Measurement of the
tt production cross section in pp collisions at
p
ffiffiffi
s
¼ 7 TeV
in dilepton final states containing a
S. Chatrchyan et al.* (CMS Collaboration)
(Received 30 March 2012; published 19 June 2012)
The top quark pair production cross section is measured in dilepton events with one electron or muon, and one hadronically decaying lepton from the decay tt ! ð‘‘ÞðhÞbb, (‘ ¼ e; ). The data sample corresponds to an integrated luminosity of 2:0 fb1for the electron channel and 2:2 fb1 for the muon channel, collected by the CMS detector at the LHC. This is the first measurement of thett cross section explicitly including leptons in proton-proton collisions at pffiffiffis¼ 7 TeV. The measured value tt¼ 143 14ðstatÞ 22ðsystÞ 3ðlumiÞ pb is consistent with the standard model predictions.
DOI:10.1103/PhysRevD.85.112007 PACS numbers: 14.65.Ha
I. INTRODUCTION
Top quarks at the Large Hadron Collider (LHC) are mostly produced in pairs with the subsequent decay . The decay modes of the two W bosons determine the observed event signature. The dilepton decay channel denotes the case where both W bosons from the decaying top quark pair decay leptonically. In this Letter, top quark decays in the ‘‘tau dilepton’’ channel are studied, where one W boson decays intoe or and the other into the hadroni-cally decaying lepton and , in the final state tt ! ð‘‘ÞðhÞb b, where ‘ ¼ e; . The expected fraction of events in the dilepton channel with at least one lepton in the final state is approximately 6% (5/81) of alltt decays, i.e. higher than the fraction of the light dilepton channels (ee, , e) which is equal to 4=81 of all tt decays. The tau dilepton channel is of particular interest because the existence of a charged Higgs boson [1,2] with a mass smaller than the top quark mass could give rise to anoma-lous lepton production, which could be directly observ-able in this decay channel. Furthermore, in the final state studied, the t ! ðÞb decay exclusively involves third generation leptons and quarks. Understanding the yield in top quark decays is important to increase the acceptance fortt events and to search for new physics processes.
This is the first measurement of thett production cross section at the LHC that explicitly includes leptons, improving over the results obtained at the Tevatron which are limited by the small number of candidate events found [3–5]. Experimentally, the lepton is identified by its decay products, either hadrons (h) or leptons (‘), with the corre-sponding branching fractions Brðh! hadrons þ Þ ’ 65% and Brð‘! ‘‘; ‘ ¼ e; Þ ’ 35%. In the first
case, a narrow jet with a distinct signature is produced; in the case of leptonic decays, the distinction from prompt electron or muon production is experimentally difficult, consequently only hadronic decays are studied here. The cross section is measured by counting the number of ehþ X and hþ X events consistent with originating fromtt, subtracting the contributions from other processes, and correcting for the efficiency of the event selection. The measurement is based on data collected by the Compact Muon Solenoid (CMS) experiment in 2011. The integrated luminosity of the data samples are 1:99 fb1and 2:22 fb1 for theeh andh final states, respectively.
The CMS detector is briefly summarized in Sec.II, de-tails of the simulated samples are given in Sec.III, a brief description of the event reconstruction and event selection is provided in Sec. IV, followed by the description of the background determination and systematic uncertainties in Secs. V and VI, respectively. The measurement of the cross section is discussed in Sec. VII, and the results are summarized in Sec.VIII.
II. THE CMS DETECTOR
The central feature of the CMS apparatus is a super-conducting solenoid, 13 m in length and 6 m in diameter, which provides an axial magnetic field of 3.8 T. Inside the solenoid, various particle detection systems are employed. Charged particle trajectories are measured by the silicon pixel and strip tracker, covering 0< ’ < 2 in azimuth and jj < 2:5, where the pseudorapidity is defined as ¼ ln½tanð=2Þ, with being the polar angle of the trajectory of the particle with respect to the counterclock-wise beam direction. A crystal electromagnetic calorimeter and a brass/scintillator hadron calorimeter surround the tracking volume; in this analysis the calorimetry provides high-resolution energy and direction measurements of electrons and hadronic jets. Muon detection systems are located outside of the solenoid and embedded in the steel return yoke. The detector is nearly hermetic, allowing for energy balance measurements in the plane transverse to the
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beam directions. A two-level trigger system selects the most interesting proton-proton collision events for use in physics analysis. A more detailed description of the CMS detector can be found elsewhere [6].
III. EVENT SIMULATION
The analysis makes use of simulated samples ofttevents as well as other processes that result ins in the final state. These samples are used to design the event selection, to calculate the acceptance tott events, and to estimate some of the backgrounds in the analysis.
Signaltt events are simulated with theMADGRAPHevent generator (v. 5.1.1.0) [7] with matrix elements correspond-ing to up to three additional partons, for a top quark mass of 172:5 GeV=c2. The number of expectedtt events is esti-mated with the approximate next-to-next-to-leading order (NNLO) expected standard model (SM) cross section value of 165þ49ðscaleÞþ77ðPDFÞ pb [8,9], where the first uncer-tainty is due to renormalization and factorization scales, and the second is due to the parton distribution function (PDF) uncertainty. This cross section is used for illustrative purposes to normalize the tt eh and h expectations discussed in SectionIV. The generated events are subse-quently processed withPYTHIA(v. 6.422) [10] to provide the showering of the partons, and to perform the matching of the soft radiation with the contributions from direct emissions accounted for in the matrix-element calcula-tions. The Z2 tune [11] is used with the CTEQ6L PDFs [12]. The decays are simulated withTAUOLA(v. 27.121.5) [13] which correctly accounts for the lepton polarization in describing the decay kinematics. The CMS detector response is simulated withGEANT4(v. 9.3 Rev01) [14].
The background samples used in the measurement of the cross section are simulated with MADGRAPH andPYTHIA. The Wþ jet samples include only the leptonic decays of the boson, and are normalized to the inclusive next-to-next-leading-order (NNLO) cross section of 31:3 1:6 nb, calculated with the FEWZ (Fully Exclusive W and Z boson) production program [15]. Drell–Yan (DY) pair production of charged leptons in the final state is generated with MADGRAPH for dilepton invariant masses above 50 GeV=c2, and is normalized to a cross section of 3:04 0:13 nb, computed with FEWZ. The DY events with masses between 10 and 50 GeV=c2 are generated with MADGRAPH with a cross section (with a k-factor of 1.33 to correct for NLO) of 12.4 nb.
The electroweak production of single top quarks is considered as a background process, and is simulated with POWHEG [16]. Thet-channel single top quark NLO cross section ist-ch ¼ 64:6þ3:43:2 pb from MCFM[17–20]. The single top quark associated production (tW) cross section amounts to tW ¼ 15:7 1:2 pb [21]. The s-channel single top quark next-to-next-leading-log (NNLL) cross section is determined as s-ch ¼ 4:6 0:06 pb [22]. Finally, the production ofWW, WZ,
and ZZ pairs, with inclusive cross sections of 43:0 1:5 pb, 18:8 0:7 pb, and 7:4 0:2 pb, respectively (all calculated at the NLO with MCFM), are simulated with PYTHIA.
IV. EVENT SELECTION
The signal topology is defined by the presence of twob jets from the top quark decays, one W boson decaying leptonically into e or , and a second boson decaying into. In the event, all objects are reconstructed with a particle-flow (PF) algorithm [23]. The PF algorithm com-bines the information from all subdetectors to identify and reconstruct all types of particles produced in the collision, namely, charged hadrons, photons, neutral hadrons, muons, and electrons. The resulting list of particles is used to construct a variety of higher-level objects and observables such as jets, missing transverse energy (Emiss
T ), leptons (includings), photons, b-tagging discriminators, and iso-lation variables. The missing transverse energy Emiss
T is
computed as the absolute value of the vectorial sum of the transverse momenta of all reconstructed particles in the event.
