The discovery potential for charged Higgs bosons at the ATLAS and CMS experiments is discussed with focus on the MSSM. Studies for several decay channels for the charged Higgs boson are presented both for production in top quark decays and gluon-gluon/gluon-bottom fusion

Flechl, M

CERN Document Server

Search for Charged Higgs Bosons at the LHCMartin Flechla (for the ATLAS and CMS collaborations)Institutionen fo¨r Ka¨rn- och Partikelfysik, Uppsala UniversitetAbstract. The discovery potential for charged Higgs bosons at the ATLAS and CMS experiments isdiscussed with focus on the MSSM. Studies for several decay channels for the charged Higgs bosonare presented both for production in top quark decays and gluon-gluon/gluon-bottom fusion.PACS. 12.60.Fr Extensions of electroweak Higgs sector – 14.80.Cp Non-standard-model Higgsbosons1 IntroductionCharged Higgs bosons (H±) are predicted in severalextensions of the Standard Model (SM). The simplestextension containing H± can be obtained by adding asecond Higgs doublet to the SM, described by the TwoHiggs Doublet Model (THDM). This model is particu-larly attractive since it describes the minimal requiredHiggs sector of supersymmetric models and is thuspart of the Minimal Supersymmetric Standard Model(MSSM). Most simulation studies for H± searches atthe LHC focus on the generic THDM and on the MSSM.The following results are for the MSSM (mh-max sce-nario [1]) unless specified otherwise.The THDM gives rise to five physical Higgs bosons,three neutral ones (h, H, A) and a charged pair (H±)1.At tree-level the THDM is fully described by two pa-rameters which can be chosen to be the charged Higgsboson mass (mH+) and the ratio of the Higgs doubletvacuum expectation values (tan β).Fig. 1: H+ SM branching ratios for tan β = 30 in an mh-max-like MSSM scenario [2].The main H+ production mode at the LHC aretop quark decays (t → H+b) if the charged Higgsboson mass mH+ < mt (the top quark mass), andaEmail: martin.flechl@tsl.uu.se1 in the following, only H+ is denoted but H− is alwaysimplicitely includedgluon-gluon and gluon-bottom fusion (gg → tbH+,gb → tH+) if mH+ > mt. The charged Higgs bo-son couplings are proportional to the particle masses,and thus the dominant decay modes are H+ → τν ifmH+ < mt, and additionally H+ → tb if mH+ > mt.In the MSSM, the lower experimental bound onthe charged Higgs boson mass is about 80 GeV, inde-pendently of tan β [3]. In the following sections, thecharged Higgs boson discovery potential for the LHCexperiments ATLAS and CMS estimated in simulationstudies will be presented. The main decay channels willbe discussed in Section 2 for mH+ < mt and in Sec-tion 3 for mH+ > mt while Section 4 briefly discussesmore exotic charged Higgs boson decay modes.2 Search for H+ in Top Quark Decaysβtan 0 10 20 30 40 50 60)+ bH→BR(t -210-110= 90 GeV+Hm=110 GeV+Hm=120 GeV+Hm=130 GeV+Hm=150 GeV+HmFig. 2: Branching ratio t→ bH+ as a function of tan β fordifferent charged Higgs boson masses, mt = 175 GeV, withPythia 6.3 [4].The main production mode for H+ at the LHCfor mH+ < mt is the decay of a top quark t → bH+in tt¯ events since the tt¯ cross section is large (794 pbat NLO [5]). The production of about 8 million topquark pairs per year at the LHC at low luminosity(L =10 fb−1 per year) is anticipated and with a typicalexpected branching ratio t → bH+ of a few percentthis implies a sizeable H+ production. The branchingATL-PHYS-CONF-2007-01826 October 2007Colliders - Higgs Phenomenology Contributed Talkratio t → bH+ as a function of tanβ for different valuesof mH+ is shown in Figure 2.Below the top quark mass, the charged Higgs bo-son decays almost exclusively to a tau lepton and aneutrino (except for very low tanβ values). Recentsearches have focused on hadronic τ decays of the H+while both hadronic and semileptonic decays of thesecond top quark in the event are considered.2.1 tt¯ → H+bWb with H+ → τν, W → lνThis channel was investigated by Baarmand et al. [6]for the