Generic signatures of supersymmetry with R-parity conservation include those of single isolated muons or like-sign isolated dimuon pairs, accompanied with energetic jets and missing transverse energy. The ability of CMS to discover supersymmetry with these signals is estimated for 10 fb^{-1} of data collected with the inclusive single-muon and dimuon High-Level-Trigger paths. The selection criteria are optimized and the systematic effects are studied for a single low-mass benchmark point of the constrained MSSM with m_0 = 60,GeV/c^2, m_{1/2} = 250,GeVc^2, tan beta=10, A_0=0 and mu> 0. Discovery contours in the m_0, m_{1/2}) plane are presented for integrated luminosities ranging from 1 to 100, fb^{-1}

Acosta, D

Bartalini, P

Cavanaugh, R J

Drozdetsky, A A

Korytov, A

Kotov, K

Matchev, K

Mitselmakher, G

Pakhotin, Yu

Schmitt, M

Scurlock, B

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Available on CMS information server CMS CR 2006/069CMS Conference Report26 September, 2006SUSY survey with inclusive muon and same-signdimuon accompanied by jets and MET with CMSYu. Pakhotin∗), B. Scurlock, D. Acosta, P. Bartalini, R. Cavanaugh, A. Drozdetskiy, A. Korytov, K. Kotov,K. Matchev, G. Mitselmakher, M. SchmittUniversity of Florida, Gainesville, FL, USAAbstractGeneric signatures of supersymmetry with R-parity conservation include those of single isolatedmuons or like-sign isolated dimuon pairs, accompanied with energetic jets and missing transverseenergy. The ability of CMS to discover supersymmetry with these signals is estimated for 10 fb−1 ofdata collected with the inclusive single-muon and dimuon High-Level-Trigger paths. The selectioncriteria are optimized and the systematic effects are studied for a single low-mass benchmark point ofthe constrained MSSM with m0 = 60 GeV/c2, m1/2 = 250GeV/c2, tan β = 10, A0 = 0 and µ > 0.Discovery contours in the (m0, m1/2) plane are presented for integrated luminosities ranging from 1to 100 fb−1.Presented at “Physics at LHC”, Cracow, Poland, July 2006Submitted to Acta Phys. Pol.∗) Contact person. e-mail: pakhotin@phys.ufl.edu1 IntroductionLow energy supersymmetry is a promising candidate for new physics beyond the Standard Model (SM). Theanalysis presented in this paper is carried out in the framework of the CMSSM [1], also known as mSUGRA.Small universal gaugino mass m1/2 values have already been excluded by LEP searches [2]. While the Tevatronsearches [3] do not have the sensitivity to extend LEP results in the CMSSM, the larger centre-of-mass energy andluminosities that will be made available at the LHC will allow a much larger domain of the parameter space to becovered. Owing to the ability of the CMS detector to identify and reconstruct muons with good efficiency [4], theanalyses presented here address the topologies with either at least one muon or a like-sign dimuon pair, accom-panied with energetic jets and large transverse missing energy (EmissT ). These signatures are experimentally cleanwhen compared to that involving only jets and missing energy, and have the anticipated advantage of an efficientand well-understood trigger shortly after LHC start-up. The analysis with two same-sign muons is complementaryto trilepton searches because it involves more diagrams [5, 6, 7]. Further, the two same-sign muons analysis isable to distinguish SUSY diagrams with good efficiency and purity by applying muon isolation and tight qualitycuts [8, 9, 10].All details of the full study, which forms the basis for the brief summary given in this paper, can be found in [11].The results were obtained with the full CMS detector simulation and reconstruction software and included pile-upeffects corresponding to an instantaneous luminosity of 2× 1033cm−2s−1.2 Supersymmetry Events SimulationThe different parameters for all fully simulated SUSY points used in this work are listed in Table 1.Table 1: Parameters of fully simulated and reconstructed SUSY benchmark points studied in this work.m0 m1/2 tan β A0 µ σLO NGen LGeV/c2 GeV/c2 pb fb−1LM1 60 250 10 0 + 41.9 98250 2.3LM2 185 350 35 0 + 7.4 