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Published for SISSA by Springer

Received: March 21, 2013

Revised: June 26, 2013

Accepted: July 5, 2013

Published: July 29, 2013

Search for microscopic black holes in pp collisions at√
s = 8TeV

The CMS collaboration

E-mail: cms-publication-committee-chair@cern.ch

Abstract: A search for microscopic black holes and string balls is presented, based on a

data sample of pp collisions at
√
s = 8 TeV recorded by the CMS experiment at the Large

Hadron Collider and corresponding to an integrated luminosity of 12 fb−1. No excess of

events with energetic multiparticle final states, typical of black hole production or of similar

new physics processes, is observed. Given the agreement of the observations with the

expected standard model background, which is dominated by QCD multijet production,

95% confidence level limits are set on the production of semiclassical or quantum black

holes, or of string balls, corresponding to the exclusions of masses below 4.3 to 6.2 TeV,

depending on model assumptions. In addition, model-independent limits are set on new

physics processes resulting in energetic multiparticle final states.

Keywords: Hadron-Hadron Scattering

ArXiv ePrint: 1303.5338

Open Access, Copyright CERN,

for the benefit of the CMS collaboration

doi:10.1007/JHEP07(2013)178

mailto:cms-publication-committee-chair@cern.ch
http://arxiv.org/abs/1303.5338
http://dx.doi.org/10.1007/JHEP07(2013)178


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Contents

1 Introduction 1

2 The CMS detector 2

3 Event reconstruction and Monte Carlo samples 3

4 Analysis method 4

5 Results 5

6 Summary 11

The CMS collaboration 17

1 Introduction

Theoretical models with low-scale quantum gravity aim to account for the origin of the large

difference between the electroweak scale (∼0.1 TeV) and the Planck scale (MPl ∼ 1016 TeV),

known as the hierarchy problem of the standard model (SM) of particle physics. One of

the predictions of such scenarios is the possibility of producing microscopic black holes or

their quantum precursors in proton-proton collisions at the CERN Large Hadron Collider

(LHC) [1, 2].

The basis of this analysis is the theoretical model proposed by Arkani-Hamed, Di-

mopoulos, and Dvali (ADD) [3, 4]. This model attempts to solve the hierarchy problem

by introducing n large, flat, extra spatial dimensions, compactified on an n-dimensional

torus or a sphere. By opening the multidimensional space only to the gravitational interac-

tion, the fundamental Planck scale in 4 + n dimensions, MD, is lowered to the electroweak

symmetry breaking scale, such that Mn+2
D ∝ M2

PlR
−n where R is the radius of the extra

dimensions. The reduction in MD is accomplished without affecting tight constraints com-

ing from precision measurements of properties of other types of fundamental interactions.

The enhanced gravity in multidimensional space allows the formation of microscopic black

holes. Production of black holes is also possible in the Randall-Sundrum (RS) model [5–7]

and in models with unparticles [8, 9]. In the former case, the hierarchy problem is addressed

by adding a single compact spatial dimension with radius comparable to the Planck length

and with the metric of the 5-dimensional space-time being exponentially “warped” in the

direction of this extra dimension (the anti-deSitter space-time).

We present an extension of previous searches for microscopic semiclassical black

holes [1, 2], quantum black holes [7, 10], and string balls [11] conducted by the Compact

Muon Solenoid (CMS) Collaboration at the CERN LHC [12, 13]. The analysis utilizes

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a data sample corresponding to an integrated luminosity of 12.1 ± 0.5 fb−1, collected by

the CMS detector in pp collisions at a centre-of-mass energy of 8 TeV. These data were

recorded in the 2012 running period of the LHC. The 14% increase in the energy of the

machine relative to the 2011 dataset would result in a larger production cross section for

black holes and other new physics with energetic multiparticle final states. This allows the

current search to penetrate a previously unexplored regime. Searches for black holes have

also been performed by the CMS collaboration in the dijet channel [14] and by the ATLAS

Collaboration [15–17].

A characteristic signature of evaporating semiclassical black holes or string balls is

a large number of energetic final-state particles of various types, while quantum black

holes typically decay into a few energetic partons. Further details of the analysis method

and the underlying models can be found in earlier publications [12, 13]. The results are

presented in terms of a set of benchmark scenarios and are also interpreted in terms of

model-independent limits on the production cross section for a new physics phenomenon

multiplied by the branching fraction of its decay into a multiparticle final state.

2 The CMS detector

A detailed description of the CMS detector can be found elsewhere [18]. The central

feature of CMS is a 3.8 T superconducting solenoid of 6 m internal diameter that encloses a

silicon pixel and strip tracker, a lead-tungstate crystal electromagnetic calorimeter (ECAL),

and a brass/scintillator hadron calorimeter (HCAL). Muons are detected in gas-ionisation

detectors embedded in the steel flux return yoke of the magnet.

The ECAL is a finely segmented calorimeter that uses crystals situated in a barrel

region (|η| < 1.48) and two endcaps that extend to |η| = 3.0. Here pseudorapidity η is

defined as − ln[tan(θ/2)], where θ is the polar angle measured from the geometrical centre

of the detector with respect to the anticlockwise proton beam. The transverse dimensions of

the lead-tungstate crystals are ∆η×∆φ = 0.0174×0.0174, where φ is the azimuthal angle in

radians. The HCAL consists of interleaved brass plates and scintillator sheets that extend

to |η| = 3.0. The granularity of the HCAL towers is ∆η ×∆φ = 0.087× 0.087. Extensive

forward calorimetry complements the coverage provided by the barrel and endcap detectors.

The CMS trigger system is composed of two levels that are used to select potentially

interesting events. The first level (L1) trigger ensures negligible dead time and is responsible

for reducing the event rate to 100 kHz using the information from calorimeters and muon

detectors. After L1 triggering, the data are passed to the software-based high-level trigger,

which decreases the event rate to several hundred Hz for further storage.

The data used for this analysis are collected with a set of triggers based on the scalar

sum of the transverse energies (HT) of the calorimeter jets found by the trigger. The

thresholds for the HT triggers increased from 200 to 750 GeV, depending on the data-taking

period, to cope with the increasing instantaneous luminosity of the LHC. For the earlier

part of the data taking, we additionally utilized HT triggers that use jets reconstructed

using the particle-flow (PF) technique [19], which are corrected for the calorimeter response

to calculate the HT variable. The trigger is measured to be fully efficient for jet-enriched

collision events with HT above 1 TeV.

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3 Event reconstruction and Monte Carlo samples

The PF technique is used offline to reconstruct and identify charged and neutral particles

using information from all the subdetectors. Jets are reconstructed by clustering the PF

candidates using an infrared-safe anti-kT algorithm with a distance parameter of 0.5 [20–

22]. In the presence of multiple interactions per beam crossing (“pileup”), we identify the

primary vertex in the event as the one that has the highest
∑
p2T of tracks associated with it.

Only charged particles originating from the chosen primary vertex are clustered in the jets.

The estimated contribution from the neutral-particle energy from the pileup interactions is

subtracted on event-by-event basis [23], using FastJet algorithm [21], making the analysis

insensitive to the effects of the pileup. Additional selection criteria are applied to jets to

remove noise and non-collision background [23]. The PF jets are required to have transverse

momentum pT > 50 GeV and to lie within |η| < 2.6. The jet energy response is further

corrected using simulated events, as well as dijet and photon+jet collision events [23].

Muons are reconstructed using the PF algorithm by matching the tracks in the silicon

detector to segments in the muon chambers. Muons with |η| < 2.1 and pT > 50 GeV are

selected. Furthermore, they are required to have an impact parameter less than 0.2 cm

to suppress the cosmic ray muon background. In addition, the scalar sum of charged and

neutral particle transverse energies, calculated in a cone of ∆R =
√

(∆φ)2 + (∆η)2 = 0.3

around the muon direction, should not exceed 20% of the muon transverse momentum.

Electrons and photons depositing energy in the ECAL are identified via clustering

algorithms, taking into account the expected cluster shapes. Electron reconstruction uses

the PF algorithm [19, 24] and requires a silicon tracker trajectory to match an energy

cluster found in the ECAL. Photon reconstruction uses ECAL clusters and requires no

matching hits in the pixel tracker and an ECAL deposit with a shape consistent with that

expected for a photon. Both objects are required to have pT > 50 GeV and to lie within the

fiducial region of the barrel (|η| < 1.44) or endcap (1.56 < |η| < 2.4). The barrel-endcap

transition region is excluded because the reconstruction of electrons and photons in this

region is not optimal; energetic electrons and photons in this region nevertheless contribute

to the reconstruction of jets. The separation ∆R between the electron candidate and any

muon candidate that has more than 10 hits in the inner tracker is required to be greater

than 0.1. We also require the scalar sum of charged and neutral particle transverse energies,

calculated in a cone of ∆R = 0.3 around the electron direction, not to exceed 20% of the

electron transverse momentum. The ratio of HCAL to ECAL energy deposits is required

to be less than 5% for photon candidates. Photons must be isolated in the tracker, ECAL,

and HCAL. The scalar sums of transverse energy (momenta in the case of the tracker)

are calculated in a cone of ∆R = 0.4 around the candidate photon direction. These sums

should not exceed 2.0, 4.2, and 2.2 GeV for the tracker, ECAL, and HCAL, respectively.

The missing transverse energy (Emiss
T ) is defined as the absolute value of the vector

sum of transverse momenta of all the PF objects reconstructed in an event. The Emiss
T mea-

surement is corrected to account for the jet energy scale calibration [25].

The minimum separation between any two objects (jet, lepton, or photon) in the event

is required to be ∆R > 0.3.

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Simulated samples of semiclassical black hole events are produced using the parton-

level BlackMax v2.01 [26, 27] and Charybdis v1.0.3 [28, 29] Monte Carlo event genera-

tors. Various models are simulated, including black holes that are produced nonrotating or

rotating; those with or without mass and angular momentum loss at the time of formation;

and those with or without a stable or “boiling” (i.e., evaporating at a fixed Hawking tem-

perature) remnant. In addition, the modified BlackMax generator settings [30] are used

to simulate the production of string balls. Detailed descriptions of each model can be found

in refs. [12, 13]. All these signal samples are generated using the MSTW2008lo68cl [31] par-

ton distribution functions (PDF). Samples of quantum black holes are generated with the

qbh v1.03 parton-level generator [32, 33] using the CTEQ6L PDF set [34]. The parton-level

events produced by these generators are then used as input to the pythia v6.426 [35] parton

showering simulation and a fast parametric simulation of the CMS detector [36, 37]. The

fast simulation was validated with the full detector simulation, based on the Geant4 [38]

framework, for several benchmark points.