CMS experiment. The analysis is a countingexperiment since mH+ cannot be reconstructed due tothe presence of neutrinos from two sources. The studywas carried out using full detector simulation includingpile-up. As main backgrounds, tt¯ with one t → b`ν andW+3 jets with W → `ν were considered. A sequence ofselection cuts based on the event signature was appliedto events accepted by a lepton trigger. At least 3 jetswith ET > 40 GeV were required, exactly one of thembeing b-tagged. A cut on at least one τ jet with ET >40 GeV and a leading track with a momentum of atleast 0.8 of the τ jet transverse energy is applied next.The sum of the charge of the τ jet and the leptonare required to be zero. Finally a cut on the missingtransverse energy of 70 GeV is applied.Fig. 3: H+ discovery contour for tt¯→ H+bWb with H+ →τν, W → lν at CMS [6].The resulting discovery contour including system-atic uncertainties is shown in Figure 3. A discovery po-tential for all values of tan β is given for mH+ . 135GeV and an integrated luminosity of 30 fb−1 (threeyears at low luminosity) and the reach goes up to aboutmH+ = 170 GeV for very high values of tan β.2.2 tt¯ → H+bWb with H+ → τν, W → qqThis analysis has been performed by Biscarat et al. [7]for the ATLAS experiment. It is based on a parame-trized simulation of the ATLAS detector. The consid-ered backgrounds are tt¯ and QCD. The trigger condi-tion is either a τ jet or a jet, combined with missingFig. 4: H+ discovery contour for tt¯→ H+bWb with H+ →τν, W → qq at ATLAS [7]transverse energy. In the first stage of the event se-lection chain, requirements following closely the eventsignature are applied: a τ jet, exactly two b jets, atleast two light jets above certain pT thresholds, a vetoon isolated leptons, EmissT > 45 GeV and the recon-struction of the W and its associated top quark withinmass windows. Additionally, a set of cuts aimed at thett¯ pattern is applied to reduce the QCD background,consisting of angular and momentum relations of thetop quarks and their decay products. Eventually cutson the relation of the τ and the b on the H+ side areapplied, as well as on the H+ transverse mass (onlyfor the analysis of mH+ > 113 GeV).The resulting discovery contour is shown in Fig-ure 4. For 30 fb−1, a discovery potential is given for alltan β for mA . 135 GeV, corresponding to mH+ ≈ 155GeV. Systematic uncertainties are included.3 Search for H+ in gg- and gb-fusionβtan 0 10 20 30 40 50 60) [pb]+ tH→(gb σ-210-1101=170 GeV+Hm=200 GeV+Hm=250 GeV+Hm=400 GeV+Hm=600 GeV+HmFig. 5: NLO cross section gb→ tH+ as function of tan β forvarious charged Higgs boson masses, mt = 175 GeV [8,9]At the LHC, charged Higgs bosons with mH+ > mtwould be dominantly produced in the processes gg →tbH+ and gb → tH+. These so-called “twin processes”correspond to two different approximations of the sameprocess which leads to an overlap in certain regions ofphase space. This overlap is resolved by the event gen-erator MATCHIG [10] which is used in recent and on-Martin Flechl (for ATLAS and CMS) Search for Charged Higgs Bosons at the LHCgoing ATLAS studies. The H+ cross section in gb/gg-fusion is much smaller than in tt¯ decays and decreasesrapidly with mass, as shown in Figure 5.The dominating decay modes are H+ → τν andH+ → tb , with the branching ratio of the latter being1-2 orders of magnitude higher for low tanβ and/orhigh mH+ . However, the τ channel provides a muchcleaner signature, as will be shown in the followingsections.3.1 gg/gb→ t[b]H+ with H+ → tbThis channel with the final state bb¯b[b¯]`νqq¯ was in-vestigated by Lowette et al. [11] for CMS and by As-samagan et al. [12] for ATLAS. In the following thefocus will be on the CMS study (differences to theATLAS study will be pointed out at the end) whichwas carried out using full detector simulation includingpile-up. The main backgrounds were considered to bett¯+b, tt¯+bb¯ and tt¯+jet(s). For the analysis requiring 4b-tags, only gg → tbH+ was simulated; an