Electron or muon candidates are required to be isolated relative to other activity in the event. The relative isolation is based on PF objects and defined as Irel¼ ðEchþ Enhþ EphÞ=pT c, where Ech is the transverse en-ergy deposited by charged hadrons in a cone of radius R ¼ 0:3 around the electron or muon track, Enh and Eph are the respective transverse energies of the neutral hadrons and photons, and pT is the electron or muon transverse momentum. The electron (muon) candidate is considered to be non-isolated and is rejected if Irel> 0:1ð>0:2Þ. Jets are reconstructed with the anti-kT[24,25] jet algorithm with a distance parameterR ¼ 0:5.
Hadronic decays are reconstructed with the Hadron Plus Strips (HPS) algorithm [26]. The identification pro-cess starts with the clustering of all PF particles into jets with the anti-kTalgorithm with a distance parameterR ¼ 0:5. For each jet, a charged hadron is combined with other nearby charged hadrons or photons to identify the decay modes. The identification of 0 mesons is enhanced by clustering electrons and photons in ‘‘strips’’ along the bending plane to take into account possible broadening of calorimeter signatures by early showering photons. Then, strips and charged hadrons are combined to recon-struct the following combinations: single hadron, hadron plus a strip, hadron plus two strips and three hadrons. To reduce the contamination from quark and gluon jets, theh candidate isolation is calculated in a cone of R ¼ 0:5 around the reconstructed -momentum direction. It is required that there be no charged hadrons with pT> 1:0 GeV=c and no photons with ET> 1:5 GeV in the isolation cone, other than the decay particles. Additional requirements are applied to discriminate genu-ine leptons from prompt electrons and muons. The
charge is taken as the sum of the charges of the charged hadrons (prongs) in the signal cone; its uncertainty is less than 1% and it is estimated from same signZ ! ! h events [27]. The reconstruction efficiency of this algo-rithm is estimated to be approximately 37% (i.e. ‘‘me-dium’’ working point in Ref. [26]) for phT > 20 GeV=c, and it is measured in a sample enriched inZ ! ! h events with a ‘‘tag-and-probe’’ technique [28]. The medium working point corresponds to a probability of approximately 0.5% for generic hadronic jets to be misidentified ash.
For the eh final state, events are triggered by the combined electron plus two jets plus Hmiss
T trigger (e þ dijet þ Hmiss
T ), where HTmiss is the absolute value of the vectorial sum of all jet momenta in the plane transverse to the beams. The thresholds for the electron and for Hmiss
T are respectively pT> 17–27 GeV=c and HmissT > 15–20 GeV depending on the data-taking period, and the pT thresholds for the two jets are 30 GeV=c and 25 GeV=c. The trigger efficiency is estimated from a suite of triggers with lower thresholds assuming the factoriza-tion trig¼ e jets MHT, where e is the electron efficiency, jets is the efficiency for selecting two jets, and MHT is the efficiency for Hmiss
T . The data-to-simulation scale factor for the electron trigger efficiency is 0:99 0:01. The efficiencies MHT¼ 1:00þ0:00
0:01andjets, which is parameterized as a function of jet pT, are esti-mated from data. In theh final state, data are collected with a trigger requiring at least one isolated muon with threshold ofpT> 17ð24Þ GeV=c, for the earlier (later) part of the data sample; the data-to-simulation scale factor for the trigger efficiency is 0:99 0:01.
Events are selected by requiring one isolated elec-tron (muon) with transverse momentum pT> 35ð30Þ GeV=c and jj < 2:5ð2:1Þ, at least two jets with pT> 35ð30Þ GeV=c and jj < 2:4, missing transverse energyEmissT > 45ð40Þ GeV and one hadronically decaying lepton ( jet) with pT> 20 GeV=c and jj < 2:4. Electrons or muons are required to be separated from any jet in the (, ’) plane by a distance R > 0:3. Events with any additional loosely isolated (Irel< 0:2) electron (muon) ofpT> 15ð10Þ GeV=c are rejected.
The jet and the lepton are required to have electric charges of opposite sign (OS). At least one of the jets is required to be identified as originating from b quark ha-dronization (b tagged). The b-tagging algorithm used (‘‘TCHEL’’ in Ref. [29]) is based on sorting tracks accord-ing to their impact parameter significance (SIP); the SIP value of the second track is used as the discriminator. The b-tagging efficiency of this algorithm is 76 1%, mea-sured in a sample of events enriched with jets from semi-leptonic b-hadron decays. The misidentification rate of light-flavor jets is obtained from inclusive jet studies and is measured to be 13 3% for jets in the pTrange relevant to this analysis. After the final event selection, a fraction of
approximately 12% of the generatedtt tau dilepton events within the geometric and kinematic fiducial region are selected.
The b-tagged jet multiplicity for the eh andh final states is shown in Fig.1for the events in the preselected sample, i.e. one isolated electron (muon), missing trans-verse energy above 45 (40) GeV, and at least three jets, two jets with pT> 35ð30Þ GeV=c and one jet with pT> 20 GeV=c. The observed numbers of events are consistent with the expected numbers of signal and background events obtained from the simulation. The distributions of theEmiss
T and of the transverse momentum of the lepton
b-tags N 0 1 2 ≥3 Events 2 10 3 10 4 10 5 10 6 10 data W+jets DY+Diboson Single t t other t +X h τ e → t t Total uncert. -1 = 7 TeV, 2.0 fb s CMS b-tags N 0 1 2 ≥3 Events 2 10 3 10 4 10 5 10 6 10 data W+jets DY+Diboson Single t t other t +X h τ µ → t t Total uncert. -1 = 7 TeV, 2.2 fb s CMS
FIG. 1 (color online). The b-tagged jet multiplicity for preselected events with one electron (top) or muon (bottom). Distributions obtained from data (points) are compared with simulation. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total system-atic uncertainty.
after the final event selection are shown in Fig.2 and in Fig.3, respectively, for both theeh andh final states. The distributions show good agreement between the ob-served numbers of events and the expected numbers of signal and background events obtained from the simula-tion. The Emiss
T distribution for the eh final state has a deficit of events in the first bin due to the higher Emiss
T threshold, when compared to theeh final state.
The top quark mass is reconstructed with the KINb [30] algorithm (Fig.4), treating the additional neutrino in the decay as a contribution to theEmiss
T . Numerical solutions
for the kinematic reconstruction of tt decays with two charged leptons in the final state are found for each event. The jet transverse momentum, theEmiss
T direction, and the longitudinal momentum of the tt system are varied inde-pendently within their measured resolutions to scan the kinematic phase space compatible with the tt system. Solutions with the lowest invariant mass of the tt system are accepted if the difference between the two top quark masses is less than 3 GeV=c2. The reconstructed top quark mass in Fig. 4shows that the kinematic properties of the
[GeV] miss T E 40 60 80 100 120 140 Events/(10 GeV) 1 10 2 10 data W+jets DY+Diboson Single t t other t +X h τ e → t t Total uncert. -1 = 7 TeV, 2.0 fb s CMS [GeV] miss T E 40 60 80 100 120 140 Events/(10 GeV) 1 10 2 10 data W+jets DY+Diboson Single t t other t +X h τ µ → t t Total uncert. -1 = 7 TeV, 2.2 fb s CMS
FIG. 2 (color online). EmissT distribution after the full event selection for the eh (top) and h (bottom) final states. Distributions obtained from data (points) are compared with simulation. The last bin includes the overflow. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total systematic uncertainty.
[GeV/c] T τ p 20 30 40 50 60 70 80 90 100 110 120 Events/(10GeV/c) 1 10 2 10 data W+jets DY+Diboson Single t t other t +X h τ e → t t Total uncert. -1 = 7 TeV, 2.0 fb s CMS [GeV/c] T τ p 20 30 40 50 60 70 80 90 100 110 120 Events/(10GeV/c) 1 10 2 10 data W+jets DY+Diboson Single t t other t +X h τ µ → t t Total uncert. -1 = 7 TeV, 2.2 fb s CMS
FIG. 3 (color online). The pT distribution after the full event selection for the eh (top) andh (bottom) final states. Distributions obtained from data (points) are compared with simulation. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total system-atic uncertainty.
selected events are statistically compatible with predictions based on a top quark mass of 172:5 GeV=c2, indicating the consistency of the selected sample in data with the sum of top quark pair production plus the background.