The small backgrounds from γ + jets, W/Z + jets (collectively referred to as V + jets

in what follows), and tt production are estimated from Monte Carlo simulations using the

MadGraph v5 [39] matrix element event generator interfaced with the pythia parton

showering simulation, followed by the full detector simulation using Geant4. These back-

ground samples are generated using the CTEQ6L PDF set. Other SM backgrounds are

negligible and therefore were not accounted for in the analysis.

4 Analysis method

The analysis strategy is identical to the one used in the previous analysis at
√
s = 7 TeV and

is described in detail in ref. [13]. The search for black holes and string balls is performed

using events with at least two jets and any number of photons and leptons. There is no

explicit requirement of missing transverse energy in the event.

The search for black holes is based on a search for a deviation from the SM background

predictions in the ST spectra observed in data. The ST variable is defined as the scalar sum

of transverse energies of all the final-state objects in the event (jets, leptons, and photons)

in excess of 50 GeV. If the Emiss
T in the event exceeds 50 GeV, its value is also added to

the ST variable. We then determine the multiplicity N of the objects in the final state

by counting all the objects in the events (excluding Emiss
T ) that enter the calculation of

ST [12, 13]. We analyse the data for various inclusive multiplicity bins, from N ≥ 2 to

N ≥ 10, and look for deviations from the SM background predictions in each of these bins.

We use object definitions and isolation requirements for leptons and photons as de-

scribed in section 3. While the isolation requirements are not explicitly used in the analysis

(as a non-isolated photon or lepton will be reconstructed as a jet and therefore does not

change the values of ST or N in the event), we keep this approach and disambiguate isolated

leptons and photons from jets in order to allow clearer interpretation of a signal should

one be observed. Indeed, if an excess in the data were observed, the relative fractions of

prompt leptons, photons, and jets in the events responsible for the excess could shed light

on the nature of the observed signal.

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The SM background is completely dominated by QCD multijet production and is

estimated directly from data using a method based on ST multiplicity invariance [12, 13, 40].

All other backgrounds are negligibly small in the ST range used in this analysis, as shown in

figure 1. The multijet background estimation method is based on the empirical observation

that the shape of the ST spectrum is approximately independent of N , so the shapes of the

ST spectrum for any number of objects can be estimated using a fit to the dijet data (N =

2). The dijet mass spectrum has been previously studied in dedicated analyses [14, 41], as

well as in the earlier searches for black holes at lower masses [12, 13] and is known not to

exhibit any signal-like features in the range of 1.8 < ST < 2.8 TeV, which is used to obtain

the background shape. The central value of the background shape and its uncertainty are

determined from the fit to several semi-empirical template functions [13], by taking the best

fit function as the central value and the envelope of the alternative fits as the measure of

systematic uncertainty in the background shape. The background shape is parameterized

with the function P0(1 + x)P1/xP2+P3 log(x), and the uncertainty envelope is defined with

two additional functions, P0/(P1 + P2x + x2)P3 and P0/(P1 + x)P2 . Here, Pi are the fit

parameters and x = ST/
√
s = ST/8 TeV. We also compare the fits to N = 2 data with fits

to N = 3 data as a measure of the ST potential non-invariance of multiplicity. This effect

is included in the total systematic uncertainty in the background prediction. Results of

the fit can be seen in figure 1.

The scaling of the background to higher multiplicities is performed by normalising the

background shape to data in each inclusive multiplicity bin in the control range (1.9 < ST <

2.3 TeV), where any significant signal contribution has been already ruled out by earlier

analyses [12, 13]. The lower boundary of the control region is chosen to be substantially

above the trigger and multiparticle (N × 50 GeV) turn-on regions.

The ST distributions for data, for predicted background, and for several semiclassical

and quantum black hole signal benchmarks are shown in figures 1–3 for a number of

exclusive and inclusive multiplicities. We do not plot the quantum black hole signal ST
distributions for inclusive multiplicities of five or more, as the search for quantum black

holes is not sensitive in higher inclusive multiplicity bins. No statistically significant excess

of events over the expected background is observed in any of these spectra.

5 Results

In the absence of an excess of data over the background prediction, we set limits on black

hole and string ball production rates. The following systematic uncertainties are taken into

account in the limit setting procedure.

The total uncertainty in the background includes the uncertainty due to the choice of

the fit function (including the uncertainties in the best-fit values of the parameters), the

statistics in the normalization region, the uncertainty due to the choice of fit range, and

the difference between the fits to N = 2 and N = 3 data as a measure of the potential non-

invariance of ST with jet multiplicity. The normalization uncertainty is derived from the

number of events in the normalization region in each jet multiplicity bin, and is negligible

compared to the shape uncertainty, except for the N ≥ 10 bin. The total uncertainty rises

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BH

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QBH
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ttbar

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BH

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BH

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T

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Figure 1. Distribution of the scalar sum of transverse energy, ST, for events with multiplicity:

(Left) N = 2 and (right) N ≥ 2 objects (photons, electrons, muons, or jets) in the final state.

Observed data are depicted as points with statistical error bars; the solid line with a shaded band

is the multijet background prediction from N = 2 fit and its systematic uncertainty. Coloured

histograms represent the γ+jets (orange), V +jets (red), and tt (green) backgrounds. Also shown are

the expected semiclassical black hole signals for three parameter sets of the BlackMax nonrotating

semiclassical black hole model, as well as a quantum black hole model. Here, Mmin
BH is the minimum

black hole mass, Mmin
QBH is the minimum quantum black hole mass, MD is the multidimensional

Planck scale, and n is the number of extra dimensions. The bottom panels in each plot show the pull

distribution (defined as (data− background)/σ(data− background)) based on combined statistical

and systematic uncertainty (dominated by the latter). Note that the systematic uncertainty is fully

correlated bin-to-bin. Also shown in the N = 2 plot, is the background optimization based on a

fit to N = 3 data (dotted line). The difference between the N = 2 and N = 3 background fits are

covered by the systematic uncertainty band used in the analysis.

with ST from 5% to as much as 200% at very high values of ST, where the background

extrapolation is unreliable, owing to insufficient data in the control regions. Typical values

of the background uncertainty are 5% at ST = 2 TeV, 18% at ST = 3 TeV, and 95% at

ST = 4 TeV. The possible violation of ST invariance with jet multiplicity can be gauged

from the bottom panes of figures 2 and 3 and does not show any trends with increasing

multiplicity. The effects of possible deviations from ST shape invariance are covered by the

above systematic uncertainties in the fit. The uncertainties in the signal include the 8%

uncertainty due to the jet energy scale, which is known to ≈ 2% [23]; a 6% uncertainty in

the signal acceptance due to the PDF choice, as determined using the prescribed PDF4LHC

recipe [42]; and the 4.4% uncertainty in the integrated luminosity [43]. As a result, the total

systematic uncertainty in the signal is calculated to be 10%. As the cross section for black

hole production is known only approximately and is highly model-dependent, no theoretical

uncertainty on the signal cross section is applied, as it is used merely as a benchmark.

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BH

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BH

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Figure 2. Distribution of the scalar sum of transverse energy, ST, for events with multiplicity: (Top

left) N ≥ 3, (top right) N ≥ 4, (bottom left) N ≥ 5, and (bottom right) N ≥ 6 objects (photons,

electrons, muons, or jets) in the final state. Observed data are depicted as points with statistical

error bars; the solid line with a shaded band is the multijet background prediction and its systematic

uncertainty. Also shown are the expected semiclassical black hole signals for three parameter sets

of the BlackMax nonrotating black hole model, as well as a quantum black hole signal of the

qbh model. Here, Mmin
BH is the minimum black hole mass, Mmin

QBH is the minimum quantum black

hole mass, MD is the multidimensional Planck scale, and n is the number of extra dimensions. The

bottom panels in each plot show the pull distribution (defined as (data − background)/σ(data −
background)) based on combined statistical and systematic uncertainty (dominated by the latter).

Note that the systematic uncertainty is fully correlated bin-to-bin.

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 (GeV)
T

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Figure 3. Distribution of the scalar sum of transverse energy, ST, for events with multiplicity: (Top

left) N ≥ 7, (top right) N ≥ 8, (bottom left) N ≥ 9, and (bottom right) N ≥ 10 objects (photons,

electrons, muons, or jets) in the final state. Observed data are depicted as points with statistical

error bars; the solid line with a shaded band is the multijet background prediction and its systematic

uncertainty. Also shown are the expected semiclassical black hole signals for three parameter sets

of the BlackMax nonrotating black hole model. Here, Mmin
BH is the minimum black hole mass, MD

is the multidimensional Planck scale, and n is the number of extra dimensions. The bottom panels

in each plot show the pull distribution (defined as (data − background)/σ(data − background))

based on combined statistical and systematic uncertainty (dominated by the latter). Note that the

systematic uncertainty is fully correlated bin-to-bin.

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Nonrotating

Rotating

Rotating (mass and angular momentum loss)

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n = 2

n = 4

n = 6

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Rotating
Nonrotating
Rotating (Yoshino-Rychkov loss)
Rotating, low multiplicity regime
Boiling remnant (Yoshino-Rychkov loss)
Stable remnant (Yoshino-Rychkov loss)

-1 = 8 TeV         L = 12.1 fbsCMS 

n = 2

 (TeV)DM
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Rotating
Nonrotating
Rotating (Yoshino-Rychkov loss)
Rotating, low multiplicity regime
Boiling remnant (Yoshino-Rychkov loss)
Stable remnant (Yoshino-Rychkov loss)

-1 = 8 TeV         L = 12.1 fbsCMS 

n = 4

 (TeV)DM
1.5 2 2.5 3 3.5 4 4.5 5

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Charybdis
Rotating
Nonrotating
Rotating (Yoshino-Rychkov loss)
Rotating, low multiplicity regime
Boiling remnant (Yoshino-Rychkov loss)
Stable remnant (Yoshino-Rychkov loss)

-1 = 8 TeV         L = 12.1 fbsCMS 

n = 6

Figure 4. The 95% CL lower limits on the semiclassical black hole mass derived from the upper

95% CL limits on cross section times branching fraction as a function of the fundamental Planck

scale MD, for various models. The areas below each curve are excluded by this search. Top left:

BlackMax black hole models without the stable remnant. Top right and bottom row: Charybdis

black hole models with or without the stable remnant. The number n of extra dimensions is labelled

accordingly.

