Search for fractionally charged particles in
pp collisions at
p
ffiffiffi
s
¼ 7 TeV
S. Chatrchyan et al.*(CMS Collaboration)
(Received 8 October 2012; published 21 May 2013)
A search is presented for free heavy long-lived fractionally charged particles produced in pp collisions at ffiffiffi
s p
¼ 7 TeV. The data sample was recorded by the CMS detector at the LHC and corresponds to an integrated luminosity of 5:0 fb1. Candidate fractionally charged particles are identified by selecting tracks with associated low charge measurements in the silicon tracking detector. Observations are found to be consistent with expectations for background processes. The results of the search are used to set upper limits on the cross section for pair production of fractionally charged, massive spin-1=2 particles that are neutral under SUð3ÞCand SUð2ÞL. We exclude at 95% confidence level such particles with electric charge2e=3
with masses below 310 GeV, and those with chargee=3 with masses below 140 GeV.
DOI:10.1103/PhysRevD.87.092008 PACS numbers: 12.60.i, 12.38.Qk, 13.85.Rm
I. INTRODUCTION
The reasons for expecting physics beyond the standard model to manifest itself in pp collisions at the Large Hadron Collider (LHC) are as compelling as ever. As suggested in Ref. [1], one example of physics beyond the standard model that may have eluded previous searches is a new particle with an electric charge less than that of the electron. Owing to their lower ionization energy loss, the trajectories of such fractionally charged particles may not pass typical track quality requirements and a dedicated analysis is required.
While fractionally charged particles are common in some theoretical scenarios (e.g., superstrings [2,3]), a variety of searches for these objects in bulk matter, cosmic rays and accelerator based experiments have reported null results [4]. Strong constraints on models with fractionally charged states come from astrophysics and cosmology [5]. These constraints, however, do not apply if the reheating temperature of the Universe after the last stage of inflation is much lower than the mass of the fractionally charged particle such that there is no thermal relic from freeze-out [6]. We search for such particles, using as a benchmark the scenario considered in [5], namely, a model with new, fractionally charged, massive spin-1=2 particles that are neutral under SUð3ÞC and SUð2ÞL and therefore couple
only to the photon and the Z. We denote such particles with fractional chargeqe, where e is the charge of the electron, as Lq, and assume they have a lifetime
suffi-ciently long such that they do not decay within the detector volume.
An interesting possibility is that these Lqcould also be
charged under a new asymptotically free gauge group
SUðNÞ with a confinement scale . This would make them a variant type of ‘‘quirk,’’ which are quarklike, natu-rally fractionally charged particles [7]. For & 100 eV, the confining string between the quirk-antiquirk pair would have a negligible impact on their trajectories over distances typical of collider-detector dimensions. Thus such quirks would have the same kinematic properties and experimental signature as the benchmark model considered in this paper. However, the existence of this string would cause eventual annihilation of any pairs formed in the early Universe resulting in a negligible relic abundance [6], thereby evad-ing the constraints cited by Ref. [5] irrespective of cosmo-logical history.
We search for Lq, Lqparticles in a sample of tracks with a muonlike signature. We identify fractionally charged particle candidates by their anomalously low ionization energy loss in the inner tracker. This study complements Compact Muon Solenoid (CMS) searches for heavy stable charged particles with anomalously high ionization energy loss [8,9].
II. SIGNAL SIMULATION
Pair production of LqLq at the LHC proceeds via a
modified Drell-Yan mechanism with weak isospin t3L¼ 0, which has Lq-Z axial coupling gA¼ 0 and vector
cou-pling gV¼ 2qsin2W. We have performed Monte Carlo
simulations of this signal using PYTHIAv6.422 [10], with q¼ 1=3, 2=3, and 1, and with masses of 100, 200, 300, 400, 500, and 600 GeV. The cross sections are calculated to leading order with the CTEQ6L1 parton distribution func-tions. The detector response is modeled with a simulation based onGEANT4[11].
III. DETECTOR AND DATA SAMPLE The central feature of the CMS apparatus [12] is a superconducting solenoid of 6 m internal diameter, provid-ing a magnetic field of 3.8 T. Within the field volume are a
*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 attridistri-bution to the author(s) and the published article’s title, journal citation, and DOI.
silicon pixel and strip tracker, a lead-tungstate crystal electromagnetic calorimeter, and a brass/scintillator had-ron calorimeter. Muons are measured in gas-ionization detectors embedded in the steel return yoke. Extensive forward calorimetry complements the coverage provided by the barrel and endcap detectors. Of particular impor-tance to this search is the inner tracker [13], which consists of 1440 silicon pixel and 15 148 silicon strip detector modules. The inner tracker records 16 measurements on average per track.
The analysis is performed on the pp collision data sample recorded by the CMS detector at pffiffiffis¼ 7 TeV in 2011, corresponding to an integrated luminosity of 5:0 fb1.
The data are selected with a single-muon trigger that requires a track reconstructed in both the inner tracker and muon detectors with transverse momentum pT> 40 GeV and pseudorapidityjj < 2:1, where ¼ ln ½tan ð=2Þ and is the polar angle. The radius of curvature of a fractionally charged particle in a magnetic field is larger than that of a particle of unit charge with the same mo-mentum, so the reconstructed pTis larger than the true pT by the inverse of the particle’s charge. The trigger require-ment that unit charge particles have pT> 40 GeV corre-sponds to a requirement of pT> 27 GeV for L2=3 and
pT> 13 GeV for L1=3.
The trigger efficiency for L2=3is in the range 67%–74% per event, which is very similar to the efficiency for unit charge particles simulated with the same mass. By contrast, the L1=3 trigger efficiency is between 8% and 18%. The lower trigger efficiency for L1=3 results from the fact that many of the energy deposits in the tracker and muon detectors are below the threshold required to record a measurement. The trigger efficiency for L1=3 depends on the particle’s velocity , since dE=dx/ 1=2 [14]. The
reconstruction efficiency for slower-moving L1=3particles is larger because the energy deposits are more likely to be above threshold. As a result, the reconstructed velocity distribution is very different from the generated distribu-tion. For L2=3 the larger overall efficiency means that the velocity distribution is less affected by the reconstruction, but slower-moving L2=3 particles fail the signal region requirement since their recorded dE=dx measurements are too large.
IV. SELECTION
In a preselection step, candidates for fractionally charged particles are defined as tracks reconstructed in the inner tracker and matched to a track in the muon detectors. The preselection criteria, which are described below, are chosen to obtain well-reconstructed tracks and to suppress background from cosmic ray muons. We con-sider candidate muon tracks with large reconstructed trans-verse momenta, pT> 45 GeV, as measured in the inner
tracker, in the rangejj < 1:5. A loose requirement on the track fit quality, 2=dof < 10, rejects very poorly
recon-structed tracks. We also require at least six dE=dx mea-surements from the tracker, where a dE=dx measurement is the signal amplitude recorded in an inner detector ule divided by the particle’s path length through the mod-ule. To ensure that the track is isolated, the sum of the pTof all other tracks within a cone of R pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiðÞ2þ ðÞ2<
0:3, where is the azimuthal angle, around the candidate must be less than 0.1 times the pT of the candidate. The sum of the electromagnetic and hadronic calorimeter en-ergy recorded within this cone, including that deposited by the candidate, must be less than 5 GeV.
Muons from cosmic rays are found in only a small fraction of the triggered events, but because they typically arrive out of coincidence with the bunch crossing, the charge is sampled away from the signal’s maximum, and the resulting low dE=dx measurement can be indistinguish-able from that of a fractionally charged particle. Several requirements help to suppress the cosmic ray background. The primary vertex with the smallest distance to the point of closest approach of the candidate track is required to be a well-reconstructed vertex [15]. The track must also have at least two dE=dx measurements in the pixel tracker. The candidate track is required to satisfy jdzj < 0:5 cm and jdxyj < 0:1 cm, where dzand dxy are the longitudinal and
transverse impact parameters with respect to the primary vertex. Based on the time of flight measurement [9] by the muon detectors, we determine the time the candidate parti-cle was at the interaction point (IP) under the assumptions that the particle had velocity ¼ 1 and was moving out-ward from the IP. This time must not be earlier than the nominal bunch crossing that triggered the event, a require-ment that rejects over half of the background from pp collisions and cosmic rays. We require max < 2:8 rad, where max is the maximum three-dimensional opening angle between the candidate track and any high-momentum (pT> 35 GeV) track reconstructed in either the inner tracker or in the muon system alone.