V. BACKGROUND ESTIMATE
The background comes from two categories of events, the ‘‘misreconstructed ’’ background (Nmisid) which is estimated from data, and the ‘‘other’’ background (Nother) which is estimated from simulation.
The main background (misreconstructed) comes from events with one lepton (electron or muon),EmissT
require-ment and three or more jets, where one jet is misidentified as a jet. The dominant contribution to this background is from events where oneW boson is produced in association with jets, and fromtt ! WþbWb ! ‘b q q 0b events. In order to estimate this background from data, the probabil-ity wðjet ! hÞ that a jet is misidentified as a jet as a function of the jetpT,, and jet width (Rjet) is determined, then applied to every jet in the preselected sample with one b-tagged jet. The quantity Rjetis defined as ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2
þ 2 q
, where ( ) expresses the extent in ( ) of the jet cluster. Thus the expected number of background is ob-tained as: Nmisid¼X N i Xn j w j iðjet ! Þ Nother; (1) wherej is the jet index of the event i. The quantity Nother is the small (’ 18%) contamination of other contributions to the misidentified background, which is estimated from simulation. This is mostly due to the presence of genuine jets in the Wþ 3 jet sample. In order to estimate this contribution, the same procedure described above is ap-plied to simulated events of Z= ! , single top quark production, diboson production, and the part of the SMtt background not included in the misidentified background estimate.
In order to estimate the misidentification probability, the hadronic multijet events are selected from a sample trig-gered by at least one jet withpT> 30 GeV=c, by requiring events to have at least two jets with pT> 20 GeV=c and jj < 2:4. The triggering jet is removed from the misiden-tification rate calculation in order to avoid a trigger bias. TheWþ 1 jet events are selected by requiring only one isolated muon withpT> 20 GeV=c and jj < 2:1, and at least one jet with pT> 20 GeV=c and jj < 2:4. The probability wðjet ! hÞ is evaluated from all jets in a sample enriched in QCD multijet events (wQCD), and all jets in another sample enriched in Wþ 1 jet events (wWþjets). The probability that a jet is misidentified as a jet as a function of jetpT, and Rjetis compared between simulated events (Z2 tune [11]) and data, and a good agreement is found [26].
Jets in QCD multijet events are mainly gluon jets (’ 75% obtained from simulation), while the jets in Wþ 1 jet events are predominantly quark jets (’ 64% obtained from simulation), where wQCD< wWþjets. Since the quark and gluon jet composition in ‘ þ EmissT þ 3 jet events lies between two categories of events, QCD multijet andWþ 1 jet events, theNmisidvalue is under- (over-) estimated by applying thewQCD(wWþjets) probability. Thus, theNmisidand its systematic uncertainty are estimated as in the following:
Nmisid¼ PN i PnjwjWþjets;iþPNi PnjwjQCD;i 2 ; (2) ] 2 [GeV/c top m 100 200 300 400 500 600 ) 2 Events / (20 GeV/c 0 5 10 15 20 25 30 35 data +X h τ e → t t t other t W+jets Single t DY+Diboson Total uncert. -1 = 7 TeV, 2.0 fb s CMS ] 2 [GeV/c top m 100 200 300 400 500 600 ) 2 Events / (20 GeV/c 0 10 20 30 40 50 60 70 data +X h τ µ → t t t other t W+jets Single t DY+Diboson Total uncert. -1 =7 TeV, 2.2 fb s CMS
FIG. 4 (color online). Reconstructed top quark massmtop dis-tribution for the dilepton candidate events after the full event selection, in the eh (top) and h (bottom) final states. Distributions obtained from data (points) are compared with simu-lation. The hatched area shows the total systematic uncertainty.
Nmisid¼ PN
i PnjwjWþjets;iPNi PnjwjQCD;i
2 : (3)
The contribution ofNotherdescribed earlier is subtracted from Eq. (2). Finally, the efficiency "OS of the OS requirement obtained from simulated events is applied to obtain the misidentified background Nmisid
OS ¼
"OS Nmisid. The estimated efficiencies for the eh and h final states are "OS¼ 0:72 0:09ðstatÞ 0:02ðsystÞ and "OS¼ 0:69 0:07ðstatÞ 0:03ðsystÞ, respectively, where the statistical uncertainty comes from the limited number of simulated events, and the systematic uncertainty is taken as half of the difference of the efficiency estimated fromW þ jets and lepton þ jet tt simulated events.
Other backgrounds in this analysis are Z=! , single top quark production, diboson production, and the part of the SMtt background not included in the misiden-tified background, and are estimated from simulation. Events from Z! ee, are also taken into account because they contain misidentified jets, where the mis-identified lepton can originate from an electron or muon misidentified as a jet. The statistical uncertainties are due to the limited number of simulated events.
VI. SYSTEMATIC UNCERTAINTIES
Different sources of systematic uncertainties on the measurement of the cross section due to signal selection efficiencies and backgrounds are considered, as shown in TableI. The main sources of systematic uncertainties are due to identification, b-tagging and mistagging efficien-cies, jet energy scale (JES), jet energy resolution (JER), Emiss
T scale, and to the estimate of the misreconstructed background (from data). The systematic uncertainties for
the determination of the misidentified background are discussed in detail in Sec. V.
The uncertainty on the jet identification includes contributions from identification efficiency and ‘ ! h (‘ ¼ e; ) misidentification. The uncertainty on identi-fication efficiency is estimated to be 6% (from an updated measurement with respect to [26]), and it includes the uncertainty on charge determination which is estimated to be smaller than 1%. The uncertainty on the ‘ ! h misidentification rate is estimated as the difference of misidentification rate measured in data and in simulated events, and is taken to be 15% [26]. These uncertainties are applied to the simulated Z! ee, , and tt dilepton background events.
The uncertainties related to b-tagging and mistagging efficiencies are estimated from a variety of control samples enriched in b quarks, and the data-to-simulation scale factors amount to 0:95 0:06 and 1:11 0:11, respec-tively [29].
The uncertainties on JES, JER, and EmissT scale are estimated according to the prescription described in Ref. [32]. These uncertainties also take into account the uncertainty due to the JES dependence on the parton flavor. The uncertainty on JES is evaluated as a function of jetpT and jet. The JES and JER uncertainties are propagated in order to estimate the uncertainty of the Emiss
T scale. An additional 10% uncertainty on the contribution to EmissT coming from the energy of particles that are not clustered into jets is also taken into account.
The theoretical uncertainty on the signal acceptance is estimated to be 4% [30]. It accounts for variations in the renormalization and factorization scales (2%), lepton and hadron decay modelling (2%), top quark mass (1.6%), leptonic branching fractions of the W boson (1.7%), and
TABLE I. List of systematic uncertainties (in %) on the cross section measurement. The Best Linear Unbiased Estimation method [31] is used to combine the cross section measurements in theehandhchannels, with the corresponding weights. Systematic uncertainties common to the two channels are assumed to be 100% correlated.
Uncertainty [%]
Source eh h Combination [%]
misidentification background 12.6 9.8 10.8
jet identification 6.4 6.3 6.3
b-jet tagging, misidentification 5.3 5.3 5.3
jet energy scale, jet energy resolution,Emiss
T 5.1 6.2 5.8
theoretical uncertainty on signal efficiency 4.0 4.0 4.0
pile-up modelling 2.3 2.3 2.3
electron selection 3.1 0 1.1
muon selection 0 2.0 1.3
cross section of MC backgrounds 1.6 1.4 1.5
luminosity 2.2 2.2 2.2
weight 0.38 0.62 2=Ndof ¼ 2:381=1
jet and Emiss
T modelling (1%). Uncertainties on the PDFs are found to be negligible.
