Search for resonant top quark plus jet production in tt + jets events with the ATLAS detector in <em>pp</em> collisions at √s=7 TeV

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Article

Reference

Search for resonant top quark plus jet production in tt + jets events with the ATLAS detector in pp collisions at √s=7 TeV

ATLAS Collaboration

ABDELALIM ALY, Ahmed Aly (Collab.), et al.

Abstract

This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying, respectively, to tq or tq, leading to a resonance within the tt+jets signature. The full 2011 ATLAS pp collision data set from the LHC (4.7 fb−1) is used to search for tt events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 Gev for both W′ boson and color triplet models is excluded at 95% confidence level, assuming unit right-handed coupling.

ATLAS Collaboration, ABDELALIM ALY, Ahmed Aly (Collab.), et al . Search for resonant top quark plus jet production in tt + jets events with the ATLAS detector in pp collisions at √s=7 TeV.

Physical Review Letters , 2012, vol. 86, no. 09, p. 091103

DOI : 10.1103/PhysRevD.86.091103

Available at:

http://archive-ouverte.unige.ch/unige:40004

Disclaimer: layout of this document may differ from the published version.

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Search for resonant top quark plus jet production in t t þ jets events with the ATLAS detector in pp collisions at ffiffiffi

p s

¼ 7 TeV

G. Aadet al.* (ATLAS Collaboration)

(Received 28 September 2012; published 26 November 2012)

This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying, respectively, totq ortq, leading to a resonance within thettþjets signature. The full 2011 ATLAS pp collision data set from the LHC (4:7 fb¹) is used to search for tt events produced in association with jets, in which one of theWbosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 Gev for bothW⁰ boson and color triplet models is excluded at 95% confidence level, assuming unit right-handed coupling.

DOI:10.1103/PhysRevD.86.091103 PACS numbers: 13.85.Rm, 12.60.Cn, 14.65.Ha, 14.70.Pw

In the past few decades, remarkable agreement has been shown between measurements in particle physics and the predictions of the Standard Model (SM). The top quark sector is one important place to look for deviations from the SM, as the large top quark mass suggests that it may play a special role in electroweak symmetry breaking. The recent top quark forward-backward asymmetry measurements from the Tevatron experiments [1,2] are in marginal agreement with SM expectations. A non-SM explanation could come from a possible top-flavor-violating process [3–5]. In these models, a new heavy particleRwould be produced at the LHC in association with a top or antitop quark. Figure1shows representative production diagrams for these new particles, for the cases ofR¼W⁰orR¼ (see below). As shown in Ref. [6], the production mecha- nism inppcollisions mainly involves quarks rather than antiquarks at pffiffiffis

¼7 TeV, even for relatively low mass particles.

The larger number of quarks relative to antiquarks produced in the initial state at the LHC leads to a resonanceR that decays predominantly to either the tþjet or tþjet final state, where baryon number conservation restricts the models that are available. Two models that can give rise to these final states are a color singlet resonance (W⁰) mostly in thetq system, and a di-quark color triplet model with a resonance () in thetqsystem. In both cases attþjet final state is produced, but a peak will be present in only one of thetþjet ortþjet invariant mass distributions. The new resonances are assumed not to be self-conjugate, which makes searches for same-sign top quarks insensitive to them [7–9], and to have only right-handed couplings.

The t or t then decays to W^þb or Wb, respectively.

This paper considers the decay signature of events in which oneWboson decays leptonically (to an electron or muon, plus neutrino final state) and the other W boson decays hadronically. The first direct search for such particles was performed at CDF [10], which excluded color triplet resonances with masses below 200 GeV and W⁰ resonances with masses below 300 GeV, for particles with unit right- handed coupling (g_R) totq. As is done in this paper, CDF used the formalism in Ref. [3] to defineg_R. CMS recently performed a search that excluded a new W⁰ with a mass less than 840 GeV [11] for particles withg_R¼2[12].

The analysis presented here uses the full ATLAS 7 TeV ppcollision data set collected in 2011, corresponding to 4:70:2 fb¹ of integrated luminosity [13,14] delivered by the LHC. ATLAS [15] is a multipurpose particle physics detector with cylindrical geometry [16]. The inner detector (ID) system consists of a high-granularity silicon pixel detector and a silicon microstrip detector, as well as a transition radiation straw-tube tracker. The ID is immersed in a 2 T axial magnetic field and provides charged particle tracking in the rangejj<2:5. Surrounding the ID, electromagnetic calorimetry is provided by barrel and endcap liquid-argon (LAr)/lead accordion calorimeters and LAr/

copper sampling calorimeters in the forward region.

Hadronic calorimetry is provided in the barrel by a steel/

scintillator tile sampling calorimeter, and in the endcaps and forward region by LAr/copper and LAr/tungsten sampling calorimeters, respectively. The muon spectrometer comprises separate trigger and high-precision tracking chambers measuring the deflection of muons in a magnetic field with a bending power of 2–8 Tm, generated by three superconducting air-core toroid systems. A three-level trigger system is used to select interesting events. The level-1 trigger is implemented in hardware and uses a subset of detector information to reduce the event rate to a design value of at most 75 kHz. This is followed by two

*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 distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

PHYSICAL REVIEW D86,091103(R) (2012)

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software-based trigger levels, level-2 and the event filter, which together reduce the event rate to300 Hz.

Events with an electron (muon) are required to have passed an electron (muon) trigger with a threshold of transverse energy E_T>20 GeV (transverse momentum p_T>18 GeV), ensuring that the trigger is fully efficient for the offline selection discussed below. Electrons reconstructed offline are required to have a shower shape in the electromagnetic calorimeter consistent with expectation, as well as a good quality track pointing to the cluster in the calorimeter. Candidate electrons with E_T>25 GeV are required to pass the ‘‘tight’’ electron quality criteria [17], to fall inside a well-instrumented region of the detector (jj<2:47, excluding 1:37<jj<1:52), and to be isolated from other objects in the event. Muons with transverse momentump_T>20 GeVare required to pass muon quality criteria [18], to be well measured in both the ID and the muon spectrometer, to fall withinjj<2:5, and to be isolated from other objects in the event.