For each set of model parameters, a test statistic S/
√
S +B, where S and B are

the numbers of signal and background events, is used to choose an optimal combination

of minimum ST and multiplicity. Limits are then set using a modified frequentist CLs

method [44, 45] with a Poisson likelihood of the observed number of events, given the

predicted background multiplied by the likelihoods of a set of measurements of the nuisance

parameters that are related to various systematic uncertainties, modelled by log-normal

distributions. Counting experiments are performed to set a 95% confidence level (CL) cross

section upper limit for each model used in this analysis. These limits can be interpreted in

terms of lower mass limits on black holes (figure 4) and string balls (figure 5) that range

from 4.3 to 6.2 TeV. The mass limit plots show lower mass limits for a number of benchmark

models as a function of the fundamental Planck scale, MD. The areas below each curve are

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σ Nmin Smin
T A N sig Ndata Nbkg σ95 〈σ95〉

(pb) (TeV) (pb) (pb)

BlackMax nonrotating BH with MD = 2.5 TeV, MBH = 4.5 TeV, and n = 4

0.15 3 3.2 0.74 1338 213 228± 111 1.3× 10−2 (1.3± 0.5)× 10−2

Charybdis nonrotating BH w/ boiling remnant; MD = 1.5 TeV, MBH = 4.5 TeV, and n = 6

0.23 4 3.0 0.76 2056 244 290± 99 1.0× 10−2 (1.3± 0.4)× 10−2

BlackMax rotating BH; MD = 2.0 TeV, MBH = 5.5 TeV, and n = 6

0.01 3 4.0 0.59 71.2 11 15.6+22.6
−15.6 1.9× 10−3 (2.0± 0.6)× 10−3

BlackMax rotating BH w/ mass loss; MD = 3.0 TeV, MBH = 5.0 TeV, and n = 4

1.4× 10−3 3 4.2 0.41 7.1 4 8.2+15.1
−8.2 1.4× 10−3 (1.5± 0.6)× 10−3

BlackMax SB; MD = 2.1 TeV, MSB = 4.0 TeV, MS = 1.7 TeV, and gS = 0.4

0.08 6 2.8 0.65 656 89 123± 29 3.6× 10−3 (5.0± 1.9)× 10−3

qbh quantum BH; MD = 2.0 TeV, MQBH = 4.0 TeV, and n = 4

1.50 2 2.8 0.67 1211 1168 1180± 274 5.0× 10−2 (5.0± 1.7)× 10−2

Table 1. Typical benchmark signal points for some of the models studied, corresponding leading-

order cross sections σ, optimal selections on the minimum decay multiplicity (N ≥ Nmin) and

minimum ST, as well as signal acceptance A, expected number of signal events N sig, number of

observed events in data Ndata, expected background Nbkg, and observed (σ95) and expected (〈σ95〉)
limits on the signal cross section at 95% confidence level. Also here, MD is the multidimensinal

Planck scale, MBH is the minimum black hole mass, MQBH is the minimum quantum black hole

mass, MSB is the minimum string ball mass, MS is the string scale, gS is the string coupling, and

n is the number of extra dimensions.

excluded by this analysis. We note that the benchmarks used for semiclassical black holes

are subject to large theoretical uncertainties and that the limits on the minimum black

hole mass numerically close to MD can not be treated as theoretically reliable.

For quantum black holes, which are characterized by a low final-state multiplicity N ,

the limits come from the N ≥ 2 samples. As the N ≥ 2 sample largely overlaps with

the sample used for the background shape determination (N = 2), we use the N ≥ 2

sample only to set limits on quantum black holes with masses above the range used for the

background fit, as can be seen in figure 1. Note that the n = 1 case for quantum black

holes corresponds to the RS black holes [7]. In this case, MD is the Planck scale times the

exponential factor coming from the warping of the anti-deSitter space, and is expected to

be of the order of the electroweak symmetry breaking scale, similar to the fundamental

Planck scale in the ADD model. The limits on the quantum black holes mass are shown

in figure 5. All other benchmark model limits set in this paper correspond to the ADD

model. The parameters used in simulations, the optimal combination of ST and multiplicity,

signal acceptance, number of expected signal, observed, and background events, as well as

observed and expected limits on the signal cross section are shown in table 1.

To extend the scope of this search, model-independent limits on the cross section times

the acceptance (A) are computed for high-ST inclusive final states for N ≥ 3, 4, 5, 6, 7, 8,

9, and 10, as a function of minimum ST (figures 6, 7). The intersection of these limits with

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 = 0.4

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 = 0.4
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 = 0.4

s
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s
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Theoretical Cross Section
 = 0.4

s
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 = 1.4 TeV, MDM

 = 0.4
s

 = 1.3 TeV, g
s

 = 1.6 TeV, MDM

 = 0.4
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 = 1.7 TeV, g
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 = 2.1 TeV, MDM

String Ball (BlackMax)

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 (TeV)DM
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6

6.2

Quantum Black Holes
 n = 1
 n = 2
 n = 3
 n = 4
 n = 5
 n = 6

-1 = 8 TeV         L = 12.1 fbsCMS 

Figure 5. (Left) The cross section upper limits at 95% CL from the counting experiments optimized

for various string ball parameter sets (solid lines) compared with predicted signal production cross

section (dashed lines) as a function of minimum string ball mass. Here, MD is the multidimensional

Planck scale, MS is the string scale, and gS = 0.4 is the string coupling. (Right) Lower quantum

black hole mass limits at 95% CL as functions of the fundamental Planck scale MD for various qbh

black hole models with a number n of extra dimensions from one to six.

theoretical predictions for the cross section within the fiducial and kinematic selections

used in this analysis could be used to constrain other models of new physics resulting in

energetic, multiparticle final states. These model-independent limits on the cross section

times acceptance are as low as 0.2 fb at 95% CL for minimum ST values above ∼4.5 TeV,

where no data events are observed.

6 Summary

A search for microscopic black holes and string balls at the LHC has been conducted, using

a data sample corresponding to an integrated luminosity of 12.1±0.5 fb−1 of
√
s = 8 TeV pp

collisions collected with the CMS detector at the LHC in 2012. Comparing the distributions

of the scalar sum of the transverse momenta of all the final-state objects in data events with

those from the estimated background, new model-independent limits are set that can be

used to constrain a wide variety of models. With this search, semiclassical and quantum

black holes with masses below 4.3–6.2 TeV are excluded in the context of a number of

benchmark models. Stringent limits on black hole precursors – string balls – are also set.

These limits extend significantly the previously probed regime of black hole production at

hadron colliders and represent the most restrictive exclusions on these objects to date.

Acknowledgments

We congratulate our colleagues in the CERN accelerator departments for the excellent per-

formance 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,

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Observed
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Observed
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Observed
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(Sσ

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 6≥Multiplicity N 

Observed
σ 1±Expected 

σ 2±Expected 

Figure 6. Model-independent 95% CL cross section times acceptance (A) upper limits for counting

experiments with ST > Smin
T as a function of Smin

T for events with multiplicity: (Top left) N ≥ 3,

(top right) N ≥ 4, (bottom left) N ≥ 5, and (bottom right) N ≥ 6. The blue solid (red dotted) lines

correspond to an observed (expected) limit for nominal signal acceptance uncertainty of 10%. The

green (dark) and yellow (light) bands represent one and two standard deviations from the expected

limits.

we gratefully acknowledge the computing centres 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 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 (Republic of Ko-

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Observed
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Observed
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-1 = 8 TeV         L = 12.1 fbsCMS 

 10≥Multiplicity N 

Observed
σ 1±Expected 

σ 2±Expected 

Figure 7. Model-independent 95% CL cross section times acceptance (A) upper limits for counting

experiments with ST > Smin
T as a function of Smin

T for events with multiplicity: (Top left) N ≥ 7,

(top right) N ≥ 8, (bottom left) N ≥ 9, and (bottom right) N ≥ 10. The blue solid (red dotted)

lines correspond to an observed (expected) limit for nominal signal acceptance uncertainty of 10%.

The green (dark) and yellow (light) bands represent one and two standard deviations from the

expected limits.

rea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI

(New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Ar-

menia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia);

MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC

(Taipei); ThEPCenter, IPST and NSTDA (Thailand); TUBITAK and TAEK (Turkey);

NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA).

Open Access. This article is distributed under the terms of the Creative Commons

Attribution License which permits any use, distribution and reproduction in any medium,

provided the original author(s) and source are credited.

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The CMS collaboration

Yerevan Physics Institute, Yerevan, Armenia

S. Chatrchyan, V. Khachatryan, A.M. Sirunyan, A. Tumasyan

Institut für Hochenergiephysik der OeAW, Wien, Austria

W. Adam, T. Bergauer, M. Dragicevic, J. Erö, C. Fabjan1, M. Friedl, R. Frühwirth1,

V.M. Ghete, N. Hörmann, J. Hrubec, M. Jeitler1, W. Kiesenhofer, V. Knünz,

M. Krammer1, I. Krätschmer, D. Liko, I. Mikulec, D. Rabady2, B. Rahbaran, C. Rohringer,

H. Rohringer, R. Schöfbeck, J. Strauss, A. Taurok, W. Treberer-treberspurg, W. Wal-

tenberger, C.-E. Wulz1

National Centre for Particle and High Energy Physics, Minsk, Belarus

V. Mossolov, N. Shumeiko, J. Suarez Gonzalez

Universiteit Antwerpen, Antwerpen, Belgium

S. Alderweireldt, M. Bansal, S. Bansal, T. Cornelis, E.A. De Wolf, X. Janssen, A. Knutsson,

S. Luyckx, L. Mucibello, S. Ochesanu, B. Roland, R. Rougny, H. Van Haevermaet, P. Van

Mechelen, N. Van Remortel, A. Van Spilbeeck

Vrije Universiteit Brussel, Brussel, Belgium

F. Blekman, S. Blyweert, J. D’Hondt, A. Kalogeropoulos, J. Keaveney, M. Maes, A. Ol-

brechts, S. Tavernier, W. Van Doninck, P. Van Mulders, G.P. Van Onsem, I. Villella