The combined efficiency of the trigger and the preselec-tion for signal events generated with mass 100 GeV is 45% per event for L2=3and 4.4% for L1=3. The largest efficiency loss is at the trigger stage for L1=3, where a signal track may fail to be reconstructed. The preselection requirements reduce the signal efficiency by roughly a factor of 2.
After the preselection, events with two Lqcandidates are rejected from the search sample if the invariant mass of the two candidates mLLis in the range 80 < mLL< 100 GeV.
This ensures that the search sample is independent of a control sample, defined below, that is used to estimate the collisions background. Although in the considered signal model, LqLq are produced in pairs, events containing a
single candidate track are retained after the preselection. Events containing more than two candidates, which make up less than 0.1% of the search sample, are excluded.
We isolate the signal using a technique that imposes few assumptions on any particular model but nonetheless has the power to suppress the large standard model back-grounds from pp collisions. A fractionally charged particle is most clearly distinguished from a standard model parti-cle by its lower rate of energy loss in the detector since dE=dx/ q2[14]. Figure1shows the distribution of dE=dx
measurements associated with tracks passing the preselec-tion, for the search sample, a control sample, and the 100 GeV L2=3 and L1=3 simulated signal samples. The measured values from data lie predominantly in the region above 2 MeV/cm. We therefore define low-ionizing measurements to be those with dE=dx < 2 MeV=cm. By requiring a number of such low dE=dx measurements, standard model backgrounds can be suppressed while most of the signal events that pass the preselection are retained. Tracks that intersect a sensor close to its edge or near the boundary between two sensor modules can result in low dE=dx measurements because of the partial collec-tion of the deposited charge, so these track measurements are not considered in the analysis. The distance to the sensor edge for which dE=dx measurements are excluded is between 0.5% and 5% of the distance to the center of the module, depending on the tracker subsystem.
A signal region is determined by maximizing the expected mass limit on the production cross section of fractionally charged particles while varying the minimum
number of low dE=dx measurements. The signal region optimization is performed for simulated samples with a Lq mass of 100 GeV and 400 GeV, and for both samples the optimum signal region is defined with the requirement that events contain a track with at least six low dE=dx mea-surements. For the 100 GeV signal events passing the preselection, 75% of L2=3 events are in the signal region, and 93% of L1=3 events are in the signal region.
V. BACKGROUND ESTIMATE
We use control samples of data to estimate the back-ground contribution from cosmic ray muons and from particles produced in pp collisions. The data-driven method provides a background estimate without the use of simulation.
To estimate the cosmic ray background, we use a sample of muons obtained with the nominal preselection except for two inverted requirements, 0:1 < jdxyj < 1:1 cm and
0:5 < jdzj < 50 cm. The yield in the signal region of this
sample is scaled by a weight factor to obtain the cosmic ray background for the nominal preselection. This weight fac-tor is the product of two weights, each determined from a cosmic ray enriched sample as the ratio of the yield in the nominal selection region to the yield after inverting a single requirement. This scaled yield gives a cosmic ray background estimate of 0.007 events.
A Z-peak control sample is used to estimate the pp collision background. This sample is selected by relaxing the transverse momentum requirement to pT> 35 GeV, requiring 80 < mLL< 100 GeV, and applying all other
preselection requirements. Figure1shows the distributions of dE=dx measurements associated with selected tracks for both the search sample and the Z-peak control sample. The two distributions agree within the statistical uncer-tainties over the full dE=dx range. The ratio of the number of tracks passing the preselection in the search sample to the number of tracks passing the preselection in the Z-peak control sample is 10.5. The control sample is scaled by this ratio to model the distribution in the search sample.
The simulation of the control sample is also shown in Fig. 1. This simulation is used only to assess the uncer-tainty in the signal efficiency, since the background esti-mate is entirely data driven. The inset in Fig. 1 is an enlargement of the region of low dE=dx, plotted on a semilogarithmic scale. This inset also shows the results of a modified simulation, which includes the effect of a possible source of anomalously low dE=dx hits not repro-duced in the nominal simulation. The background simula-tions are discussed in the next section.
To estimate the background in the signal region, we extrapolate from the background-dominated region of events containing a preselected track with zero to five low dE=dx measurements. For a muon from a Z decay, the dE=dx measurements associated with the track are
dE/dx (MeV/cm) 0 2 4 6 8 10 Hits 50 100 150 200 250 3 10 × -1 = 7 TeV, 5.0 fb s CMS, 0 1 2 3 4 1 10 2 10 3 10 4 10 5 10
search sample (CMS data) control sample (CMS data) background simulation modified simulation (signal simulation) 2/3 L (signal simulation) 1/3 L
FIG. 1 (color online). Distribution of dE=dx measurements associated with tracks passing the preselection in the search sample and the Z-peak control sample. Simulated LqLq signal
samples for a mass of 100 GeV are shown for q¼ 2=3, 1=3. The distributions are normalized to the area of the search sample. The magenta vertical line at dE=dx¼ 2 MeV=cm indicates the upper limit of the range of measurements considered to be low ionizing. The inset is an enlargement of the region of low dE=dx, plotted on a semilogarithmic scale.
expected to be uncorrelated, and the number of measure-ments below a given dE=dx value can be described by a generalized binomial function,
Nevts¼ N0 n ! pnð1 pÞn; n ! ¼ ð þ 1Þ ðn þ 1Þð n þ 1Þ;
where Nevtsis the number of events containing at least one track with n low dE=dx measurements, is the average number of measurements per track, p is the probability for a single measurement to be low dE=dx, N0 is a normal-ization factor, and ðnÞ is the gamma function. The fit of the binomial function to the background-dominated region of the Z-peak control sample is shown in Fig.2. The fitted parameters are ¼ 17:5 1:7, p ¼ 0:0125 0:0013, and N0¼ ð5:03 0:03Þ 106; the values of and p are
close to those expected based on the number of ments per track and the fraction of low dE=dx measure-ments. This function describes the distribution in the control sample well, with 2=dof ¼ 0:07=1, correspond-ing to a 2 probability of 79%. This is strong support for the hypothesis that the data are distributed binomially and therefore that the dE=dx measurements are uncorrelated.
Extrapolation of the fitted binomial function into the signal region yields a pp background estimate of 0.005 events.
VI. SYSTEMATIC UNCERTAINTIES
The systematic uncertainties that significantly impact the results are the uncertainties in the integrated luminos-ity, the background estimate, and the signal efficiency. The uncertainty in the integrated luminosity is 2.2% [16].
The cosmic ray background estimate has a statistical uncertainty of 71% that arises from the relatively small size of the sample with inverted dxy and dzrequirements used
for its determination. The statistical uncertainties in the weighting factors are 1% and 24% for the dxy and dz requirements, respectively. The systematic uncertainty as-sociated with the assumption that the dxyand dzvariables
are uncorrelated is assessed by examining a sample defined by replacing the inverted dz selection with an inverted
max requirement. This sample, obtained by requiring 0:1 < jdxyj < 1:1 cm, max > 2:8 rad, and all other
prese-lection criteria, provides a second estimate of the cosmic ray background, which differs from the nominal estimate by 42%. The statistical and systematic uncertainties are summed in quadrature; the total cosmic ray background estimate is 0:007 0:006 events.
We assess three potential sources of uncertainty in the pp background estimate in the signal region. The first source is from the choice of the function used to fit the control sample. While this is often a large source of un-certainty in many a posteriori fits to data, our hypothesis that a binomial function describes the distribution of the number of low dE=dx measurements is motivated a priori from first principles. We do not expect a large uncertainty from this source. For completeness, however, other func-tions are also compared to the data. Fits of several modified exponential, power-law, and polynomial functions fail to converge or have very low 2 probabilities. One function
that does fit the distribution reasonably well is Nevts¼ p0np1þp2n, where p
i are free parameters. The difference
between the background estimate from this function and the nominal background estimate is 0.001 events.