Jets are reconstructed in the calorimeter using the anti-k_t [19] algorithm with a radius parameter of 0.4. Jets are required to satisfy p_T>25 GeV and jj<2:5. Events with jets arising from electronic noise bursts and beam backgrounds are rejected [20]. Jets are calibrated to the hadronic energy scale usingp_T- and-dependent correc- tions derived from simulation, as well as from test-beam and collision data [21]. Jets from the decay of heavy flavor hadrons are selected by a multivariateb-tagging algorithm [22] at an operating point with 70% efficiency forb jets and a mistag rate for light quark jets of less than 1% in simulatedttevents. Neutrinos are inferred from the magnitude of the missing transverse momentum (E^miss_T ) in the event [23].

The signal region for this analysis is defined by requiring exactly one charged lepton and five or more jets, including at least oneb-tagged jet. To select events with a leptonically decaying W boson, events are required to have E^miss_T >30 GeV (E^miss_T >20 GeV) in the electron (muon) channel. Additionally, the event must have a transverse mass of the leptonically decayingWbosonm^W_T >30 GeV in the electron channel, or scalar sum E^miss_T þm^W_T >

60 GeV in the muon channel [24]. Here, ðm^W_TÞ² ¼ 2E^miss_T E^‘_Tð1cosÞ, where E^‘_T is the magnitude of the

transverse momentum of the lepton, and is the angle between the lepton and the missing transverse momentum in the event.

A variety of Monte Carlo generators are used to study and estimate backgrounds. The generated events are pro- cessed through full detector simulation [25], based on GEANT4 [26], and include the effect of multiple pp interactions per bunch crossing. To predict the event yield, the simulation is given an event-by-event weight such that FIG. 1. Example production and decay Feynman diagrams for

the (a)W⁰ and (b)models.

100 200 300

Events / 40 GeV

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103

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400 GeV φ

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[GeV]

mtj

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1 Uncertainty

FIG. 2 (color online). The leading jet p_T in the four-jet tt control region (a), and m_tj in the five-jetttcontrol region (b).

The example signal-only distributions are overlaid for comparison, where unit coupling for the new physics process is assumed.

The total uncertainty shown on the ratio includes both statistical and systematic effects. The ‘‘other’’ background category includes single top production, diboson production, and multijet events.

G. AADet al. PHYSICAL REVIEW D86,091103(R) (2012)

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the distribution of the number of pp collisions matches that in data.

The tt background is modeled with MC@NLO v4.01 [27] interfaced to HERWIG v6.520 [28] and JIMMY v4.31 [29]. An additional tt sample modeled with MC@NLO interfaced to PYTHIA v6.425 [30] is used to study potential systematic uncertainties. Otherttsamples use POWHEG [31] interfaced either to PYTHIA or HERWIG, as well as AcerMC v3.8 [32]. The background from the production of singleWbosons in association with extra jets is modeled by the ALPGEN v2.13 [33] generator interfaced to HERWIG. The MLM matching scheme [34]

is used to form inclusiveWbosonþjets samples such that overlapping events produced in both the hard scatter and parton showering are removed. In addition, the heavy flavor contributions are reweighted using the data-driven procedures of Ref. [24] using the full 2011 LHC data set.

Diboson events are generated using HERWIG. Single- top-quark events are modeled by MC@NLO, interfaced with HERWIG for the parton showering, in theschannel and Wt channel, and by AcerMC v3.8 in the t channel.

The small background in which multijet processes are misidentified as prompt leptons is modeled from a data- driven matrix method [35]. In determining the expected event yields, thettcross section is normalized to approxi- mate next-to-next-to-leading-order QCD calculations of 167^þ17₁₈ pb for a top quark mass of 172.5 GeV [36,37], and the totalWþjets background is normalized to inclu- sive next-to-next-to-leading-order predictions [38]. Signal

events are produced, for a range of W⁰ and masses, with MadGraph v5.1.3.16 [39] and interfaced to PYTHIA v6.425. Next-to-leading-order (NLO) cross sections are used for the predictedW⁰ boson signal normalization [6], and leading-order (LO) cross sections using MSTW2008 are used for the-resonance normalization [3].

Events are reconstructed with a kinematic fitting algorithm that utilizes knowledge of the overconstrained tt system to assign jets to partons. In the fit, the two top quark masses are each constrained at the particle level to

500

Events / 175 GeV

1 10 102

103

104 ^Data

∫

L dt = 4.7 fb^-1

400 GeV φ

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[GeV]

mtj

500 1000 1500 2000 2500

(data-SM)/SM

-1 -0.5 0 0.5

1 Uncertainty

FIG. 3 (color online). Expected and observed distribution of m_tj in the Wþjets control region. The example signal-only distributions are overlaid for comparison, where unit coupling for the new physics process is assumed. The total uncertainty shown on the ratio includes both statistical and systematic effects. The other background category includes single top production, diboson production, and multijet events.

500 1000 1500 2000

Events / 175 GeV

1 10 102

103

104

L dt = 4.7 fb-1

∫

Data t t W + jets Other W' 300 GeV

400 GeV φ

ATLAS

[GeV]

mtj

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(data-SM)/SM -1

-0.5 0 0.5

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500 1000 1500 2000

Events / 175 GeV

1 10 102

103

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∫

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400 GeV φ

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j

mt

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(data-SM)/SM

-1 -0.5 0 0.5

1 Uncertainty

FIG. 4 (color online). Expected and observed distributions of (a) m_tj and (b) m_tj in the signal region. The example signal distributions assume unit coupling for the new physics process.

The total uncertainty shown on the ratio includes both statistical and systematic effects. The other background category includes single top production, diboson production, and multijet events.