93000 12.6LM4 210 285 10 0 + 19 96500 5.1LM5 230 360 10 0 + 6 84000 13.9LM6 85 400 10 0 + 4 99250 24.6LM7 3000 230 10 0 + 10.2 7500 0.7LM8 500 300 10 -300 + 8.8 58250 6.6LM10 3000 500 10 0 + 0.178 19750 110.7HM1 180 850 10 0 + 0.052 80000 1538.5HM2 350 800 35 0 + 0.068 28500 419.2In addition to the fully simulated points, a scan of the (m0, m1/2) plane with a (100 GeV/c2, 100 GeV/c2) grid isperformed with a fast simulation, for tanβ = 10, A0 = 0 and µ > 0. For comparison, validation and efficiencycalibration purposes, several of the benchmark samples of Table 1 are also processed with the fast simulation.The LM1 benchmark point is chosen for selection optimization in this study.3 Standard Model (SM) BackgroundsMulti-jet QCD events do not intrinsically involve Feynman diagrams with final states similar to the topologicalsignature required by this analysis. Owing to its enormous cross section (σjj ∼ 55 mb), however, multi-jet eventscan produce configurations which are experimentally close. The number of multi-jet QCD events expected forintegrated luminosity of 10 fb−1 is so large at small pˆT (defined as the transverse momentum of one of the twooriginal hard scattered partons) that it is practically impossible to generate and simulate such a large amount ofevents. Consequently, events were generated almost uniformly in 21 pˆT bins.Top pair production is another particularly important source of background, due to its modestly large cross sec-tion σt¯t ∼ 490pb (at leading order) and its intrinsic multi-jet, high missing transverse energy, and significant lep-tonic final state nature. A total of approximately 3.4 million tt¯ events (corresponding to an equivalent integratedluminosity of 6.9 fb−1) were simulated and used in this analysis.2The production of single W and Z bosons is expected to be plentiful at the LHC due to their high cross sec-tions, σW ∼ 1.2 × 105 pb and σZ ∼ 3.3 × 104 pb (at leading order). Because it is nearly impossible to generateand simulate all the needed events for integrated luminosity of 10 fb−1, the single-boson electroweak events weregenerated uniformly in 20 pˆT bins.Diboson production, such as WW + jets, WZ + jets, and ZZ + jets, also contributes as a source of background.Because of the additional weak vertex, the cross sections, while significant with respect to this study, are much lessthan for single-boson production: σWW ∼ 190 pb, σWZ ∼ 27 pb and σZZ ∼ 10 pb (at leading order).4 Cuts optimization and search for the signalThe strategy of the analyses presented here involves searching for an excess in the number of events over theexpected number from Standard Model backgrounds (i.e. a counting experiment) for an integrated luminosityof 10 fb−1. The algorithms to reconstruct the physical objects (muon, jets, etc) as well as their identification at theonline and offline levels are described in Ref. [4].This work uses event samples selected by the inclusive single-muon and the dimuon triggers, which are relativelyclean and easier to understand than other triggers based purely on jets and EmissT .In the single-muon analysis, the leading muon is required to be reconstructed with a momentum in excess of 30GeV/c,and both muons must be reconstructed with a pT in excess of 10 GeV/c in the dimuon analysis. These cuts en-sure the muon candidates are reconstructed with good efficiency, and with a momentum well above the triggerthresholds.In addition, muons from prompt sparticle decays are best recognized by the requirement that the χ2 of the globaltrajectory fit be smaller than 3.0 per degree of freedom, and the total number of hits associated to the muon trackexceed 12. These quality cuts are ∼ 100% efficient for prompt muons, but allow a fair fraction of fake muons ormuons from long-lived particle (pi±, K±) decays to be rejected.Further, the leading muon (single-muon analysis) and the two leading muons (dimuon analysis) are required to beisolated with less than 10 GeV in a cone of radius 0.3 around the muon direction. These isolation requirementsreject many of the muons, from b- or c-quark semi-leptonic