Evidence for Collective Multiparticle Correlations in p-Pb Collisions V. Khachatryan et al. * (CMS Collaboration) (Received 18 February 2015; revised manuscript received 19 April 2015; published 29 June 2015) The second-order azimuthal anisotropy Fourier harmonics, v2, are obtained in p-Pb and PbPb collisions over a wide pseudorapidity (η) range based on correlations among six or more charged particles. The p-Pb data, corresponding to an integrated luminosity of 35 nb−1, were collected during the 2013 LHC p-Pb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. A sample of semiperipheral PbPb collision data at ffiffiffiffiffiffiffiffi sNN p ¼ 2.76 TeV, corresponding to an integrated luminosity of 2.5 μb−1 and covering a similar range of particle multiplicities as the p-Pb data, is also analyzed for comparison. The six- and eight-particle cumulant and the Lee-Yang zeros methods are used to extract the v2 coefficients, extending previous studies of two- and four-particle correlations. For both the p-Pb and PbPb systems, the v2 values obtained with correlations among more than four particles are consistent with previously published four-particle results. These data support the interpretation of a collective origin for the previously observed long-range (large Δη) correlations in both systems. The ratios of v2 values corresponding to correlations including different numbers of particles are compared to theoretical predictions that assume a hydrodynamic behavior of a p-Pb system dominated by fluctuations in the positions of participant nucleons. These results provide new insights into the multiparticle dynamics of collision systems with a very small overlapping region. DOI: 10.1103/PhysRevLett.115.012301 PACS numbers: 25.75.Gz Measurements at the CERN LHC have led to the discovery of two-particle azimuthal correlation structures at large relative pseudorapidity (long range) in proton- proton (pp) [1] and proton-lead (p-Pb) [2–5] collisions. Similar long-range structure has also been observed forffiffiffiffiffiffiffiffi sNN p ¼ 200 GeV deuteron-gold (dþ Au) collisions at RHIC [6,7]. The results extend previous studies of rela- tivistic heavy-ion collisions, such as for the copper-copper [8], gold-gold [8–12], and lead-lead (PbPb) [13–18] sys- tems, where similar long-range, two-particle correlations at small relative azimuthal angle jΔϕj ≈ 0were first observed. A fundamental question is whether the observed behavior results from correlations exclusively between particle pairs, or if it is a multiparticle, collective effect. It has been suggested that the hydrodynamic collective flow of a strongly interacting and expanding medium [19–21] is responsible for these long-range correlations in central and midcentral heavy-ion collisions. The origin of the observed long-range correlations in collision systems with a small overlapping region, such as for pp and p-Pb collisions, is not clear since for these systems the formation of an extended hot medium is not necessarily expected. Various theoretical models have been proposed to interpret the pp [22,23] and p-Pb results, including initial-state gluon saturation without any final state interactions [24,25] and, similar to what is thought to occur in heavier systems, hydrodynamic behavior that develops in a conjectured high-density medium [26–28]. These models have been successful in describing different aspects of the previous experimental results. To further investigate the multiparticle nature of the observed long-range correlation phenomena, in this Letter we present measurements of correlations among six or more charged particles for p-Pb collisions at a center-of- mass energy per nucleon pair of ffiffiffiffiffiffiffiffi sNN p ¼ 5.02 TeV. The azimuthal dependence of particle production is typically characterized by an expansion in Fourier harmonics (vn) [29]. In hydrodynamic models, the second (v2) and third (v3) harmonics, called “elliptic” and “triangular” flow [30], respectively, directly reflect the response to the initial collision geometry and fluctuations [31–33], providing insight into the fundamental transport properties of the medium. First attempts to establish the multiparticle nature of the correlations observed in p-Pb collisions were presented in Refs. [34,35] by directly measuring four- particle azimuthal correlations, where the elliptic flow signal was obtained using the four-particle cumulant method [36]. However, four-particle correlations can still be affected by contributions from noncollective effects such as fragmentation of back-to-back jets. By extending the studies to six- and eight-particle cumulants [36] and by also obtaining results using the Lee-Yang zeros (LYZ) method, which involves correlations among all detected particles *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. PRL 115, 012301 (2015) Selected for a Viewpoint in Physics PHY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 0031-9007=15=115(1)=012301(17) 012301-1 © 2015 CERN, for the CMS Collaboration http://dx.doi.org/10.1103/PhysRevLett.115.012301 http://dx.doi.org/10.1103/PhysRevLett.115.012301 http://dx.doi.org/10.1103/PhysRevLett.115.012301 http://dx.doi.org/10.1103/PhysRevLett.115.012301 http://creativecommons.org/licenses/by/3.0/ http://creativecommons.org/licenses/by/3.0/ [37,38], it is possible to further explore the collective nature of the correlations. High-statistics data obtained by the CMS experiment during the 2013 p-Pb run at the LHC are used. With a sample of very high final state multiplicity p-Pb collisions, the correlation data have been studied in a regime that is comparable to the charged particle multi- plicity of the 50% most peripheral (semiperipheral) PbPb collisions at ffiffiffiffiffiffiffiffi sNN p ¼ 2.76 TeV. The CMS detector comprises a number of subsystems [39]. The results in this Letter are mainly based on the silicon tracker information. The silicon tracker, located in the 3.8 T field of a superconducting solenoid, consists of 1440 silicon pixel and 15148 silicon strip detector modules. The silicon tracker measures charged particles within the pseudorapidity range jηj < 2.5, and it provides an impact parameter resolution of ≈15 μm and a transverse momen- tum (pT) resolution better than 1.5% at pT ≈ 100 GeV=c. The electromagnetic (ECAL) and hadron (HCAL) calo- rimeters are also located inside the solenoid and cover the pseudorapidity range jηj < 3.0. The HCAL barrel and end caps are sampling calorimeters composed of brass and scintillator plates. The ECAL consists of lead tungstate crystals arranged in a quasiprojective geometry. Iron and quartz-fiber Čerenkov hadron forward (HF) calorimeters cover the range 2.9 < jηj < 5.2 on either side of the interaction region. These HF calorimeters are azimuthally subdivided into 20° modular wedges and further segmented to form 0.175 × 0.175 rad ðΔη × ΔϕÞ “towers.” The detailed Monte Carlo (MC) simulation of the CMS detector response is based on GEANT4 [40]. The analysis is performed using data recorded by CMS during the LHC p-Pb run in 2013. The data set corresponds to an integrated luminosity of 35 nb−1. The beam energies were 4 TeV for protons and 1.58 TeV per nucleon for lead nuclei, resulting in ffiffiffiffiffiffiffiffi sNN p ¼ 5.02 TeV. The beam direc- tions were reversed during the run, allowing a check of one potential source of systematic uncertainties. As a result of the energy difference between the colliding beams, the nucleon-nucleon center of mass in the p-Pb collisions is not at rest with respect to the laboratory frame. Massless particles emitted at ηcm ¼ 0 in the nucleon-nucleon center-of-mass frame will be detected at η ¼ −0.465 (clockwise proton beam) or 0.465 (counterclockwise pro- ton beam) in the laboratory frame. A sample of ffiffiffiffiffiffiffiffi sNN p ¼ 2.76 TeV PbPb data collected