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172.5 GeV by a penalty in the likelihood, computed from variations from this nominal value and the natural top quark width of 1.5 GeV. The two W boson masses are similarly constrained to 80.4 GeV within a width of 2.1 GeV. This allows thezcomponent of the momentum of the neutrino from the leptonically decayingW boson to be computed. Both solutions from the quadratic ambiguity of this computation are tested when computing the likelihood. Charged lepton, neutrino, and jet four-momenta are constrained in the fit by resolution transfer functions derived from simulated tt events that relate the measured momenta in the detector to true particle momenta. The full shapes of these transfer functions are used in the likelihood computation. All assignments of any four jets to partons from the tt decay are tested and the assignment with the largest likelihood output for thett hypothesis is selected. After the assignment is selected, the originally measured jet and lepton momenta andE^miss_T are used. The remaining jets not associated with the tt partons are included to form m_tj and m_tj masses, where the charge of the lepton is used to infer which is the top candidate and which is the antitop candidate. All combinations of extra jets with the top and antitop quark candidates are

considered, and the pairings that give the largest m_tj and m_tjmasses are used. In this way, the same extra jet can (but does not necessarily have to) be used to formm_tjandm_tj. These two masses are used as observables for the search.

Several control regions are used to ensure good model- ing and understanding of the backgrounds before the signal region is examined. The preselection control region requires at least four jets, but does not require a b tag.

The dominant tt background is tested in a control region with exactly four jets (including at least oneb-tagged jet).

The rejection of events with more than four jets reduces signal contamination. A secondttcontrol region is defined by events with exactly four jets withp_Tabove 25 GeV, one of which must be b tagged, and exactly one additional jet withp_Tbetween 20 GeV and 25 GeV. Signal contamination is further reduced by requiring that theffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi R

ðÞ²þ ðÞ²

p between the fifth jet and both the reconstructed top and antitop quarks is greater than =2.

Figure2shows distributions in the twottcontrol regions, where good agreement is observed between data and the prediction. The second major background, production of singleWbosons in association with extra jets, is tested in a

TABLE II. Expected and observed yields in different signal regions. The errors include all systematic uncertainties. Total refers to the total expected background, includingtt,Wþjets, and the other smaller backgrounds: single top production, diboson production, and multijet events, which are not tabulated separately here. Signal window eff. refers to the efficiency for the signal to fall inside the optimized two-dimensional mass window. The signal region yield is calculated in the mass window at each benchmark signal point.

Signalrefers to the total expected signal cross section, not taking into account thet(ort) plus jet branching fraction.

Entire signal region 300 GeVW⁰ 600 GevW⁰ 400 GeV 800 GeV

m_tj window [GeV] 344< m_tj<494 566< m_tj<904 401< m_tj<455 766< m_tj<819 m_tj window [GeV] 292< m_tj <339 549< m_tj <650 371< m_tj <608 628< m_tj<973

Signal window eff. 7.5% 9.9% 11.9% 5.7%

tt 180003000 740160 27060 660150 6010

Wþjets 1700560 6030 3020 8040 85

Total 220003700 820190 32080 780180 7020

Observed 22731 970 343 923 77

Signal region yield 560120 9824 410100 206

Signal 19.0 pb 1.55 pb 7.9 pb 0.67 pb

TABLE I. Expected and observed yields in the four control regions (CR). Total refers to the total expected background, includingtt,Wþjets, and the other smaller backgrounds: single top production, diboson production, and multijet events. The last two lines show the expected number of events for two benchmark signal samples in each of these control regions. The errors include all systematic uncertainties.

Preselection CR Wþjets CR Four-jetttCR Five-jetttCR

tt 500004700 2000400 19000600 2100200

Wþjets 4600014000 70002900 3800800 360170

Total 11600021000 120003600 260001300 2900440

Observed 110933 11858 26197 2736

300 GeVW⁰ 13900670 930110 3000400 40080

400 GeV 6100200 43060 1100100 20020

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control region with five or more jets, vetoing events with b-tagged jets. The requirement of zero b-tagged jets reduces both signal andttcontamination. The distribution in Fig. 3 shows good agreement between data and the prediction within uncertainties. Table I summarizes the expected and observed yields in the control regions.

Figure4shows the expected and observedm_tj andm_tj distributions in the signal region. The data are found to be consistent with the SM expectation. A variety of potential systematic effects are evaluated for the predicted signal and the background rates and shapes. The dominant systematic effects of the jet energy scale [21] and resolution

[40] lead to uncertainties of up to 10% on the total background rate and up to 21% on the total signal expectation, depending on the mass of the new particle. The other dominant systematic uncertainty from the difference in b-tagging efficiency between simulation and data leads to uncertainties of roughly 16% on both the signal and background rates. Effects due to lepton trigger uncertainties and ID efficiency as well as the energy scale and resolution are

W' mass [GeV]

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R = 1

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± 2

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σ

± 1 σ

± 2

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ATLAS = 7 TeV s

L dt = 4.7 fb-1

∫

FIG. 5 (color online). Expected and observed 95% C.L. upper limits on the (a)W⁰and (b)model cross sections. The CDF result is documented in Ref. [10]. TheW⁰cross sections are NLO calculations, and thecross sections are LO calculations.

W' mass [GeV]

500 1000 1500 2000 2500

RCoupling g

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Expected exclusion

95% C.L. exclusion CDF exclusion

(M. Gresham et al.)

t

σt

and

Favored by Tevatron AFB

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95% C.L. exclusion CDF exclusion

(M. Gresham et al.)

t

σt

and

Favored by Tevatron AFB

ATLAS

L dt = 4.7 fb-1

∫

= 7 TeV s

FIG. 6 (color online). Expected and observed 95% C.L. upper limits on the (a)W⁰and (b)model cross sections assuming a cross section that scales with g²_R. The hatched area shows the region of parameter space excluded by this search at 95% C.L.

The CDF result is documented in Ref. [10]. The W⁰ cross sections are NLO calculations, and the cross sections are LO calculations. The region favored by the TevatronA_FBand_t_t measurements is shown as the dark band [42].