Université Libre de Bruxelles, Bruxelles, Belgium

B. Clerbaux, G. De Lentdecker, L. Favart, A.P.R. Gay, T. Hreus, A. Léonard, P.E. Marage,

A. Mohammadi, T. Reis, L. Thomas, C. Vander Velde, P. Vanlaer, J. Wang

Ghent University, Ghent, Belgium

V. Adler, K. Beernaert, L. Benucci, A. Cimmino, S. Costantini, S. Dildick, G. Garcia,

B. Klein, J. Lellouch, A. Marinov, J. Mccartin, A.A. Ocampo Rios, D. Ryckbosch,

M. Sigamani, N. Strobbe, F. Thyssen, M. Tytgat, S. Walsh, E. Yazgan, N. Zaganidis

Université Catholique de Louvain, Louvain-la-Neuve, Belgium

S. Basegmez, C. Beluffi3, G. Bruno, R. Castello, A. Caudron, L. Ceard, C. Delaere,

T. du Pree, D. Favart, L. Forthomme, A. Giammanco4, J. Hollar, V. Lemaitre, J. Liao,

O. Militaru, C. Nuttens, D. Pagano, A. Pin, K. Piotrzkowski, A. Popov5, M. Selvaggi,

J.M. Vizan Garcia

Université de Mons, Mons, Belgium

N. Beliy, T. Caebergs, E. Daubie, G.H. Hammad

Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil

G.A. Alves, M. Correa Martins Junior, T. Martins, M.E. Pol, M.H.G. Souza

Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil

W.L. Aldá Júnior, W. Carvalho, J. Chinellato6, A. Custódio, E.M. Da Costa, D. De Jesus

Damiao, C. De Oliveira Martins, S. Fonseca De Souza, H. Malbouisson, M. Malek, D. Matos

– 17 –



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Figueiredo, L. Mundim, H. Nogima, W.L. Prado Da Silva, A. Santoro, L. Soares Jorge,

A. Sznajder, E.J. Tonelli Manganote6, A. Vilela Pereira

Universidade Estadual Paulista a, Universidade Federal do ABC b, São Paulo,

Brazil

T.S. Anjosb, C.A. Bernardesb, F.A. Diasa,7, T.R. Fernandez Perez Tomeia, E.M. Gregoresb,

C. Laganaa, F. Marinhoa, P.G. Mercadanteb, S.F. Novaesa, Sandra S. Padulaa

Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria

V. Genchev2, P. Iaydjiev2, S. Piperov, M. Rodozov, G. Sultanov, M. Vutova

University of Sofia, Sofia, Bulgaria

A. Dimitrov, R. Hadjiiska, V. Kozhuharov, L. Litov, B. Pavlov, P. Petkov

Institute of High Energy Physics, Beijing, China

J.G. Bian, G.M. Chen, H.S. Chen, C.H. Jiang, D. Liang, S. Liang, X. Meng, J. Tao,

J. Wang, X. Wang, Z. Wang, H. Xiao, M. Xu

State Key Laboratory of Nuclear Physics and Technology, Peking University,

Beijing, China

C. Asawatangtrakuldee, Y. Ban, Y. Guo, W. Li, S. Liu, Y. Mao, S.J. Qian, H. Teng,

D. Wang, L. Zhang, W. Zou

Universidad de Los Andes, Bogota, Colombia

C. Avila, C.A. Carrillo Montoya, J.P. Gomez, B. Gomez Moreno, J.C. Sanabria

Technical University of Split, Split, Croatia

N. Godinovic, D. Lelas, R. Plestina8, D. Polic, I. Puljak

University of Split, Split, Croatia

Z. Antunovic, M. Kovac

Institute Rudjer Boskovic, Zagreb, Croatia

V. Brigljevic, S. Duric, K. Kadija, J. Luetic, D. Mekterovic, S. Morovic, L. Tikvica

University of Cyprus, Nicosia, Cyprus

A. Attikis, G. Mavromanolakis, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis

Charles University, Prague, Czech Republic

M. Finger, M. Finger Jr.

Academy of Scientific Research and Technology of the Arab Republic of Egypt,

Egyptian Network of High Energy Physics, Cairo, Egypt

Y. Assran9, A. Ellithi Kamel10, A.M. Kuotb Awad11, M.A. Mahmoud11, A. Radi12,13

National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

M. Kadastik, M. Müntel, M. Murumaa, M. Raidal, L. Rebane, A. Tiko

Department of Physics, University of Helsinki, Helsinki, Finland

P. Eerola, G. Fedi, M. Voutilainen

– 18 –



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Helsinki Institute of Physics, Helsinki, Finland

J. Härkönen, V. Karimäki, R. Kinnunen, M.J. Kortelainen, T. Lampén, K. Lassila-Perini,

S. Lehti, T. Lindén, P. Luukka, T. Mäenpää, T. Peltola, E. Tuominen, J. Tuominiemi,

E. Tuovinen, L. Wendland

Lappeenranta University of Technology, Lappeenranta, Finland

A. Korpela, T. Tuuva

DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France

M. Besancon, S. Choudhury, F. Couderc, M. Dejardin, D. Denegri, B. Fabbro, J.L. Faure,

F. Ferri, S. Ganjour, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, E. Locci,

J. Malcles, L. Millischer, A. Nayak, J. Rander, A. Rosowsky, M. Titov

Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau,

France

S. Baffioni, F. Beaudette, L. Benhabib, L. Bianchini, M. Bluj14, P. Busson, C. Charlot,

N. Daci, T. Dahms, M. Dalchenko, L. Dobrzynski, A. Florent, R. Granier de Cassagnac,

M. Haguenauer, P. Miné, C. Mironov, I.N. Naranjo, M. Nguyen, C. Ochando, P. Paganini,

D. Sabes, R. Salerno, Y. Sirois, C. Veelken, A. Zabi

Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Univer-

sité de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France

J.-L. Agram15, J. Andrea, D. Bloch, D. Bodin, J.-M. Brom, E.C. Chabert, C. Collard,

E. Conte15, F. Drouhin15, J.-C. Fontaine15, D. Gelé, U. Goerlach, C. Goetzmann, P. Juillot,

A.-C. Le Bihan, P. Van Hove

Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique

des Particules, CNRS/IN2P3, Villeurbanne, France

S. Gadrat

Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut

de Physique Nucléaire de Lyon, Villeurbanne, France

S. Beauceron, N. Beaupere, G. Boudoul, S. Brochet, J. Chasserat, R. Chierici, D. Contardo,

P. Depasse, H. El Mamouni, J. Fay, S. Gascon, M. Gouzevitch, B. Ille, T. Kurca,

M. Lethuillier, L. Mirabito, S. Perries, L. Sgandurra, V. Sordini, Y. Tschudi, M. Vander

Donckt, P. Verdier, S. Viret

Institute of High Energy Physics and Informatization, Tbilisi State University,

Tbilisi, Georgia

Z. Tsamalaidze16

RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany

C. Autermann, S. Beranek, B. Calpas, M. Edelhoff, L. Feld, N. Heracleous, O. Hindrichs,

K. Klein, J. Merz, A. Ostapchuk, A. Perieanu, F. Raupach, J. Sammet, S. Schael,

D. Sprenger, H. Weber, B. Wittmer, V. Zhukov5

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RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany

M. Ata, J. Caudron, E. Dietz-Laursonn, D. Duchardt, M. Erdmann, R. Fischer, A. Güth,

T. Hebbeker, C. Heidemann, K. Hoepfner, D. Klingebiel, P. Kreuzer, M. Merschmeyer,

A. Meyer, M. Olschewski, K. Padeken, P. Papacz, H. Pieta, H. Reithler, S.A. Schmitz,

L. Sonnenschein, J. Steggemann, D. Teyssier, S. Thüer, M. Weber

RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany

V. Cherepanov, Y. Erdogan, G. Flügge, H. Geenen, M. Geisler, W. Haj Ahmad, F. Hoehle,

B. Kargoll, T. Kress, Y. Kuessel, J. Lingemann2, A. Nowack, I.M. Nugent, L. Perchalla,

O. Pooth, A. Stahl

Deutsches Elektronen-Synchrotron, Hamburg, Germany

M. Aldaya Martin, I. Asin, N. Bartosik, J. Behr, W. Behrenhoff, U. Behrens, M. Bergholz17,

A. Bethani, K. Borras, A. Burgmeier, A. Cakir, L. Calligaris, A. Campbell, F. Costanza,

C. Diez Pardos, T. Dorland, G. Eckerlin, D. Eckstein, G. Flucke, A. Geiser, I. Glushkov,

P. Gunnellini, S. Habib, J. Hauk, G. Hellwig, H. Jung, M. Kasemann, P. Katsas, C. Klein-

wort, H. Kluge, M. Krämer, D. Krücker, E. Kuznetsova, W. Lange, J. Leonard, K. Lipka,

W. Lohmann17, B. Lutz, R. Mankel, I. Marfin, I.-A. Melzer-Pellmann, A.B. Meyer,

J. Mnich, A. Mussgiller, S. Naumann-Emme, O. Novgorodova, F. Nowak, J. Olzem,

H. Perrey, A. Petrukhin, D. Pitzl, R. Placakyte, A. Raspereza, P.M. Ribeiro Cipriano,

C. Riedl, E. Ron, J. Salfeld-Nebgen, R. Schmidt17, T. Schoerner-Sadenius, N. Sen, M. Stein,

R. Walsh, C. Wissing

University of Hamburg, Hamburg, Germany

V. Blobel, H. Enderle, J. Erfle, U. Gebbert, M. Görner, M. Gosselink, J. Haller, K. Heine,

R.S. Höing, G. Kaussen, H. Kirschenmann, R. Klanner, J. Lange, T. Peiffer, N. Pietsch,

D. Rathjens, C. Sander, H. Schettler, P. Schleper, E. Schlieckau, A. Schmidt, T. Schum,

M. Seidel, J. Sibille18, V. Sola, H. Stadie, G. Steinbrück, J. Thomsen, L. Vanelderen

Institut für Experimentelle Kernphysik, Karlsruhe, Germany

C. Barth, C. Baus, J. Berger, C. Böser, T. Chwalek, W. De Boer, A. Descroix, A. Dierlamm,

M. Feindt, M. Guthoff2, C. Hackstein, F. Hartmann2, T. Hauth2, M. Heinrich, H. Held,

K.H. Hoffmann, U. Husemann, I. Katkov5, J.R. Komaragiri, A. Kornmayer2, P. Lobelle

Pardo, D. Martschei, S. Mueller, Th. Müller, M. Niegel, A. Nürnberg, O. Oberst, J. Ott,

G. Quast, K. Rabbertz, F. Ratnikov, N. Ratnikova, S. Röcker, F.-P. Schilling, G. Schott,

H.J. Simonis, F.M. Stober, D. Troendle, R. Ulrich, J. Wagner-Kuhr, S. Wayand, T. Weiler,

M. Zeise

Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia

Paraskevi, Greece

G. Anagnostou, G. Daskalakis, T. Geralis, S. Kesisoglou, A. Kyriakis, D. Loukas,

A. Markou, C. Markou, E. Ntomari

University of Athens, Athens, Greece

L. Gouskos, T.J. Mertzimekis, A. Panagiotou, N. Saoulidou, E. Stiliaris

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University of Ioánnina, Ioánnina, Greece