decays, not rejected by the aforementioned qualitycuts.Events from SUSY tend to have jet multiplicities higher than those of the SM events. Both studies thus requireat least 3 jets. The three leading jets must each have an ET of at least 50 GeV which guarantees that jets arereconstructed with good efficiency. No quality pre-selection requirements are made on the EmissT .Signal and background can be disentangled with a series of cuts on observables that carry some discriminationpower. A genetic algorithm tool, known as GARCON [12], is used to search a multi-dimensional space of cuts,with the aim of maximizing the significance for potential discovery.In the single-muon analysis, the primary features which are exploited to separate signal from the remaining back-grounds are the distinctly harder jets and EmissT spectra, the centrality of the leading jets, as well as the azimuthalangles between the EmissT vector and jets. No additional tightening of the muon pT cut is made when applying thefinal selection cuts.A total of eleven variables is provided as input to the genetic algorithm and the results of that search are displayedin Table 2. Background contamination into the signal region is estimated to be 2.5± 0.5 SM events. The inclusivesingle-muon analysis re-optimizes the cuts to select the HM1 point assuming higher integrated luminosity.In the dimuon analysis, there is a large EmissT excess for signal events compared with background. The ET spectrafor the three leading jets in SUSY events tend to be significantly harder than in SM events. No additional tighteningof the muons pT cuts is made when applying the final selection cuts. The leading muon, for both signal andbackground, already tends to be isolated and hence does not discriminate well. However, the second leading muontends to be more isolated in the signal than in the background.A total of nine variables are used in the genetic algorithm. Table 3 provides a summary of the final cuts. The totalnumber of remaining SM background events is estimated to be 1.5±0.3 and comes solely from tt¯ production. Themuon isolation requirements are a key factor in selecting events corresponding to SUSY diagrams with promptmuons. Indeed, the dimuon analysis selects such diagrams with ∼ 65% efficiency and over∼ 90% purity.3Table 2: All selection cuts as applied in the inclusive single-muon analysis.Cut CriteriaPre-selection number of muons≥ 1 “AND” pT > 30 GeV/cµ calo. iso. (R = 0.3) ET < 10 GeVnumber of jets ≥ 3 “AND” ET > 50 GeVSelection leading jet (Jet1) EJet1T > 440 GeVnext-to-leading jet (Jet2) EJet2T > 440 GeV|ηJet1| < 1.9, |ηJet2| < 1.5, |ηJet3| < 3.0−1 < cos[∆φ(Jet1, Jet2)]< 0.2−0.95 < cos[∆φ(EmissT , Jet1)]< 0.3−1 < cos[∆φ(EmissT , Jet2)]< 0.85EmissT > 130 GeVTrigger single-µ “OR” di-µ = “Accept”Table 3: All selection cuts as applied in the dimuon analysis.Cut CriteriaPre-selection 2 same-sign muons with pT > 10 GeV/cnumber of hits per µ track≥ 13 and χ2µ < 3isolation Isoµ1 < 10 GeV and Isoµ2 < 6 GeVnumber of jets ≥ 3 with ET > 50 GeVSelection next-to-next-to-leading jet EJet3T > 55 GeVnext-to-leading jet EJet2T > 130 GeVleading jet EJet1T > 175 GeVEmissT > 200 GeVTrigger di-µ = “Accept”5 Systematic UncertaintiesBy the time 10 fb−1 of integrated luminosity is gathered, the CMS Jet Energy Scale is expected to be calibratedat the level of 3% via a W mass constraint in semi-leptonic tt¯ events. Accordingly, a scaling is applied to allreconstructed jet ET ’s and the EmissT .With 10 fb−1 of integrated luminosity, the CMS Jet Energy Resolution is expected to be known to within 10% viadijet balancing. Accordingly, a Gaussian smearing is applied to all reconstructed jet ET ’s and the EmissT , event byevent.The systematic uncertainty in the muon pT , due to uncertainties in the magnetic field translates to a negligibleuncertainty in the efficiency to trigger and reconstruct muons in these analyses. The systematic uncertainty on therate of backgrounds passing the selection cuts due to fake muons is also estimated to be negligible.Reference [4] indicates that once approximately 10 fb−1 of