The second potential source of uncertainty in the pp background estimate arises from the statistical uncertain-ties in the fitted parameters of the binomial function. The propagation of these uncertainties results in an uncertainty in the background estimate of0:0004 events.
A third source of uncertainty arises from the small dis-agreement between the distribution of low dE=dx measure-ments from the control sample and that from the search sample. In the background-dominated region, the largest statistically significant discrepancy between the two samples is 9%, for zero low dE=dx measurements. To assess the resulting systematic uncertainty, the control sample fit is repeated for a large number of trials, in each case setting the value of the distribution in each bin randomly, according to a Gaussian distribution with a mean of the original value
Events -2 10 1 2 10 4 10 6 10
search sample (CMS data) control sample (CMS data) binomial fit to control sample
-1
= 7 TeV, 5.0 fb s
CMS,
Hits with dE/dx < 2 MeV/cm
0 1 2 3 4 5 6 Data / fit 0 0.5 1 1.5 2
FIG. 2 (color online). Number of events with at least one track with the given number of low dE=dx measurements, for search data and the scaled Z-peak control sample background estimate. The binomial function fit to the control sample is shown, with the band representing its uncertainty. The ratio of the data to the binomial fit is also presented. No tracks in the search sample have five or more low dE=dx measurements.
and width of 9% of the original value. The RMS of the background estimates from all of these trials is 0.004 events, which is taken as the uncertainty due to the accuracy with which the control sample models the search sample.
The three sources of uncertainty in the pp background estimate are summed in quadrature giving a total estimate of 0:005 0:004 events. The high precision of this esti-mate is due to the large statistics of the control sample, which leads to small statistical uncertainties in the fitted parameters. Likewise, the high degree of accuracy of the background estimate is reflected in the relatively small systematic uncertainty assigned. This is a direct conse-quence of the somewhat unusual aspect of this analysis that the functional form with which the data would be distributed under the background-only hypothesis was de-rived from first principles.
The sum of the pp and cosmic ray backgrounds gives a total background estimate of 0:012 0:007 events.
This search uses the data themselves to estimate all backgrounds, so the uncertainties in the simulation only impact the determination of the efficiency of the bench-mark signal model. The systematic uncertainties in the signal efficiencies are summarized in TableI.
The simulation of the trigger efficiency for a fractionally charged particle is sensitive to the accurate modeling of the muon detectors’ electronics and gas gain as well as the threshold for recording a hit because it has less ionization energy loss, and thus the peak of its Landau distribution is closer to the threshold than that of a muon. We assess the impact on the signal region efficiency of a variation in the simulated gain of the muon system by a conservative estimate of its uncertainty. The impact of such a variation on L2=3is small, since the charge distributions are typically far above the threshold. However, for L1=3, the probability to record a hit degrades significantly as the gain decreases. The impact of this variation for L2=3is 1%, and for L1=3is 8.5%. The systematic uncertainty in the offline global muon identification requirement is negligible by comparison.
The modeling of the tracker dE=dx measurements im-pacts the simulated signal efficiency by affecting the effi-ciency of track reconstruction and signal region selection. Larger tracker energy deposits are more likely to be above the threshold required to record a measurement, and the track reconstruction efficiency increases with more mea-surements. Larger dE=dx measurements also reduce the
fraction of reconstructed tracks that are in the signal re-gion, since fewer measurements are below the 2 MeV=cm limit. To evaluate the accuracy of the simulation of the dE=dx measurements, we compare the dE=dx distribu-tions of the Z-peak control sample in simulation and in data, as shown in Fig.1. The agreement in the low dE=dx region is evaluated as the shift of all dE=dx measurements required to obtain the same fraction below 2 MeV=cm in both samples. For the nominal selection, the simulated dE=dx distribution must be shifted by 2.6% to obtain the same fraction below 2 MeV=cm as in the data. For a larger sample obtained with looser selection criteria, the required shift is 5%. We use the larger of these values, 5%, as an estimate of the agreement between simulation and data. To assess the resulting uncertainty in the signal efficiency, we vary the amplitude of the dE=dx measurements by 5% before resimulating the trigger emulation, track recon-struction, and full selection. A variation of þ5% in the dE=dx measurements changes the signal efficiency by þ16% for L1=3 particles and 7:5% for L2=3. The
effi-ciency changes in opposite directions because for L1=3 the increased reconstruction efficiency is the dominant effect, while for L2=3 the smaller signal region efficiency has a greater impact. These variations in the signal efficiency are taken as the systematic uncertainties associated with the modeling of the tracker dE=dx measurements.
Potential causes of incorrect modeling of dE=dx in our simulation that could produce a disagreement at low dE=dx have been examined. The most likely possibility is a residual source of low dE=dx hits that are not removed by the sensor-edge fiducial cuts. Such a source could be
TABLE I. Systematic uncertainties (in %) in the signal efficiency.
Source L1=3 L2=3
Muon trigger 8.5 1
Tracker dE=dx measurements 16 7.5
Track momentum scale <1 <1
Muon timing 2 2
Total 18 8
TABLE III. The signal efficiency and average velocityhi of events in the signal region for different mass points and charge hypotheses.
Mass L2=3 L1=3
(GeV) Signal eff. hi Signal eff. hi
100 0:341 0:026 0.84 0:041 0:007 0.52 200 0:357 0:027 0.83 0:060 0:011 0.51 300 0:337 0:026 0.82 0:074 0:013 0.51 400 0:314 0:024 0.80 0:091 0:016 0.51 500 0:265 0:020 0.79 0:104 0:019 0.51 600 0:251 0:019 0.78 0:109 0:019 0.51 TABLE II. Numbers of events in the signal region, containing a track with at least six dE=dx measurements with dE=dx < 2 MeV=cm, estimated from the background and observed in the search data.
Cosmic rays 0:007 0:006
pp collisions 0:005 0:004
Total background 0:012 0:007
accommodated by the control sample data if, at most, 0.06% of all measurements are affected. A simulation assuming a mismeasurement rate at this level reproduces the observed data distribution, as shown in the inset of Fig. 1. Such an effect would impact less than 1% of all tracks and change the signal efficiency by an even smaller amount. Furthermore, the likelihood of a track to have six such anomalous measurements is extremely small, so the effect on the background estimate would be negligible.
The uncertainty associated with the track momentum scale is less than 1%. The impact of the uncertainty in the muon timing measurements is 2%. This is assessed by varying the timing measurements according to the mea-sured discrepancy between the data and simulation, as described in [9].
VII. RESULTS
The numbers of expected background and observed events are summarized in TableII. We observe zero events in the data search sample in the signal region, which is consistent with the background estimate of 0:012 0:007 events. The LqLq signal efficiency and average for
different signal masses and charges are listed in TableIII. Ninety-five percent confidence level (CL) upper limits on the LqLqproduction cross section are calculated using the CLs criterion [17,18]. Expected and observed 95% CL
limits are shown in Fig.3. These limits vary from 1.7 to
2.3 fb, for q¼ 2=3, and from 14 to 5.4 fb, for q ¼ 1=3, for masses between 100 and 600 GeV. We exclude the pro-duction of L2=3 with a mass below 310 GeV and the production of L1=3with a mass below 140 GeV at 95% CL.
VIII. CONCLUSION
A search has been performed for heavy, long-lived, leptonlike fractionally charged particles, using the signa-ture of at least six low dE=dx measurements. The search is based on a pp collision sample recorded by the CMS detector at pffiffiffis¼ 7 GeV, corresponding to an integrated luminosity of 5:0 fb1. Zero events are observed in the signal region, consistent with the background estimate. Upper limits are set with 95% confidence on the cross section of pair produced, spin-1=2 particles that are neutral under SUð3ÞCand SUð2ÞL. The existence of such particles
with masses less than 310 GeV is excluded by these cross section limits for the case q¼ 2=3, and with masses less than 140 GeV for q¼ 1=3.
ACKNOWLEDGMENTS
We thank Nathaniel Craig for performing checks of the signal model considered in this analysis. We congratulate our colleagues in the CERN accelerator departments for the ex-cellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from the following: BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA).