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assessed usingZ!ee and Z! data, which lead to systematic uncertainties of a few percent. Other potential systematic effects considered are the size of the small multijet background (assigned 100% uncertainty);ttgen- erator uncertainties (evaluated by comparing different results using the MC@NLO and POWHEG generators, 1–10%); tt showering and fragmentation uncertainties (evaluated by comparing samples using both PYTHIA and HERWIG, 1%–6%); an uncertainty on the total integrated luminosity (3.9%) [13,14]; and the amount of QCD radiation for the signal and the tt background (approxi- mately 10%, evaluated using AcerMC). Total cross section uncertainties of 10% (55%) are used for thett(Wþjets) backgrounds.

Expected and observed upper limits on the signal cross section are computed at discrete mass points as follows.

For each benchmark signal mass point under consideration, a signal region is defined in the m_tj-m_tj plane. When setting limits for theW⁰ () model, them_tj (m_tj) window is significantly wider than them_tj (m_tj) window to account for the fact that the resonance is predominantly in them_tj (m_tj) system. The windows are optimized to maximize sensitivity, accounting for the full effect of systematic uncertainties. Typical mass windows are shown in Table II. For each mass window, 95% confidence level (C.L.) upper limits on the signal cross section (times the branching ratio totort) are computed using a single bin frequentistCL_smethod [41]. No shape information is used within the mass windows. TableIIshows the expected and observed event yields in several of the signal region windows. Expected and observed 95% C.L. lower limits on the signal mass are derived, assuming a coupling of g_R¼1 andg_R¼2, and are shown in Fig. 5. Assuming that the cross section scales as g²_R, the exclusion in the mass- coupling plane is shown in Fig.6. As shown, most of the parameter space in this model, which was favored by the Tevatron forward-backward asymmetry and cross section measurements [42], has been excluded.

In conclusion, this paper presents a search for a new heavy particleRin thetjortj system ofttplus extra jet events with the ATLAS detector. Such new particles have been proposed as a potential explanation of the difference from the SM values of the forward-backward asymmetries measured in top quark pair production at the Tevatron. The full 2011 ATLAS pp data set (4:7 fb¹) is used in the

search. Assuming unit coupling, the expected 95% C.L.

lower limit on the mass of the new particle is 500 (700) GeV in the W⁰ () model. No significant excess of data above SM expectation is observed, and 95% C.L.

lower limits of 430 GeV for both the W⁰ and models are set. Atg_R¼2, the limits are 1.10 (1.45) TeV for theW⁰ () model, with expected limits of 0.93 (1.30) TeV. These are the most stringent limits to date on such models. Most of the regions of parameter space for these models that are more consistent with the Tevatron forward-backward asymmetry and tt cross section measurements than the SM are excluded at 95% C.L. by these results.

We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently.

We acknowledge the support of ANPCyT, Argentina;

YerPhI, Armenia; ARC, Australia; BMWF and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC, and CFI, Canada;

CERN; CONICYT, Chile; CAS, MOST, and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR, and VSC CR, Czech Republic; DNRF, DNSRC, and Lundbeck Foundation, Denmark; EPLANET and ERC, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG, and AvH Foundation, Germany; GSRT, Greece; ISF, MINERVA, GIF, DIP, and Benoziyo Center, Israel;

INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco;

FOM and NWO, Netherlands; BRF and RCN, Norway;

MNiSW, Poland; GRICES and FCT, Portugal; MERYS (MECTS), Romania; MES of Russia and ROSATOM, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and MVZT, Slovenia; DST/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF, and Cantons of Bern and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society and Leverhulme Trust, United Kingdom;

DOE and NSF, U.S.A. The crucial computing support from all WLCG partners is acknowledged gratefully, in particu- lar, from CERN and the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN- CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK), and BNL (USA) and in the Tier-2 facilities worldwide.

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[42] This region simultaneously satisfies the observed high-mttA_FB, low-mttA_FB, and _t_t observed at the Tevatron. Mathematically it is defined as the region with ²<2:8, where ² is defined in Eq. (22) in M. Gresham, I.-W. Kim, and K. Zurek, Phys. Rev. D 85, 014022 (2012). The ² for the Standard Model is 2.8.

G. Aad,⁴⁸T. Abajyan,²¹B. Abbott,¹¹¹J. Abdallah,¹²S. Abdel Khalek,¹¹⁵A. A. Abdelalim,⁴⁹O. Abdinov,¹¹ R. Aben,¹⁰⁵B. Abi,¹¹²M. Abolins,⁸⁸O. S. AbouZeid,¹⁵⁸H. Abramowicz,¹⁵³H. Abreu,¹³⁶E. Acerbi,^89a,89b B. S. Acharya,^164a,164bL. Adamczyk,³⁸D. L. Adams,²⁵T. N. Addy,⁵⁶J. Adelman,¹⁷⁶S. Adomeit,⁹⁸P. Adragna,⁷⁵ T. Adye,¹²⁹S. Aefsky,²³J. A. Aguilar-Saavedra,^124b,bM. Agustoni,¹⁷M. Aharrouche,⁸¹S. P. Ahlen,²²F. Ahles,⁴⁸ A. Ahmad,¹⁴⁸M. Ahsan,⁴¹G. Aielli,^133a,133bT. Akdogan,^19aT. P. A. A˚ kesson,⁷⁹G. Akimoto,¹⁵⁵A. V. Akimov,⁹⁴

M. S. Alam,²M. A. Alam,⁷⁶J. Albert,¹⁶⁹S. Albrand,⁵⁵M. Aleksa,³⁰I. N. Aleksandrov,⁶⁴F. Alessandria,^89a C. Alexa,^26aG. Alexander,¹⁵³G. Alexandre,⁴⁹T. Alexopoulos,¹⁰M. Alhroob,^164a,164cM. Aliev,¹⁶G. Alimonti,^89a

J. Alison,¹²⁰B. M. M. Allbrooke,¹⁸P. P. Allport,⁷³S. E. Allwood-Spiers,⁵³J. Almond,⁸²A. Aloisio,^102a,102b R. Alon,¹⁷²A. Alonso,⁷⁹F. Alonso,⁷⁰B. Alvarez Gonzalez,⁸⁸M. G. Alviggi,^102a,102bK. Amako,⁶⁵C. Amelung,²³ SEARCH FOR RESONANT TOP QUARK PLUS JET. . . PHYSICAL REVIEW D86,091103(R) (2012)