The uncertainty on the integrated luminosity is esti-mated to be 2.2% [33]. The number of interactions per bunch crossing in the data (pile-up) is estimated from the measured luminosity in each bunch crossing times an average total inelastic cross section (with an uncertainty of 6.5%). The estimated number of interactions has a total uncertainty of approximately 8%, which corresponds to an overall uncertainty of the pile-up distribution. The mean of pile-up in the data sample is about 5–6 interactions, with the uncertainty estimated conservatively by shifting the overall mean up or down by 0.6 interactions.
The lepton trigger, identification, and isolation efficien-cies are measured with the ‘‘tag-and-probe’’ method in events containing a lepton pair of invariant mass between 76 and 106 GeV=c2. Within the precision of the present measurement, the scale factors between efficiencies mea-sured in data and in simulation are estimated to be equal to one. The combined uncertainty on the electron (muon) trigger, identification and isolation efficiencies is 3% (2%). Theoretical uncertainties on the cross sections of single top quark, diboson, and DY processes are estimated as in Ref. [34]. The uncertainties include the scale and PDF uncertainties on theoretical cross sections.
VII. CROSS SECTION MEASUREMENT The number of events expected from the backgrounds, the number of signal events from tt, and the number of observed events after all selection cuts are summarized in Table II. The statistical and systematic uncertainties are also shown.
The tt production cross section measured from tau dilepton events is:
tt¼L AtotN B; (4)
whereN is the number of observed candidate events, B is the estimate of the background, L is the integrated lumi-nosity. The total acceptance Atot is the product of all branching fractions, geometrical and kinematical accep-tance, efficiencies for trigger, lepton identification and the overall reconstruction efficiency, and it is evaluated with respect to the inclusive tt sample. After the OS require-ment:
AtotðehÞ ¼ ½0:03040:0009ðstatÞ0:0031ðsystÞ%; (5) AtotðhÞ ¼ ½0:04430:0011ðstatÞ0:0047ðsystÞ%: (6) The statistical uncertainties are due to the limited num-ber of simulated events and the systematic uncertainties are estimated by varying all sources of systematics in TableI affecting the signal (i.e., all uncertainties except for the luminosity and for the background). All systematic and statistical uncertainties in Table II are propagated from Eq. (4) to the final cross section measurement. The mea-suredtt cross section is:
ttðehÞ ¼ 13623ðstatÞ23ðsystÞ3ðlumiÞ pb; (7) ttðhÞ ¼ 147 18ðstatÞ 22ðsystÞ 3ðlumiÞ pb: (8) The Best Linear Unbiased Estimation method [31] is used to combine the cross section measurements in theeh and h channels with the associated uncertainties and correlation factors. Systematic uncertainties common to the two channels are assumed to be 100% correlated. The combined result is
tt¼ 143 14ðstatÞ 22ðsystÞ 3ðlumiÞ pb; (9) in agreement with the measured values in the dilepton [30] and leptonþ jet [34,35] final states, and with the SM expectations in the approximate NNLO calculation of 163þ75ðscaleÞ 9ðPDFÞ pb [36].
VIII. SUMMARY
We present the first measurement of the tt pro-duction cross section in the tau dilepton channel tt ! ð‘‘ÞðhÞb b, (‘ ¼ e; ) with data samples correspond-ing to an integrated luminosity of 2:0–2:2 fb1collected in proton-proton collisions at pffiffiffis¼ 7 TeV. Events are se-lected by requiring the presence of one electron or muon, two or more jets (at least one jet is b tagged), missing transverse energy, and one hadronically decaying lepton. The largest background contributions come from events where oneW boson is produced in association with jets, and fromtt ! WþbWb ! ‘b (q q 0b) events, where one jet is misidentified as the , and from Z ! events. The measured cross section is tt¼ 143 14ðstatÞ 22ðsystÞ 3ðlumiÞ pb, in agreement with SM expectations.
TABLE II. Number of expected events for signal and back-grounds. The background from ‘‘misidentified ’’ is estimated from data, while the other backgrounds are estimated from simulation. Statistical and systematic uncertainties are shown.
Neventsðstat systÞ
Source eh h tt ! WbWb ! ‘bb 99:9 3:0 10:1 162:0 4:0 16:7 misidentified 54:3 6:4 8:1 88:5 8:9 10:8 Z=! 16:6 3:3 2:9 25:8 4:3 6:1 tt ! WbWb ! ‘b‘b 9:0 0:9 1:7 13:3 1:2 2:5 Z=! ee; 4:8 1:8 1:3 0:7 0:7 0:7 Single top 7:9 0:4 1:1 13:5 0:5 1:9 VV 1:3 0:1 0:2 2:0 0:2 0:3 Total expected 193:9 4:9 18:0 306:1 6:1 27:9 Data 176 288
ACKNOWLEDGMENTS
We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administra-tive staff at CERN and other CMS institutes, and acknowl-edge support from: FMSR (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); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie programme and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation a` la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the Council of Science and Industrial Research, India; and the HOMING PLUS pro-gramme of Foundation for Polish Science, cofinanced from European Union, Regional Development Fund.
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P. Lariccia,64a,64bA. Lucaroni,64a,64b,bG. Mantovani,64a,64bM. Menichelli,64aA. Nappi,64a,64bF. Romeo,64a,64b A. Saha,64aA. Santocchia,64a,64bS. Taroni,64a,64b,bP. Azzurri,65a,65cG. Bagliesi,65aT. Boccali,65aG. Broccolo,65a,65c
R. Castaldi,65aR. T. D’Agnolo,65a,65cR. Dell’Orso,65aF. Fiori,65a,65bL. Foa`,65a,65cA. Giassi,65aA. Kraan,65a F. Ligabue,65a,65cT. Lomtadze,65aL. Martini,65a,zA. Messineo,65a,65bF. Palla,65aF. Palmonari,65aA. Rizzi,65a,65b A. T. Serban,65aP. Spagnolo,65aR. Tenchini,65aG. Tonelli,65a,65b,bA. Venturi,65a,bP. G. Verdini,65aL. Barone,66a,66b F. Cavallari,66aD. Del Re,66a,66b,bM. Diemoz,66aC. Fanelli,66a,66bM. Grassi,66a,bE. Longo,66a,66bP. Meridiani,66a,b