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M. Rodozov,13S. Stoykova,13G. Sultanov,13V. Tcholakov,13R. Trayanov,13M. Vutova,13A. Dimitrov,14 R. Hadjiiska,14V. Kozhuharov,14L. Litov,14B. Pavlov,14P. Petkov,14J. G. Bian,15G. M. Chen,15H. S. Chen,15 C. H. Jiang,15D. Liang,15S. Liang,15X. Meng,15J. Tao,15J. Wang,15X. Wang,15Z. Wang,15H. Xiao,15M. Xu,15
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P. Giacomelli,54aC. Grandi,54aL. Guiducci,54a,54bS. Marcellini,54aG. Masetti,54aM. Meneghelli,54a,54b,f A. Montanari,54aF. L. Navarria,54a,54bF. Odorici,54aA. Perrotta,54aF. Primavera,54a,54bA. M. Rossi,54a,54b T. Rovelli,54a,54bG. P. Siroli,54a,54bR. Travaglini,54a,54bS. Albergo,55a,55bG. Cappello,55a,55bM. Chiorboli,55a,55b S. Costa,55a,55bR. Potenza,55a,55bA. Tricomi,55a,55bC. Tuve,55a,55bG. Barbagli,56aV. Ciulli,56a,56bC. Civinini,56a R. D’Alessandro,56a,56bE. Focardi,56a,56bS. Frosali,56a,56bE. Gallo,56aS. Gonzi,56a,56bM. Meschini,56aS. Paoletti,56a
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A. Massironi,59a,59b,fD. Menasce,59aL. Moroni,59aM. Paganoni,59a,59bD. Pedrini,59aS. Ragazzi,59a,59b N. Redaelli,59aS. Sala,59aT. Tabarelli de Fatis,59a,59bS. Buontempo,60aC. A. Carrillo Montoya,60aN. Cavallo,60a,aa
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P. Checchia,61aT. Dorigo,61aF. Gasparini,61a,61bU. Gasparini,61a,61bA. Gozzelino,61aK. Kanishchev,61a,61c S. Lacaprara,61aI. Lazzizzera,61a,61cM. Margoni,61a,61bA. T. Meneguzzo,61a,61bJ. Pazzini,61a,61bN. Pozzobon,61a,61b
P. Ronchese,61a,61bF. Simonetto,61a,61bE. Torassa,61aM. Tosi,61a,61bS. Vanini,61a,61bP. Zotto,61a,61b A. Zucchetta,61a,61bG. Zumerle,61a,61bM. Gabusi,62a,62bS. P. Ratti,62a,62bC. Riccardi,62a,62bP. Torre,62a,62b
P. Vitulo,62a,62bM. Biasini,63a,63bG. M. Bilei,63aL. Fano`,63a,63bP. Lariccia,63a,63bG. Mantovani,63a,63b M. Menichelli,63aA. Nappi,63a,63b,aF. Romeo,63a,63bA. Saha,63aA. Santocchia,63a,63bA. Spiezia,63a,63b S. Taroni,63a,63bP. Azzurri,64a,64cG. Bagliesi,64aJ. Bernardini,64aT. Boccali,64aG. Broccolo,64a,64cR. Castaldi,64a R. T. D’Agnolo,64a,64c,fR. Dell’Orso,64aF. Fiori,64a,64b,fL. Foa`,64a,64cA. Giassi,64aA. Kraan,64aF. Ligabue,64a,64c T. Lomtadze,64aL. Martini,64a,ccA. Messineo,64a,64bF. Palla,64aA. Rizzi,64a,64bA. T. Serban,64a,ddP. Spagnolo,64a P. Squillacioti,64a,fR. Tenchini,64aG. Tonelli,64a,64bA. Venturi,64aP. G. Verdini,64aL. Barone,65a,65bF. Cavallari,65a
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L. Soffi,65a,65bN. Amapane,66a,66bR. Arcidiacono,66a,66cS. Argiro,66a,66bM. Arneodo,66a,66cC. Biino,66a N. Cartiglia,66aM. Costa,66a,66bN. Demaria,66aC. Mariotti,66a,fS. Maselli,66aE. Migliore,66a,66bV. Monaco,66a,66b
M. Musich,66a,fM. M. Obertino,66a,66cN. Pastrone,66aM. Pelliccioni,66aA. Potenza,66a,66bA. Romero,66a,66b M. Ruspa,66a,66cR. Sacchi,66a,66bA. Solano,66a,66bA. Staiano,66aA. Vilela Pereira,66aS. Belforte,67a V. Candelise,67a,67bM. Casarsa,67aF. Cossutti,67aG. Della Ricca,67a,67bB. Gobbo,67aM. Marone,67a,67b,f D. Montanino,67a,67b,fA. Penzo,67aA. Schizzi,67a,67bS. G. Heo,68T. Y. Kim,68S. K. Nam,68S. Chang,69D. H. Kim,69
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R. Magan˜a Villalba,75J. Martı´nez-Ortega,75A. Sa´nchez-Herna´ndez,75L. M. Villasenor-Cendejas,75 S. Carrillo Moreno,76F. Vazquez Valencia,76H. A. Salazar Ibarguen,77E. Casimiro Linares,78A. Morelos Pineda,78
M. A. Reyes-Santos,78D. Krofcheck,79A. J. Bell,80P. H. Butler,80R. Doesburg,80S. Reucroft,80H. Silverwood,80 M. Ahmad,81M. H. Ansari,81M. I. Asghar,81H. R. Hoorani,81S. Khalid,81W. A. Khan,81T. Khurshid,81S. Qazi,81 M. A. Shah,81M. Shoaib,81H. Bialkowska,82B. Boimska,82T. Frueboes,82R. Gokieli,82M. Go´rski,82M. Kazana,82
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N. Krasnikov,87V. Matveev,87A. Pashenkov,87D. Tlisov,87A. Toropin,87V. Epshteyn,88M. Erofeeva,88 V. Gavrilov,88M. Kossov,88N. Lychkovskaya,88V. Popov,88G. Safronov,88S. Semenov,88V. Stolin,88E. Vlasov,88
O. Kodolova,89I. Lokhtin,89A. Markina,89S. Obraztsov,89M. Perfilov,89S. Petrushanko,89A. Popov,89 L. Sarycheva,89,aV. Savrin,89A. Snigirev,89V. Andreev,90M. Azarkin,90I. Dremin,90M. Kirakosyan,90 A. Leonidov,90G. Mesyats,90S. V. Rusakov,90A. Vinogradov,90I. Azhgirey,91I. Bayshev,91S. Bitioukov,91
V. Grishin,91,fV. Kachanov,91D. Konstantinov,91V. Krychkine,91V. Petrov,91R. Ryutin,91A. Sobol,91 L. Tourtchanovitch,91S. Troshin,91N. Tyurin,91A. Uzunian,91A. Volkov,91P. Adzic,92,eeM. Djordjevic,92 M. Ekmedzic,92D. Krpic,92,eeJ. Milosevic,92M. Aguilar-Benitez,93J. Alcaraz Maestre,93P. Arce,93C. Battilana,93
E. Calvo,93M. Cerrada,93M. Chamizo Llatas,93N. Colino,93B. De La Cruz,93A. Delgado Peris,93 D. Domı´nguez Va´zquez,93C. Fernandez Bedoya,93J. P. Ferna´ndez Ramos,93A. Ferrando,93J. Flix,93M. C. Fouz,93
P. Garcia-Abia,93O. Gonzalez Lopez,93S. Goy Lopez,93J. M. Hernandez,93M. I. Josa,93G. Merino,93 J. Puerta Pelayo,93A. Quintario Olmeda,93I. Redondo,93L. Romero,93J. Santaolalla,93M. S. Soares,93 C. Willmott,93C. Albajar,94G. Codispoti,94J. F. de Troco´niz,94H. Brun,95J. Cuevas,95J. Fernandez Menendez,95
S. Folgueras,95I. Gonzalez Caballero,95L. Lloret Iglesias,95J. Piedra Gomez,95J. A. Brochero Cifuentes,96 I. J. Cabrillo,96A. Calderon,96S. H. Chuang,96J. Duarte Campderros,96M. Felcini,96,ffM. Fernandez,96G. Gomez,96 J. Gonzalez Sanchez,96A. Graziano,96C. Jorda,96A. Lopez Virto,96J. Marco,96R. Marco,96C. Martinez Rivero,96 F. Matorras,96F. J. Munoz Sanchez,96T. Rodrigo,96A. Y. Rodrı´guez-Marrero,96A. Ruiz-Jimeno,96L. Scodellaro,96 I. Vila,96R. Vilar Cortabitarte,96D. Abbaneo,97E. Auffray,97G. Auzinger,97M. Bachtis,97P. Baillon,97A. H. Ball,97