integrated luminosity has been collected by CMS, theuncertainty in measuring that integrated luminosity is estimated to be ∼ 5%.The acceptance of high ET ISR/FSR jets as generated by PYTHIA [13] can be significantly underestimated inthese studies. The full matrix element calculation (obtained via CompHEP [14], for example) increases the rela-tive acceptance of tt¯ + 1 jet events by approximately 10%, which is taken as a systematic uncertainty. In additionto ISR/FSR, other theoretical effects involving (1) pile-up, (2) underlying event and (3) parton distribution func-tion (PDF) uncertainties are each assumed to be at the level of 5%.Table 4 shows the final list of all systematic uncertainties considered in this analysis.6 ResultsThis work demonstrates that the low mass CMSSM benchmark point, LM1, could be easily observable be-fore 1 fb−1 of data has been collected, including systematic uncertainties. The optimized cuts are used in a scan4Table 4: List of systematic uncertainties considered in this work.Systematic Uncertainty (δN/N )single-muon dimuonJet Energy Scale 10% 15%Jet Energy Resolution 5% 10%Luminosity 5% 5%Theory 13% 13%Background Total 18% 23%across the (m0, m1/2) plane, and the results indicate that most of the low mass region for tan β = 10, A0 = 0and µ > 0 can be observed up to mass scales of∼ 1.5 TeV/c2, including systematic effects. Figure 1 shows the 5σreach contours for both analyses (including systematic uncertainties) in the CMSSM (m0, m1/2) plane, assumingintegrated luminosity of 10 fb−1. With 30 fb−1 of data, the high mass SUSY benchmark points become interestingfor possible discovery and with 60 fb−1 of data, SUSY mass scales beyond 2 TeV/c2 can be probed, includingsystematic uncertainties.References[1] S. Abel, et al., hep-ph/0003154 (2000).[2] LEPSUSYWG, ALEPH, DELPHI, L3 and OPAL experiments, “LEP2 SUSY Working Group Web Page”,http://lepsusy.web.cern.ch/lepsusy/ .[3] V. Abazov, et al (D∅ Collaboration), Phys. Lett. B638, 119-127 (2006).[4] CMS Collaboration, CERN/LHCC 2006-001 (2006).[5] H. Baer et al., Phys. Rev. D41, vol. 3 (1990).[6] R. Barnett et al., Phys. Lett. B315, 349 (1993).[7] K. Matchev, D. Pierce, hep-ph/9904282 (1999).[8] J. Done, FNAL-Thesis-1999-13 (1999).[9] M. Worcester, FNAL-Thesis-2004-05 (2004).[10] A. Yurkewicz, FNAL-Thesis-2004-11 (2004).[11] Yu. Pakhotin, B. Scurlock, CMS Note 2006/134 (2006).[12] S. Abdullin, et al, hep-ph/0605143 (2006).[13] T. Sjostrand, S. Mrenna and P. Skands, hep-ph/0603175 (2006).[14] A. Pukhov, et al, hep-ph/9908288 (1999).50 500 1000 1500 2000 2500 3000 3500020040060080010001200(a)HM1HM2LM1LM2 LM4LM5LM6LM7LM8LM10NO EWSBτ˜ 1=LSPm0 (GeV/c2)m1/2(GeV/c2)60 fb−130 fb−110 fb−11 fb−1CMStan β = 10, A0 = 0, µ > 0inclusive muon + jets + EmissTsystematic uncertainties included0 500 1000 1500 2000 2500 3000 3500020040060080010001200(b)HM1HM2LM1LM2 LM4LM5LM6LM7LM8LM10NO EWSBτ˜ 1=LSPm0 (GeV/c2)m1/2(GeV/c2)100 fb−130 fb−110 fb−11 fb−1CMStan β = 10, A0 = 0, µ > 0same-sign dimuons + jets + EmissTsystematic uncertainties includedFigure 1: The top plot (a) displays the inclusive single-muon 5σ CMS reach contours in the (m0, m1/2) plane for inte-grated luminosity of 1 fb−1 (dot-dashed line), 10 fb−1 (solid line), 30 fb−1 (dotted line) and 60 fb−1 (dashed line) includingsystematic uncertainties; the reach curves for 1 fb−1 and 10 fb−1 are optimized to select the point LM1; the reach curvesfor 30 fb−1 and 60 fb−1 are optimized to select the point HM1. The lower plot (b) displays the dimuon 5σ CMS reach con-tours in the (m0, m1/2) plane for integrated luminosity of 1 fb−1 (dot-dashed line), 10 fb−1 (solid line), 30 fb−1 (dotted line)and 100 fb−1 (dashed line) including systematic uncertainties, collectively optimized to select all benchmark points. Both reachcontour plots assume fixed CMSSM parameters of: tan β = 10, A0 = 0 and µ > 0.6

SUSY Survey with Inclusive Muon and Same-Sign Dimuon Accompanied by Jets and MET with CMS

SUSY Survey with Inclusive Muon and Same-Sign Dimuon Accompanied by Jets and MET with CMS

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