during the 2011 LHC heavy- ion run, corresponding to an integrated luminosity of 2.3 μb−1, is also analyzed for comparison purposes. The triggers and event selection, as well as track reconstruction and selection, are summarized below and are identical to those used in Ref. [35]. Minimum bias (MB) p-Pb events were triggered by requiring at least one track with pT > 0.4 GeV=c to be found in the pixel tracker for a p-Pb bunch crossing. Only a small fraction (∼10−3) of all MB triggered events were recorded (i.e., the trigger was “prescaled”) because of hardware limits on the data acquisition rate. In order to select high-multiplicity p-Pb collisions, a dedicated high- multiplicity trigger was implemented using the CMS level- 1 (L1) and high-level trigger (HLT) systems. At L1, three triggers requiring the total transverse energy summed over ECAL and HCAL to be greater than 20, 40, and 60 GeV were used since these cuts selected roughly the same events as the three HLT multiplicity selections discussed below. On-line track reconstruction for the HLT was based on the three layers of pixel detectors, and it required a track origin within a cylindrical region of length 30 cm along the beam and a radius 0.2 cm perpendicular to the beam around the nominal interaction point. For each event, the vertex reconstructed with the highest number of pixel tracks was selected. The number of pixel tracks (Non-line trk ) with jηj < 2.4, pT > 0.4 GeV=c, and a distance of closest approach to this vertex of 0.4 cm or less, was determined for each event. Several high-multiplicity ranges were defined with prescale factors that were progressively reduced until, for the highest multiplicity events, no prescaling was applied. In the off-line analysis, hadronic collisions are selected by requiring a coincidence of at least one HF calorimeter tower containing more than 3 GeVof total energy in each of the HF detectors. Only towers within 3 < jηj < 5 are used to avoid the edges of the HF acceptance. Events are also required to contain at least one reconstructed primary vertex within 15 cm of the nominal interaction point along the beam axis and within 0.15 cm transverse to the beam trajectory. At least two reconstructed tracks are required to be associated with the primary vertex. The beam related background is suppressed by rejecting events for which less than 25% of all reconstructed tracks pass the track selection criteria of this analysis. The p-Pb instantaneous luminosity provided by the LHC in the 2013 run resulted in an approximately 3% probability of at least one additional interaction occurring in the same bunch crossing. Following the procedure developed in Ref. [35] for rejecting such “pileup” events, a 99.8% purity of single- interaction events is achieved for the p-Pb collisions belonging to the highest multiplicity class studied in this Letter. In p-Pb interactions simulated with the EPOS [41] and HIJING [42] event generators, requiring at least one primary particle with total energy E > 3 GeV in each of the η ranges −5 < η < −3 and 3 < η < 5 is found to select 97%–98% of the total inelastic hadronic cross section. The CMS “high-quality” tracks described in Ref. [43] are used in this analysis. Additionally, a reconstructed track is only considered as a candidate track from the primary vertex if the significance of the separation along the beam axis (z) between the track and the best vertex, dz=σðdzÞ, and the significance of the track-vertex impact parameter measured transverse to the beam, dT=σðdTÞ, are each less than 3. The relative uncertainty in the transverse momen- tum measurement, σðpTÞ=pT, is required to be less than PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-2 10%. To ensure high tracking efficiency and to reduce the rate of incorrectly reconstructed tracks, only tracks within jηj < 2.4 and with 0.3 < pT < 3.0 GeV=c are used in the analysis. A different pT cutoff of 0.4 GeV=c is used in the multiplicity determination because of constraints on the on- line processing time for the HLT. The entire p-Pb data set is divided into classes of reconstructed track multiplicity, Noff-line trk . The multiplicity classification in this analysis is identical to that used in Ref. [35], where more details are provided, including a table relating Noff-line trk to the fraction of the MB triggered events. A subset of semiperipheral PbPb data collected during the 2011 LHC heavy-ion run with a MB trigger is also reanalyzed in order to directly compare the p-Pb and PbPb systems at the same track multiplicity. This PbPb sample is reprocessed using the same event selection and track reconstruction as for the present p-Pb analysis. A description of the 2011 PbPb data can be found in Ref. [44]. Extending the previous two- and four-particle azimuthal correlation measurements of Ref. [35], six- and eight- particle azimuthal correlations [36] are evaluated in this analysis as ⟪6⟫≡ ⟪einðϕ1þϕ2þϕ3−ϕ4−ϕ5−ϕ6Þ⟫; ⟪8⟫≡ ⟪einðϕ1þϕ2þϕ3þϕ4−ϕ5−ϕ6−ϕ7−ϕ8Þ⟫: ð1Þ Here ϕi ði ¼ 1;…; 8Þ are the azimuthal angles of one unique combination of multiple particles in an event, n is the harmonic number, and ⟪ � � �⟫ represents the average over all combinations from all events within a given multiplicity range. The corresponding cumulants, cnf6g and cnf8g, are calculated as follows: cnf6g ¼ ⟪6⟫ − 9 × ⟪4⟫⟪2⟫þ 12 × ⟪2⟫3; cnf8g ¼ ⟪8⟫ − 16 × ⟪6⟫⟪2⟫ − 18 × ⟪4⟫2 þ 144 × ⟪4⟫⟪2⟫2 − 144⟪2⟫4; ð2Þ using the Q-cumulant method as formulated in Ref. [36], where ⟪2⟫ and ⟪4⟫ are defined similarly as in Eq. (1). The Fourier harmonics vn that characterize the global azimuthal behavior are related to the multiparticle correlations [45] using vnf6g ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 4 cnf6g6 r ; vnf8g ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi − 1 33 cnf8g8 r : ð3Þ To account for detector effects, such as the tracking efficiency, the Q-cumulant method was extended in Ref. [45] to allow for particles having different weights. Each reconstructed track is weighted by a correction factor to account for the reconstruction efficiency, detector acceptance, and fraction of misreconstructed tracks. This factor is derived as a function of pT and η, as described in Refs. [13,14], based on MC simulations. The combined geometrical acceptance and efficiency for track reconstruction exceeds 60% for pT ≈ 0.3 GeV=c and jηj < 2.4. The efficiency is greater than 90% in the jηj < 1 region for pT > 0.6 GeV=c. For the entire multiplicity range (up to Noff-line trk ∼350) studied in this Letter, no dependence of the tracking efficiency on multiplicity is found and the rate of misreconstructed tracks remains at the 1%–2% level. The software package provided by Ref. [45] is used to implement the weights of the individual tracks in the cumulant calculations. The LYZ method [37,38] allows a direct study of the large-order behavior by using the asymptotic form of the cumulant expansion to relate locations of the zeros of a generating function to the azimuthal correlations. This method has been employed in previous CMS PbPb analy- ses [17,46]. For each multiplicity bin, the v2 harmonic averaged over 0.3 < pT < 3.0 GeV=c is found using an integral generating function [17]. Similar to the cumulant methods, a weight for each track is implemented to account for detector-related effects. In both methods, the statistical uncertainties are evaluated from data by dividing the data set into 20 subsets with roughly equal numbers of events and evaluating the standard deviation of the resulting distributions of the cumulant or v2fLYZg values. In the case of a low multiplicity or small flow signal, the LYZ method may overestimate the true collective flow. This effect was studied using MC pseudoexperiments for the event multiplicities covered in this analysis, and a small correction is applied to the