D. Barney,97J. F. Benitez,97C. Bernet,97,gG. Bianchi,97P. Bloch,97A. Bocci,97A. Bonato,97C. Botta,97 H. Breuker,97T. Camporesi,97G. Cerminara,97T. Christiansen,97J. A. Coarasa Perez,97D. D’Enterria,97 A. Dabrowski,97A. De Roeck,97S. Di Guida,97M. Dobson,97N. Dupont-Sagorin,97A. Elliott-Peisert,97B. Frisch,97 W. Funk,97G. Georgiou,97M. Giffels,97D. Gigi,97K. Gill,97D. Giordano,97M. Girone,97M. Giunta,97F. Glege,97 R. Gomez-Reino Garrido,97P. Govoni,97S. Gowdy,97R. Guida,97M. Hansen,97P. Harris,97C. Hartl,97J. Harvey,97 B. Hegner,97A. Hinzmann,97V. Innocente,97P. Janot,97K. Kaadze,97E. Karavakis,97K. Kousouris,97P. Lecoq,97
Y.-J. Lee,97P. Lenzi,97C. Lourenc¸o,97N. Magini,97T. Ma¨ki,97M. Malberti,97L. Malgeri,97M. Mannelli,97 L. Masetti,97F. Meijers,97S. Mersi,97E. Meschi,97R. Moser,97M. U. Mozer,97M. Mulders,97P. Musella,97 E. Nesvold,97T. Orimoto,97L. Orsini,97E. Palencia Cortezon,97E. Perez,97L. Perrozzi,97A. Petrilli,97A. Pfeiffer,97
M. Pierini,97M. Pimia¨,97D. Piparo,97G. Polese,97L. Quertenmont,97A. Racz,97W. Reece,97
J. Rodrigues Antunes,97G. Rolandi,97,ggC. Rovelli,97,hhM. Rovere,97H. Sakulin,97F. Santanastasio,97C. Scha¨fer,97 C. Schwick,97I. Segoni,97S. Sekmen,97A. Sharma,97P. Siegrist,97P. Silva,97M. Simon,97P. Sphicas,97,iiD. Spiga,97 A. Tsirou,97G. I. Veres,97,tJ. R. Vlimant,97H. K. Wo¨hri,97S. D. Worm,97,jjW. D. Zeuner,97W. Bertl,98K. Deiters,98
W. Erdmann,98K. Gabathuler,98R. Horisberger,98Q. Ingram,98H. C. Kaestli,98S. Ko¨nig,98D. Kotlinski,98 U. Langenegger,98F. Meier,98D. Renker,98T. Rohe,98J. Sibille,98,kkL. Ba¨ni,99P. Bortignon,99M. A. Buchmann,99
B. Casal,99N. Chanon,99A. Deisher,99G. Dissertori,99M. Dittmar,99M. Donega`,99M. Du¨nser,99J. Eugster,99 K. Freudenreich,99C. Grab,99D. Hits,99P. Lecomte,99W. Lustermann,99A. C. Marini,99
P. Martinez Ruiz del Arbol,99N. Mohr,99F. Moortgat,99C. Na¨geli,99,llP. Nef,99F. Nessi-Tedaldi,99F. Pandolfi,99 L. Pape,99F. Pauss,99M. Peruzzi,99F. J. Ronga,99M. Rossini,99L. Sala,99A. K. Sanchez,99A. Starodumov,99,mm B. Stieger,99M. Takahashi,99L. Tauscher,99,aA. Thea,99K. Theofilatos,99D. Treille,99C. Urscheler,99R. Wallny,99
H. A. Weber,99L. Wehrli,99C. Amsler,100V. Chiochia,100S. De Visscher,100C. Favaro,100M. Ivova Rikova,100 B. Millan Mejias,100P. Otiougova,100P. Robmann,100H. Snoek,100S. Tupputi,100M. Verzetti,100Y. H. Chang,101
K. H. Chen,101C. M. Kuo,101S. W. Li,101W. Lin,101Z. K. Liu,101Y. J. Lu,101D. Mekterovic,101A. P. Singh,101 R. Volpe,101S. S. Yu,101P. Bartalini,102P. Chang,102Y. H. Chang,102Y. W. Chang,102Y. Chao,102K. F. Chen,102 C. Dietz,102U. Grundler,102W.-S. Hou,102Y. Hsiung,102K. Y. Kao,102Y. J. Lei,102R.-S. Lu,102D. Majumder,102
E. Petrakou,102X. Shi,102J. G. Shiu,102Y. M. Tzeng,102X. Wan,102M. Wang,102B. Asavapibhop,103 N. Srimanobhas,103A. Adiguzel,104M. N. Bakirci,104,nnS. Cerci,104,ooC. Dozen,104I. Dumanoglu,104E. Eskut,104
S. Girgis,104G. Gokbulut,104E. Gurpinar,104I. Hos,104E. E. Kangal,104T. Karaman,104G. Karapinar,104,pp A. Kayis Topaksu,104G. Onengut,104K. Ozdemir,104S. Ozturk,104,qqA. Polatoz,104K. Sogut,104,rr D. Sunar Cerci,104,ooB. Tali,104,ooH. Topakli,104,nnL. N. Vergili,104M. Vergili,104I. V. Akin,105T. Aliev,105 B. Bilin,105S. Bilmis,105M. Deniz,105H. Gamsizkan,105A. M. Guler,105K. Ocalan,105A. Ozpineci,105M. Serin,105 R. Sever,105U. E. Surat,105M. Yalvac,105E. Yildirim,105M. Zeyrek,105E. Gu¨lmez,106B. Isildak,106,ssM. Kaya,106,tt O. Kaya,106,ttS. Ozkorucuklu,106,uuN. Sonmez,106,vvK. Cankocak,107L. Levchuk,108F. Bostock,109J. J. Brooke,109
E. Clement,109D. Cussans,109H. Flacher,109R. Frazier,109J. Goldstein,109M. Grimes,109G. P. Heath,109 H. F. Heath,109L. Kreczko,109S. Metson,109D. M. Newbold,109,jjK. Nirunpong,109A. Poll,109S. Senkin,109
V. J. Smith,109T. Williams,109L. Basso,110,wwK. W. Bell,110A. Belyaev,110,wwC. Brew,110R. M. Brown,110 D. J. A. Cockerill,110J. A. Coughlan,110K. Harder,110S. Harper,110J. Jackson,110B. W. Kennedy,110E. Olaiya,110
D. Petyt,110B. C. Radburn-Smith,110C. H. Shepherd-Themistocleous,110I. R. Tomalin,110W. J. Womersley,110 R. Bainbridge,111G. Ball,111R. Beuselinck,111O. Buchmuller,111D. Colling,111N. Cripps,111M. Cutajar,111
P. Dauncey,111G. Davies,111M. Della Negra,111W. Ferguson,111J. Fulcher,111D. Futyan,111A. Gilbert,111 A. Guneratne Bryer,111G. Hall,111Z. Hatherell,111J. Hays,111G. Iles,111M. Jarvis,111G. Karapostoli,111 L. Lyons,111A.-M. Magnan,111J. Marrouche,111B. Mathias,111R. Nandi,111J. Nash,111A. Nikitenko,111,mm A. Papageorgiou,111J. Pela,111M. Pesaresi,111K. Petridis,111M. Pioppi,111,xxD. M. Raymond,111S. Rogerson,111 A. Rose,111M. J. Ryan,111C. Seez,111P. Sharp,111,aA. Sparrow,111M. Stoye,111A. Tapper,111M. Vazquez Acosta,111
T. Virdee,111S. Wakefield,111N. Wardle,111T. Whyntie,111M. Chadwick,112J. E. Cole,112P. R. Hobson,112 A. Khan,112P. Kyberd,112D. Leggat,112D. Leslie,112W. Martin,112I. D. Reid,112P. Symonds,112L. Teodorescu,112
M. Turner,112K. Hatakeyama,113H. Liu,113T. Scarborough,113O. Charaf,114C. Henderson,114P. Rumerio,114 A. Avetisyan,115T. Bose,115C. Fantasia,115A. Heister,115J. St. John,115P. Lawson,115D. Lazic,115J. Rohlf,115
D. Sperka,115L. Sulak,115J. Alimena,116S. Bhattacharya,116D. Cutts,116Z. Demiragli,116A. Ferapontov,116 U. Heintz,116S. Jabeen,116G. Kukartsev,116E. Laird,116G. Landsberg,116M. Luk,116M. Narain,116D. Nguyen,116
M. Segala,116T. Sinthuprasith,116T. Speer,116K. V. Tsang,116R. Breedon,117G. Breto,117
M. Calderon De La Barca Sanchez,117S. Chauhan,117M. Chertok,117J. Conway,117R. Conway,117P. T. Cox,117 J. Dolen,117R. Erbacher,117M. Gardner,117R. Houtz,117W. Ko,117A. Kopecky,117R. Lander,117O. Mall,117 T. Miceli,117D. Pellett,117F. Ricci-tam,117B. Rutherford,117M. Searle,117J. Smith,117M. Squires,117M. Tripathi,117 R. Vasquez Sierra,117R. Yohay,117V. Andreev,118D. Cline,118R. Cousins,118J. Duris,118S. Erhan,118P. Everaerts,118 C. Farrell,118J. Hauser,118M. Ignatenko,118C. Jarvis,118C. Plager,118G. Rakness,118P. Schlein,118,aP. Traczyk,118 V. Valuev,118M. Weber,118J. Babb,119R. Clare,119M. E. Dinardo,119J. Ellison,119J. W. Gary,119F. Giordano,119