X. Aslanoglou, I. Evangelou, G. Flouris, C. Foudas, P. Kokkas, N. Manthos, I. Papadopou-

los, E. Paradas

KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary

G. Bencze, C. Hajdu, P. Hidas, D. Horvath19, B. Radics, F. Sikler, V. Veszpremi,

G. Vesztergombi20, A.J. Zsigmond

Institute of Nuclear Research ATOMKI, Debrecen, Hungary

N. Beni, S. Czellar, J. Molnar, J. Palinkas, Z. Szillasi

University of Debrecen, Debrecen, Hungary

J. Karancsi, P. Raics, Z.L. Trocsanyi, B. Ujvari

Panjab University, Chandigarh, India

S.B. Beri, V. Bhatnagar, N. Dhingra, R. Gupta, M. Kaur, M.Z. Mehta, M. Mittal, N. Nishu,

L.K. Saini, A. Sharma, J.B. Singh

University of Delhi, Delhi, India

Ashok Kumar, Arun Kumar, S. Ahuja, A. Bhardwaj, B.C. Choudhary, S. Malhotra,

M. Naimuddin, K. Ranjan, P. Saxena, V. Sharma, R.K. Shivpuri

Saha Institute of Nuclear Physics, Kolkata, India

S. Banerjee, S. Bhattacharya, K. Chatterjee, S. Dutta, B. Gomber, Sa. Jain, Sh. Jain,

R. Khurana, A. Modak, S. Mukherjee, D. Roy, S. Sarkar, M. Sharan

Bhabha Atomic Research Centre, Mumbai, India

A. Abdulsalam, D. Dutta, S. Kailas, V. Kumar, A.K. Mohanty2, L.M. Pant, P. Shukla,

A. Topkar

Tata Institute of Fundamental Research - EHEP, Mumbai, India

T. Aziz, R.M. Chatterjee, S. Ganguly, S. Ghosh, M. Guchait21, A. Gurtu22, G. Kole, S. Ku-

mar, M. Maity23, G. Majumder, K. Mazumdar, G.B. Mohanty, B. Parida, K. Sudhakar,

N. Wickramage

Tata Institute of Fundamental Research - HECR, Mumbai, India

S. Banerjee, S. Dugad

Institute for Research in Fundamental Sciences (IPM), Tehran, Iran

H. Arfaei24, H. Bakhshiansohi, S.M. Etesami25, A. Fahim24, H. Hesari, A. Jafari,

M. Khakzad, M. Mohammadi Najafabadi, S. Paktinat Mehdiabadi, B. Safarzadeh26,

M. Zeinali

University College Dublin, Dublin, Ireland

M. Grunewald

INFN Sezione di Bari a, Università di Bari b, Politecnico di Bari c, Bari, Italy

M. Abbresciaa,b, L. Barbonea,b, C. Calabriaa,b, S.S. Chhibraa,b, A. Colaleoa, D. Creanzaa,c,

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G. Selvaggia,b, L. Silvestrisa, G. Singha,b, R. Vendittia,b, P. Verwilligena, G. Zitoa

INFN Sezione di Bologna a, Università di Bologna b, Bologna, Italy

G. Abbiendia, A.C. Benvenutia, D. Bonacorsia,b, S. Braibant-Giacomellia,b,

L. Brigliadoria,b, R. Campaninia,b, P. Capiluppia,b, A. Castroa,b, F.R. Cavalloa,

M. Cuffiania,b, G.M. Dallavallea, F. Fabbria, A. Fanfania,b, D. Fasanellaa,b, P. Giacomellia,

C. Grandia, L. Guiduccia,b, S. Marcellinia, G. Masettia,2, M. Meneghellia,b, A. Montanaria,

F.L. Navarriaa,b, F. Odoricia, A. Perrottaa, F. Primaveraa,b, A.M. Rossia,b, T. Rovellia,b,

G.P. Sirolia,b, N. Tosia,b, R. Travaglinia,b

INFN Sezione di Catania a, Università di Catania b, Catania, Italy

S. Albergoa,b, M. Chiorbolia,b, S. Costaa,b, R. Potenzaa,b, A. Tricomia,b, C. Tuvea,b

INFN Sezione di Firenze a, Università di Firenze b, Firenze, Italy

G. Barbaglia, V. Ciullia,b, C. Civininia, R. D’Alessandroa,b, E. Focardia,b, S. Frosalia,b,

E. Galloa, S. Gonzia,b, V. Goria,b, P. Lenzia,b, M. Meschinia, S. Paolettia, G. Sguazzonia,

A. Tropianoa,b

INFN Laboratori Nazionali di Frascati, Frascati, Italy

L. Benussi, S. Bianco, F. Fabbri, D. Piccolo

INFN Sezione di Genova a, Università di Genova b, Genova, Italy

P. Fabbricatorea, R. Musenicha, S. Tosia,b

INFN Sezione di Milano-Bicocca a, Università di Milano-Bicocca b, Milano,

Italy

A. Benagliaa, F. De Guioa,b, L. Di Matteoa,b, S. Fiorendia,b, S. Gennaia,2, A. Ghezzia,b,

P. Govoni, M.T. Lucchini2, S. Malvezzia, R.A. Manzonia,b,2, A. Martellia,b,2,

A. Massironia,b, D. Menascea, L. Moronia, M. Paganonia,b, D. Pedrinia, S. Ragazzia,b,

N. Redaellia, T. Tabarelli de Fatisa,b

INFN Sezione di Napoli a, Università di Napoli ’Federico II’ b, Università della

Basilicata (Potenza) c, Università G. Marconi (Roma) d, Napoli, Italy

S. Buontempoa, N. Cavalloa,c, A. De Cosaa,b, O. Doganguna,b, F. Fabozzia,c,

A.O.M. Iorioa,b, L. Listaa, S. Meolaa,d,2, M. Merolaa, P. Paoluccia,2

INFN Sezione di Padova a, Università di Padova b, Università di

Trento (Trento) c, Padova, Italy

P. Azzia, N. Bacchettaa, M. Bellatoa, A. Brancaa,b, R. Carlina,b, T. Dorigoa, U. Dossellia,

M. Galantia,b,2, F. Gasparinia,b, P. Giubilatoa,b, A. Gozzelinoa, K. Kanishcheva,c,

S. Lacapraraa, I. Lazzizzeraa,c, M. Margonia,b, A.T. Meneguzzoa,b, M. Nespoloa,

J. Pazzinia,b, M. Pegoraroa, N. Pozzobona,b, P. Ronchesea,b, F. Simonettoa,b, E. Torassaa,

M. Tosia,b, A. Triossia, S. Vaninia,b, S. Venturaa, P. Zottoa,b, A. Zucchettaa,b, G. Zumerlea,b

INFN Sezione di Pavia a, Università di Pavia b, Pavia, Italy

M. Gabusia,b, S.P. Rattia,b, C. Riccardia,b, P. Vituloa,b

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INFN Sezione di Perugia a, Università di Perugia b, Perugia, Italy

M. Biasinia,b, G.M. Bileia, L. Fanòa,b, P. Laricciaa,b, G. Mantovania,b, M. Menichellia,

A. Nappia,b†, F. Romeoa,b, A. Sahaa, A. Santocchiaa,b, A. Spieziaa,b

INFN Sezione di Pisa a, Università di Pisa b, Scuola Normale Superiore di

Pisa c, Pisa, Italy

K. Androsova,27, P. Azzurria, G. Bagliesia, T. Boccalia, G. Broccoloa,c, R. Castaldia,

R.T. D’Agnoloa,c,2, R. Dell’Orsoa, F. Fioria,c, L. Foàa,c, A. Giassia, A. Kraana,

F. Ligabuea,c, T. Lomtadzea, L. Martinia,27, A. Messineoa,b, F. Pallaa, A. Rizzia,b,

A.T. Serbana, P. Spagnoloa, P. Squillaciotia, R. Tenchinia, G. Tonellia,b, A. Venturia,

P.G. Verdinia, C. Vernieria,c

INFN Sezione di Roma a, Università di Roma b, Roma, Italy

L. Baronea,b, F. Cavallaria, D. Del Rea,b, M. Diemoza, C. Fanellia,b, M. Grassia,b,2,

E. Longoa,b, F. Margarolia,b, P. Meridiania, F. Michelia,b, S. Nourbakhsha,b,

G. Organtinia,b, R. Paramattia, S. Rahatloua,b, L. Soffia,b

INFN Sezione di Torino a, Università di Torino b, Università del Piemonte

Orientale (Novara) c, Torino, Italy

N. Amapanea,b, R. Arcidiaconoa,c, S. Argiroa,b, M. Arneodoa,c, C. Biinoa, N. Cartigliaa,

S. Casassoa,b, M. Costaa,b, P. De Remigisa, N. Demariaa, C. Mariottia, S. Masellia,

E. Migliorea,b, V. Monacoa,b, M. Musicha, M.M. Obertinoa,c, N. Pastronea,

M. Pelliccionia,2, A. Potenzaa,b, A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, A. Solanoa,b,

A. Staianoa, U. Tamponia

INFN Sezione di Trieste a, Università di Trieste b, Trieste, Italy

S. Belfortea, V. Candelisea,b, M. Casarsaa, F. Cossuttia,2, G. Della Riccaa,b, B. Gobboa,

C. La Licataa,b, M. Maronea,b, D. Montaninoa,b, A. Penzoa, A. Schizzia,b, A. Zanettia

Kangwon National University, Chunchon, Korea

T.Y. Kim, S.K. Nam

Kyungpook National University, Daegu, Korea

S. Chang, D.H. Kim, G.N. Kim, J.E. Kim, D.J. Kong, Y.D. Oh, H. Park, D.C. Son

Chonnam National University, Institute for Universe and Elementary Particles,

Kwangju, Korea

J.Y. Kim, Zero J. Kim, S. Song

Korea University, Seoul, Korea

S. Choi, D. Gyun, B. Hong, M. Jo, H. Kim, T.J. Kim, K.S. Lee, S.K. Park, Y. Roh

University of Seoul, Seoul, Korea

M. Choi, J.H. Kim, C. Park, I.C. Park, S. Park, G. Ryu

Sungkyunkwan University, Suwon, Korea

Y. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, B. Lee, J. Lee, S. Lee, H. Seo, I. Yu

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Vilnius University, Vilnius, Lithuania

I. Grigelionis, A. Juodagalvis

Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico

H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-de La Cruz28, R. Lopez-Fernandez,