additional3 b-tag analysis with parametrized detector simulationused gb → tH+ events. In both cases the cross sectionwas rescaled to the NLO value for the tH+X finalstate. Only final states with ` = µ were considered.The following requirements were placed on events ac-Fig. 6: CMS discovery contour for gg/gb → t[b]H+ withH+ → tb [11]. Left: 3 b-tag analysis. Right: 4 b-tag analysis.cepted by a muon trigger for the 4 b-tag analysis (inbrackets: 3 b-tag analysis): a reconstructed muon withpT > 20 GeV, at least 6 (5) jets with pT > 25 GeV,4 (3) of them b-tagged, and a kinematic fit imposingmass constraints for both W bosons and top quarks. Inthe next step a likelihood method is used to suppressthe combinatorial background, using information fromthe kinematic fit and properties of the b jets. Finallythe tt¯ + X background is further suppressed via a se-lection likelihood using b-tagging information (in the 3b-tag analysis, additionally information about the lightjets and from the kinematic fit is used).The main difference between this study and the cor-responding ATLAS analysis [12] is that the latter isbased upon parametrized detector simulation withoutpile-up, that it considers the electron mode in additionto the muon mode and that only gg → tbH+ requiring4 b-tags is investigated. Additionally, different b jet-related variables are used for background suppression.The resulting discovery contour for CMS is shown inFigure 6, the results for ATLAS are similar. As can beseen, even assuming very low systematic uncertainties,very little sensitivity is given in the MSSM parameterspace.3.2 gg/gb→ t[b]H+ with H+ → τνThe τ decay mode for a heavy H+ was studied forATLAS by Mohn et al. [13], and for CMS by Kin-nunen [14]. In the ATLAS study, the considered back-grounds are tt¯, single top, QCD dijets and W+jets.Full detector simulation was used for the H+ signaland a parametrized detector response for the back-grounds. The event generator MATCHIG [10] allowedfor the first time a consistent treatment of the tran-sition region mH+ ≈ mt. The selection cuts were op-timised for three different mass ranges (mH+ ≤ 250GeV, 250 < mH+ < 450 GeV and mH+ ≥ 450 GeV).The following selection cuts are applied (for the low/ medium / high mass range): one τ jet with pT >65/80/100 GeV within |η| < 1.1/1.2/1.3, EmissT >120/135/165 GeV, no isolated lepton, at least 3 jets(exactly one of them b-tagged), the W boson and topquark masses reconstructed within 25 GeV-windows,and pτT /padd. jetT > 6.0/5.5/5.0 (“add. jet” is the hard-est jet not used for the top quark reconstruction).The main differences in the CMS study are that fulldetector simulation with pile-up and trigger simula-tion was used both for signal and background. Nomatched signal event generation has been performed,only gg → tbH+ was simulated and scaled to thematched production cross section. Instead of the cuton pτT /padd. jetT , a veto on additional central jets wasapplied. To exploit the τ helicity correlations, an addi-tional cut on the ratio of the leading τ track momen-tum and the energy of the τ jet was applied. The dis-Fig. 7: ATLAS discov-ery contour for heavyH+ → τν [13] excludingsystematic uncertainties.Fig. 8: CMS discov-ery contour for heavyH+ → τν [14].covery contours are shown in Figure 7 for ATLAS, andFigure 8 for CMS. The sensitivity is significantly betterthan in the H+ → tb channel since the smaller signal-to-background ratio leads to more robustness with re-gard to systematic uncertainties. However, the regiontan β . 