G. Hanson,119G. Y. Jeng,119,yyH. Liu,119O. R. Long,119A. Luthra,119H. Nguyen,119S. Paramesvaran,119 J. Sturdy,119S. Sumowidagdo,119R. Wilken,119S. Wimpenny,119W. Andrews,120J. G. Branson,120G. B. Cerati,120
S. Cittolin,120D. Evans,120F. Golf,120A. Holzner,120R. Kelley,120M. Lebourgeois,120J. Letts,120I. Macneill,120 B. Mangano,120S. Padhi,120C. Palmer,120G. Petrucciani,120M. Pieri,120M. Sani,120V. Sharma,120S. Simon,120 E. Sudano,120M. Tadel,120Y. Tu,120A. Vartak,120S. Wasserbaech,120,zzF. Wu¨rthwein,120A. Yagil,120J. Yoo,120 D. Barge,121R. Bellan,121C. Campagnari,121M. D’Alfonso,121T. Danielson,121K. Flowers,121P. Geffert,121
J. Incandela,121C. Justus,121P. Kalavase,121S. A. Koay,121D. Kovalskyi,121V. Krutelyov,121S. Lowette,121 N. Mccoll,121V. Pavlunin,121F. Rebassoo,121J. Ribnik,121J. Richman,121R. Rossin,121D. Stuart,121W. To,121 C. West,121A. Apresyan,122A. Bornheim,122Y. Chen,122E. Di Marco,122J. Duarte,122M. Gataullin,122Y. Ma,122
A. Mott,122H. B. Newman,122C. Rogan,122M. Spiropulu,122V. Timciuc,122J. Veverka,122R. Wilkinson,122 S. Xie,122Y. Yang,122R. Y. Zhu,122B. Akgun,123V. Azzolini,123A. Calamba,123R. Carroll,123T. Ferguson,123 Y. Iiyama,123D. W. Jang,123Y. F. Liu,123M. Paulini,123H. Vogel,123I. Vorobiev,123J. P. Cumalat,124B. R. Drell,124
W. T. Ford,124A. Gaz,124E. Luiggi Lopez,124J. G. Smith,124K. Stenson,124K. A. Ulmer,124S. R. Wagner,124 J. Alexander,125A. Chatterjee,125N. Eggert,125L. K. Gibbons,125B. Heltsley,125A. Khukhunaishvili,125B. Kreis,125
N. Mirman,125G. Nicolas Kaufman,125J. R. Patterson,125A. Ryd,125E. Salvati,125W. Sun,125W. D. Teo,125 J. Thom,125J. Thompson,125J. Tucker,125J. Vaughan,125Y. Weng,125L. Winstrom,125P. Wittich,125D. Winn,126 S. Abdullin,127M. Albrow,127J. Anderson,127L. A. T. Bauerdick,127A. Beretvas,127J. Berryhill,127P. C. Bhat,127 I. Bloch,127K. Burkett,127J. N. Butler,127V. Chetluru,127H. W. K. Cheung,127F. Chlebana,127V. D. Elvira,127 I. Fisk,127J. Freeman,127Y. Gao,127D. Green,127O. Gutsche,127J. Hanlon,127R. M. Harris,127J. Hirschauer,127
B. Hooberman,127S. Jindariani,127M. Johnson,127U. Joshi,127B. Kilminster,127B. Klima,127S. Kunori,127 S. Kwan,127C. Leonidopoulos,127J. Linacre,127D. Lincoln,127R. Lipton,127J. Lykken,127K. Maeshima,127 J. M. Marraffino,127S. Maruyama,127D. Mason,127P. McBride,127K. Mishra,127S. Mrenna,127Y. Musienko,127,aaa
C. Newman-Holmes,127V. O’Dell,127O. Prokofyev,127E. Sexton-Kennedy,127S. Sharma,127W. J. Spalding,127 L. Spiegel,127L. Taylor,127S. Tkaczyk,127N. V. Tran,127L. Uplegger,127E. W. Vaandering,127R. Vidal,127 J. Whitmore,127W. Wu,127F. Yang,127F. Yumiceva,127J. C. Yun,127D. Acosta,128P. Avery,128D. Bourilkov,128
M. Chen,128T. Cheng,128S. Das,128M. De Gruttola,128G. P. Di Giovanni,128D. Dobur,128A. Drozdetskiy,128 R. D. Field,128M. Fisher,128Y. Fu,128I. K. Furic,128J. Gartner,128J. Hugon,128B. Kim,128J. Konigsberg,128
A. Korytov,128A. Kropivnitskaya,128T. Kypreos,128J. F. Low,128K. Matchev,128P. Milenovic,128,bbb G. Mitselmakher,128L. Muniz,128M. Park,128R. Remington,128A. Rinkevicius,128P. Sellers,128N. Skhirtladze,128
M. Snowball,128J. Yelton,128M. Zakaria,128V. Gaultney,129S. Hewamanage,129L. M. Lebolo,129S. Linn,129 P. Markowitz,129G. Martinez,129J. L. Rodriguez,129T. Adams,130A. Askew,130J. Bochenek,130J. Chen,130 B. Diamond,130S. V. Gleyzer,130J. Haas,130S. Hagopian,130V. Hagopian,130M. Jenkins,130K. F. Johnson,130
H. Prosper,130V. Veeraraghavan,130M. Weinberg,130M. M. Baarmand,131B. Dorney,131M. Hohlmann,131 H. Kalakhety,131I. Vodopiyanov,131M. R. Adams,132I. M. Anghel,132L. Apanasevich,132Y. Bai,132 V. E. Bazterra,132R. R. Betts,132I. Bucinskaite,132J. Callner,132R. Cavanaugh,132O. Evdokimov,132L. Gauthier,132
C. E. Gerber,132D. J. Hofman,132S. Khalatyan,132F. Lacroix,132M. Malek,132C. O’Brien,132C. Silkworth,132 D. Strom,132P. Turner,132N. Varelas,132U. Akgun,133E. A. Albayrak,133B. Bilki,133,cccW. Clarida,133F. Duru,133
J.-P. Merlo,133H. Mermerkaya,133,dddA. Mestvirishvili,133A. Moeller,133J. Nachtman,133C. R. Newsom,133 E. Norbeck,133Y. Onel,133F. Ozok,133,eeeS. Sen,133P. Tan,133E. Tiras,133J. Wetzel,133T. Yetkin,133K. Yi,133 B. A. Barnett,134B. Blumenfeld,134S. Bolognesi,134D. Fehling,134G. Giurgiu,134A. V. Gritsan,134Z. J. Guo,134
G. Hu,134P. Maksimovic,134S. Rappoccio,134M. Swartz,134A. Whitbeck,134P. Baringer,135A. Bean,135 G. Benelli,135R. P. Kenny Iii,135M. Murray,135D. Noonan,135S. Sanders,135R. Stringer,135G. Tinti,135 J. S. Wood,135V. Zhukova,135A. F. Barfuss,136T. Bolton,136I. Chakaberia,136A. Ivanov,136S. Khalil,136 M. Makouski,136Y. Maravin,136S. Shrestha,136I. Svintradze,136J. Gronberg,137D. Lange,137D. Wright,137 A. Baden,138M. Boutemeur,138B. Calvert,138S. C. Eno,138J. A. Gomez,138N. J. Hadley,138R. G. Kellogg,138 M. Kirn,138T. Kolberg,138Y. Lu,138M. Marionneau,138A. C. Mignerey,138K. Pedro,138A. Peterman,138A. Skuja,138 J. Temple,138M. B. Tonjes,138S. C. Tonwar,138E. Twedt,138A. Apyan,139G. Bauer,139J. Bendavid,139W. Busza,139
E. Butz,139I. A. Cali,139M. Chan,139V. Dutta,139G. Gomez Ceballos,139M. Goncharov,139K. A. Hahn,139 Y. Kim,139M. Klute,139K. Krajczar,139,fffP. D. Luckey,139T. Ma,139S. Nahn,139C. Paus,139D. Ralph,139 C. Roland,139G. Roland,139M. Rudolph,139G. S. F. Stephans,139F. Sto¨ckli,139K. Sumorok,139K. Sung,139 D. Velicanu,139E. A. Wenger,139R. Wolf,139B. Wyslouch,139M. Yang,139Y. Yilmaz,139A. S. Yoon,139M. Zanetti,139
S. I. Cooper,140B. Dahmes,140A. De Benedetti,140G. Franzoni,140A. Gude,140S. C. Kao,140K. Klapoetke,140 Y. Kubota,140J. Mans,140N. Pastika,140R. Rusack,140M. Sasseville,140A. Singovsky,140N. Tambe,140 J. Turkewitz,140L. M. Cremaldi,141R. Kroeger,141L. Perera,141R. Rahmat,141D. A. Sanders,141E. Avdeeva,142 K. Bloom,142S. Bose,142J. Butt,142D. R. Claes,142A. Dominguez,142M. Eads,142J. Keller,142I. Kravchenko,142