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V. V. Ammosov,^128,aS. P. Amor Dos Santos,^124aA. Amorim,^124a,cN. Amram,¹⁵³C. Anastopoulos,³⁰L. S. Ancu,¹⁷ N. Andari,¹¹⁵T. Andeen,³⁵C. F. Anders,^58bG. Anders,^58aK. J. Anderson,³¹A. Andreazza,^89a,89bV. Andrei,^58a

X. S. Anduaga,⁷⁰P. Anger,⁴⁴A. Angerami,³⁵F. Anghinolfi,³⁰A. Anisenkov,¹⁰⁷N. Anjos,^124aA. Annovi,⁴⁷ A. Antonaki,⁹M. Antonelli,⁴⁷A. Antonov,⁹⁶J. Antos,^144bF. Anulli,^132aM. Aoki,¹⁰¹S. Aoun,⁸³L. Aperio Bella,⁵

R. Apolle,^118,dG. Arabidze,⁸⁸I. Aracena,¹⁴³Y. Arai,⁶⁵A. T. H. Arce,⁴⁵S. Arfaoui,¹⁴⁸J-F. Arguin,¹⁵E. Arik,^19a,a M. Arik,^19aA. J. Armbruster,⁸⁷O. Arnaez,⁸¹V. Arnal,⁸⁰C. Arnault,¹¹⁵A. Artamonov,⁹⁵G. Artoni,^132a,132b

D. Arutinov,²¹S. Asai,¹⁵⁵R. Asfandiyarov,¹⁷³S. Ask,²⁸B. A˚ sman,^146a,146bL. Asquith,⁶K. Assamagan,²⁵ A. Astbury,¹⁶⁹M. Atkinson,¹⁶⁵B. Aubert,⁵E. Auge,¹¹⁵K. Augsten,¹²⁷M. Aurousseau,^145aG. Avolio,¹⁶³ R. Avramidou,¹⁰D. Axen,¹⁶⁸G. Azuelos,^93,eY. Azuma,¹⁵⁵M. A. Baak,³⁰G. Baccaglioni,^89aC. Bacci,^134a,134b

A. M. Bach,¹⁵H. Bachacou,¹³⁶K. Bachas,³⁰M. Backes,⁴⁹M. Backhaus,²¹E. Badescu,^26aP. Bagnaia,^132a,132b S. Bahinipati,³Y. Bai,^33aD. C. Bailey,¹⁵⁸T. Bain,¹⁵⁸J. T. Baines,¹²⁹O. K. Baker,¹⁷⁶M. D. Baker,²⁵S. Baker,⁷⁷ E. Banas,³⁹P. Banerjee,⁹³Sw. Banerjee,¹⁷³D. Banfi,³⁰A. Bangert,¹⁵⁰V. Bansal,¹⁶⁹H. S. Bansil,¹⁸L. Barak,¹⁷² S. P. Baranov,⁹⁴A. Barbaro Galtieri,¹⁵T. Barber,⁴⁸E. L. Barberio,⁸⁶D. Barberis,^50a,50bM. Barbero,²¹D. Y. Bardin,⁶⁴

T. Barillari,⁹⁹M. Barisonzi,¹⁷⁵T. Barklow,¹⁴³N. Barlow,²⁸B. M. Barnett,¹²⁹R. M. Barnett,¹⁵A. Baroncelli,^134a G. Barone,⁴⁹A. J. Barr,¹¹⁸F. Barreiro,⁸⁰J. Barreiro Guimara˜es da Costa,⁵⁷P. Barrillon,¹¹⁵R. Bartoldus,¹⁴³ A. E. Barton,⁷¹V. Bartsch,¹⁴⁹A. Basye,¹⁶⁵R. L. Bates,⁵³L. Batkova,^144aJ. R. Batley,²⁸A. Battaglia,¹⁷M. Battistin,³⁰ F. Bauer,¹³⁶H. S. Bawa,^143,fS. Beale,⁹⁸T. Beau,⁷⁸P. H. Beauchemin,¹⁶¹R. Beccherle,^50aP. Bechtle,²¹H. P. Beck,¹⁷ A. K. Becker,¹⁷⁵S. Becker,⁹⁸M. Beckingham,¹³⁸K. H. Becks,¹⁷⁵A. J. Beddall,^19cA. Beddall,^19cS. Bedikian,¹⁷⁶ V. A. Bednyakov,⁶⁴C. P. Bee,⁸³L. J. Beemster,¹⁰⁵M. Begel,²⁵S. Behar Harpaz,¹⁵²P. K. Behera,⁶²M. Beimforde,⁹⁹

C. Belanger-Champagne,⁸⁵P. J. Bell,⁴⁹W. H. Bell,⁴⁹G. Bella,¹⁵³L. Bellagamba,^20aF. Bellina,³⁰M. Bellomo,³⁰ A. Belloni,⁵⁷O. Beloborodova,^107,gK. Belotskiy,⁹⁶O. Beltramello,³⁰O. Benary,¹⁵³D. Benchekroun,^135a

K. Bendtz,^146a,146bN. Benekos,¹⁶⁵Y. Benhammou,¹⁵³E. Benhar Noccioli,⁴⁹J. A. Benitez Garcia,^159b D. P. Benjamin,⁴⁵M. Benoit,¹¹⁵J. R. Bensinger,²³K. Benslama,¹³⁰S. Bentvelsen,¹⁰⁵D. Berge,³⁰ E. Bergeaas Kuutmann,⁴²N. Berger,⁵F. Berghaus,¹⁶⁹E. Berglund,¹⁰⁵J. Beringer,¹⁵P. Bernat,⁷⁷R. Bernhard,⁴⁸ C. Bernius,²⁵T. Berry,⁷⁶C. Bertella,⁸³A. Bertin,^20a,20bF. Bertolucci,^122a,122bM. I. Besana,^89a,89bG. J. Besjes,¹⁰⁴