data. The correction is less than 3% in the lowest multiplicity bin and becomes much smaller in higher-multiplicity bins. This correction is also included in the quoted LYZ systematic uncertainties. Systematic uncertainties are estimated by varying the track quality requirements, by comparing the results using efficiency correction tables from different MC event gen- erators, and by exploring the sensitivity of the results to the vertex position and to the Noff-line trk bin width. For the p-Pb data, potential HLT bias and pileup effects are also studied by requiring the presence of only a single reconstructed vertex. No evident Noff-line trk or beam direction dependent systematic effects are observed. For p-Pb collisions, a 5% systematic uncertainty is obtained for v2f6g and a 6% uncertainty is found for both v2f8g and v2fLYZg. The corresponding uncertainties for PbPb collisions are 2% for v2f6g and v2f8g, and 4% for v2fLYZg. In Fig. 1, the six- and eight-particle cumulants, c2f6g and c2f8g, for particle pT of 0.3–3.0 GeV=c in 2.76 TeV PbPb and 5.02 TeV p-Pb collisions are shown as a function of event multiplicity. The cumulants shown are required to be at least 2 standard deviations away from their physics boundaries (c2f6g=σc2f6g > 2, c2f8g=σc2f8g < −2) so that the statistical uncertainties can be propagated as Gaussian PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-3 fluctuations [47]. Nonzero multiparticle correlation signals are observed in both PbPb and p-Pb collisions. The p-Pb data exhibit larger statistical uncertainties than the PbPb results, mainly because of the smaller magnitudes of the correlation signals. Because of the limited sample size, the c2f6g and c2f8g values in p-Pb collisions are derived for a smaller range in Noff-line trk . The second-order anisotropy Fourier harmonics, v2, averaged over the pT range of 0.3–3.0 GeV=c, are shown in Fig. 2 based on six- and eight-particle cumulants [Eq. (3)] for 2.76 TeV PbPb (left panel) and 5.02 TeV p-Pb (right panel) collisions, as a function of event multiplicity. The open symbols are v2 results extracted by CMS using two- and four-particle correlations [35]. The v2 values derived using the LYZ method involving corre- lations among all particles are also shown. For each multiplicity bin, the values of v2f4g, v2f6g, v2f8g, and v2fLYZg for p-Pb collisions are found to be in agreement within 10%. For part of the multiplicity range, the values for v2f4g are larger than the others by a statistically significant amount, although still within 10%. The corre- sponding PbPb values are consistently higher than for p-Pb collisions, but within the PbPb system are found to be in agreement within 2% for most multiplicity ranges and within 10% for all multiplicities. This supports the collec- tive nature of the observed correlations, i.e., involving all particles from each system, and is inconsistent with a jet- related origin involving correlations among only a few particles. The v2 data from two-particle correlations are consistently above the multiparticle correlation data. This behavior can be understood in hydrodynamic models, where event-by-event participant geometry fluctuations of the v2 coefficient are expected to affect the two- and multiparticle cumulants differently [48,49]. Note that, to minimize jet-related nonflow effects, the v2f2g values are obtained with an η gap of 2 units between the two particles. Possible residual nonflow effects resulting from back-to- back jet correlations are estimated using very low multi- plicity events in Ref. [35]. Based on this analysis, such nonflow effects are expected to make a negligible con- tribution to v2f2g in very high multiplicity events. In PbPb collisions, the v2 values from all methods show an increase with multiplicity, while little multiplicity dependence is seen for the p-Pb data. This difference might reflect the presence of a lenticular overlap geometry in PbPb collisions—which is not expected in p-Pb collisions—that gives rise to a large (and varying) initial elliptic asymmetry in the PbPb system. The effect of fluctuation-driven initial-state eccentricities on multiparticle cumulants has recently been explored in the context of hydrodynamic behavior of the resulting medium [50,51]. For fluctuation-driven initial-state con- ditions, ratios of v2 values derived from various orders of multiparticle cumulants are predicted to follow a universal behavior [50]. In Fig. 3, ratios of v2f6g=v2f4g (top panel) and v2f8g=v2f6g (bottom panel) are calculated and plotted against v2f4g=v2f2g in p-Pb collisions atffiffiffiffiffiffiffiffi sNN p ¼ 5.02 TeV. The v2f2g and v2f4g data are taken from previously published CMS results [35]. The solid curves correspond to theoretical predictions for both large and small systems based on hydrodynamics and the assumption that the initial-state geometry is purely driven off-line trkN 0 100 200 300 {6 } 2 an d c {8 } 2 c− 10−10 9−10 8−10 7−10 6−10 CMS | < 2.4η| < 3.0 GeV/c T 0.3 < p {6}2c {8}2c = 2.76 TeVNNsPbPb {6}2c {8}2c = 5.02 TeVNNsp-Pb FIG. 1 (color online). The cumulant c2f6g and −c2f8g results as a function of Noff-line trk for PbPb and p-Pb reactions. Error bars and shaded areas denote the statistical and systematic uncertain- ties, respectively. off-line trkN 0 100 200 300 2v 0.05 0.10 |>2}ηΔ{2, |2v {4}2v {6}2v {8}2v {LYZ}2v | < 2.4η < 3.0 GeV/c; | T 0.3 < p = 2.76 TeV NN sCMS PbPb off-line trkN 0 100 200 300 | < 2.4η < 3.0 GeV/c; | T 0.3 < p = 5.02 TeV NN sCMS p-Pb FIG. 2 (color online). The v2 values as a function of Noff-line trk . Open data points are the published two- and four-particle v2 results [35]. Solid data points are v2 results obtained from six- and eight-particle cumulants, and LYZ methods, averaged over the particle pT range of 0.3–3.0 GeV=c, in PbPb at ffiffiffiffiffiffiffiffi sNN p ¼ 2.76 TeV (left panel) and p-Pb at ffiffiffiffiffiffiffiffi sNN p ¼ 5.02 TeV (right panel). Statistical and systematic uncertainties are indicated by the error bars and the shaded regions, respectively. PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-4 by fluctuations [50]. The ratios from PbPb collisions are also shown for comparison. Note that the geometry of very central PbPb collisions might be dominated by fluctuations, but for these semiperipheral PbPb collisions the lenticular shape of the overlap region should also strongly contribute to the v2 values. The CMS p-Pb data are consistent with the predictions, within statistical and systematic uncertainties. The systematic uncertainties in the ratios presented in Fig. 3 are estimated to be 2.4% for v2f4g=v2f2g for both the p-Pb and the PbPb collisions, 1% for v2f6g=v2f4g in the p-Pb and PbPb collisions, and 3.6% and 1% for v2f8g=v2f6g in the p-Pb and the PbPb collisions, respectively. Since they are all derived from the same data, the systematic uncer- tainties for the different cumulant orders are highly corre- lated and therefore partially cancel in the ratios. Recently, other theoretical models based on quantum chromodynamics, and not involving hydrodynamics, have also been suggested to explain the observed multiparticle correlations in p-Pb collisions [52,53]. Unlike the descrip- tions based on hydrodynamic behavior, these models do not require significant final state interactions among quarks and gluons. They suggest similar values for v2f4g, v2f6g, v2f8g, and v2fLYZg—without yet, however, providing quantitative predictions. In summary, multiparticle azimuthal correlations among six, eight, and all particles have been measured in p-Pb collisions at ffiffiffiffiffiffiffiffi sNN p ¼ 5.02 TeV by the CMS experiment. The new measurements extend previous CMS two- and four-particle correlation analyses of p-Pb collisions and strongly constrain possible explanations for the observed correlations. A direct comparison of the correlation data for p-Pb and PbPb collisions is presented as a function of particle multiplicity. Averaging over the particle pT range of 0.3–3.0 GeV=c, multiparticle correlation signals are observed in both p-Pb and PbPb collisions. The second- order azimuthal anisotropy Fourier harmonic, v2, is extracted using six- and eight-particle cumulants and using the LYZ method which involves all particles. The v2 values obtained using correlation methods including four or more particles are consistent within �2% for the PbPb system, and within �10% for the p-Pb system. This measurement supports the collective nature of the observed correlations. The ratios of v2 values obtained using different numbers of particles are found to be consistent with hydrodynamic model calculations for p-Pb collisions. 