J. Mart́ınez-Ortega, A. Sanchez-Hernandez, L.M. Villasenor-Cendejas

Universidad Iberoamericana, Mexico City, Mexico

S. Carrillo Moreno, F. Vazquez Valencia

Benemerita Universidad Autonoma de Puebla, Puebla, Mexico

H.A. Salazar Ibarguen

Universidad Autónoma de San Luis Potośı, San Luis Potośı, Mexico

E. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos

University of Auckland, Auckland, New Zealand

D. Krofcheck

University of Canterbury, Christchurch, New Zealand

A.J. Bell, P.H. Butler, R. Doesburg, S. Reucroft, H. Silverwood

National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan

M. Ahmad, M.I. Asghar, J. Butt, H.R. Hoorani, S. Khalid, W.A. Khan, T. Khurshid,

S. Qazi, M.A. Shah, M. Shoaib

National Centre for Nuclear Research, Swierk, Poland

H. Bialkowska, B. Boimska, T. Frueboes, M. Górski, M. Kazana, K. Nawrocki,

K. Romanowska-Rybinska, M. Szleper, G. Wrochna, P. Zalewski

Institute of Experimental Physics, Faculty of Physics, University of Warsaw,

Warsaw, Poland

G. Brona, K. Bunkowski, M. Cwiok, W. Dominik, K. Doroba, A. Kalinowski, M. Konecki,

J. Krolikowski, M. Misiura, W. Wolszczak

Laboratório de Instrumentação e F́ısica Experimental de Part́ıculas, Lisboa,

Portugal

N. Almeida, P. Bargassa, A. David, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro,

J. Rodrigues Antunes, J. Seixas2, J. Varela, P. Vischia

Joint Institute for Nuclear Research, Dubna, Russia

I. Belotelov, M. Gavrilenko, I. Golutvin, I. Gorbunov, V. Karjavin, V. Konoplyanikov,

V. Korenkov, A. Lanev, A. Malakhov, V. Matveev, P. Moisenz, V. Palichik, V. Perelygin,

M. Savina, S. Shmatov, V. Smirnov, E. Tikhonenko, A. Zarubin

Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia

S. Evstyukhin, V. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko, V. Murzin, V. Oreshkin,

I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev, An. Vorobyev

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Institute for Nuclear Research, Moscow, Russia

Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov, N. Krasnikov,

A. Pashenkov, D. Tlisov, A. Toropin

Institute for Theoretical and Experimental Physics, Moscow, Russia

V. Epshteyn, M. Erofeeva, V. Gavrilov, N. Lychkovskaya, V. Popov, G. Safronov, S. Se-

menov, A. Spiridonov, V. Stolin, E. Vlasov, A. Zhokin

P.N. Lebedev Physical Institute, Moscow, Russia

V. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, G. Mesyats,

S.V. Rusakov, A. Vinogradov

Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University,

Moscow, Russia

A. Belyaev, E. Boos, V. Bunichev, M. Dubinin7, L. Dudko, A. Ershov, A. Gribushin,

V. Klyukhin, O. Kodolova, I. Lokhtin, A. Markina, S. Obraztsov, S. Petrushanko, V. Savrin

State Research Center of Russian Federation, Institute for High Energy

Physics, Protvino, Russia

I. Azhgirey, I. Bayshev, S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov,

V. Krychkine, V. Petrov, R. Ryutin, A. Sobol, L. Tourtchanovitch, S. Troshin, N. Tyurin,

A. Uzunian, A. Volkov

University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear

Sciences, Belgrade, Serbia

P. Adzic29, M. Ekmedzic, D. Krpic29, J. Milosevic

Centro de Investigaciones Energéticas Medioambientales y Tec-

nológicas (CIEMAT), Madrid, Spain

M. Aguilar-Benitez, J. Alcaraz Maestre, C. Battilana, E. Calvo, M. Cerrada, M. Chamizo

Llatas2, N. Colino, B. De La Cruz, A. Delgado Peris, D. Domı́nguez Vázquez, C. Fer-

nandez Bedoya, J.P. Fernández Ramos, A. Ferrando, J. Flix, M.C. Fouz, P. Garcia-Abia,

O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, G. Merino, E. Navarro De

Martino, J. Puerta Pelayo, A. Quintario Olmeda, I. Redondo, L. Romero, J. Santaolalla,

M.S. Soares, C. Willmott

Universidad Autónoma de Madrid, Madrid, Spain

C. Albajar, J.F. de Trocóniz

Universidad de Oviedo, Oviedo, Spain

H. Brun, J. Cuevas, J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, L. Lloret

Iglesias, J. Piedra Gomez

Instituto de F́ısica de Cantabria (IFCA), CSIC-Universidad de Cantabria,

Santander, Spain

J.A. Brochero Cifuentes, I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros,

M. Fernandez, G. Gomez, J. Gonzalez Sanchez, A. Graziano, C. Jorda, A. Lopez Virto,

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J. Marco, R. Marco, C. Martinez Rivero, F. Matorras, F.J. Munoz Sanchez, T. Rodrigo,

A.Y. Rodŕıguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, I. Vila, R. Vilar Cortabitarte

CERN, European Organization for Nuclear Research, Geneva, Switzerland

D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis, P. Baillon, A.H. Ball, D. Barney,

J. Bendavid, J.F. Benitez, C. Bernet8, G. Bianchi, P. Bloch, A. Bocci, A. Bonato, O. Bondu,

C. Botta, H. Breuker, T. Camporesi, G. Cerminara, T. Christiansen, J.A. Coarasa Perez,

S. Colafranceschi30, D. d’Enterria, A. Dabrowski, A. De Roeck, S. De Visscher, S. Di Guida,

M. Dobson, N. Dupont-Sagorin, A. Elliott-Peisert, J. Eugster, W. Funk, G. Georgiou,

M. Giffels, D. Gigi, K. Gill, D. Giordano, M. Girone, M. Giunta, F. Glege, R. Gomez-

Reino Garrido, S. Gowdy, R. Guida, J. Hammer, M. Hansen, P. Harris, C. Hartl, B. Hegner,

A. Hinzmann, V. Innocente, P. Janot, K. Kaadze, E. Karavakis, K. Kousouris, K. Krajczar,

P. Lecoq, Y.-J. Lee, C. Lourenço, N. Magini, M. Malberti, L. Malgeri, M. Mannelli,

L. Masetti, F. Meijers, S. Mersi, E. Meschi, R. Moser, M. Mulders, P. Musella, E. Nesvold,

L. Orsini, E. Palencia Cortezon, E. Perez, L. Perrozzi, A. Petrilli, A. Pfeiffer, M. Pierini,

M. Pimiä, D. Piparo, G. Polese, L. Quertenmont, A. Racz, W. Reece, G. Rolandi31,

C. Rovelli32, M. Rovere, H. Sakulin, F. Santanastasio, C. Schäfer, C. Schwick, I. Segoni,

S. Sekmen, A. Sharma, P. Siegrist, P. Silva, M. Simon, P. Sphicas33, D. Spiga, M. Stoye,

A. Tsirou, G.I. Veres20, J.R. Vlimant, H.K. Wöhri, S.D. Worm34, W.D. Zeuner

Paul Scherrer Institut, Villigen, Switzerland

W. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram,

H.C. Kaestli, S. König, D. Kotlinski, U. Langenegger, F. Meier, D. Renker, T. Rohe

Institute for Particle Physics, ETH Zurich, Zurich, Switzerland

F. Bachmair, L. Bäni, P. Bortignon, M.A. Buchmann, B. Casal, N. Chanon, A. Deisher,

G. Dissertori, M. Dittmar, M. Donegà, M. Dünser, P. Eller, C. Grab, D. Hits, P. Lecomte,

W. Lustermann, A.C. Marini, P. Martinez Ruiz del Arbol, N. Mohr, F. Moortgat,

C. Nägeli35, P. Nef, F. Nessi-Tedaldi, F. Pandolfi, L. Pape, F. Pauss, M. Peruzzi,

F.J. Ronga, M. Rossini, L. Sala, A.K. Sanchez, A. Starodumov36, B. Stieger, M. Takahashi,

L. Tauscher†, A. Thea, K. Theofilatos, D. Treille, C. Urscheler, R. Wallny, H.A. Weber

Universität Zürich, Zurich, Switzerland

C. Amsler37, V. Chiochia, C. Favaro, M. Ivova Rikova, B. Kilminster, B. Millan Mejias,

P. Otiougova, P. Robmann, H. Snoek, S. Taroni, S. Tupputi, M. Verzetti

National Central University, Chung-Li, Taiwan

M. Cardaci, K.H. Chen, C. Ferro, C.M. Kuo, S.W. Li, W. Lin, Y.J. Lu, R. Volpe, S.S. Yu

National Taiwan University (NTU), Taipei, Taiwan

P. Bartalini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, C. Dietz,

U. Grundler, W.-S. Hou, Y. Hsiung, K.Y. Kao, Y.J. Lei, R.-S. Lu, D. Majumder,

E. Petrakou, X. Shi, J.G. Shiu, Y.M. Tzeng, M. Wang

Chulalongkorn University, Bangkok, Thailand

B. Asavapibhop, N. Suwonjandee

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Cukurova University, Adana, Turkey

A. Adiguzel, M.N. Bakirci38, S. Cerci39, C. Dozen, I. Dumanoglu, E. Eskut, S. Gir-

gis, G. Gokbulut, E. Gurpinar, I. Hos, E.E. Kangal, A. Kayis Topaksu, G. Onengut,

K. Ozdemir, S. Ozturk40, A. Polatoz, K. Sogut41, D. Sunar Cerci39, B. Tali39, H. Topakli38,

M. Vergili

Middle East Technical University, Physics Department, Ankara, Turkey

I.V. Akin, T. Aliev, B. Bilin, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler,

G. Karapinar42, K. Ocalan, A. Ozpineci, M. Serin, R. Sever, U.E. Surat, M. Yalvac,

M. Zeyrek

Bogazici University, Istanbul, Turkey

E. Gülmez, B. Isildak43, M. Kaya44, O. Kaya44, S. Ozkorucuklu45, N. Sonmez46

Istanbul Technical University, Istanbul, Turkey

H. Bahtiyar47, E. Barlas, K. Cankocak, Y.O. Günaydin48, F.I. Vardarlı, M. Yücel

National Scientific Center, Kharkov Institute of Physics and Technology,

Kharkov, Ukraine

L. Levchuk, P. Sorokin

University of Bristol, Bristol, United Kingdom

J.J. Brooke, E. Clement, D. Cussans, H. Flacher, R. Frazier, J. Goldstein, M. Grimes,

G.P. Heath, H.F. Heath, L. Kreczko, S. Metson, D.M. Newbold34, K. Nirunpong, A. Poll,