N. Besson,¹³⁶S. Bethke,⁹⁹W. Bhimji,⁴⁶R. M. Bianchi,³⁰M. Bianco,^72a,72bO. Biebel,⁹⁸S. P. Bieniek,⁷⁷ K. Bierwagen,⁵⁴J. Biesiada,¹⁵M. Biglietti,^134aH. Bilokon,⁴⁷M. Bindi,^20a,20bS. Binet,¹¹⁵A. Bingul,^19c C. Bini,^132a,132bC. Biscarat,¹⁷⁸B. Bittner,⁹⁹K. M. Black,²²R. E. Blair,⁶J.-B. Blanchard,¹³⁶G. Blanchot,³⁰ T. Blazek,^144aI. Bloch,⁴²C. Blocker,²³J. Blocki,³⁹A. Blondel,⁴⁹W. Blum,⁸¹U. Blumenschein,⁵⁴G. J. Bobbink,¹⁰⁵

V. B. Bobrovnikov,¹⁰⁷S. S. Bocchetta,⁷⁹A. Bocci,⁴⁵C. R. Boddy,¹¹⁸M. Boehler,⁴⁸J. Boek,¹⁷⁵N. Boelaert,³⁶ J. A. Bogaerts,³⁰A. Bogdanchikov,¹⁰⁷A. Bogouch,^90,aC. Bohm,^146aJ. Bohm,¹²⁵V. Boisvert,⁷⁶T. Bold,³⁸ V. Boldea,^26aN. M. Bolnet,¹³⁶M. Bomben,⁷⁸M. Bona,⁷⁵M. Boonekamp,¹³⁶C. N. Booth,¹³⁹S. Bordoni,⁷⁸ C. Borer,¹⁷A. Borisov,¹²⁸G. Borissov,⁷¹I. Borjanovic,^13aM. Borri,⁸²S. Borroni,⁸⁷V. Bortolotto,^134a,134bK. Bos,¹⁰⁵

D. Boscherini,^20aM. Bosman,¹²H. Boterenbrood,¹⁰⁵J. Bouchami,⁹³J. Boudreau,¹²³E. V. Bouhova-Thacker,⁷¹ D. Boumediene,³⁴C. Bourdarios,¹¹⁵N. Bousson,⁸³A. Boveia,³¹J. Boyd,³⁰I. R. Boyko,⁶⁴I. Bozovic-Jelisavcic,^13b

J. Bracinik,¹⁸P. Branchini,^134aG. W. Brandenburg,⁵⁷A. Brandt,⁸G. Brandt,¹¹⁸O. Brandt,⁵⁴U. Bratzler,¹⁵⁶ B. Brau,⁸⁴J. E. Brau,¹¹⁴H. M. Braun,^175,aS. F. Brazzale,^164a,164cB. Brelier,¹⁵⁸J. Bremer,³⁰K. Brendlinger,¹²⁰ R. Brenner,¹⁶⁶S. Bressler,¹⁷²D. Britton,⁵³F. M. Brochu,²⁸I. Brock,²¹R. Brock,⁸⁸F. Broggi,^89aC. Bromberg,⁸⁸

J. Bronner,⁹⁹G. Brooijmans,³⁵T. Brooks,⁷⁶W. K. Brooks,^32bG. Brown,⁸²H. Brown,⁸

P. A. Bruckman de Renstrom,³⁹D. Bruncko,^144bR. Bruneliere,⁴⁸S. Brunet,⁶⁰A. Bruni,^20aG. Bruni,^20a M. Bruschi,^20aT. Buanes,¹⁴Q. Buat,⁵⁵F. Bucci,⁴⁹J. Buchanan,¹¹⁸P. Buchholz,¹⁴¹R. M. Buckingham,¹¹⁸

A. G. Buckley,⁴⁶S. I. Buda,^26aI. A. Budagov,⁶⁴B. Budick,¹⁰⁸V. Bu¨scher,⁸¹L. Bugge,¹¹⁷O. Bulekov,⁹⁶ A. C. Bundock,⁷³M. Bunse,⁴³T. Buran,¹¹⁷H. Burckhart,³⁰S. Burdin,⁷³T. Burgess,¹⁴S. Burke,¹²⁹E. Busato,³⁴

P. Bussey,⁵³C. P. Buszello,¹⁶⁶B. Butler,¹⁴³J. M. Butler,²²C. M. Buttar,⁵³J. M. Butterworth,⁷⁷W. Buttinger,²⁸ S. Cabrera Urba´n,¹⁶⁷D. Caforio,^20a,20bO. Cakir,^4aP. Calafiura,¹⁵G. Calderini,⁷⁸P. Calfayan,⁹⁸R. Calkins,¹⁰⁶ L. P. Caloba,^24aR. Caloi,^132a,132bD. Calvet,³⁴S. Calvet,³⁴R. Camacho Toro,³⁴P. Camarri,^133a,133bD. Cameron,¹¹⁷

L. M. Caminada,¹⁵R. Caminal Armadans,¹²S. Campana,³⁰M. Campanelli,⁷⁷V. Canale,^102a,102bF. Canelli,^31,h A. Canepa,^159aJ. Cantero,⁸⁰R. Cantrill,⁷⁶L. Capasso,^102a,102bM. D. M. Capeans Garrido,³⁰I. Caprini,^26a

M. Caprini,^26aD. Capriotti,⁹⁹M. Capua,^37a,37bR. Caputo,⁸¹R. Cardarelli,^133aT. Carli,³⁰G. Carlino,^102a L. Carminati,^89a,89bB. Caron,⁸⁵S. Caron,¹⁰⁴E. Carquin,^32bG. D. Carrillo Montoya,¹⁷³A. A. Carter,⁷⁵J. R. Carter,²⁸