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 success of the CMS effort. In addition, we gratefully acknowledge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and the operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); MoER, ERC IUT, and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/ IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain); {4 } 2 / v {6 } 2v 0.8 1.0 1.2 1.4 | < 2.4η < 3.0 GeV/c; | T 0.3 < p = 2.76 TeV NN s = 5.02 TeV, PbPb NN sp-Pb CMS p-Pb PbPb {2}2 / v{4}2v 0.6 0.7 0.8 0.9 {6 } 2 / v {8 } 2v 0.8 1.0 1.2 1.4 Fluctuation-Driven Eccentricities p-Pb PbPb FIG. 3 (color online). Cumulant ratios v2f6g=v2f4g (top panel) and v2f8g=v2f6g (bottom panel) as a function of v2f4g=v2f2g in p-Pb collisions at ffiffiffiffiffiffiffiffi sNN p ¼ 5.02 TeV and PbPb collisions atffiffiffiffiffiffiffiffi sNN p ¼ 2.76 TeV. Error bars and shaded areas denote statistical and systematic uncertainties, respectively. The solid curves show the expected behavior based on a hydrodynamics motivated study of the role of initial-state fluctuations [50]. PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-5 Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC (United Kingdom); DOE and NSF (U.S.). [1] CMS Collaboration, Observation of long-range near-side angular correlations in proton-proton collisions at the LHC, J. High Energy Phys. 09 (2010) 091. 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Markou,40 A. Psallidas,40 I. Topsis-Giotis,40 A. Agapitos,41 S. Kesisoglou,41 A. Panagiotou,41 N. Saoulidou,41 E. Stiliaris,41 E. Tziaferi,41 X. Aslanoglou,42 I. Evangelou,42 G. Flouris,42 C. Foudas,42 P. Kokkas,42 N. Manthos,42 I. Papadopoulos,42 E. Paradas,42 J. Strologas,42 G. Bencze,43 C. Hajdu,43 P. Hidas,43 D. Horvath,43,r F. Sikler,43 V. Veszpremi,43 G. Vesztergombi,43,s A. J. Zsigmond,43 N. Beni,44 S. Czellar,44 J. Karancsi,44,t J. Molnar,44 J. Palinkas,44 Z. Szillasi,44 A. Makovec,45 P. Raics,45 Z. L. Trocsanyi,45 B. Ujvari,45 S. K. Swain,46 S. B. Beri,47 V. Bhatnagar,47 R. Gupta,47 U. Bhawandeep,47 A. K. Kalsi,47 M. Kaur,47 R. Kumar,47 M. Mittal,47 N. Nishu,47 J. B. Singh,47 Ashok Kumar,48 Arun Kumar,48 S. Ahuja,48 A. Bhardwaj,48 B. C. Choudhary,48 A. Kumar,48 S. Malhotra,48 M. Naimuddin,48 K. Ranjan,48 V. Sharma,48 S. Banerjee,49 S. Bhattacharya,49 K. Chatterjee,49 S. Dutta,49 B. Gomber,49 Sa. Jain,49 Sh. Jain,49 R. Khurana,49 A. Modak,49 S. Mukherjee,49 D. Roy,49 S. Sarkar,49 M. Sharan,49 A. Abdulsalam,50 D. Dutta,50 V. Kumar,50 A. K. Mohanty,50,c L. M. Pant,50 P. Shukla,50 A. Topkar,50 T. Aziz,51 S. Banerjee,51 S. Bhowmik,51,u R. M. Chatterjee,51 R. K. Dewanjee,51 S. Dugad,51 S. Ganguly,51 S. Ghosh,51 M. Guchait,51 A. Gurtu,51,v G. Kole,51 S. Kumar,51 M. Maity,51,u G. Majumder,51 K. Mazumdar,51 G. B. Mohanty,51 B. Parida,51 K. Sudhakar,51 N. Wickramage,51,w S. Sharma,52 H. Bakhshiansohi,53 H. Behnamian,53 S. M. Etesami,53,x A. Fahim,53,y R. Goldouzian,53 M. Khakzad,53 M. Mohammadi Najafabadi,53 M. Naseri,53 S. Paktinat Mehdiabadi,53 F. Rezaei Hosseinabadi,53 B. Safarzadeh,53,z M. Zeinali,53 M. Felcini,54 M. Grunewald,54 M. Abbrescia,55a,55b C. Calabria,55a,55b S. S. Chhibra,55a,55b A. Colaleo,55a D. Creanza,55a,55c L. Cristella,55a,55b N. De Filippis,55a,55c M. De Palma,55a,55b L. Fiore,55a G. Iaselli,55a,55c G. Maggi,55a,55c M. Maggi,55a S. My,55a,55c S. Nuzzo,55a,55b A. Pompili,55a,55b G. Pugliese,55a,55c R. Radogna,55a,55b,c G. Selvaggi,55a,55b A. Sharma,55a L. Silvestris,55a,c R. Venditti,55a,55b P. Verwilligen,55a G. Abbiendi,56a A. C. Benvenuti,56a D. Bonacorsi,56a,56b S. Braibant-Giacomelli,56a,56b L. Brigliadori,56a,56b R. Campanini,56a,56b P. Capiluppi,56a,56b A. Castro,56a,56b F. R. Cavallo,56a G. Codispoti,56a,56b M. Cuffiani,56a,56b G. M. Dallavalle,56a F. Fabbri,56a A. Fanfani,56a,56b D. Fasanella,56a,56b P. Giacomelli,56a C. Grandi,56a L. Guiducci,56a,56b S. Marcellini,56a G. Masetti,56a A. Montanari,56a F. L. Navarria,56a,56b A. Perrotta,56a A. M. Rossi,56a,56b T. Rovelli,56a,56b G. P. Siroli,56a,56b N. Tosi,56a,56b R. Travaglini,56a,56b S. Albergo,57a,57b G. Cappello,57a M. Chiorboli,57a,57b S. Costa,57a,57b F. Giordano,57a,c R. Potenza,57a,57b A. Tricomi,57a,57b C. Tuve,57a,57b G. Barbagli,58a V. Ciulli,58a,58b C. Civinini,58a R. D’Alessandro,58a,58b E. Focardi,58a,58b E. Gallo,58a S. Gonzi,58a,58b V. Gori,58a,58b P. Lenzi,58a,58b M. Meschini,58a S. Paoletti,58a G. Sguazzoni,58a A. Tropiano,58a,58b L. Benussi,59 S. Bianco,59 F. Fabbri,59 D. Piccolo,59 R. Ferretti,60a,60b F. Ferro,60a M. Lo Vetere,60a,60b E. Robutti,60a S. Tosi,60a,60b M. E. Dinardo,61a,61b S. Fiorendi,61a,61b S. Gennai,61a,c R. Gerosa,61a,61b,c A. Ghezzi,61a,61b P. Govoni,61a,61b M. T. Lucchini,61a,61b,c S. Malvezzi,61a R. A. Manzoni,61a,61b A. Martelli,61a,61b B. Marzocchi,61a,61b,c D. Menasce,61a L. Moroni,61a M. Paganoni,61a,61b D. Pedrini,61a S. Ragazzi,61a,61b N. Redaelli,61a T. Tabarelli de Fatis,61a,61b S. Buontempo,62a N. Cavallo,62a,62c S. Di Guida,62a,62d,c F. Fabozzi,62a,62c A. O. M. Iorio,62a,62b L. Lista,62a S. Meola,62a,62d,c M. Merola,62a P. Paolucci,62a,c P. Azzi,63a N. Bacchetta,63a D. Bisello,63a,63b R. Carlin,63a,63b P. Checchia,63a M. Dall’Osso,63a,63b T. Dorigo,63a U. Dosselli,63a U. Gasparini,63a,63b A. Gozzelino,63a S. Lacaprara,63a M. Margoni,63a,63b A. T. Meneguzzo,63a,63b J. Pazzini,63a,63b M. Pegoraro,63a N. Pozzobon,63a,63b P. Ronchese,63a,63b F. Simonetto,63a,63b E. Torassa,63a M. Tosi,63a,63b S. Vanini,63a,63b S. Ventura,63a P. Zotto,63a,63b A. Zucchetta,63a,63b G. Zumerle,63a,63b M. Gabusi,64a,64b S. P. Ratti,64a,64b V. Re,64a C. Riccardi,64a,64b P. Salvini,64a P. Vitulo,64a,64b M. Biasini,65a,65b G. M. Bilei,65a D. Ciangottini,65a,65b,c L. Fanò,65a,65b P. Lariccia,65a,65b G. Mantovani,65a,65b M. Menichelli,65a A. Saha,65a A. Santocchia,65a,65b A. Spiezia,65a,65b,c K. Androsov,66a,aa P. Azzurri,66a G. Bagliesi,66a J. Bernardini,66a T. Boccali,66a G. Broccolo,66a,66c R. Castaldi,66a M. A. Ciocci,66a,aa R. Dell’Orso,66a S. Donato,66a,66c,c G. Fedi,66a F. Fiori,66a,66c L. Foà,66a,66c A. Giassi,66a M. T. Grippo,66a,aa F. Ligabue,66a,66c T. Lomtadze,66a L. Martini,66a,66b A. Messineo,66a,66b C. S. Moon,66a,bb F. Palla,66a,c A. Rizzi,66a,66b A. Savoy-Navarro,66a,cc A. T. Serban,66a P. Spagnolo,66a P. Squillacioti,66a,aa R. Tenchini,66a G. Tonelli,66a,66b A. Venturi,66a P. G. Verdini,66a C. Vernieri,66a,66c L. Barone,67a,67b F. Cavallari,67a G. D’imperio,67a,67b D. Del Re,67a,67b M. Diemoz,67a C. Jorda,67a E. Longo,67a,67b F. Margaroli,67a,67b P. Meridiani,67a F. Micheli,67a,67b,c G. Organtini,67a,67b R. Paramatti,67a S. Rahatlou,67a,67b C. Rovelli,67a F. Santanastasio,67a,67b L. Soffi,67a,67b P. Traczyk,67a,67b,c N. Amapane,68a,68b R. Arcidiacono,68a,68c S. Argiro,68a,68b M. Arneodo,68a,68c R. Bellan,68a,68b C. Biino,68a N. Cartiglia,68a S. Casasso,68a,68b,c M. Costa,68a,68b R. Covarelli,68a A. Degano,68a,68b N. Demaria,68a L. Finco,68a,68b,c C. Mariotti,68a S. Maselli,68a E. Migliore,68a,68b V. Monaco,68a,68b M. Musich,68a M. M. Obertino,68a,68c L. Pacher,68a,68b N. Pastrone,68a M. Pelliccioni,68a