20 is currently uncovered for mH+ > mt atan integrated luminosity of 30 fb−1 and the discoverypotential decreases rapidly with increasing mH+ dueto the diminishing cross section.Colliders - Higgs Phenomenology Contributed Talk4 Search for H+ in Exotic ChannelsCharged Higgs boson simulation studies were also per-formed in non-SM and in rare H+ channels. Two ex-amples are briefly presented.The mode H+ → Wh0 has been studied by Assam-agan [15], and H+ → WH0 in a large mass splittingMSSM scenario by Mohn et al. [16]. Both studies con-clude that even in the most favourable scenarios, withknowledge of the neutral Higgs boson masses and athigh luminosity no MSSM discovery sensitivity is givenvia these channels.The channel H+ → χ˜±1,2χ˜01,2,3,4 for a heavy chargedHiggs boson produced via gb → tH+ was studied byHansen et al. [17] for ATLAS and Bisset et al. [18]for CMS using parametrized detector simulation. Bothstudies represent counting experiments and require themeasurement of cross sections of several SUSY pro-cesses in order to be able to evaluate the background.Particularly high precision is needed in the case ofthe ATLAS study since the signal-to-background ratiois low (typically, ≈ 0.1). Discovery contours for bothstudies for a very favourable MSSM scenario and with-out systematic uncertainties are shown in Figure 9.The most important conclusion is that in principlethere is sensitivity in the intermediate tan β-region notcovered by any other channels.Fig. 9: H+ → χ˜±1,2χ˜01,2,3,4 discovery contour for ATLASand CMS for a favourable MSSM scenario [17]. Systematicuncertainties are not taken into account.5 Combined Discovery ContoursThe combined discovery contours are shown in Fig-ure 10 (CMS) and Figure 11 (ATLAS). The two con-tours cannot be compared as the ATLAS contour isbased on parametrized detector simulation, does notinclude systematics and assumes L = 300 fb−1 whilethe CMS contour is for L = 30 fb−1, and based on fulldetector simulation including pile-up and systematics.An ATLAS update is expected for the end of 2007.The current studies suggest that the parameterspace up to mH+ values close to the top quark masswill be covered by the LHC in a few years of runningat low luminosity except for a small region of interme-diate tanβ (≈ 4− 15) which requires high luminosityruns. For mH+ > mt, sensitivity is present only fortan β higher than about 15 − 20, and the discoverypotential diminishes rapidly with increasing mH+ .Fig. 10: CMS combined H+discovery contour [19].Fig. 11: ATLAS combinedH+ discovery contour [17].6 Conclusions and OutlookH+ → τν is the prime MSSM charged Higgs bosondiscovery channel at the LHC. H+ → tb does not addany sensitivity. The MSSM parameter space will becovered for all tanβ for values of mH+ up to close tomt. For mH+ > mt, only tan β greater than about15-20 will be covered in low luminosity runs (and theuncovered region increases with mH+). H+ in the gapregion 4 < tan β < 10, which will probably not even becovered in high luminosity runs by SM decay modes,could be discovered in decays to SUSY particles aftermeasurement of SUSY cross sections.All standard channels investigated with parame-trized detector response are in the process of beingupdated with full detector simulation. Additionally,simulation results for new channels like H+ → τν withleptonic τ decays as well as for associated productionAH+ are expected in the near future. Preparationsfor the first LHC data in 2008 are in their final phaseknowing that charged Higgs bosons could be the firstBeyond the Standard Model-signal we see.References1. Carena M S et al, Eur. Phys. J. C26 (2003) 601–607.2. Carena M S et al, Prog. Part. Nucl. Phys. 50 (2003)63–152.3. LEP Higgs Working Group, hep-ex/0107031.4. Sjo¨strand T et al, JHEP 05 (2006) 026.5. Kidonakis N et al, Phys. Rev. D68 (2003) 114014.6. Baarmand M et al, J. Phys. G32 (2006) N21.7. Biscarat C et al, ATL-PHYS-2003-038.8. Plehn T, Phys. Rev. D67 (2003) 014018.9. Boos E et al, Phys. Rev. D69 (2004) 094005.10. Alwall J et al, JHEP 12 (2004) 050.11. Lowette S et al, CERN-CMS-NOTE-2006-109.12. Assamagan K et al, Eur. Phys. J. C39S2 (2005) 25–40.13. Mohn B et al, ATL-PHYS-PUB-2007-006.14. Kinnunen R, CERN-CMS-NOTE-2006-100.15. Assamagan K, ATL-PHYS-99-025.16. Mohn B et al, ATL-PHYS-PUB-2005-017.17. Hansen C et al, Eur. Phys. J. C44S2 (2005) 1–9.18. Bisset M et al, Eur. Phys. J. C30 (2003) 419–434.19. Ball A et al, CMS-TDR-008-2, 2006.