J. Carvalho,^124a,iD. Casadei,¹⁰⁸M. P. Casado,¹²M. Cascella,^122a,122bC. Caso,^50a,50b,a

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A. M. Castaneda Hernandez,^173,jE. Castaneda-Miranda,¹⁷³V. Castillo Gimenez,¹⁶⁷N. F. Castro,^124aG. Cataldi,^72a P. Catastini,⁵⁷A. Catinaccio,³⁰J. R. Catmore,³⁰A. Cattai,³⁰G. Cattani,^133a,133bS. Caughron,⁸⁸V. Cavaliere,¹⁶⁵ P. Cavalleri,⁷⁸D. Cavalli,^89aM. Cavalli-Sforza,¹²V. Cavasinni,^122a,122bF. Ceradini,^134a,134bA. S. Cerqueira,^24b A. Cerri,³⁰L. Cerrito,⁷⁵F. Cerutti,⁴⁷S. A. Cetin,^19bA. Chafaq,^135aD. Chakraborty,¹⁰⁶I. Chalupkova,¹²⁶K. Chan,³

P. Chang,¹⁶⁵B. Chapleau,⁸⁵J. D. Chapman,²⁸J. W. Chapman,⁸⁷E. Chareyre,⁷⁸D. G. Charlton,¹⁸V. Chavda,⁸² C. A. Chavez Barajas,³⁰S. Cheatham,⁸⁵S. Chekanov,⁶S. V. Chekulaev,^159aG. A. Chelkov,⁶⁴M. A. Chelstowska,¹⁰⁴

C. Chen,⁶³H. Chen,²⁵S. Chen,^33cX. Chen,¹⁷³Y. Chen,³⁵A. Cheplakov,⁶⁴R. Cherkaoui El Moursli,^135e V. Chernyatin,²⁵E. Cheu,⁷S. L. Cheung,¹⁵⁸L. Chevalier,¹³⁶G. Chiefari,^102a,102bL. Chikovani,^51a,aJ. T. Childers,³⁰ A. Chilingarov,⁷¹G. Chiodini,^72aA. S. Chisholm,¹⁸R. T. Chislett,⁷⁷A. Chitan,^26aM. V. Chizhov,⁶⁴G. Choudalakis,³¹

S. Chouridou,¹³⁷I. A. Christidi,⁷⁷A. Christov,⁴⁸D. Chromek-Burckhart,³⁰M. L. Chu,¹⁵¹J. Chudoba,¹²⁵ G. Ciapetti,^132a,132bA. K. Ciftci,^4aR. Ciftci,^4aD. Cinca,³⁴V. Cindro,⁷⁴C. Ciocca,^20a,20bA. Ciocio,¹⁵M. Cirilli,⁸⁷

P. Cirkovic,^13bZ. H. Citron,¹⁷²M. Citterio,^89aM. Ciubancan,^26aA. Clark,⁴⁹P. J. Clark,⁴⁶R. N. Clarke,¹⁵ W. Cleland,¹²³J. C. Clemens,⁸³B. Clement,⁵⁵C. Clement,^146a,146bY. Coadou,⁸³M. Cobal,^164a,164cA. Coccaro,¹³⁸ J. Cochran,⁶³J. G. Cogan,¹⁴³J. Coggeshall,¹⁶⁵E. Cogneras,¹⁷⁸J. Colas,⁵S. Cole,¹⁰⁶A. P. Colijn,¹⁰⁵N. J. Collins,¹⁸

C. Collins-Tooth,⁵³J. Collot,⁵⁵T. Colombo,^119a,119bG. Colon,⁸⁴P. Conde Muin˜o,^124aE. Coniavitis,¹¹⁸ M. C. Conidi,¹²S. M. Consonni,^89a,89bV. Consorti,⁴⁸S. Constantinescu,^26aC. Conta,^119a,119bG. Conti,⁵⁷ F. Conventi,^102a,kM. Cooke,¹⁵B. D. Cooper,⁷⁷A. M. Cooper-Sarkar,¹¹⁸K. Copic,¹⁵T. Cornelissen,¹⁷⁵M. Corradi,^20a

F. Corriveau,^85,lA. Cortes-Gonzalez,¹⁶⁵G. Cortiana,⁹⁹G. Costa,^89aM. J. Costa,¹⁶⁷D. Costanzo,¹³⁹D. Coˆte´,³⁰ L. Courneyea,¹⁶⁹G. Cowan,⁷⁶C. Cowden,²⁸B. E. Cox,⁸²K. Cranmer,¹⁰⁸F. Crescioli,^122a,122bM. Cristinziani,²¹

G. Crosetti,^37a,37bS. Cre´pe´-Renaudin,⁵⁵C.-M. Cuciuc,^26aC. Cuenca Almenar,¹⁷⁶T. Cuhadar Donszelmann,¹³⁹ M. Curatolo,⁴⁷C. J. Curtis,¹⁸C. Cuthbert,¹⁵⁰P. Cwetanski,⁶⁰H. Czirr,¹⁴¹P. Czodrowski,⁴⁴Z. Czyczula,¹⁷⁶

S. D’Auria,⁵³M. D’Onofrio,⁷³A. D’Orazio,^132a,132bM. J. Da Cunha Sargedas De Sousa,^124aC. Da Via,⁸² W. Dabrowski,³⁸A. Dafinca,¹¹⁸T. Dai,⁸⁷C. Dallapiccola,⁸⁴M. Dam,³⁶M. Dameri,^50a,50bD. S. Damiani,¹³⁷

H. O. Danielsson,³⁰V. Dao,⁴⁹G. Darbo,^50aG. L. Darlea,^26bJ. A. Dassoulas,⁴²W. Davey,²¹T. Davidek,¹²⁶ N. Davidson,⁸⁶R. Davidson,⁷¹E. Davies,^118,dM. Davies,⁹³O. Davignon,⁷⁸A. R. Davison,⁷⁷Y. Davygora,^58a

E. Dawe,¹⁴²I. Dawson,¹³⁹R. K. Daya-Ishmukhametova,²³K. De,⁸R. de Asmundis,^102aS. De Castro,^20a,20b S. De Cecco,⁷⁸J. de Graat,⁹⁸N. De Groot,¹⁰⁴P. de Jong,¹⁰⁵C. De La Taille,¹¹⁵H. De la Torre,⁸⁰F. De Lorenzi,⁶³

