionali di Frascati, Frascati, Italy 58aINFN Sezione di Genova, Genova, Italy 58bUniversità di Genova, Genova, Italy 59aINFN Sezione di Milano-Bicocca, Milano, Italy 59bUniversità di Milano-Bicocca, Milano, Italy 60aINFN Sezione di Napoli, Napoli, Italy 60bUniversità di Napoli ’Federico II’, Napoli, Italy 60cUniversità della Basilicata (Potenza), Napoli, Italy 60dUniversità G. Marconi (Roma), Napoli, Italy 61aINFN Sezione di Padova, Padova, Italy 61bUniversità di Padova, Padova, Italy 61cUniversità di Trento, Trento, Italy 62aINFN Sezione di Pavia, Pavia, Italy 62bUniversità di Pavia, Pavia, Italy 63aINFN Sezione di Perugia, Perugia, Italy 63bUniversità di Perugia, Perugia, Italy 64aINFN Sezione di Pisa, Pisa, Italy 64bUniversità di Pisa, Pisa, Italy 64cScuola Normale Superiore di Pisa, Pisa, Italy 65aINFN Sezione di Roma, Roma, Italy S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-16 65bUniversità di Roma, Roma, Italy 66aINFN Sezione di Torino, Torino, Italy 66bUniversità di Torino, Torino, Italy 66cUniversità del Piemonte Orientale (Novara), Torino, Italy 67aINFN Sezione di Trieste, Trieste, Italy 67bUniversità di Trieste, Trieste, Italy 68Kangwon National University, Chunchon, Korea 69Kyungpook National University, Daegu, Korea 70Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea 71Korea University, Seoul, Korea 72University of Seoul, Seoul, Korea 73Sungkyunkwan University, Suwon, Korea 74Vilnius University, Vilnius, Lithuania 75Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico 76Universidad Iberoamericana, Mexico City, Mexico 77Benemerita Universidad Autonoma de Puebla, Puebla, Mexico 78Universidad Autónoma de San Luis Potosı́, San Luis Potosı́, Mexico 79University of Auckland, Auckland, New Zealand 80University of Canterbury, Christchurch, New Zealand 81National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan 82National Centre for Nuclear Research, Swierk, Poland 83Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland 84Laboratório de Instrumentação e Fı́sica Experimental de Partı́culas, Lisboa, Portugal 85Joint Institute for Nuclear Research, Dubna, Russia 86Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia 87Institute for Nuclear Research, Moscow, Russia 88Institute for Theoretical and Experimental Physics, Moscow, Russia 89Moscow State University, Moscow, Russia 90P. N. Lebedev Physical Institute, Moscow, Russia 91State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia 92University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia 93Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain 94Universidad Autónoma de Madrid, Madrid, Spain 95Universidad de Oviedo, Oviedo, Spain 96Instituto de Fı́sica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain 97CERN, European Organization for Nuclear Research, Geneva, Switzerland 98Paul Scherrer Institut, Villigen, Switzerland 99Institute for Particle Physics, ETH Zurich, Zurich, Switzerland 100Universität Zürich, Zurich, Switzerland 101National Central University, Chung-Li, Taiwan 102National Taiwan University (NTU), Taipei, Taiwan 103Cukurova University, Adana, Turkey 104Middle East Technical University, Physics Department, Ankara, Turkey 105Bogazici University, Istanbul, Turkey 106Istanbul Technical University, Istanbul, Turkey 107National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine 108University of Bristol, Bristol, United Kingdom 109Rutherford Appleton Laboratory, Didcot, United Kingdom 110Imperial College, London, United Kingdom 111Brunel University, Uxbridge, United Kingdom 112Baylor University, Waco, Texas, USA 113The University of Alabama, Tuscaloosa, Alabama, USA 114Boston University, Boston, Massachusetts, USA 115Brown University, Providence, Rhode Island, USA 116University of California, Davis, Davis, California, USA 117University of California, Los Angeles, California, USA 118University of California, Riverside, Riverside, California, USA 119University of California, San Diego, La Jolla, California, USA 120University of California, Santa Barbara, Santa Barbara, California, USA 121California Institute of Technology, Pasadena, California, USA 122Carnegie Mellon University, Pittsburgh, Pennsylvania, USA SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-17 123University of Colorado at Boulder, Boulder, Colorado, USA 124Cornell University, Ithaca, New York, USA 125Fairfield University, Fairfield, Connecticut, USA 126Fermi National Accelerator Laboratory, Batavia, Illinois, USA 127University of Florida, Gainesville, Florida, USA 128Florida International University, Miami, Florida, USA 129Florida State University, Tallahassee, Florida, USA 130Florida Institute of Technology, Melbourne, Florida, USA 131University of Illinois at Chicago (UIC), Chicago, Illinois, USA 132The University of Iowa, Iowa City, Iowa, USA 133Johns Hopkins University, Baltimore, Maryland, USA 134The University of Kansas, Lawrence, Kansas, USA 