F. Micheli,66a,66bS. Nourbakhsh,66aG. Organtini,66a,66bF. Pandolfi,66a,66bR. Paramatti,66aS. Rahatlou,66a,66b M. Sigamani,66aL. Soffi,66a,66bN. Amapane,67a,67bR. Arcidiacono,67a,67cS. Argiro,67a,67bM. Arneodo,67a,67c C. Biino,67aC. Botta,67a,67bN. Cartiglia,67aR. Castello,67a,67bM. Costa,67a,67bN. Demaria,67aA. Graziano,67a,67b
C. Mariotti,67a,bS. Maselli,67aE. Migliore,67a,67bV. Monaco,67a,67bM. Musich,67a,bM. M. Obertino,67a,67c N. Pastrone,67aM. Pelliccioni,67aA. Potenza,67a,67bA. Romero,67a,67bM. Ruspa,67a,67cR. Sacchi,67a,67b
V. Sola,67a,67bA. Solano,67a,67bA. Staiano,67aA. Vilela Pereira,67aS. Belforte,68aF. Cossutti,68a G. Della Ricca,68a,68bB. Gobbo,68aM. Marone,68a,68b,bD. Montanino,68a,68b,bA. Penzo,68aA. Schizzi,68a,68b S. G. Heo,69T. Y. Kim,69S. K. Nam,69S. Chang,70J. Chung,70D. H. Kim,70G. N. Kim,70D. J. Kong,70H. Park,70 S. R. Ro,70D. C. Son,70J. Y. Kim,71Zero J. Kim,71S. Song,71H. Y. Jo,72S. Choi,73D. Gyun,73B. Hong,73M. Jo,73 H. Kim,73T. J. Kim,73K. S. Lee,73D. H. Moon,73S. K. Park,73E. Seo,73M. Choi,74S. Kang,74H. Kim,74J. H. Kim,74 C. Park,74I. C. Park,74S. Park,74G. Ryu,74Y. Cho,75Y. Choi,75Y. K. Choi,75J. Goh,75M. S. Kim,75B. Lee,75
J. Lee,75S. Lee,75H. Seo,75I. Yu,75M. J. Bilinskas,76I. Grigelionis,76M. Janulis,76A. Juodagalvis,76 H. Castilla-Valdez,77E. De La Cruz-Burelo,77I. Heredia-de La Cruz,77R. Lopez-Fernandez,77R. Magan˜a Villalba,77
J. Martı´nez-Ortega,77A. Sa´nchez-Herna´ndez,77L. M. Villasenor-Cendejas,77S. Carrillo Moreno,78 F. Vazquez Valencia,78H. A. Salazar Ibarguen,79E. Casimiro Linares,80A. Morelos Pineda,80M. A. Reyes-Santos,80
D. Krofcheck,81A. J. Bell,82P. H. Butler,82R. Doesburg,82S. Reucroft,82H. Silverwood,82M. Ahmad,83 M. I. Asghar,83H. R. Hoorani,83S. Khalid,83W. A. Khan,83T. Khurshid,83S. Qazi,83M. A. Shah,83M. Shoaib,83
G. Brona,84M. Cwiok,84W. Dominik,84K. Doroba,84A. Kalinowski,84M. Konecki,84J. Krolikowski,84 H. Bialkowska,85B. Boimska,85T. Frueboes,85R. Gokieli,85M. Go´rski,85M. Kazana,85K. Nawrocki,85 K. Romanowska-Rybinska,85M. Szleper,85G. Wrochna,85P. Zalewski,85N. Almeida,86P. Bargassa,86A. David,86 P. Faccioli,86P. G. Ferreira Parracho,86M. Gallinaro,86P. Musella,86J. Pela,86,bJ. Seixas,86J. Varela,86P. Vischia,86 I. Belotelov,87P. Bunin,87M. Gavrilenko,87I. Golutvin,87I. Gorbunov,87A. Kamenev,87V. Karjavin,87G. Kozlov,87 A. Lanev,87A. Malakhov,87P. Moisenz,87V. Palichik,87V. Perelygin,87S. Shmatov,87V. Smirnov,87A. Volodko,87 A. Zarubin,87S. Evstyukhin,88V. Golovtsov,88Y. Ivanov,88V. Kim,88P. Levchenko,88V. Murzin,88V. Oreshkin,88
I. Smirnov,88V. Sulimov,88L. Uvarov,88S. Vavilov,88A. Vorobyev,88An. Vorobyev,88Yu. Andreev,89 A. Dermenev,89S. Gninenko,89N. Golubev,89M. Kirsanov,89N. Krasnikov,89V. Matveev,89A. Pashenkov,89
D. Tlisov,89A. Toropin,89V. Epshteyn,90M. Erofeeva,90V. Gavrilov,90M. Kossov,90,bN. Lychkovskaya,90 V. Popov,90G. Safronov,90S. Semenov,90V. Stolin,90E. Vlasov,90A. Zhokin,90A. Belyaev,91E. Boos,91 V. Bunichev,91M. Dubinin,91,eL. Dudko,91A. Ershov,91A. Gribushin,91V. Klyukhin,91O. Kodolova,91I. Lokhtin,91
A. Markina,91S. Obraztsov,91M. Perfilov,91S. Petrushanko,91L. Sarycheva,91,aV. Savrin,91V. Andreev,92 M. Azarkin,92I. Dremin,92M. Kirakosyan,92A. Leonidov,92G. Mesyats,92S. V. Rusakov,92A. Vinogradov,92
I. Azhgirey,93I. Bayshev,93S. Bitioukov,93V. Grishin,93,bV. Kachanov,93D. Konstantinov,93A. Korablev,93 V. Krychkine,93V. Petrov,93R. Ryutin,93A. Sobol,93L. Tourtchanovitch,93S. Troshin,93N. Tyurin,93A. Uzunian,93
A. Volkov,93P. Adzic,94,aaM. Djordjevic,94M. Ekmedzic,94D. Krpic,94,aaJ. Milosevic,94M. Aguilar-Benitez,95 J. Alcaraz Maestre,95P. Arce,95C. Battilana,95E. Calvo,95M. Cerrada,95M. Chamizo Llatas,95N. Colino,95
B. De La Cruz,95A. Delgado Peris,95C. Diez Pardos,95D. Domı´nguez Va´zquez,95C. Fernandez Bedoya,95 J. P. Ferna´ndez Ramos,95A. Ferrando,95J. Flix,95M. C. Fouz,95P. Garcia-Abia,95O. Gonzalez Lopez,95 S. Goy Lopez,95J. M. Hernandez,95M. I. Josa,95G. Merino,95J. Puerta Pelayo,95I. Redondo,95L. Romero,95
J. Santaolalla,95M. S. Soares,95C. Willmott,95C. Albajar,96G. Codispoti,96J. F. de Troco´niz,96J. Cuevas,97 J. Fernandez Menendez,97S. Folgueras,97I. Gonzalez Caballero,97L. Lloret Iglesias,97J. Piedra Gomez,97,bb
J. M. Vizan Garcia,97J. A. Brochero Cifuentes,98I. J. Cabrillo,98A. Calderon,98S. H. Chuang,98 J. Duarte Campderros,98M. Felcini,98,ccM. Fernandez,98G. Gomez,98J. Gonzalez Sanchez,98C. Jorda,98
F. J. Munoz Sanchez,98T. Rodrigo,98A. Y. Rodrı´guez-Marrero,98A. Ruiz-Jimeno,98L. Scodellaro,98 M. Sobron Sanudo,98I. Vila,98R. Vilar Cortabitarte,98D. Abbaneo,99E. Auffray,99G. Auzinger,99P. Baillon,99
A. H. Ball,99D. Barney,99C. Bernet,99,fG. Bianchi,99P. Bloch,99A. Bocci,99A. Bonato,99H. Breuker,99 K. Bunkowski,99T. Camporesi,99G. Cerminara,99T. Christiansen,99J. A. Coarasa Perez,99D. D’Enterria,99 A. De Roeck,99S. Di Guida,99M. Dobson,99N. Dupont-Sagorin,99A. Elliott-Peisert,99B. Frisch,99W. Funk,99
G. Georgiou,99M. Giffels,99D. Gigi,99K. Gill,99D. Giordano,99M. Giunta,99F. Glege,99
R. Gomez-Reino Garrido,99P. Govoni,99S. Gowdy,99R. Guida,99M. Hansen,99P. Harris,99C. Hartl,99J. Harvey,99 B. Hegner,99A. Hinzmann,99V. Innocente,99P. Janot,99K. Kaadze,99E. Karavakis,99K. Kousouris,99P. Lecoq,99
P. Lenzi,99C. Lourenc¸o,99T. Ma¨ki,99M. Malberti,99L. Malgeri,99M. Mannelli,99L. Masetti,99F. Meijers,99 S. Mersi,99E. Meschi,99R. Moser,99M. U. Mozer,99M. Mulders,99E. Nesvold,99M. Nguyen,99T. Orimoto,99 L. Orsini,99E. Palencia Cortezon,99E. Perez,99A. Petrilli,99A. Pfeiffer,99M. Pierini,99M. Pimia¨,99D. Piparo,99
G. Polese,99L. Quertenmont,99A. Racz,99W. Reece,99J. Rodrigues Antunes,99G. Rolandi,99,dd