G. L. Pinna Angioni,68a,68b A. Potenza,68a,68b A. Romero,68a,68b M. Ruspa,68a,68c R. Sacchi,68a,68b A. Solano,68a,68b A. Staiano,68a U. Tamponi,68a S. Belforte,69a V. Candelise,69a,69b,c M. Casarsa,69a F. Cossutti,69a G. Della Ricca,69a,69b B. Gobbo,69a C. La Licata,69a,69b PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-9 M.Marone,69a,69b A. Schizzi,69a,69b T. Umer,69a,69b A. Zanetti,69a S. Chang,70 A. Kropivnitskaya,70 S. K. Nam,70 D. H. Kim,71 G. N. Kim,71 M. S. Kim,71 D. J. Kong,71 S. Lee,71 Y. D. Oh,71 H. Park,71 A. Sakharov,71 D. C. Son,71 T. J. Kim,72 M. S. Ryu,72 J. Y. Kim,73 D. H. Moon,73 S. Song,73 S. Choi,74 D. Gyun,74 B. Hong,74 M. Jo,74 H. Kim,74 Y. Kim,74 B. Lee,74 K. S. Lee,74 S. K. Park,74 Y. Roh,74 H. D. Yoo,75 M. Choi,76 J. H. Kim,76 I. C. Park,76 G. Ryu,76 Y. Choi,77 Y. K. Choi,77 J. Goh,77 D. Kim,77 E. Kwon,77 J. Lee,77 I. Yu,77 A. Juodagalvis,78 J. R. Komaragiri,79 M. A. B. Md Ali,79,dd W. A. T. Wan Abdullah,79 E. Casimiro Linares,80 H. Castilla-Valdez,80 E. De La Cruz-Burelo,80 I. Heredia-de La Cruz,80 A. Hernandez-Almada,80 R. Lopez-Fernandez,80 A. Sanchez-Hernandez,80 S. Carrillo Moreno,81 F. Vazquez Valencia,81 I. Pedraza,82 H. A. Salazar Ibarguen,82 A. Morelos Pineda,83 D. Krofcheck,84 P. H. Butler,85 S. Reucroft,85 A. Ahmad,86 M. Ahmad,86 Q. Hassan,86 H. R. Hoorani,86 W. A. Khan,86 T. Khurshid,86 M. Shoaib,86 H. Bialkowska,87 M. Bluj,87 B. Boimska,87 T. Frueboes,87 M. Górski,87 M. Kazana,87 K. Nawrocki,87 K. Romanowska-Rybinska,87 M. Szleper,87 P. Zalewski,87 G. Brona,88 K. Bunkowski,88 M. Cwiok,88 W. Dominik,88 K. Doroba,88 A. Kalinowski,88 M. Konecki,88 J. Krolikowski,88 M. Misiura,88 M. Olszewski,88 P. Bargassa,89 C. Beirão Da Cruz E Silva,89 P. Faccioli,89 P. G. Ferreira Parracho,89 M. Gallinaro,89 L. Lloret Iglesias,89 F. Nguyen,89 J. Rodrigues Antunes,89 J. Seixas,89 D. Vadruccio,89 J. Varela,89 P. Vischia,89 S. Afanasiev,90 P. Bunin,90 M. Gavrilenko,90 I. Golutvin,90 I. Gorbunov,90 A. Kamenev,90 V. Karjavin,90 V. Konoplyanikov,90 A. Lanev,90 A. Malakhov,90 V. Matveev,90,ee P. Moisenz,90 V. Palichik,90 V. Perelygin,90 S. Shmatov,90 N. Skatchkov,90 V. Smirnov,90 A. Zarubin,90 V. Golovtsov,91 Y. Ivanov,91 V. Kim,91,ff E. Kuznetsova,91 P. Levchenko,91 V. Murzin,91 V. Oreshkin,91 I. Smirnov,91 V. Sulimov,91 L. Uvarov,91 S. Vavilov,91 A. Vorobyev,91 An. Vorobyev,91 Yu. Andreev,92 A. Dermenev,92 S. Gninenko,92 N. Golubev,92 M. Kirsanov,92 N. Krasnikov,92 A. Pashenkov,92 D. Tlisov,92 A. Toropin,92 V. Epshteyn,93 V. Gavrilov,93 N. Lychkovskaya,93 V. Popov,93 I. Pozdnyakov,93 G. Safronov,93 S. Semenov,93 A. Spiridonov,93 V. Stolin,93 E. Vlasov,93 A. Zhokin,93 V. Andreev,94 M. Azarkin,94 I. Dremin,94 M. Kirakosyan,94 A. Leonidov,94 G. Mesyats,94 S. V. Rusakov,94 A. Vinogradov,94 A. Belyaev,95 E. Boos,95 A. Ershov,95 A. Gribushin,95 A. Kaminskiy,95,gg O. Kodolova,95 V. Korotkikh,95 I. Lokhtin,95 S. Obraztsov,95 S. Petrushanko,95 V. Savrin,95 A. Snigirev,95 I. Vardanyan,95 I. Azhgirey,96 I. Bayshev,96 S. Bitioukov,96 V. Kachanov,96 A. Kalinin,96 D. Konstantinov,96 V. Krychkine,96 V. Petrov,96 R. Ryutin,96 A. Sobol,96 L. Tourtchanovitch,96 S. Troshin,96 N. Tyurin,96 A. Uzunian,96 A. Volkov,96 P. Adzic,97,hh M. Ekmedzic,97 J. Milosevic,97 V. Rekovic,97 J. Alcaraz Maestre,98 C. Battilana,98 E. Calvo,98 M. Cerrada,98 M. Chamizo Llatas,98 N. Colino,98 B. De La Cruz,98 A. Delgado Peris,98 D. Domínguez Vázquez,98 A. Escalante Del Valle,98 C. Fernandez Bedoya,98 J. P. Fernández Ramos,98 J. Flix,98 M. C. Fouz,98 P. Garcia-Abia,98 O. Gonzalez Lopez,98 S. Goy Lopez,98 J. M. Hernandez,98 M. I. Josa,98 E. Navarro De Martino,98 A. Pérez-Calero Yzquierdo,98 J. Puerta Pelayo,98 A. Quintario Olmeda,98 I. Redondo,98 L. Romero,98 M. S. Soares,98 C. Albajar,99 J. F. de Trocóniz,99 M. Missiroli,99 D. Moran,99 H. Brun,100 J. Cuevas,100 J. Fernandez Menendez,100 S. Folgueras,100 I. Gonzalez Caballero,100 J. A. Brochero Cifuentes,101 I. J. Cabrillo,101 A. Calderon,101 J. Duarte Campderros,101 M. Fernandez,101 G. Gomez,101 A. Graziano,101 A. Lopez Virto,101 J. Marco,101 R. Marco,101 C. Martinez Rivero,101 F. Matorras,101 F. J. Munoz Sanchez,101 J. Piedra Gomez,101 T. Rodrigo,101 A. Y. Rodríguez-Marrero,101 A. Ruiz-Jimeno,101 L. Scodellaro,101 I. Vila,101 R. Vilar Cortabitarte,101 D. Abbaneo,102 E. Auffray,102 G. Auzinger,102 M. Bachtis,102 P. Baillon,102 A. H. Ball,102 D. Barney,102 A. Benaglia,102 J. Bendavid,102 L. Benhabib,102 J. F. Benitez,102 P. Bloch,102 A. Bocci,102 A. Bonato,102 O. Bondu,102 C. Botta,102 H. Breuker,102 T. Camporesi,102 G. Cerminara,102 S. Colafranceschi,102,ii M. D’Alfonso,102 D. d’Enterria,102 A. Dabrowski,102 A. David,102 F. De Guio,102 A. De Roeck,102 S. De Visscher,102 E. Di Marco,102 M. Dobson,102 M. Dordevic,102 B. Dorney,102 N. Dupont-Sagorin,102 A. Elliott-Peisert,102 G. Franzoni,102 W. Funk,102 D. Gigi,102 K. Gill,102 D. Giordano,102 M. Girone,102 F. Glege,102 R. Guida,102 S. Gundacker,102 M. Guthoff,102 J. Hammer,102 M. Hansen,102 P. Harris,102 J. Hegeman,102 V. Innocente,102 P. Janot,102 K. Kousouris,102 K. Krajczar,102 P. Lecoq,102 C. Lourenço,102 N. Magini,102 L. Malgeri,102 M. Mannelli,102 J. Marrouche,102 L. Masetti,102 F. Meijers,102 S. Mersi,102 E. Meschi,102 F. Moortgat,102 S. Morovic,102 M. Mulders,102 S. Orfanelli,102 L. Orsini,102 L. Pape,102 E. Perez,102 A. Petrilli,102 G. Petrucciani,102 A. Pfeiffer,102 M. Pimiä,102 D. Piparo,102 M. Plagge,102 A. Racz,102 G. Rolandi,102,jj M. Rovere,102 H. Sakulin,102 C. Schäfer,102 C. Schwick,102 A. Sharma,102 P. Siegrist,102 P. Silva,102 M. Simon,102 P. Sphicas,102,kk D. Spiga,102 J. Steggemann,102 B. Stieger,102 M. Stoye,102 Y. Takahashi,102 D. Treille,102 A. Tsirou,102 G. I. Veres,102,s N. Wardle,102 H. K. Wöhri,102 H. Wollny,102 W. D. Zeuner,102 W. Bertl,103 K. Deiters,103 W. Erdmann,103 R. Horisberger,103 Q. Ingram,103 H. C. Kaestli,103 D. Kotlinski,103 U. Langenegger,103 D. Renker,103 T. Rohe,103 F. Bachmair,104 L. Bäni,104 L. Bianchini,104 M. A. Buchmann,104 B. Casal,104 N. Chanon,104 G. Dissertori,104 M. Dittmar,104 M. Donegà,104 M. Dünser,104 P. Eller,104 PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-10 C. Grab,104 D. Hits,104 J. Hoss,104 G. Kasieczka,104 W. Lustermann,104 B. Mangano,104 A. C. Marini,104 M. Marionneau,104 P. Martinez Ruiz del Arbol,104 M. Masciovecchio,104 D. Meister,104 N. Mohr,104 P. Musella,104 C. Nägeli,104,ll F. Nessi-Tedaldi,104 F. Pandolfi,104 F. Pauss,104 L. Perrozzi,104 M. Peruzzi,104 M. Quittnat,104 L. Rebane,104 M. Rossini,104 A. Starodumov,104,mm M. Takahashi,104 K. Theofilatos,104 R. Wallny,104 H. A. Weber,104 C. Amsler,105,nn M. F. Canelli,105 V. Chiochia,105 A. De Cosa,105 A. Hinzmann,105 T. Hreus,105 B. Kilminster,105 C. Lange,105 J. Ngadiuba,105 D. Pinna,105 P. Robmann,105 F. J. Ronga,105 S. Taroni,105 Y. Yang,105 M. Cardaci,106 K. H. Chen,106 C. Ferro,106 C. M. Kuo,106 W. Lin,106 Y. J. Lu,106 R. Volpe,106 S. S. Yu,106 P. Chang,107 Y. H. Chang,107 Y. Chao,107 K. F. Chen,107 P. H. Chen,107 C. Dietz,107 U. Grundler,107 W.-S. Hou,107 Y. F. Liu,107 R.