Search for Charged Higgs Bosons at the LHC

Slides for the presentation at SUSY07. The discovery potential for charged Higgs bosons at the ATLAS and CMS experiments is discussed with focus on the MSSM. Studies for several decay channels for the charged Higgs boson are presented both for production in top quark decays and gluon-gluon/gluon-bottom fusion

Search for ChargedHiggs Bosons at the LHCMartin Flechl (Uppsala Universitet)for the ATLAS and CMS CollaborationsSUSY 2007,Karlsruhe, July 28, 2007M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007The ATLAS and CMS Detectors1ATLAS, July 2007CMS, Jan 2007ATLASCMSM. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Outline● The Charged Higgs Boson (H+)● H+ channels investigated for CMS and/or ATLAS(in detail: publications from 2006/07)– H+ from top quark decays– H+ from gg- and gb-fusion– “exotic” channels● Discovery reach2M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007The Charged Higgs Boson● Two Higgs Doublet Model (THDM): 5 Higgs Bosons A0, h0, H0, H±. - Simple Extension to SM- required Higgs Sector of MSSM- possible in other SUSY models (fermiophobic models, ...)or: H+ from triplets; several doublets/triplets; Little Higgs; ...● Charged Higgs searches currently focus on generic THDM (producing cross section limits) and MSSM scenarios(unless stated otherwise, the following plots/numbers refer to the mh-max MSSM scenario)- MSSM Higgs sector: at tree-level 2 free parameters, e.g.:mH+ and tan β  (Ratio of the Higgs doublet vacuum expectation values)● The Charged Higgs Boson (H+) is a heavy1) charged colorless scalar→ Production Modes (LHC):  t→H+b gg→tbH+ gb→tH+→ Decay Modes: H+→ tb H+→ tn H+→ cs1)e.g. mh­max MSSM, all tan b: mH+ > 80 GeV [1]3M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Overview: mH+ < mtop● Production: top quark decays, viattbar→bW- bH+● BR(t → bH+) depends on mH+ and tan b● BR(H+ → τν) ≈ 1→ Main channels of interest:W DecayqqqqH+ Decaytn, t→hadtn, t→had lntn, t→lep4[2][3]M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007tt→H+bWb, H+→τhadν, W→lν  (1)CMS NOTE 2006/056, Baarmand/Hashemi/NikitenkoSignature:- lepton- tau-jet- 2 b-jets- missing ET Main Backgrounds:- ttbar with one t→bl- W+3 jets with W→lEvent Selection:- a triggered lepton- ≥ 3 jets with ET>40 GeV- = 1 of them b-tagged- Q(l)+Q()=0- a -jet with ET>40 GeVand ptrack/E > 0.8- Missing ET>70 GeVExploited difference signal/ttbar:- mH+ > mW: pT, ETmiss larger- Spin: H+→0, W→15M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007tt→H+bWb, H+→τhadν , W→lν  (2)CMS NOTE 2006/056, Baarmand/Hashemi/NikitenkoEfficiency10700 5105060 2541830 92516293366107xBR [fb] Events/10fb-1mH+=140 GeV 4.8x10-3mH+=150 