T. Rommerskirchen,99C. Rovelli,99,eeM. Rovere,99H. Sakulin,99F. Santanastasio,99C. Scha¨fer,99C. Schwick,99 I. Segoni,99S. Sekmen,99A. Sharma,99P. Siegrist,99P. Silva,99M. Simon,99P. Sphicas,99,ffD. Spiga,99 M. Spiropulu,99,eM. Stoye,99A. Tsirou,99G. I. Veres,99,pJ. R. Vlimant,99H. K. Wo¨hri,99S. D. Worm,99,gg W. D. Zeuner,99W. Bertl,100K. Deiters,100W. Erdmann,100K. Gabathuler,100R. Horisberger,100Q. Ingram,100
H. C. Kaestli,100S. Ko¨nig,100D. Kotlinski,100U. Langenegger,100F. Meier,100D. Renker,100T. Rohe,100 J. Sibille,100,hhL. Ba¨ni,101P. Bortignon,101M. A. Buchmann,101B. Casal,101N. Chanon,101Z. Chen,101 A. Deisher,101G. Dissertori,101M. Dittmar,101M. Du¨nser,101J. Eugster,101K. Freudenreich,101C. Grab,101 P. Lecomte,101W. Lustermann,101A. C. Marini,101P. Martinez Ruiz del Arbol,101N. Mohr,101F. Moortgat,101 C. Na¨geli,101,iiP. Nef,101F. Nessi-Tedaldi,101L. Pape,101F. Pauss,101M. Peruzzi,101F. J. Ronga,101M. Rossini,101
L. Sala,101A. K. Sanchez,101A. Starodumov,101,jjB. Stieger,101M. Takahashi,101L. Tauscher,101,aA. Thea,101 K. Theofilatos,101D. Treille,101C. Urscheler,101R. Wallny,101H. A. Weber,101L. Wehrli,101E. Aguilo,102
C. Amsler,102V. Chiochia,102S. De Visscher,102C. Favaro,102M. Ivova Rikova,102B. Millan Mejias,102 P. Otiougova,102P. Robmann,102H. Snoek,102S. Tupputi,102M. Verzetti,102Y. H. Chang,103K. H. Chen,103A. Go,103
C. M. Kuo,103S. W. Li,103W. Lin,103Z. K. Liu,103Y. J. Lu,103D. Mekterovic,103A. P. Singh,103R. Volpe,103 S. S. Yu,103P. Bartalini,104P. Chang,104Y. H. Chang,104Y. W. Chang,104Y. Chao,104K. F. Chen,104C. Dietz,104 U. Grundler,104W.-S. Hou,104Y. Hsiung,104K. Y. Kao,104Y. J. Lei,104R.-S. Lu,104D. Majumder,104E. Petrakou,104 X. Shi,104J. G. Shiu,104Y. M. Tzeng,104M. Wang,104A. Adiguzel,105M. N. Bakirci,105,kkS. Cerci,105,llC. Dozen,105
I. Dumanoglu,105E. Eskut,105S. Girgis,105G. Gokbulut,105I. Hos,105E. E. Kangal,105G. Karapinar,105 A. Kayis Topaksu,105G. Onengut,105K. Ozdemir,105S. Ozturk,105,mmA. Polatoz,105K. Sogut,105,nn D. Sunar Cerci,105,llB. Tali,105,llH. Topakli,105,kkL. N. Vergili,105M. Vergili,105I. V. Akin,106T. Aliev,106B. Bilin,106 S. Bilmis,106M. Deniz,106H. Gamsizkan,106A. M. Guler,106K. Ocalan,106A. Ozpineci,106M. Serin,106R. Sever,106
U. E. Surat,106M. Yalvac,106E. Yildirim,106M. Zeyrek,106M. Deliomeroglu,107E. Gu¨lmez,107B. Isildak,107 M. Kaya,107,ooO. Kaya,107,ooS. Ozkorucuklu,107,ppN. Sonmez,107,qqK. Cankocak,108L. Levchuk,109F. Bostock,110
J. J. Brooke,110E. Clement,110D. Cussans,110H. Flacher,110R. Frazier,110J. Goldstein,110M. Grimes,110 G. P. Heath,110H. F. Heath,110L. Kreczko,110S. Metson,110D. M. Newbold,110,ggK. Nirunpong,110A. Poll,110
S. Senkin,110V. J. Smith,110T. Williams,110L. Basso,111,rrK. W. Bell,111A. Belyaev,111,rrC. Brew,111 R. M. Brown,111D. J. A. Cockerill,111J. A. Coughlan,111K. Harder,111S. Harper,111J. Jackson,111B. W. Kennedy,111
E. Olaiya,111D. Petyt,111B. C. Radburn-Smith,111C. H. Shepherd-Themistocleous,111I. R. Tomalin,111 W. J. Womersley,111R. Bainbridge,112G. Ball,112R. Beuselinck,112O. Buchmuller,112D. Colling,112N. Cripps,112
M. Cutajar,112P. Dauncey,112G. Davies,112M. Della Negra,112W. Ferguson,112J. Fulcher,112D. Futyan,112 A. Gilbert,112A. Guneratne Bryer,112G. Hall,112Z. Hatherell,112J. Hays,112G. Iles,112M. Jarvis,112 G. Karapostoli,112L. Lyons,112A.-M. Magnan,112J. Marrouche,112B. Mathias,112R. Nandi,112J. Nash,112
A. Nikitenko,112,jjA. Papageorgiou,112M. Pesaresi,112K. Petridis,112M. Pioppi,112,ssD. M. Raymond,112 S. Rogerson,112N. Rompotis,112A. Rose,112M. J. Ryan,112C. Seez,112P. Sharp,112,aA. Sparrow,112A. Tapper,112 M. Vazquez Acosta,112T. Virdee,112S. Wakefield,112N. Wardle,112T. Whyntie,112M. Barrett,113M. Chadwick,113 J. E. Cole,113P. R. Hobson,113A. Khan,113P. Kyberd,113D. Leggat,113D. Leslie,113W. Martin,113I. D. Reid,113 P. Symonds,113L. Teodorescu,113M. Turner,113K. Hatakeyama,114H. Liu,114T. Scarborough,114C. Henderson,115 P. Rumerio,115A. Avetisyan,116T. Bose,116C. Fantasia,116A. Heister,116J. St. John,116P. Lawson,116D. Lazic,116 J. Rohlf,116D. Sperka,116L. Sulak,116J. Alimena,117S. Bhattacharya,117D. Cutts,117A. Ferapontov,117U. Heintz,117
S. Jabeen,117G. Kukartsev,117G. Landsberg,117M. Luk,117M. Narain,117D. Nguyen,117M. Segala,117 T. Sinthuprasith,117T. Speer,117K. V. Tsang,117R. Breedon,118G. Breto,118M. Calderon De La Barca Sanchez,118 S. Chauhan,118M. Chertok,118J. Conway,118R. Conway,118P. T. Cox,118J. Dolen,118R. Erbacher,118M. Gardner,118
R. Houtz,118W. Ko,118A. Kopecky,118R. Lander,118O. Mall,118T. Miceli,118R. Nelson,118D. Pellett,118 B. Rutherford,118M. Searle,118J. Smith,118M. Squires,118M. Tripathi,118R. Vasquez Sierra,118V. Andreev,119 D. Cline,119R. Cousins,119J. Duris,119S. Erhan,119P. Everaerts,119C. Farrell,119J. Hauser,119M. Ignatenko,119
C. Plager,119G. Rakness,119P. Schlein,119,aJ. Tucker,119V. Valuev,119M. Weber,119J. Babb,120R. Clare,120 M. E. Dinardo,120J. Ellison,120J. W. Gary,120F. Giordano,120G. Hanson,120G. Y. Jeng,120,ttH. Liu,120O. R. Long,120 A. Luthra,120H. Nguyen,120S. Paramesvaran,120J. Sturdy,120S. Sumowidagdo,120R. Wilken,120S. Wimpenny,120 W. Andrews,121J. G. Branson,121G. B. Cerati,121S. Cittolin,121D. Evans,121F. Golf,121A. Holzner,121R. Kelley,121
M. Lebourgeois,121J. Letts,121I. Macneill,121B. Mangano,121J. Muelmenstaedt,121S. Padhi,121C. Palmer,121 G. Petrucciani,121M. Pieri,121R. Ranieri,121M. Sani,121V. Sharma,121S. Simon,121E. Sudano,121M. Tadel,121 Y. Tu,121A. Vartak,121S. Wasserbaech,121,uuF. Wu¨rthwein,121A. Yagil,121J. Yoo,121D. Barge,122R. Bellan,122 C. Campagnari,122M. D’Alfonso,122T. Danielson,122K. Flowers,122P. Geffert,122J. Incandela,122C. Justus,122 P. Kalavase,122S. A. Koay,122D. Kovalskyi,122,bV. Krutelyov,122S. Lowette,122N. Mccoll,122V. Pavlunin,122 F. Rebassoo,122J. Ribnik,122J. Richman,122R. Rossin,122D. Stuart,122W. To,122C. West,122A. Apresyan,123 A. Bornheim,123Y. Chen,123E. Di Marco,123J. Duarte,123M. Gataullin,123Y. Ma,123A. Mott,123H. B. Newman,123