S. Senkin, V.J. Smith, T. Williams

Rutherford Appleton Laboratory, Didcot, United Kingdom

L. Basso49, K.W. Bell, A. Belyaev49, C. Brew, R.M. Brown, D.J.A. Cockerill, J.A. Cough-

lan, K. Harder, S. Harper, J. Jackson, E. Olaiya, D. Petyt, B.C. Radburn-Smith,

C.H. Shepherd-Themistocleous, I.R. Tomalin, W.J. Womersley

Imperial College, London, United Kingdom

R. Bainbridge, O. Buchmuller, D. Burton, D. Colling, N. Cripps, M. Cutajar, P. Dauncey,

G. Davies, M. Della Negra, W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert, A. Guneratne

Bryer, G. Hall, Z. Hatherell, J. Hays, G. Iles, M. Jarvis, G. Karapostoli, M. Kenzie,

R. Lane, R. Lucas34, L. Lyons, A.-M. Magnan, J. Marrouche, B. Mathias, R. Nandi,

J. Nash, A. Nikitenko36, J. Pela, M. Pesaresi, K. Petridis, M. Pioppi50, D.M. Raymond,

S. Rogerson, A. Rose, C. Seez, P. Sharp†, A. Sparrow, A. Tapper, M. Vazquez Acosta,

T. Virdee, S. Wakefield, N. Wardle, T. Whyntie

Brunel University, Uxbridge, United Kingdom

M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, D. Leggat, D. Leslie,

W. Martin, I.D. Reid, P. Symonds, L. Teodorescu, M. Turner

Baylor University, Waco, USA

J. Dittmann, K. Hatakeyama, A. Kasmi, H. Liu, T. Scarborough

The University of Alabama, Tuscaloosa, USA

O. Charaf, S.I. Cooper, C. Henderson, P. Rumerio

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Boston University, Boston, USA

A. Avetisyan, T. Bose, C. Fantasia, A. Heister, P. Lawson, D. Lazic, J. Rohlf, D. Sperka,

J. St. John, L. Sulak

Brown University, Providence, USA

J. Alimena, S. Bhattacharya, G. Christopher, D. Cutts, Z. Demiragli, A. Ferapontov,

A. Garabedian, U. Heintz, G. Kukartsev, E. Laird, G. Landsberg, M. Luk, M. Narain,

M. Segala, T. Sinthuprasith, T. Speer

University of California, Davis, Davis, USA

R. Breedon, G. Breto, M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok,

J. Conway, R. Conway, P.T. Cox, R. Erbacher, M. Gardner, R. Houtz, W. Ko, A. Kopecky,

R. Lander, O. Mall, T. Miceli, R. Nelson, D. Pellett, F. Ricci-Tam, B. Rutherford,

M. Searle, J. Smith, M. Squires, M. Tripathi, S. Wilbur, R. Yohay

University of California, Los Angeles, USA

V. Andreev, D. Cline, R. Cousins, S. Erhan, P. Everaerts, C. Farrell, M. Felcini, J. Hauser,

M. Ignatenko, C. Jarvis, G. Rakness, P. Schlein†, E. Takasugi, P. Traczyk, V. Valuev,

M. Weber

University of California, Riverside, Riverside, USA

J. Babb, R. Clare, M.E. Dinardo, J. Ellison, J.W. Gary, F. Giordano2, G. Hanson, H. Liu,

O.R. Long, A. Luthra, H. Nguyen, S. Paramesvaran, J. Sturdy, S. Sumowidagdo, R. Wilken,

S. Wimpenny

University of California, San Diego, La Jolla, USA

W. Andrews, J.G. Branson, G.B. Cerati, S. Cittolin, D. Evans, A. Holzner, R. Kelley,

M. Lebourgeois, J. Letts, I. Macneill, B. Mangano, S. Padhi, C. Palmer, G. Petrucciani,

M. Pieri, M. Sani, V. Sharma, S. Simon, E. Sudano, M. Tadel, Y. Tu, A. Vartak,

S. Wasserbaech51, F. Würthwein, A. Yagil, J. Yoo

University of California, Santa Barbara, Santa Barbara, USA

D. Barge, R. Bellan, C. Campagnari, M. D’Alfonso, T. Danielson, K. Flowers, P. Geffert,

C. George, F. Golf, J. Incandela, C. Justus, P. Kalavase, D. Kovalskyi, V. Krutelyov,

S. Lowette, R. Magaña Villalba, N. Mccoll, V. Pavlunin, J. Ribnik, J. Richman, R. Rossin,

D. Stuart, W. To, C. West

California Institute of Technology, Pasadena, USA

A. Apresyan, A. Bornheim, J. Bunn, Y. Chen, E. Di Marco, J. Duarte, D. Kcira, Y. Ma,

A. Mott, H.B. Newman, C. Rogan, M. Spiropulu, V. Timciuc, J. Veverka, R. Wilkinson,

S. Xie, Y. Yang, R.Y. Zhu

Carnegie Mellon University, Pittsburgh, USA

V. Azzolini, A. Calamba, R. Carroll, T. Ferguson, Y. Iiyama, D.W. Jang, Y.F. Liu,

M. Paulini, J. Russ, H. Vogel, I. Vorobiev

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University of Colorado at Boulder, Boulder, USA

J.P. Cumalat, B.R. Drell, W.T. Ford, A. Gaz, E. Luiggi Lopez, U. Nauenberg, J.G. Smith,

K. Stenson, K.A. Ulmer, S.R. Wagner

Cornell University, Ithaca, USA

J. Alexander, A. Chatterjee, N. Eggert, L.K. Gibbons, W. Hopkins, A. Khukhunaishvili,

B. Kreis, N. Mirman, G. Nicolas Kaufman, J.R. Patterson, A. Ryd, E. Salvati, W. Sun,

W.D. Teo, J. Thom, J. Thompson, J. Tucker, Y. Weng, L. Winstrom, P. Wittich

Fairfield University, Fairfield, USA

D. Winn

Fermi National Accelerator Laboratory, Batavia, USA

S. Abdullin, M. Albrow, J. Anderson, G. Apollinari, L.A.T. Bauerdick, A. Beretvas,

J. Berryhill, P.C. Bhat, K. Burkett, J.N. Butler, V. Chetluru, H.W.K. Cheung, F. Chle-

bana, S. Cihangir, V.D. Elvira, I. Fisk, J. Freeman, Y. Gao, E. Gottschalk, L. Gray,

D. Green, O. Gutsche, R.M. Harris, J. Hirschauer, B. Hooberman, S. Jindariani, M. John-

son, U. Joshi, B. Klima, S. Kunori, S. Kwan, J. Linacre, D. Lincoln, R. Lipton, J. Lykken,

K. Maeshima, J.M. Marraffino, V.I. Martinez Outschoorn, S. Maruyama, D. Mason,

P. McBride, K. Mishra, S. Mrenna, Y. Musienko52, C. Newman-Holmes, V. O’Dell,

O. Prokofyev, E. Sexton-Kennedy, S. Sharma, W.J. Spalding, L. Spiegel, L. Taylor,

S. Tkaczyk, N.V. Tran, L. Uplegger, E.W. Vaandering, R. Vidal, J. Whitmore, W. Wu,

F. Yang, J.C. Yun

University of Florida, Gainesville, USA

D. Acosta, P. Avery, D. Bourilkov, M. Chen, T. Cheng, S. Das, M. De Gruttola, G.P. Di

Giovanni, D. Dobur, A. Drozdetskiy, R.D. Field, M. Fisher, Y. Fu, I.K. Furic, J. Hugon,

B. Kim, J. Konigsberg, A. Korytov, A. Kropivnitskaya, T. Kypreos, J.F. Low, K. Matchev,

P. Milenovic53, G. Mitselmakher, L. Muniz, R. Remington, A. Rinkevicius, N. Skhirtladze,

M. Snowball, J. Yelton, M. Zakaria

Florida International University, Miami, USA

V. Gaultney, S. Hewamanage, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez, J.L. Ro-

driguez

Florida State University, Tallahassee, USA

T. Adams, A. Askew, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyzer, J. Haas,

S. Hagopian, V. Hagopian, K.F. Johnson, H. Prosper, V. Veeraraghavan, M. Weinberg

Florida Institute of Technology, Melbourne, USA

M.M. Baarmand, B. Dorney, M. Hohlmann, H. Kalakhety, F. Yumiceva

University of Illinois at Chicago (UIC), Chicago, USA

M.R. Adams, L. Apanasevich, V.E. Bazterra, R.R. Betts, I. Bucinskaite, J. Callner,

R. Cavanaugh, O. Evdokimov, L. Gauthier, C.E. Gerber, D.J. Hofman, S. Khalatyan,

P. Kurt, F. Lacroix, D.H. Moon, C. O’Brien, C. Silkworth, D. Strom, P. Turner, N. Varelas

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The University of Iowa, Iowa City, USA

U. Akgun, E.A. Albayrak, B. Bilki54, W. Clarida, K. Dilsiz, F. Duru, S. Griffiths, J.-

P. Merlo, H. Mermerkaya55, A. Mestvirishvili, A. Moeller, J. Nachtman, C.R. Newsom,

H. Ogul, Y. Onel, F. Ozok47, S. Sen, P. Tan, E. Tiras, J. Wetzel, T. Yetkin56, K. Yi

Johns Hopkins University, Baltimore, USA

B.A. Barnett, B. Blumenfeld, S. Bolognesi, D. Fehling, G. Giurgiu, A.V. Gritsan, G. Hu,

P. Maksimovic, M. Swartz, A. Whitbeck

The University of Kansas, Lawrence, USA

P. Baringer, A. Bean, G. Benelli, R.P. Kenny III, M. Murray, D. Noonan, S. Sanders,

R. Stringer, J.S. Wood

Kansas State University, Manhattan, USA

A.F. Barfuss, I. Chakaberia, A. Ivanov, S. Khalil, M. Makouski, Y. Maravin, S. Shrestha,