-S. Lu,107 M. Miñano Moya,107 E. Petrakou,107 J. F. Tsai,107 Y. M. Tzeng,107 R. Wilken,107 B. Asavapibhop,108 G. Singh,108 N. Srimanobhas,108 N. Suwonjandee,108 A. Adiguzel,109 M. N. Bakirci,109,oo S. Cerci,109,pp C. Dozen,109 I. Dumanoglu,109 E. Eskut,109 S. Girgis,109 G. Gokbulut,109 Y. Guler,109 E. Gurpinar,109 I. Hos,109 E. E. Kangal,109,qq A. Kayis Topaksu,109 G. Onengut,109,rr K. Ozdemir,109,ss S. Ozturk,109,oo A. Polatoz,109 D. Sunar Cerci,109,pp B. Tali,109,pp H. Topakli,109,oo M. Vergili,109 C. Zorbilmez,109 I. V. Akin,110 B. Bilin,110 S. Bilmis,110 H. Gamsizkan,110,tt B. Isildak,110,uu G. Karapinar,110,vv K. Ocalan,110,ww S. Sekmen,110 U. E. Surat,110 M. Yalvac,110 M. Zeyrek,110 E. A. Albayrak,111,xx E. Gülmez,111 M. Kaya,111,yy O. Kaya,111,zz T. Yetkin,111,aaa K. Cankocak,112 F. I. Vardarlı,112 L. Levchuk,113 P. Sorokin,113 J. J. Brooke,114 E. Clement,114 D. Cussans,114 H. Flacher,114 J. Goldstein,114 M. Grimes,114 G. P. Heath,114 H. F. Heath,114 J. Jacob,114 L. Kreczko,114 C. Lucas,114 Z. Meng,114 D. M. Newbold,114,bbb S. Paramesvaran,114 A. Poll,114 T. Sakuma,114 S. Seif El Nasr-storey,114 S. Senkin,114 V. J. Smith,114 A. Belyaev,115,ccc C. Brew,115 R. M. Brown,115 D. J. A. Cockerill,115 J. A. Coughlan,115 K. Harder,115 S. Harper,115 E. Olaiya,115 D. Petyt,115 C. H. Shepherd-Themistocleous,115 A. Thea,115 I. R. Tomalin,115 T. Williams,115 W. J. Womersley,115 S. D. Worm,115 M. Baber,116 R. Bainbridge,116 O. Buchmuller,116 D. Burton,116 D. Colling,116 N. Cripps,116 P. Dauncey,116 G. Davies,116 M. Della Negra,116 P. Dunne,116 A. Elwood,116 W. Ferguson,116 J. Fulcher,116 D. Futyan,116 G. Hall,116 G. Iles,116 M. Jarvis,116 G. Karapostoli,116 M. Kenzie,116 R. Lane,116 R. Lucas,116,bbb L. Lyons,116 A.-M. Magnan,116 S. Malik,116 B. Mathias,116 J. Nash,116 A. Nikitenko,116,mm J. Pela,116 M. Pesaresi,116 K. Petridis,116 D. M. Raymond,116 S. Rogerson,116 A. Rose,116 C. Seez,116 P. Sharp,116,a A. Tapper,116 M. Vazquez Acosta,116 T. Virdee,116 S. C. Zenz,116 J. E. Cole,117 P. R. Hobson,117 A. Khan,117 P. Kyberd,117 D. Leggat,117 D. Leslie,117 I. D. Reid,117 P. Symonds,117 L. Teodorescu,117 M. Turner,117 J. Dittmann,118 K. Hatakeyama,118 A. Kasmi,118 H. Liu,118 N. Pastika,118 T. Scarborough,118 Z. Wu,118 O. Charaf,119 S. I. Cooper,119 C. Henderson,119 P. Rumerio,119 A. Avetisyan,120 T. Bose,120 C. Fantasia,120 P. Lawson,120 C. Richardson,120 J. Rohlf,120 J. St. John,120 L. Sulak,120 J. Alimena,121 E. Berry,121 S. Bhattacharya,121 G. Christopher,121 D. Cutts,121 Z. Demiragli,121 N. Dhingra,121 A. Ferapontov,121 A. Garabedian,121 U. Heintz,121 E. Laird,121 G. Landsberg,121 Z. Mao,121 M. Narain,121 S. Sagir,121 T. Sinthuprasith,121 T. Speer,121 J. Swanson,121 R. Breedon,122 G. Breto,122 M. Calderon De La Barca Sanchez,122 S. Chauhan,122 M. Chertok,122 J. Conway,122 R. Conway,122 P. T. Cox,122 R. Erbacher,122 M. Gardner,122 W. Ko,122 R. Lander,122 M. Mulhearn,122 D. Pellett,122 J. Pilot,122 F. Ricci-Tam,122 S. Shalhout,122 J. Smith,122 M. Squires,122 D. Stolp,122 M. Tripathi,122 S. Wilbur,122 R. Yohay,122 R. Cousins,123 P. Everaerts,123 C. Farrell,123 J. Hauser,123 M. Ignatenko,123 G. Rakness,123 E. Takasugi,123 V. Valuev,123 M. Weber,123 K. Burt,124 R. Clare,124 J. Ellison,124 J. W. Gary,124 G. Hanson,124 J. Heilman,124 M. Ivova Rikova,124 P. Jandir,124 E. Kennedy,124 F. Lacroix,124 O. R. Long,124 A. Luthra,124 M. Malberti,124 M. Olmedo Negrete,124 A. Shrinivas,124 S. Sumowidagdo,124 S. Wimpenny,124 J. G. Branson,125 G. B. Cerati,125 S. Cittolin,125 R. T. D’Agnolo,125 A. Holzner,125 R. Kelley,125 D. Klein,125 J. Letts,125 I. Macneill,125 D. Olivito,125 S. Padhi,125 C. Palmer,125 M. Pieri,125 M. Sani,125 V. Sharma,125 S. Simon,125 M. Tadel,125 Y. Tu,125 A. Vartak,125 C. Welke,125 F. Würthwein,125 A. Yagil,125 G. Zevi Della Porta,125 D. Barge,126 J. Bradmiller-Feld,126 C. Campagnari,126 T. Danielson,126 A. Dishaw,126 V. Dutta,126 K. Flowers,126 M. Franco Sevilla,126 P. Geffert,126 C. George,126 F. Golf,126 L. Gouskos,126 J. Incandela,126 C. Justus,126 N. Mccoll,126 S. D. Mullin,126 J. Richman,126 D. Stuart,126 W. To,126 C. West,126 J. Yoo,126 A. Apresyan,127 A. Bornheim,127 J. Bunn,127 Y. Chen,127 J. Duarte,127 A. Mott,127 H. B. Newman,127 C. Pena,127 M. Pierini,127 M. Spiropulu,127 J. R. Vlimant,127 R. Wilkinson,127 S. Xie,127 R. Y. Zhu,127 V. Azzolini,128 A. Calamba,128 B. Carlson,128 T. Ferguson,128 Y. Iiyama,128 M. Paulini,128 J. Russ,128 H. Vogel,128 I. Vorobiev,128 J. P. Cumalat,129 W. T. Ford,129 A. Gaz,129 M. Krohn,129 E. Luiggi Lopez,129 U. Nauenberg,129 J. G. Smith,129 K. Stenson,129 S. R. Wagner,129 J. Alexander,130 A. Chatterjee,130 J. Chaves,130 J. Chu,130 S. Dittmer,130 N. Eggert,130 N. Mirman,130 G. Nicolas Kaufman,130 J. R. Patterson,130 A. Ryd,130 E. Salvati,130 L. Skinnari,130 W. Sun,130 W. D. Teo,130 J. Thom,130 J. Thompson,130 J. Tucker,130 Y. Weng,130 L. Winstrom,130 P. Wittich,130 D. Winn,131 S. Abdullin,132 M. Albrow,132 J. Anderson,132 G. Apollinari,132 L. A. T. Bauerdick,132 PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-11 A. Beretvas,132 J. Berryhill,132 P. C. Bhat,132 G. Bolla,132 K. Burkett,132 J. N. Butler,132 H.W. K. Cheung,132 F. Chlebana,132 S. Cihangir,132 V. D. Elvira,132 I. Fisk,132 J. Freeman,132 E. Gottschalk,132 L. Gray,132 D. Green,132 S. Grünendahl,132 O. Gutsche,132 J. Hanlon,132 D. Hare,132 R. M. Harris,132 J. Hirschauer,132 B. Hooberman,132 S. Jindariani,132 M. Johnson,132 U. Joshi,132 B. Klima,132 B. Kreis,132 S. Kwan,132,a J. Linacre,132 D. Lincoln,132 R. Lipton,132 T. Liu,132 R. Lopes De Sá,132 J. Lykken,132 K. Maeshima,132 J. M. Marraffino,132 V. I. Martinez Outschoorn,132 S. Maruyama,132 D. Mason,132 P. McBride,132 P. Merkel,132 K. Mishra,132 S. Mrenna,132 S. Nahn,132 C. Newman-Holmes,132 V. O’Dell,132 O. Prokofyev,132 E. Sexton-Kennedy,132 A. Soha,132 W. J. Spalding,132 L. Spiegel,132 L. Taylor,132 S. Tkaczyk,132 N. V. Tran,132 L. Uplegger,132 E. W. Vaandering,132 R. Vidal,132 A. Whitbeck,132 J. Whitmore,132 F. Yang,132 D. Acosta,133 P. Avery,133 P. Bortignon,133 D. Bourilkov,133 M. Carver,133 D. Curry,133 S. Das,133 M. De Gruttola,133 G. P. Di Giovanni,133 R. D. Field,133 M. Fisher,133 I. K. Furic,133 J. Hugon,133 J. Konigsberg,133 A. Korytov,133 T. Kypreos,133 J. F. Low,133 K. Matchev,133 H. Mei,133 P. Milenovic,133,ddd G. Mitselmakher,133 L. Muniz,133 A. Rinkevicius,133 L. Shchutska,133 M. Snowball,133 D. Sperka,133 J. Yelton,133 M. Zakaria,133 S. Hewamanage,134 S. Linn,134 P. Markowitz,134 G. Martinez,134 J. L. Rodriguez,134 J. R. Adams,135 T. Adams,135 A. Askew,135 J. Bochenek,135 B. Diamond,135 J. Haas,135 S. Hagopian,135 V. Hagopian,135 K. F. Johnson,135 H. Prosper,135 V. Veeraraghavan,135 M. Weinberg,135 M. M. Baarmand,136 M. Hohlmann,136 H. Kalakhety,136 F. Yumiceva,136 M. R. Adams,137 L. Apanasevich,137 D. Berry,137 R. R. Betts,137 I. Bucinskaite,137 R. Cavanaugh,137 O. Evdokimov,137 L. Gauthier,137 C. E. Gerber,137 D. J. Hofman,137 P. Kurt,137 C. O’Brien,137 I. D. Sandoval Gonzalez,137 C. Silkworth,137 P. Turner,137 N. Varelas,137 B. Bilki,138,eee W. Clarida,138 K. Dilsiz,138 M. Haytmyradov,138 V. Khristenko,138 J.-P. Merlo,138 H. Mermerkaya,138,fff A. Mestvirishvili,138 A. Moeller,138 J. Nachtman,138 H. Ogul,138 Y. Onel,138 F. Ozok,138,xx A. Penzo,138 R. Rahmat,138 S. Sen,138 P. Tan,138 E. Tiras,138 J. Wetzel,138 K. Yi,138 I. Anderson,139 B. A. Barnett,139 B. Blumenfeld,139 S. Bolognesi,139 D. Fehling,139 A. V. Gritsan,139 P. Maksimovic,139 C. Martin,139 M. Swartz,139 M. Xiao,139 P. Baringer,140 A. Bean,140 G. Benelli,140 C. Bruner,140 J. Gray,140 R. P. Kenny III,140 D. Majumder,140 M. Malek,140 M. Murray,140 D. Noonan,140 S. Sanders,140 J. Sekaric,140 R. Stringer,140 Q. Wang,140 J. S. Wood,140 I. Chakaberia,141 A. Ivanov,141 K. Kaadze,141 S. Khalil,141 M. Makouski,141 Y. Maravin,141 L. K. Saini,141 N. Skhirtladze,141 I. Svintradze,141 J. Gronberg,142 D. Lange,142 F. Rebassoo,142 D. Wright,142 C. Anelli,143 A. Baden,143 A. Belloni,143 B. Calvert,143 S. C. Eno,143 J. A. Gomez,143 N. J. Hadley,143 S. Jabeen,143 R. G. Kellogg,143 T. Kolberg,143 Y. Lu,143 A. C. Mignerey,143 K. Pedro,143 Y. H. Shin,143 A. Skuja,143 M. B. Tonjes,143 S. C. Tonwar,143 A. Apyan,144 R. Barbieri,144 K. Bierwagen,144 W. Busza,144 I. A. Cali,144 L. Di Matteo,144 G. Gomez Ceballos,144 M. Goncharov,144 D. Gulhan,144 M. Klute,144 Y. S. Lai,144 Y.