C. Rogan,123V. Timciuc,123P. Traczyk,123J. Veverka,123R. Wilkinson,123Y. Yang,123R. Y. Zhu,123B. Akgun,124 R. Carroll,124T. Ferguson,124Y. Iiyama,124D. W. Jang,124Y. F. Liu,124M. Paulini,124H. Vogel,124I. Vorobiev,124 J. P. Cumalat,125B. R. Drell,125C. J. Edelmaier,125W. T. Ford,125A. Gaz,125B. Heyburn,125E. Luiggi Lopez,125 J. G. Smith,125K. Stenson,125K. A. Ulmer,125S. R. Wagner,125L. Agostino,126J. Alexander,126A. Chatterjee,126 N. Eggert,126L. K. Gibbons,126B. Heltsley,126W. Hopkins,126A. Khukhunaishvili,126B. Kreis,126N. Mirman,126
G. Nicolas Kaufman,126J. R. Patterson,126A. Ryd,126E. Salvati,126W. Sun,126W. D. Teo,126J. Thom,126 J. Thompson,126J. Vaughan,126Y. Weng,126L. Winstrom,126P. Wittich,126D. Winn,127S. Abdullin,128M. Albrow,128
J. Anderson,128L. A. T. Bauerdick,128A. Beretvas,128J. Berryhill,128P. C. Bhat,128I. Bloch,128K. Burkett,128 J. N. Butler,128V. Chetluru,128H. W. K. Cheung,128F. Chlebana,128V. D. Elvira,128I. Fisk,128J. Freeman,128 Y. Gao,128D. Green,128O. Gutsche,128A. Hahn,128J. Hanlon,128R. M. Harris,128J. Hirschauer,128B. Hooberman,128 S. Jindariani,128M. Johnson,128U. Joshi,128B. Kilminster,128B. Klima,128S. Kunori,128S. Kwan,128D. Lincoln,128 R. Lipton,128L. Lueking,128J. Lykken,128K. Maeshima,128J. M. Marraffino,128S. Maruyama,128D. Mason,128
P. McBride,128K. Mishra,128S. Mrenna,128Y. Musienko,128,vvC. Newman-Holmes,128V. O’Dell,128 O. Prokofyev,128E. Sexton-Kennedy,128S. Sharma,128W. J. Spalding,128L. Spiegel,128P. Tan,128L. Taylor,128
S. Tkaczyk,128N. V. Tran,128L. Uplegger,128E. W. Vaandering,128R. Vidal,128J. Whitmore,128W. Wu,128 F. Yang,128F. Yumiceva,128J. C. Yun,128D. Acosta,129P. Avery,129D. Bourilkov,129M. Chen,129S. Das,129 M. De Gruttola,129G. P. Di Giovanni,129D. Dobur,129A. Drozdetskiy,129R. D. Field,129M. Fisher,129Y. Fu,129
I. K. Furic,129J. Gartner,129J. Hugon,129B. Kim,129J. Konigsberg,129A. Korytov,129A. Kropivnitskaya,129 T. Kypreos,129J. F. Low,129K. Matchev,129P. Milenovic,129,wwG. Mitselmakher,129L. Muniz,129R. Remington,129
A. Rinkevicius,129P. Sellers,129N. Skhirtladze,129M. Snowball,129J. Yelton,129M. Zakaria,129V. Gaultney,130 L. M. Lebolo,130S. Linn,130P. Markowitz,130G. Martinez,130J. L. Rodriguez,130T. Adams,131A. Askew,131
J. Bochenek,131J. Chen,131B. Diamond,131S. V. Gleyzer,131J. Haas,131S. Hagopian,131V. Hagopian,131 M. Jenkins,131K. F. Johnson,131H. Prosper,131V. Veeraraghavan,131M. Weinberg,131M. M. Baarmand,132
B. Dorney,132M. Hohlmann,132H. Kalakhety,132I. Vodopiyanov,132M. R. Adams,133I. M. Anghel,133 L. Apanasevich,133Y. Bai,133V. E. Bazterra,133R. R. Betts,133J. Callner,133R. Cavanaugh,133C. Dragoiu,133
O. Evdokimov,133E. J. Garcia-Solis,133L. Gauthier,133C. E. Gerber,133D. J. Hofman,133S. Khalatyan,133 F. Lacroix,133M. Malek,133C. O’Brien,133C. Silkworth,133D. Strom,133N. Varelas,133U. Akgun,134 E. A. Albayrak,134B. Bilki,134,xxK. Chung,134W. Clarida,134F. Duru,134S. Griffiths,134C. K. Lae,134J.-P. Merlo,134
H. Mermerkaya,134,yyA. Mestvirishvili,134A. Moeller,134J. Nachtman,134C. R. Newsom,134E. Norbeck,134 J. Olson,134Y. Onel,134F. Ozok,134S. Sen,134E. Tiras,134J. Wetzel,134T. Yetkin,134K. Yi,134B. A. Barnett,135
B. Blumenfeld,135S. Bolognesi,135D. Fehling,135G. Giurgiu,135A. V. Gritsan,135Z. J. Guo,135G. Hu,135 P. Maksimovic,135S. Rappoccio,135M. Swartz,135A. Whitbeck,135P. Baringer,136A. Bean,136G. Benelli,136
O. Grachov,136R. P. Kenny Iii,136M. Murray,136D. Noonan,136V. Radicci,136S. Sanders,136R. Stringer,136 G. Tinti,136J. S. Wood,136V. Zhukova,136A. F. Barfuss,137T. Bolton,137I. Chakaberia,137A. Ivanov,137S. Khalil,137
M. Makouski,137Y. Maravin,137S. Shrestha,137I. Svintradze,137J. Gronberg,138D. Lange,138D. Wright,138 A. Baden,139M. Boutemeur,139B. Calvert,139S. C. Eno,139J. A. Gomez,139N. J. Hadley,139R. G. Kellogg,139
M. Kirn,139T. Kolberg,139Y. Lu,139M. Marionneau,139A. C. Mignerey,139A. Peterman,139K. Rossato,139 A. Skuja,139J. Temple,139M. B. Tonjes,139S. C. Tonwar,139E. Twedt,139G. Bauer,140J. Bendavid,140W. Busza,140
E. Butz,140I. A. Cali,140M. Chan,140V. Dutta,140G. Gomez Ceballos,140M. Goncharov,140K. A. Hahn,140 Y. Kim,140M. Klute,140Y.-J. Lee,140W. Li,140P. D. Luckey,140T. Ma,140S. Nahn,140C. Paus,140D. Ralph,140
C. Roland,140G. Roland,140M. Rudolph,140G. S. F. Stephans,140F. Sto¨ckli,140K. Sumorok,140K. Sung,140 D. Velicanu,140E. A. Wenger,140R. Wolf,140B. Wyslouch,140S. Xie,140M. Yang,140Y. Yilmaz,140A. S. Yoon,140
M. Zanetti,140S. I. Cooper,141P. Cushman,141B. Dahmes,141A. De Benedetti,141G. Franzoni,141A. Gude,141 J. Haupt,141S. C. Kao,141K. Klapoetke,141Y. Kubota,141J. Mans,141N. Pastika,141V. Rekovic,141R. Rusack,141 M. Sasseville,141A. Singovsky,141N. Tambe,141J. Turkewitz,141L. M. Cremaldi,142R. Kroeger,142L. Perera,142
R. Rahmat,142D. A. Sanders,142E. Avdeeva,143K. Bloom,143S. Bose,143J. Butt,143D. R. Claes,143 A. Dominguez,143M. Eads,143P. Jindal,143J. Keller,143I. Kravchenko,143J. Lazo-Flores,143H. Malbouisson,143 S. Malik,143G. R. Snow,143U. Baur,144A. Godshalk,144I. Iashvili,144S. Jain,144A. Kharchilava,144A. Kumar,144
S. P. Shipkowski,144K. Smith,144G. Alverson,145E. Barberis,145D. Baumgartel,145M. Chasco,145J. Haley,145 D. Trocino,145D. Wood,145J. Zhang,145A. Anastassov,146A. Kubik,146N. Mucia,146N. Odell,146 R. A. Ofierzynski,146B. Pollack,146A. Pozdnyakov,146M. Schmitt,146S. Stoynev,146M. Velasco,146S. Won,146
L. Antonelli,147D. Berry,147A. Brinkerhoff,147M. Hildreth,147C. Jessop,147D. J. Karmgard,147J. Kolb,147 K. Lannon,147W. Luo,147S. Lynch,147N. Marinelli,147D. M. Morse,147T. Pearson,147R. Ruchti,147J. Slaunwhite,147
N. Valls,147J. Warchol,147M. Wayne,147M. Wolf,147J. Ziegler,147B. Bylsma,148L. S. Durkin,148C. Hill,148 R. Hughes,148P. Killewald,148K. Kotov,148T. Y. Ling,148D. Puigh,148M. Rodenburg,148C. Vuosalo,148 G. Williams,148B. L. Winer,148N. Adam,149E. Berry,149P. Elmer,149D. Gerbaudo,149V. Halyo,149P. Hebda,149