I. Svintradze

Lawrence Livermore National Laboratory, Livermore, USA

J. Gronberg, D. Lange, F. Rebassoo, D. Wright

University of Maryland, College Park, USA

A. Baden, B. Calvert, S.C. Eno, J.A. Gomez, N.J. Hadley, R.G. Kellogg, T. Kolberg, Y. Lu,

M. Marionneau, A.C. Mignerey, K. Pedro, A. Peterman, A. Skuja, J. Temple, M.B. Tonjes,

S.C. Tonwar

Massachusetts Institute of Technology, Cambridge, USA

A. Apyan, G. Bauer, W. Busza, E. Butz, I.A. Cali, M. Chan, V. Dutta, G. Gomez Ceballos,

M. Goncharov, Y. Kim, M. Klute, Y.S. Lai, A. Levin, P.D. Luckey, T. Ma, S. Nahn,

C. Paus, D. Ralph, C. Roland, G. Roland, G.S.F. Stephans, F. Stöckli, K. Sumorok,

K. Sung, D. Velicanu, R. Wolf, B. Wyslouch, M. Yang, Y. Yilmaz, A.S. Yoon, M. Zanetti,

V. Zhukova

University of Minnesota, Minneapolis, USA

B. Dahmes, A. De Benedetti, G. Franzoni, A. Gude, J. Haupt, S.C. Kao, K. Klapoetke,

Y. Kubota, J. Mans, N. Pastika, R. Rusack, M. Sasseville, A. Singovsky, N. Tambe,

J. Turkewitz

University of Mississippi, Oxford, USA

L.M. Cremaldi, R. Kroeger, L. Perera, R. Rahmat, D.A. Sanders, D. Summers

University of Nebraska-Lincoln, Lincoln, USA

E. Avdeeva, K. Bloom, S. Bose, D.R. Claes, A. Dominguez, M. Eads, R. Gonzalez Suarez,

J. Keller, I. Kravchenko, J. Lazo-Flores, S. Malik, G.R. Snow

State University of New York at Buffalo, Buffalo, USA

J. Dolen, A. Godshalk, I. Iashvili, S. Jain, A. Kharchilava, A. Kumar, S. Rappoccio, Z. Wan

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Northeastern University, Boston, USA

G. Alverson, E. Barberis, D. Baumgartel, M. Chasco, J. Haley, D. Nash, T. Orimoto,

D. Trocino, D. Wood, J. Zhang

Northwestern University, Evanston, USA

A. Anastassov, K.A. Hahn, A. Kubik, L. Lusito, N. Mucia, N. Odell, B. Pollack, A. Pozd-

nyakov, M. Schmitt, S. Stoynev, M. Velasco, S. Won

University of Notre Dame, Notre Dame, USA

D. Berry, A. Brinkerhoff, K.M. Chan, M. Hildreth, C. Jessop, D.J. Karmgard, J. Kolb,

K. Lannon, W. Luo, S. Lynch, N. Marinelli, D.M. Morse, T. Pearson, M. Planer, R. Ruchti,

J. Slaunwhite, N. Valls, M. Wayne, M. Wolf

The Ohio State University, Columbus, USA

L. Antonelli, B. Bylsma, L.S. Durkin, C. Hill, R. Hughes, K. Kotov, T.Y. Ling, D. Puigh,

M. Rodenburg, G. Smith, C. Vuosalo, G. Williams, B.L. Winer, H. Wolfe

Princeton University, Princeton, USA

E. Berry, P. Elmer, V. Halyo, P. Hebda, J. Hegeman, A. Hunt, P. Jindal, S.A. Koay,

D. Lopes Pegna, P. Lujan, D. Marlow, T. Medvedeva, M. Mooney, J. Olsen, P. Piroué,

X. Quan, A. Raval, H. Saka, D. Stickland, C. Tully, J.S. Werner, S.C. Zenz, A. Zuranski

University of Puerto Rico, Mayaguez, USA

E. Brownson, A. Lopez, H. Mendez, J.E. Ramirez Vargas

Purdue University, West Lafayette, USA

E. Alagoz, D. Benedetti, G. Bolla, D. Bortoletto, M. De Mattia, A. Everett, Z. Hu,

M. Jones, K. Jung, O. Koybasi, M. Kress, N. Leonardo, V. Maroussov, P. Merkel,

D.H. Miller, N. Neumeister, I. Shipsey, D. Silvers, A. Svyatkovskiy, M. Vidal Marono,

F.W. Wang, L. Xu, H.D. Yoo, J. Zablocki, Y. Zheng

Purdue University Calumet, Hammond, USA

S. Guragain, N. Parashar

Rice University, Houston, USA

A. Adair, B. Akgun, K.M. Ecklund, F.J.M. Geurts, W. Li, B.P. Padley, R. Redjimi,

J. Roberts, J. Zabel

University of Rochester, Rochester, USA

B. Betchart, A. Bodek, R. Covarelli, P. de Barbaro, R. Demina, Y. Eshaq, T. Ferbel,

A. Garcia-Bellido, P. Goldenzweig, J. Han, A. Harel, D.C. Miner, G. Petrillo, D. Vish-

nevskiy, M. Zielinski

The Rockefeller University, New York, USA

A. Bhatti, R. Ciesielski, L. Demortier, K. Goulianos, G. Lungu, S. Malik, C. Mesropian

Rutgers, The State University of New Jersey, Piscataway, USA

S. Arora, A. Barker, J.P. Chou, C. Contreras-Campana, E. Contreras-Campana, D. Dug-

gan, D. Ferencek, Y. Gershtein, R. Gray, E. Halkiadakis, D. Hidas, A. Lath, S. Panwalkar,

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M. Park, R. Patel, V. Rekovic, J. Robles, K. Rose, S. Salur, S. Schnetzer, C. Seitz,

S. Somalwar, R. Stone, M. Walker

University of Tennessee, Knoxville, USA

G. Cerizza, M. Hollingsworth, S. Spanier, Z.C. Yang, A. York

Texas A&M University, College Station, USA

R. Eusebi, W. Flanagan, J. Gilmore, T. Kamon57, V. Khotilovich, R. Montalvo, I. Os-

ipenkov, Y. Pakhotin, A. Perloff, J. Roe, A. Safonov, T. Sakuma, I. Suarez, A. Tatarinov,

D. Toback

Texas Tech University, Lubbock, USA

N. Akchurin, J. Damgov, C. Dragoiu, P.R. Dudero, C. Jeong, K. Kovitanggoon, S.W. Lee,

T. Libeiro, I. Volobouev

Vanderbilt University, Nashville, USA

E. Appelt, A.G. Delannoy, S. Greene, A. Gurrola, W. Johns, C. Maguire, Y. Mao, A. Melo,

M. Sharma, P. Sheldon, B. Snook, S. Tuo, J. Velkovska

University of Virginia, Charlottesville, USA

M.W. Arenton, S. Boutle, B. Cox, B. Francis, J. Goodell, R. Hirosky, A. Ledovskoy, C. Lin,

C. Neu, J. Wood

Wayne State University, Detroit, USA

S. Gollapinni, R. Harr, P.E. Karchin, C. Kottachchi Kankanamge Don, P. Lamichhane,

A. Sakharov

University of Wisconsin, Madison, USA

M. Anderson, D.A. Belknap, L. Borrello, D. Carlsmith, M. Cepeda, S. Dasu, E. Friis,

K.S. Grogg, M. Grothe, R. Hall-Wilton, M. Herndon, A. Hervé, P. Klabbers, J. Klukas,

A. Lanaro, C. Lazaridis, R. Loveless, A. Mohapatra, M.U. Mozer, I. Ojalvo, G.A. Pierro,

I. Ross, A. Savin, W.H. Smith, J. Swanson

†: Deceased

1: Also at Vienna University of Technology, Vienna, Austria

2: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland

3: Also at Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de

Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France

4: Also at National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

5: Also at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University,

Moscow, Russia

6: Also at Universidade Estadual de Campinas, Campinas, Brazil

7: Also at California Institute of Technology, Pasadena, USA

8: Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France

9: Also at Suez Canal University, Suez, Egypt

10: Also at Cairo University, Cairo, Egypt

11: Also at Fayoum University, El-Fayoum, Egypt

12: Also at British University in Egypt, Cairo, Egypt

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13: Now at Ain Shams University, Cairo, Egypt

14: Also at National Centre for Nuclear Research, Swierk, Poland

15: Also at Université de Haute Alsace, Mulhouse, France

16: Also at Joint Institute for Nuclear Research, Dubna, Russia

17: Also at Brandenburg University of Technology, Cottbus, Germany

18: Also at The University of Kansas, Lawrence, USA

19: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary

20: Also at Eötvös Loránd University, Budapest, Hungary

21: Also at Tata Institute of Fundamental Research - HECR, Mumbai, India

22: Now at King Abdulaziz University, Jeddah, Saudi Arabia

23: Also at University of Visva-Bharati, Santiniketan, India

24: Also at Sharif University of Technology, Tehran, Iran

25: Also at Isfahan University of Technology, Isfahan, Iran

26: Also at Plasma Physics Research Center, Science and Research Branch, Islamic Azad

University, Tehran, Iran

27: Also at Università degli Studi di Siena, Siena, Italy

28: Also at Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Mexico

29: Also at Faculty of Physics, University of Belgrade, Belgrade, Serbia

30: Also at Facoltà Ingegneria, Università di Roma, Roma, Italy

31: Also at Scuola Normale e Sezione dell’INFN, Pisa, Italy

32: Also at INFN Sezione di Roma, Roma, Italy

33: Also at University of Athens, Athens, Greece

34: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom

35: Also at Paul Scherrer Institut, Villigen, Switzerland

36: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia

37: Also at Albert Einstein Center for Fundamental Physics, Bern, Switzerland

38: Also at Gaziosmanpasa University, Tokat, Turkey

39: Also at Adiyaman University, Adiyaman, Turkey

40: Also at The University of Iowa, Iowa City, USA

41: Also at Mersin University, Mersin, Turkey

42: Also at Izmir Institute of Technology, Izmir, Turkey

43: Also at Ozyegin University, Istanbul, Turkey

44: Also at Kafkas University, Kars, Turkey

45: Also at Suleyman Demirel University, Isparta, Turkey

46: Also at Ege University, Izmir, Turkey

47: Also at Mimar Sinan University, Istanbul, Istanbul, Turkey

48: Also at Kahramanmaras Sütcü Imam University, Kahramanmaras, Turkey

49: Also at School of Physics and Astronomy, University of Southampton, Southampton, United

Kingdom

50: Also at INFN Sezione di Perugia; Università di Perugia, Perugia, Italy

51: Also at Utah Valley University, Orem, USA

52: Also at Institute for Nuclear Research, Moscow, Russia

53: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences,

Belgrade, Serbia

54: Also at Argonne National Laboratory, Argonne, USA

55: Also at Erzincan University, Erzincan, Turkey

56: Also at Yildiz Technical University, Istanbul, Turkey

57: Also at Kyungpook National University, Daegu, Korea

– 33 –


	Introduction
	The CMS detector
	Event reconstruction and Monte Carlo samples
	Analysis method
	Results
	Summary
	The CMS collaboration