-J. Lee,144 A. Levin,144 P. D. Luckey,144 C. Paus,144 D. Ralph,144 C. Roland,144 G. Roland,144 G. S. F. Stephans,144 K. Sumorok,144 D. Velicanu,144 J. Veverka,144 B. Wyslouch,144 M. Yang,144 M. Zanetti,144 V. Zhukova,144 B. Dahmes,145 A. Gude,145 S. C. Kao,145 K. Klapoetke,145 Y. Kubota,145 J. Mans,145 S. Nourbakhsh,145 R. Rusack,145 A. Singovsky,145 N. Tambe,145 J. Turkewitz,145 J. G. Acosta,146 S. Oliveros,146 E. Avdeeva,147 K. Bloom,147 S. Bose,147 D. R. Claes,147 A. Dominguez,147 R. Gonzalez Suarez,147 J. Keller,147 D. Knowlton,147 I. Kravchenko,147 J. Lazo-Flores,147 F. Meier,147 F. Ratnikov,147 G. R. Snow,147 M. Zvada,147 J. Dolen,148 A. Godshalk,148 I. Iashvili,148 A. Kharchilava,148 A. Kumar,148 S. Rappoccio,148 G. Alverson,149 E. Barberis,149 D. Baumgartel,149 M. Chasco,149 A. Massironi,149 D. M. Morse,149 D. Nash,149 T. Orimoto,149 D. Trocino,149 R.-J. Wang,149 D. Wood,149 J. Zhang,149 K. A. Hahn,150 A. Kubik,150 N. Mucia,150 N. Odell,150 B. Pollack,150 A. Pozdnyakov,150 M. Schmitt,150 S. Stoynev,150 K. Sung,150 M. Trovato,150 M. Velasco,150 S. Won,150 A. Brinkerhoff,151 K. M. Chan,151 A. Drozdetskiy,151 M. Hildreth,151 C. Jessop,151 D. J. Karmgard,151 N. Kellams,151 K. Lannon,151 S. Lynch,151 N. Marinelli,151 Y. Musienko,151,ee T. Pearson,151 M. Planer,151 R. Ruchti,151 G. Smith,151 N. Valls,151 M. Wayne,151 M. Wolf,151 A. Woodard,151 L. Antonelli,152 J. Brinson,152 B. Bylsma,152 L. S. Durkin,152 S. Flowers,152 A. Hart,152 C. Hill,152 R. Hughes,152 K. Kotov,152 T. Y. Ling,152 W. Luo,152 D. Puigh,152 M. Rodenburg,152 B. L. Winer,152 H. Wolfe,152 H.W. Wulsin,152 O. Driga,153 P. Elmer,153 J. Hardenbrook,153 P. Hebda,153 S. A. Koay,153 P. Lujan,153 D. Marlow,153 T. Medvedeva,153 M. Mooney,153 J. Olsen,153 P. Piroué,153 X. Quan,153 H. Saka,153 D. Stickland,153,c C. Tully,153 J. S. Werner,153 A. Zuranski,153 E. Brownson,154 S. Malik,154 H. Mendez,154 J. E. Ramirez Vargas,154 V. E. Barnes,155 D. Benedetti,155 D. Bortoletto,155 L. Gutay,155 Z. Hu,155 M. K. Jha,155 M. Jones,155 K. Jung,155 M. Kress,155 N. Leonardo,155 D. H. Miller,155 N. Neumeister,155 F. Primavera,155 B. C. Radburn-Smith,155 X. Shi,155 I. Shipsey,155 D. Silvers,155 A. Svyatkovskiy,155 F. Wang,155 W. Xie,155 L. Xu,155 J. Zablocki,155 N. Parashar,156 J. Stupak,156 A. Adair,157 B. Akgun,157 K. M. Ecklund,157 F. J. M. Geurts,157 W. Li,157 B. Michlin,157 B. P. Padley,157 R. Redjimi,157 J. Roberts,157 J. Zabel,157 B. Betchart,158 A. Bodek,158 P. de Barbaro,158 R. Demina,158 Y. Eshaq,158 T. Ferbel,158 M. Galanti,158 A. Garcia-Bellido,158 PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-12 P. Goldenzweig,158 J. Han,158 A. Harel,158 O. Hindrichs,158 A. Khukhunaishvili,158 S. Korjenevski,158 G. Petrillo,158 M. Verzetti,158 D. Vishnevskiy,158 R. Ciesielski,159 L. Demortier,159 K. Goulianos,159 C. Mesropian,159 S. Arora,160 A. Barker,160 J. P. Chou,160 C. Contreras-Campana,160 E. Contreras-Campana,160 D. Duggan,160 D. Ferencek,160 Y. Gershtein,160 R. Gray,160 E. Halkiadakis,160 D. Hidas,160 E. Hughes,160 S. Kaplan,160 A. Lath,160 S. Panwalkar,160 M. Park,160 S. Salur,160 S. Schnetzer,160 D. Sheffield,160 S. Somalwar,160 R. Stone,160 S. Thomas,160 P. Thomassen,160 M. Walker,160 K. Rose,161 S. Spanier,161 A. York,161 O. Bouhali,162,ggg A. Castaneda Hernandez,162 M. Dalchenko,162 M. De Mattia,162 S. Dildick,162 R. Eusebi,162 W. Flanagan,162 J. Gilmore,162 T. Kamon,162,hhh V. Khotilovich,162 V. Krutelyov,162 R. Montalvo,162 I. Osipenkov,162 Y. Pakhotin,162 R. Patel,162 A. Perloff,162 J. Roe,162 A. Rose,162 A. Safonov,162 I. Suarez,162 A. Tatarinov,162 K. A. Ulmer,162 N. Akchurin,163 C. Cowden,163 J. Damgov,163 C. Dragoiu,163 P. R. Dudero,163 J. Faulkner,163 K. Kovitanggoon,163 S. Kunori,163 S.W. Lee,163 T. Libeiro,163 I. Volobouev,163 E. Appelt,164 A. G. Delannoy,164 S. Greene,164 A. Gurrola,164 W. Johns,164 C. Maguire,164 Y. Mao,164 A. Melo,164 M. Sharma,164 P. Sheldon,164 B. Snook,164 S. Tuo,164 J. Velkovska,164 M.W. Arenton,165 S. Boutle,165 B. Cox,165 B. Francis,165 J. Goodell,165 R. Hirosky,165 A. Ledovskoy,165 H. Li,165 C. Lin,165 C. Neu,165 E. Wolfe,165 J. Wood,165 C. Clarke,166 R. Harr,166 P. E. Karchin,166 C. Kottachchi Kankanamge Don,166 P. Lamichhane,166 J. Sturdy,166 D. A. Belknap,167 D. Carlsmith,167 M. Cepeda,167 S. Dasu,167 L. Dodd,167 S. Duric,167 E. Friis,167 R. Hall-Wilton,167 M. Herndon,167 A. Hervé,167 P. Klabbers,167 A. Lanaro,167 C. Lazaridis,167 A. Levine,167 R. Loveless,167 A. Mohapatra,167 I. Ojalvo,167 T. Perry,167 G. A. Pierro,167 G. Polese,167 I. Ross,167 T. Sarangi,167 A. Savin,167 W. H. Smith,167 D. Taylor,167 C. Vuosalo,167 and N. Woods167 (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 18University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split, Croatia 19University of Split, Faculty of Science, Split, Croatia 20Institute Rudjer Boskovic, Zagreb, Croatia 21University of Cyprus, Nicosia, Cyprus 22Charles University, Prague, Czech Republic 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 PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-13 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 and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece 41University of Athens, Athens, Greece 42University of Ioánnina, Ioánnina, Greece 43Wigner Research Centre for Physics, Budapest, Hungary 44Institute of Nuclear Research ATOMKI, Debrecen, Hungary 45University of Debrecen, Debrecen, Hungary 46National Institute of Science Education and Research, Bhubaneswar, India 47Panjab University, Chandigarh, India 48University of Delhi, Delhi, India 49Saha Institute of Nuclear Physics, Kolkata, India 50Bhabha Atomic Research Centre, Mumbai, India 51Tata Institute of Fundamental Research, Mumbai, India 52Indian Institute of Science Education and Research (IISER), Pune, India 53Institute for Research in Fundamental Sciences (IPM), Tehran, Iran 54University College Dublin, Dublin, Ireland 55aINFN Sezione di Bari, Bari, Italy 55bUniversità di Bari, Bari, Italy 55cPolitecnico di Bari, Bari, Italy 56aINFN Sezione di Bologna, Bologna, Italy 56bUniversità di Bologna, Bologna, Italy 57aINFN Sezione di Catania, Catania, Italy 57bUniversità di Catania, Catania, Italy 57cCSFNSM, Catania, Italy 58aINFN Sezione di Firenze, Firenze, Italy 58bUniversità di Firenze, Firenze, Italy 59INFN Laboratori Nazionali di Frascati, Frascati, Italy 60aINFN Sezione di Genova, Genova, Italy 60bUniversità di Genova, Genova, Italy 61aINFN Sezione di Milano-Bicocca, Milano, Italy 61bUniversità di Milano-Bicocca, Milano, Italy 62aINFN Sezione di Napoli, Napoli, Italy 62bUniversità di Napoli ‘Federico II’, Napoli, Italy 62cUniversità della Basilicata (Potenza), Napoli, Italy 62dUniversità G. Marconi (Roma), Napoli, Italy 63aINFN Sezione di Padova, Padova, Italy 63bUniversità di Padova, Padova, Italy 63cUniversità di Trento (Trento), Padova, Italy 64aINFN Sezione di Pavia, Pavia, Italy 64bUniversità di Pavia, Pavia, Italy 65aINFN Sezione di Perugia, Perugia, Italy 65bUniversità di Perugia, Perugia, Italy 66aINFN Sezione di Pisa, Pisa, Italy 66bUniversità di Pisa, Pisa, Italy 66cScuola Normale Superiore di Pisa, Pisa, Italy 67aINFN Sezione di Roma, Roma, Italy 67bUniversità di Roma, Roma, Italy 68aINFN Sezione di Torino, Torino, Italy 68bUniversità di Torino, Torino, Italy 68cUniversità del Piemonte Orientale (Novara), Torino, Italy 69aINFN Sezione di Trieste, Trieste, Italy 69bUniversità di Trieste, Trieste, Italy PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-14 70Kangwon National University, Chunchon, Korea 71Kyungpook National University, Daegu, Korea 72Chonbuk National University, Jeonju, Korea 73Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea 74Korea University, Seoul, Korea 75Seoul National University, Seoul, Korea 76University of Seoul, Seoul, Korea 77Sungkyunkwan University, Suwon, Korea 78Vilnius University, Vilnius, Lithuania 79National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia 80Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico 81Universidad Iberoamericana, Mexico City, Mexico 82Benemerita Universidad Autonoma de Puebla, Puebla, Mexico 83Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico 84University of Auckland, Auckland, New Zealand 85University of Canterbury, Christchurch, New