J. Hegeman,149A. Hunt,149E. Laird,149D. Lopes Pegna,149P. Lujan,149D. Marlow,149T. Medvedeva,149 M. Mooney,149J. Olsen,149P. Piroue´,149X. Quan,149A. Raval,149H. Saka,149D. Stickland,149C. Tully,149 J. S. Werner,149A. Zuranski,149J. G. Acosta,150X. T. Huang,150A. Lopez,150H. Mendez,150S. Oliveros,150
J. E. Ramirez Vargas,150A. Zatserklyaniy,150E. Alagoz,151V. E. Barnes,151D. Benedetti,151G. Bolla,151 D. Bortoletto,151M. De Mattia,151A. Everett,151Z. Hu,151M. Jones,151O. Koybasi,151M. Kress,151 A. T. Laasanen,151N. Leonardo,151V. Maroussov,151P. Merkel,151D. H. Miller,151N. Neumeister,151I. Shipsey,151 D. Silvers,151A. Svyatkovskiy,151M. Vidal Marono,151H. D. Yoo,151J. Zablocki,151Y. Zheng,151S. Guragain,152 N. Parashar,152A. Adair,153C. Boulahouache,153V. Cuplov,153K. M. Ecklund,153F. J. M. Geurts,153B. P. Padley,153
R. Redjimi,153J. Roberts,153J. Zabel,153B. Betchart,154A. Bodek,154Y. S. Chung,154R. Covarelli,154 P. de Barbaro,154R. Demina,154Y. Eshaq,154A. Garcia-Bellido,154P. Goldenzweig,154Y. Gotra,154J. Han,154 A. Harel,154S. Korjenevski,154D. C. Miner,154D. Vishnevskiy,154M. Zielinski,154A. Bhatti,155R. Ciesielski,155
L. Demortier,155K. Goulianos,155G. Lungu,155S. Malik,155C. Mesropian,155S. Arora,156A. Barker,156 J. P. Chou,156C. Contreras-Campana,156E. Contreras-Campana,156D. Duggan,156D. Ferencek,156Y. Gershtein,156
R. Gray,156E. Halkiadakis,156D. Hidas,156D. Hits,156A. Lath,156S. Panwalkar,156M. Park,156R. Patel,156 A. Richards,156J. Robles,156K. Rose,156S. Salur,156S. Schnetzer,156C. Seitz,156S. Somalwar,156R. Stone,156
S. Thomas,156G. Cerizza,157M. Hollingsworth,157S. Spanier,157Z. C. Yang,157A. York,157R. Eusebi,158 W. Flanagan,158J. Gilmore,158T. Kamon,158,zzV. Khotilovich,158R. Montalvo,158I. Osipenkov,158Y. Pakhotin,158
A. Perloff,158J. Roe,158A. Safonov,158T. Sakuma,158S. Sengupta,158I. Suarez,158A. Tatarinov,158D. Toback,158 N. Akchurin,159J. Damgov,159P. R. Dudero,159C. Jeong,159K. Kovitanggoon,159S. W. Lee,159T. Libeiro,159 Y. Roh,159I. Volobouev,159E. Appelt,160D. Engh,160C. Florez,160S. Greene,160A. Gurrola,160W. Johns,160 P. Kurt,160C. Maguire,160A. Melo,160P. Sheldon,160B. Snook,160S. Tuo,160J. Velkovska,160M. W. Arenton,161
M. Balazs,161S. Boutle,161B. Cox,161B. Francis,161J. Goodell,161R. Hirosky,161A. Ledovskoy,161C. Lin,161 C. Neu,161J. Wood,161R. Yohay,161S. Gollapinni,162R. Harr,162P. E. Karchin,162
C. Kottachchi Kankanamge Don,162P. Lamichhane,162A. Sakharov,162M. Anderson,163M. Bachtis,163 D. Belknap,163L. Borrello,163D. Carlsmith,163M. Cepeda,163S. Dasu,163L. Gray,163K. S. Grogg,163 M. Grothe,163R. Hall-Wilton,163M. Herndon,163A. Herve´,163P. Klabbers,163J. Klukas,163A. Lanaro,163
C. Lazaridis,163J. Leonard,163R. Loveless,163A. Mohapatra,163I. Ojalvo,163G. A. Pierro,163I. Ross,163 A. Savin,163W. H. Smith,163and J. Swanson163
(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
4
Universiteit 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 12Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil
13
Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria 14University of Sofia, Sofia, Bulgaria
15Institute of High Energy Physics, Beijing, China
16State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, China 17Universidad de Los Andes, Bogota, Colombia
18Technical University of Split, Split, Croatia 19University of Split, Split, Croatia 20Institute Rudjer Boskovic, Zagreb, Croatia
21University of Cyprus, Nicosia, Cyprus 22Charles University, Prague, Czech Republic
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 28
Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France 29DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France
30Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
31Institut Pluridisciplinaire Hubert Curien, Universite´ de Strasbourg, Universite´ de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France
32Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules (IN2P3), Villeurbanne, France 33Universite´ de Lyon, Universite´ Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucle´aire de Lyon, Villeurbanne, France
34Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia 35RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany
36
RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany 37RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany
38Deutsches Elektronen-Synchrotron, Hamburg, Germany 39University of Hamburg, Hamburg, Germany 40Institut fu¨r Experimentelle Kernphysik, Karlsruhe, Germany 41Institute of Nuclear Physics ‘‘Demokritos’’, Aghia Paraskevi, Greece
42University of Athens, Athens, Greece 43University of Ioa´nnina, Ioa´nnina, Greece
44KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary 45Institute of Nuclear Research ATOMKI, Debrecen, Hungary
46University of Debrecen, Debrecen, Hungary 47Panjab University, Chandigarh, India
48University of Delhi, Delhi, India 49Saha Institute of Nuclear Physics, Kolkata, India
50Bhabha Atomic Research Centre, Mumbai, India 51Tata Institute of Fundamental Research-EHEP, Mumbai, India 52
Tata Institute of Fundamental Research - HECR, Mumbai, India 53Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
54aINFN Sezione di Bari, Politecnico di Bari, Bari, Italy 54bUniversita` di Bari, Politecnico di Bari, Bari, Italy
![TABLE I. List of systematic uncertainties (in %) on the cross section measurement. The Best Linear Unbiased Estimation method [ 31 ] is used to combine the cross section measurements in the e h and h channels, with the corresponding weights](https://thumb-eu.123doks.com/thumbv2/123dokorg/5527262.64682/6.918.188.734.806.1075/systematic-uncertainties-measurement-unbiased-estimation-measurements-channels-corresponding.webp)