L. de Mora,⁷¹L. De Nooij,¹⁰⁵D. De Pedis,^132aA. De Salvo,^132aU. De Sanctis,^164a,164cA. De Santo,¹⁴⁹ J. B. De Vivie De Regie,¹¹⁵G. De Zorzi,^132a,132bW. J. Dearnaley,⁷¹R. Debbe,²⁵C. Debenedetti,⁴⁶B. Dechenaux,⁵⁵

D. V. Dedovich,⁶⁴J. Degenhardt,¹²⁰C. Del Papa,^164a,164cJ. Del Peso,⁸⁰T. Del Prete,^122a,122bT. Delemontex,⁵⁵ M. Deliyergiyev,⁷⁴A. Dell’Acqua,³⁰L. Dell’Asta,²²M. Della Pietra,^102a,kD. della Volpe,^102a,102bM. Delmastro,⁵

P. A. Delsart,⁵⁵C. Deluca,¹⁰⁵S. Demers,¹⁷⁶M. Demichev,⁶⁴B. Demirkoz,^12,mJ. Deng,¹⁶³S. P. Denisov,¹²⁸ D. Derendarz,³⁹J. E. Derkaoui,^135dF. Derue,⁷⁸P. Dervan,⁷³K. Desch,²¹E. Devetak,¹⁴⁸P. O. Deviveiros,¹⁰⁵ A. Dewhurst,¹²⁹B. DeWilde,¹⁴⁸S. Dhaliwal,¹⁵⁸R. Dhullipudi,^25,nA. Di Ciaccio,^133a,133bL. Di Ciaccio,⁵ A. Di Girolamo,³⁰B. Di Girolamo,³⁰S. Di Luise,^134a,134bA. Di Mattia,¹⁷³B. Di Micco,³⁰R. Di Nardo,⁴⁷ A. Di Simone,^133a,133bR. Di Sipio,^20a,20bM. A. Diaz,^32aE. B. Diehl,⁸⁷J. Dietrich,⁴²T. A. Dietzsch,^58aS. Diglio,⁸⁶

K. Dindar Yagci,⁴⁰J. Dingfelder,²¹F. Dinut,^26aC. Dionisi,^132a,132bP. Dita,^26aS. Dita,^26aF. Dittus,³⁰F. Djama,⁸³ T. Djobava,^51bM. A. B. do Vale,^24cA. Do Valle Wemans,^124a,oT. K. O. Doan,⁵M. Dobbs,⁸⁵R. Dobinson,^30,a

D. Dobos,³⁰E. Dobson,^30,pJ. Dodd,³⁵C. Doglioni,⁴⁹T. Doherty,⁵³Y. Doi,^65,aJ. Dolejsi,¹²⁶I. Dolenc,⁷⁴ Z. Dolezal,¹²⁶B. A. Dolgoshein,^96,aT. Dohmae,¹⁵⁵M. Donadelli,^24dJ. Donini,³⁴J. Dopke,³⁰A. Doria,^102a A. Dos Anjos,¹⁷³A. Dotti,^122a,122bM. T. Dova,⁷⁰A. D. Doxiadis,¹⁰⁵A. T. Doyle,⁵³M. Dris,¹⁰J. Dubbert,⁹⁹S. Dube,¹⁵

E. Duchovni,¹⁷²G. Duckeck,⁹⁸D. Duda,¹⁷⁵A. Dudarev,³⁰F. Dudziak,⁶³M. Du¨hrssen,³⁰I. P. Duerdoth,⁸² L. Duflot,¹¹⁵M-A. Dufour,⁸⁵L. Duguid,⁷⁶M. Dunford,³⁰H. Duran Yildiz,^4aR. Duxfield,¹³⁹M. Dwuznik,³⁸ F. Dydak,³⁰M. Du¨ren,⁵²W. L. Ebenstein,⁴⁵J. Ebke,⁹⁸S. Eckweiler,⁸¹K. Edmonds,⁸¹W. Edson,²C. A. Edwards,⁷⁶

N. C. Edwards,⁵³W. Ehrenfeld,⁴²T. Eifert,¹⁴³G. Eigen,¹⁴K. Einsweiler,¹⁵E. Eisenhandler,⁷⁵T. Ekelof,¹⁶⁶ M. El Kacimi,^135cM. Ellert,¹⁶⁶S. Elles,⁵F. Ellinghaus,⁸¹K. Ellis,⁷⁵N. Ellis,³⁰J. Elmsheuser,⁹⁸M. Elsing,³⁰ D. Emeliyanov,¹²⁹R. Engelmann,¹⁴⁸A. Engl,⁹⁸B. Epp,⁶¹J. Erdmann,⁵⁴A. Ereditato,¹⁷D. Eriksson,^146aJ. Ernst,²

M. Ernst,²⁵J. Ernwein,¹³⁶D. Errede,¹⁶⁵S. Errede,¹⁶⁵E. Ertel,⁸¹M. Escalier,¹¹⁵H. Esch,⁴³C. Escobar,¹²³ X. Espinal Curull,¹²B. Esposito,⁴⁷F. Etienne,⁸³A. I. Etienvre,¹³⁶E. Etzion,¹⁵³D. Evangelakou,⁵⁴H. Evans,⁶⁰

L. Fabbri,^20a,20bC. Fabre,³⁰R. M. Fakhrutdinov,¹²⁸S. Falciano,^132aY. Fang,¹⁷³M. Fanti,^89a,89bA. Farbin,⁸ A. Farilla,^134aJ. Farley,¹⁴⁸T. Farooque,¹⁵⁸S. Farrell,¹⁶³S. M. Farrington,¹⁷⁰P. Farthouat,³⁰F. Fassi,¹⁶⁷ SEARCH FOR RESONANT TOP QUARK PLUS JET. . . PHYSICAL REVIEW D86,091103(R) (2012)