Zealand 86National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan 87National Centre for Nuclear Research, Swierk, Poland 88Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland 89Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal 90Joint Institute for Nuclear Research, Dubna, Russia 91Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia 92Institute for Nuclear Research, Moscow, Russia 93Institute for Theoretical and Experimental Physics, Moscow, Russia 94P.N. Lebedev Physical Institute, Moscow, Russia 95Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia 96State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia 97University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia 98Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain 99Universidad Autónoma de Madrid, Madrid, Spain 100Universidad de Oviedo, Oviedo, Spain 101Instituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain 102CERN, European Organization for Nuclear Research, Geneva, Switzerland 103Paul Scherrer Institut, Villigen, Switzerland 104Institute for Particle Physics, ETH Zurich, Zurich, Switzerland 105Universität Zürich, Zurich, Switzerland 106National Central University, Chung-Li, Taiwan 107National Taiwan University (NTU), Taipei, Taiwan 108Chulalongkorn University, Faculty of Science, Department of Physics, Bangkok, Thailand 109Cukurova University, Adana, Turkey 110Middle East Technical University, Physics Department, Ankara, Turkey 111Bogazici University, Istanbul, Turkey 112Istanbul Technical University, Istanbul, Turkey 113National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine 114University of Bristol, Bristol, United Kingdom 115Rutherford Appleton Laboratory, Didcot, United Kingdom 116Imperial College, London, United Kingdom 117Brunel University, Uxbridge, United Kingdom 118Baylor University, Waco, USA 119The University of Alabama, Tuscaloosa, USA 120Boston University, Boston, USA 121Brown University, Providence, USA 122University of California, Davis, Davis, USA 123University of California, Los Angeles, USA 124University of California, Riverside, Riverside, USA 125University of California, San Diego, La Jolla, USA 126University of California, Santa Barbara, Santa Barbara, USA 127California Institute of Technology, Pasadena, USA 128Carnegie Mellon University, Pittsburgh, USA 129University of Colorado at Boulder, Boulder, USA PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-15 130Cornell University, Ithaca, USA 131Fairfield University, Fairfield, USA 132Fermi National Accelerator Laboratory, Batavia, USA 133University of Florida, Gainesville, USA 134Florida International University, Miami, USA 135Florida State University, Tallahassee, USA 136Florida Institute of Technology, Melbourne, USA 137University of Illinois at Chicago (UIC), Chicago, USA 138The University of Iowa, Iowa City, USA 139Johns Hopkins University, Baltimore, USA 140The University of Kansas, Lawrence, USA 141Kansas State University, Manhattan, USA 142Lawrence Livermore National Laboratory, Livermore, USA 143University of Maryland, College Park, USA 144Massachusetts Institute of Technology, Cambridge, USA 145University of Minnesota, Minneapolis, USA 146University of Mississippi, Oxford, USA 147University of Nebraska-Lincoln, Lincoln, USA 148State University of New York at Buffalo, Buffalo, USA 149Northeastern University, Boston, USA 150Northwestern University, Evanston, USA 151University of Notre Dame, Notre Dame, USA 152The Ohio State University, Columbus, USA 153Princeton University, Princeton, USA 154University of Puerto Rico, Mayaguez, USA 155Purdue University, West Lafayette, USA 156Purdue University Calumet, Hammond, USA 157Rice University, Houston, USA 158University of Rochester, Rochester, USA 159The Rockefeller University, New York, USA 160Rutgers, The State University of New Jersey, Piscataway, USA 161University of Tennessee, Knoxville, USA 162Texas A&M University, College Station, USA 163Texas Tech University, Lubbock, USA 164Vanderbilt University, Nashville, USA 165University of Virginia, Charlottesville, USA 166Wayne State University, Detroit, USA 167University of Wisconsin, Madison, USA aDeceased. bAlso at Vienna University of Technology, Vienna, Austria. cAlso at CERN, European Organization for Nuclear Research, Geneva, Switzerland. dAlso at Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France. eAlso at National Institute of Chemical Physics and Biophysics, Tallinn, Estonia. fAlso at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia. gAlso at Universidade Estadual de Campinas, Campinas, Brazil. hAlso at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France. iAlso at Université Libre de Bruxelles, Bruxelles, Belgium. jAlso at Joint Institute for Nuclear Research, Dubna, Russia. kAlso at Suez University, Suez, Egypt. lAlso at Cairo University, Cairo, Egypt. mAlso at Fayoum University, El-Fayoum, Egypt. nAlso at British University in Egypt, Cairo, Egypt. oAlso at Ain Shams University, Cairo, Egypt. pAlso at Université de Haute Alsace, Mulhouse, France. qAlso at Brandenburg University of Technology, Cottbus, Germany. rAlso at Institute of Nuclear Research ATOMKI, Debrecen, Hungary. sAlso at Eötvös Loránd University, Budapest, Hungary. tAlso at University of Debrecen, Debrecen, Hungary. PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-16 uAlso at University of Visva-Bharati, Santiniketan, India. vAlso at King Abdulaziz University, Jeddah, Saudi Arabia. wAlso at University of Ruhuna, Matara, Sri Lanka. xAlso at Isfahan University of Technology, Isfahan, Iran. yAlso at University of Tehran, Department of Engineering Science, Tehran, Iran. zAlso at Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran. aaAlso at Università degli Studi di Siena, Siena, Italy. bbAlso at Centre National de la Recherche Scientifique (CNRS)-IN2P3, Paris, France. ccAlso at Purdue University, West Lafayette, USA. ddAlso at International Islamic University of Malaysia, Kuala Lumpur, Malaysia. eeAlso at Institute for Nuclear Research, Moscow, Russia. ffAlso at St. Petersburg State Polytechnical University, St. Petersburg, Russia. ggAlso at INFN Sezione di Padova, Università di Padova, Università di Trento (Trento), Padova, Italy. hhAlso at Faculty of Physics, University of Belgrade, Belgrade, Serbia. iiAlso at Facoltà Ingegneria, Università di Roma, Roma, Italy. jjAlso at Scuola Normale e Sezione dell’INFN, Pisa, Italy. kkAlso at University of Athens, Athens, Greece. llAlso at Paul Scherrer Institut, Villigen, Switzerland. mmAlso at Institute for Theoretical and Experimental Physics, Moscow, Russia. nnAlso at Albert Einstein Center for Fundamental Physics, Bern, Switzerland. ooAlso at Gaziosmanpasa University, Tokat, Turkey. ppAlso at Adiyaman University, Adiyaman, Turkey. qqAlso at Mersin University, Mersin, Turkey. rrAlso at Cag University, Mersin, Turkey. ssAlso at Piri Reis University, Istanbul, Turkey. ttAlso at Anadolu University, Eskisehir, Turkey. uuAlso at Ozyegin University, Istanbul, Turkey. vvAlso at Izmir Institute of Technology, Izmir, Turkey. wwAlso at Necmettin Erbakan University, Konya, Turkey. xxAlso at Mimar Sinan University, Istanbul, Istanbul, Turkey. yyAlso at Marmara University, Istanbul, Turkey. zzAlso at Kafkas University, Kars, Turkey. aaaAlso at Yildiz Technical University, Istanbul, Turkey. bbbAlso at Rutherford Appleton Laboratory, Didcot, United Kingdom. cccAlso at School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom. dddAlso at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia. eeeAlso at Argonne National Laboratory, Argonne, USA. fffAlso at Erzincan University, Erzincan, Turkey. gggAlso at Texas A&M University at Qatar, Doha, Qatar. hhhAlso at Kyungpook National University, Daegu, Korea. PRL 115, 012301 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 3 JULY 2015 012301-17