135Kansas State University, Manhattan, Kansas, USA 136Lawrence Livermore National Laboratory, Livermore, California, USA 137University of Maryland, College Park, Maryland, USA 138Massachusetts Institute of Technology, Cambridge, Massachusetts, USA 139University of Minnesota, Minneapolis, Minnesota, USA 140University of Mississippi, Oxford, Mississippi, USA 141University of Nebraska-Lincoln, Lincoln, Nebraska, USA 142State University of New York at Buffalo, Buffalo, New York, USA 143Northeastern University, Boston, Massachusetts, USA 144Northwestern University, Evanston, Illinois, USA 145University of Notre Dame, Notre Dame, Indiana, USA 146The Ohio State University, Columbus, Ohio, USA 147Princeton University, Princeton, New Jersey, USA 148University of Puerto Rico, Mayaguez, Puerto Rico 149Purdue University, West Lafayette, Indiana, USA 150Purdue University Calumet, Hammond, Indiana, USA 151Rice University, Houston, Texas, USA 152University of Rochester, Rochester, New York, USA 153The Rockefeller University, New York, New York, USA 154Rutgers, The State University of New Jersey, Piscataway, New Jersey, USA 155University of Tennessee, Knoxville, Tennessee, USA 156Texas A&M University, College Station, Texas, USA 157Texas Tech University, Lubbock, Texas, USA 158Vanderbilt University, Nashville, Tennessee, USA 159University of Virginia, Charlottesville, Virginia, USA 160Wayne State University, Detroit, Michigan, USA 161University of Wisconsin, Madison, Wisconsin, USA aDeceased. bAlso at Vienna University of Technology, Vienna, Austria. cAlso at National Institute of Chemical Physics and Biophysics, Tallinn, Estonia. dAlso at California Institute of Technology, Pasadena, California, USA. eAlso at CERN, European Organization for Nuclear Research, Geneva, Switzerland. fAlso at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France. gAlso at Suez Canal University, Suez, Egypt. hAlso at Zewail City of Science and Technology, Zewail, Egypt. iAlso at Cairo University, Cairo, Egypt. jAlso at Fayoum University, El-Fayoum, Egypt. kAlso at British University in Egypt, Cairo, Egypt. lAlso at Ain Shams University, Cairo, Egypt. mAlso at National Centre for Nuclear Research, Swierk, Poland. nAlso at Université de Haute-Alsace, Mulhouse, France. oAlso at Joint Institute for Nuclear Research, Dubna, Russia. pAlso at Moscow State University, Moscow, Russia. qAlso at Brandenburg University of Technology, Cottbus, Germany. rAlso at Institute of Nuclear Research ATOMKI, Debrecen, Hungary. sAlso at Eötvös Loránd University, Budapest, Hungary. S. CHATRCHYAN et al. PHYSICAL REVIEW D 87, 032001 (2013) 032001-18 tAlso at Tata Institute of Fundamental Research—HECR, Mumbai, India. uAlso at University of Visva-Bharati, Santiniketan, India. vAlso at Sharif University of Technology, Tehran, Iran. wAlso at Isfahan University of Technology, Isfahan, Iran. xAlso at Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran. yAlso at Facoltà Ingegneria, Università di Roma, Roma, Italy. zAlso at Università degli Studi Guglielmo Marconi, Roma, Italy. aaAlso at Università degli Studi di Siena, Siena, Italy. bbAlso at University of Bucharest, Faculty of Physics, Bucuresti-Magurele, Romania. ccAlso at Faculty of Physics, University of Belgrade, Belgrade, Serbia. ddAlso at University of California, Los Angeles, CA, USA. eeAlso at Scuola Normale e Sezione dell’INFN, Pisa, Italy. ffAlso at INFN Sezione di Roma, Università di Roma, Roma, Italy. ggAlso at University of Athens, Athens, Greece. hhAlso at Rutherford Appleton Laboratory, Didcot, United Kingdom. iiAlso at The University of Kansas, Lawrence, KS, USA. jjAlso at Paul Scherrer Institut, Villigen, Switzerland. kkAlso at Institute for Theoretical and Experimental Physics, Moscow, Russia. llAlso at Gaziosmanpasa University, Tokat, Turkey. mmAlso at Adiyaman University, Adiyaman, Turkey. nnAlso at Izmir Institute of Technology, Izmir, Turkey. ooAlso at The University of Iowa, Iowa City, USA. ppAlso at Mersin University, Mersin, Turkey. qqAlso at Ozyegin University, Istanbul, Turkey. rrAlso at Kafkas University, Kars, Turkey. ssAlso at Suleyman Demirel University, Isparta, Turkey. ttAlso at Ege University, Izmir, Turkey. uuAlso at School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom. vvAlso at INFN Sezione di Perugia, Università di Perugia, Perugia, Italy. wwAlso at University of Sydney, Sydney, Australia. xxAlso at Utah Valley University, Orem, UT, USA. yyAlso at Institute for Nuclear Research, Moscow, Russia. zzAlso at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia. aaaAlso at Argonne National Laboratory, Argonne, Illinois, USA. bbbAlso at Erzincan University, Erzincan, Turkey. cccAlso at KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary. dddAlso at Kyungpook National University, Daegu, Korea. SEARCH FOR CONTACT INTERACTIONS IN �þ�� . . . PHYSICAL REVIEW D 87, 032001 (2013) 032001-19