J. Lazo-Flores,142H. Malbouisson,142S. Malik,142G. R. Snow,142A. Godshalk,143I. Iashvili,143S. Jain,143 A. Kharchilava,143A. Kumar,143G. Alverson,144E. Barberis,144D. Baumgartel,144M. Chasco,144J. Haley,144 D. Nash,144D. Trocino,144D. Wood,144J. Zhang,144A. Anastassov,145A. Kubik,145N. Mucia,145N. Odell,145 R. A. Ofierzynski,145B. Pollack,145A. Pozdnyakov,145M. Schmitt,145S. Stoynev,145M. Velasco,145S. Won,145 L. Antonelli,146D. Berry,146A. Brinkerhoff,146K. M. Chan,146M. Hildreth,146C. Jessop,146D. J. Karmgard,146 J. Kolb,146K. Lannon,146W. Luo,146S. Lynch,146N. Marinelli,146D. M. Morse,146T. Pearson,146M. Planer,146 R. Ruchti,146J. Slaunwhite,146N. Valls,146M. Wayne,146M. Wolf,146B. Bylsma,147L. S. Durkin,147C. Hill,147
R. Hughes,147K. Kotov,147T. Y. Ling,147D. Puigh,147M. Rodenburg,147C. Vuosalo,147G. Williams,147 B. L. Winer,147N. Adam,148E. Berry,148P. Elmer,148D. Gerbaudo,148V. Halyo,148P. Hebda,148J. Hegeman,148 A. Hunt,148P. Jindal,148D. Lopes Pegna,148P. Lujan,148D. Marlow,148T. Medvedeva,148M. Mooney,148J. Olsen,148
P. Piroue´,148X. Quan,148A. Raval,148B. Safdi,148H. Saka,148D. Stickland,148C. Tully,148J. S. Werner,148 A. Zuranski,148E. Brownson,149A. Lopez,149H. Mendez,149J. E. Ramirez Vargas,149E. Alagoz,150V. E. Barnes,150 D. Benedetti,150G. Bolla,150D. Bortoletto,150M. De Mattia,150A. Everett,150Z. Hu,150M. Jones,150O. Koybasi,150 M. Kress,150A. T. Laasanen,150N. Leonardo,150V. Maroussov,150P. Merkel,150D. H. Miller,150N. Neumeister,150 I. Shipsey,150D. Silvers,150A. Svyatkovskiy,150M. Vidal Marono,150H. D. Yoo,150J. Zablocki,150Y. Zheng,150 S. Guragain,151N. Parashar,151A. Adair,152C. Boulahouache,152K. M. Ecklund,152F. J. M. Geurts,152W. Li,152 B. P. Padley,152R. Redjimi,152J. Roberts,152J. Zabel,152B. Betchart,153A. Bodek,153Y. S. Chung,153R. Covarelli,153
P. de Barbaro,153R. Demina,153Y. Eshaq,153T. Ferbel,153A. Garcia-Bellido,153P. Goldenzweig,153J. Han,153 A. Harel,153D. C. Miner,153D. Vishnevskiy,153M. Zielinski,153A. Bhatti,154R. Ciesielski,154L. Demortier,154
K. Goulianos,154G. Lungu,154S. Malik,154C. Mesropian,154S. Arora,155A. Barker,155J. P. Chou,155 C. Contreras-Campana,155E. Contreras-Campana,155D. Duggan,155D. Ferencek,155Y. Gershtein,155R. Gray,155 E. Halkiadakis,155D. Hidas,155A. Lath,155S. Panwalkar,155M. Park,155R. Patel,155V. Rekovic,155J. Robles,155 K. Rose,155S. Salur,155S. Schnetzer,155C. Seitz,155S. Somalwar,155R. Stone,155S. Thomas,155G. Cerizza,156
M. Hollingsworth,156S. Spanier,156Z. C. Yang,156A. York,156R. Eusebi,157W. Flanagan,157J. Gilmore,157 T. Kamon,157,gggV. Khotilovich,157R. Montalvo,157I. Osipenkov,157Y. Pakhotin,157A. Perloff,157J. Roe,157
A. Safonov,157T. Sakuma,157S. Sengupta,157I. Suarez,157A. Tatarinov,157D. Toback,157N. Akchurin,158 J. Damgov,158C. Dragoiu,158P. R. Dudero,158C. Jeong,158K. Kovitanggoon,158S. W. Lee,158T. Libeiro,158 Y. Roh,158I. Volobouev,158E. Appelt,159A. G. Delannoy,159C. Florez,159S. Greene,159A. Gurrola,159W. Johns,159
P. Kurt,159C. Maguire,159A. Melo,159M. Sharma,159P. Sheldon,159B. Snook,159S. Tuo,159J. Velkovska,159 M. W. Arenton,160M. Balazs,160S. Boutle,160B. Cox,160B. Francis,160J. Goodell,160R. Hirosky,160
A. Ledovskoy,160C. Lin,160C. Neu,160J. Wood,160S. Gollapinni,161R. Harr,161P. E. Karchin,161 C. Kottachchi Kankanamge Don,161P. Lamichhane,161A. Sakharov,161M. Anderson,162D. Belknap,162 L. Borrello,162D. Carlsmith,162M. Cepeda,162S. Dasu,162E. Friis,162L. Gray,162K. S. Grogg,162M. Grothe,162
R. Hall-Wilton,162M. Herndon,162A. Herve´,162P. Klabbers,162J. Klukas,162A. Lanaro,162C. Lazaridis,162 J. Leonard,162R. Loveless,162A. Mohapatra,162I. Ojalvo,162F. Palmonari,162G. A. Pierro,162I. Ross,162A. Savin,162
W. H. Smith,162and J. Swanson162
(CMS Collaboration)
1Yerevan Physics Institute, Yerevan, Armenia 2Institut fu¨r Hochenergiephysik der OeAW, Wien, Austria 3National Centre for Particle and High Energy Physics, Minsk, Belarus
4Universiteit Antwerpen, Antwerpen, Belgium 5Vrije Universiteit Brussel, Brussel, Belgium 6Universite´ Libre de Bruxelles, Bruxelles, Belgium
7Ghent University, Ghent, Belgium
8Universite´ Catholique de Louvain, Louvain-la-Neuve, Belgium 9Universite´ de Mons, Mons, Belgium
10Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil 11Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil 12
Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil
13Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria 14University of Sofia, Sofia, Bulgaria
15Institute of High Energy Physics, Beijing, China
16State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China 17Universidad de Los Andes, Bogota, Colombia
18Technical University of Split, Split, Croatia 19University of Split, Split, Croatia 20Institute Rudjer Boskovic, Zagreb, Croatia
21
University 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, Universite´ de Strasbourg, Universite´ 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, Villeurbanne, France
32Universite´ de Lyon, Universite´ Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucle´aire 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 fu¨r Experimentelle Kernphysik, Karlsruhe, Germany 40Institute of Nuclear Physics ‘‘Demokritos’’, Aghia Paraskevi, Greece
41
42University of Ioa´nnina, Ioa´nnina, Greece
43KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary 44Institute of Nuclear Research ATOMKI, Debrecen, Hungary
45University of Debrecen, Debrecen, Hungary 46Panjab University, Chandigarh, India
47University of Delhi, Delhi, India 48Saha Institute of Nuclear Physics, Kolkata, India
49Bhabha Atomic Research Centre, Mumbai, India 50
Tata Institute of Fundamental Research—EHEP, Mumbai, India
51Tata Institute of Fundamental Research—HECR, Mumbai, India 52Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
53aINFN Sezione di Bari, Bari, Italy 53bUniversita` di Bari, Bari, Italy 53cPolitecnico di Bari, Bari, Italy 54aINFN Sezione di Bologna, Bologna, Italy
54bUniversita` di Bologna, Bologna, Italy 55aINFN Sezione di Catania, Catania, Italy
55bUniversita` di Catania, Catania, Italy 56aINFN Sezione di Firenze, Firenze, Italy
56bUniversita` di Firenze, Firenze, Italy
57INFN Laboratori Nazionali di Frascati, Frascati, Italy 58aINFN Sezione di Genova, Genova, Italy
58bUniversita` di Genova, Genova, Italy 59aINFN Sezione di Milano-Bicocca, Milano, Italy
59b
Universita` di Milano-Bicocca, Milano, Italy
60aINFN Sezione di Napoli, Napoli, Italy 60bUniversita` di Napoli ‘‘Federico II’’, Napoli, Italy
61aINFN Sezione di Padova, Padova, Italy 61bUniversita` di Padova, Padova, Italy 61cUniversita` di Trento (Trento), Padova, Italy
62aINFN Sezione di Pavia, Pavia, Italy 62bUniversita` di Pavia, Pavia, Italy 63aINFN Sezione di Perugia, Perugia, Italy
63bUniversita` di Perugia, Perugia, Italy 64aINFN Sezione di Pisa, Pisa, Italy
64bUniversita` di Pisa, Pisa, Italy 64cScuola Normale Superiore di Pisa, Pisa, Italy
65aINFN Sezione di Roma, Roma, Italy 65bUniversita` di Roma, Roma, Italy 66aINFN Sezione di Torino, Torino, Italy
66bUniversita` di Torino, Torino, Italy
66cUniversita` del Piemonte Orientale (Novara), Torino, Italy 67aINFN Sezione di Trieste, Trieste, Italy
67bUniversita` di Trieste, Trieste, Italy 68Kangwon National University, Chunchon, Korea
69Kyungpook National University, Daegu, Korea
70Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea 71
Korea University, Seoul, Korea
72University of Seoul, Seoul, Korea 73Sungkyunkwan University, Suwon, Korea
74Vilnius University, Vilnius, Lithuania
75Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico 76Universidad Iberoamericana, Mexico City, Mexico
77Benemerita Universidad Autonoma de Puebla, Puebla, Mexico 78Universidad Auto´noma de San Luis Potosı´, San Luis Potosı´, Mexico
79University of Auckland, Auckland, New Zealand 80
University of Canterbury, Christchurch, New Zealand
81National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan 82National Centre for Nuclear Research, Swierk, Poland
83Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland 84Laborato´rio de Instrumentac¸a˜o e Fı´sica Experimental de Partı´culas, Lisboa, Portugal
85Joint Institute for Nuclear Research, Dubna, Russia
86Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia 87Institute for Nuclear Research, Moscow, Russia
88Institute for Theoretical and Experimental Physics, Moscow, Russia 89Moscow State University, Moscow, Russia
90P. N. Lebedev Physical Institute, Moscow, Russia
91State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia 92University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia
93
Centro de Investigaciones Energe´ticas Medioambientales y Tecnolo´gicas (CIEMAT), Madrid, Spain
94Universidad Auto´noma de Madrid, Madrid, Spain 95Universidad de Oviedo, Oviedo, Spain
96Instituto de Fı´sica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain 97CERN, European Organization for Nuclear Research, Geneva, Switzerland
98Paul Scherrer Institut, Villigen, Switzerland
99Institute for Particle Physics, ETH Zurich, Zurich, Switzerland 100Universita¨t Zu¨rich, Zurich, Switzerland
101National Central University, Chung-Li, Taiwan 102National Taiwan University (NTU), Taipei, Taiwan
103Chulalongkorn University, Bangkok, Thailand 104Cukurova University, Adana, Turkey
105Middle East Technical University, Physics Department, Ankara, Turkey 106Bogazici University, Istanbul, Turkey
107Istanbul Technical University, Istanbul, Turkey
108National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine 109
University of Bristol, Bristol, United Kingdom
110Rutherford Appleton Laboratory, Didcot, United Kingdom 111Imperial College, London, United Kingdom 112Brunel University, Uxbridge, United Kingdom
113Baylor University, Waco, Texas, USA
114The University of Alabama, Tuscaloosa, Alabama, USA 115Boston University, Boston, Massachusetts, USA 116Brown University, Providence, Rhode, Island, USA 117University of California, Davis, Davis, California, USA 118University of California, Los Angeles, Los Angeles, California, USA
119University of California, Riverside, Riverside, California, USA 120University of California, San Diego, La Jolla, USA
121University of California, Santa Barbara, Santa Barbara, California, USA 122California Institute of Technology, Pasadena, California, USA
123Carnegie Mellon University, Pittsburgh, Pennsylvania, USA 124University of Colorado at Boulder, Boulder, Colorado, USA
125Cornell University, Ithaca, New York, USA 126Fairfield University, Fairfield, Connecticut, USA 127Fermi National Accelerator Laboratory, Batavia, Illinois, USA
128University of Florida, Gainesville, Florida, USA 129Florida International University, Miami, Florida, USA
130Florida State University, Tallahassee, Florida, USA 131Florida Institute of Technology, Melbourne, Florida, USA 132
University of Illinois at Chicago (UIC), Chicago, Illinois, USA
133The University of Iowa, Iowa City, Iowa, USA 134Johns Hopkins University, Baltimore, Maryland, USA
135The University of Kansas, Lawrence, Kansas, USA 136Kansas State University, Manhattan, Kansas, USA
137Lawrence Livermore National Laboratory, Livermore, California, USA 138University of Maryland, College Park, Maryland, USA 139Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
140University of Minnesota, Minneapolis, USA 141
University of Mississippi, Oxford, Mississippi, USA
142University of Nebraska-Lincoln, Lincoln, Nebraska, USA 143State University of New York at Buffalo, Buffalo, New York, USA
144Northeastern University, Boston, Massachusetts, USA 145Northwestern University, Evanston, Illinois, USA