GeV 5.0x10-3mH+=160 GeV 5.0x10-3tt→l bb 2.6x104 2.0x10-3tt→llbb 4.0x104 7.4x10-4tt→lqqbb 2.5x105 1.5x10-4W+3 jets, W→l 8.4x105 1.3x10-5Main Systematics Sources:- ttbar cross section- luminosity measurement- -tagging (efficiency/rejection)- b-tagging (efficiency/rejection)- jet energy scaleAfter all selection cuts (tan =20):Discovery Sensitivity:- tan >50: up to almost mtop- all tan : for mH+<130 GeV6M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007tt→H+bWb, H+→τhadν , W→qq (1)ATL-PHYS-2003-038, Biscarat/DosilSignature:- tau-jet- missing ET- 2 b-jets- hadronic W/topMain Backgrounds:- ttbar- QCDEvent Selection:- tau+MET or jet+MET trigger- = -jet, pT > 25 GeV- =2 b-jets, pTb1>35 GeV, pTb2>20 GeV- ≥2 light jets, pTj1>30 GeV, pTj2>20 GeV- Missing ET > 45 GeV- W/top Reco (20/40 GeV mass window)- ttbar pattern (angle/pT relations of tops)- Veto on isolated leptons- pT / pTb> 0.8 (H+ side)- H+ Transverse MassExploited difference signal/ttbar:- mH+ > mW: pT, ETmiss larger- Spin: H+→0, W→17M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007tt→H+bWb, H+→τhadν , W→qq (2)ATL-PHYS-2003-038, Biscarat/DosilAfter all selection cuts (tan =30):Discovery Sensitivity (30fb-1):- all tan : up to almost mtopstandard cuts 5100 -4200 20002900 1700410 240ttbar   2300 350QCD 20 0Events/10fb-1MTH+>80 GeV Pt>30 GeVmH+=  85 GeVmH+=127 GeVmH+=140 GeVmH+=160 GeV10 fb-1, W→qq30 fb-1, W→qq N.B.: This is Fast Simulation!... an ATLAS study using a more realistic simulation is on the way.W→lH+ Transverse Mass(mH+ = 127 GeV, tan =30)150 MA (GeV)tan incl. systematics8mA=153 GeV => mH+≈ mtopM. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Overview: mH+ > mtop● Production: gg/gb-fusiongg→tbH+, gb→tH+ (→double-counting term, resolvedby MC Generator “Matchig”)● BR(H+ → tb) ≈ 0.8-1→ Main channels of interest:W DecayqqtbH+ Decaytn, t→hadln & qq (2 Ws)9For each channel, only the most recent CMS or ATLAS study is presented in detail; reference to the study of the other experiment is given in [brackets], differences to the presented publication are briefly discussed and results are given[4][3]M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007gg/gb→tH+[b], H+→tb (1)CMS NOTE 2006/109, Lowette/D'Hondt/Vanlaer[SN-ATLAS-2004-042, Assamagan/Gollub]Signature:- 3-4 b-jets- lepton- 2 W, 2 topMain Backgrounds:- ttbar+b, ttbar+bbar- ttbar+jet(s)Event Selection, for 3 (4) b-tag-analysis:- a muon, pT>20 GeV- at least 5 (6) jets, pT>25 GeV- at least 3 (4) b-tags- kinematic fit imposing mass constraints for both Ws and both top quarks- LH to suppress combinatorial background- 3 b-tags: LH to suppress ttbar+X usinga) pT: softest jet from W, b) 2 of the fit,c) discriminator: b from H+, d) ETj6/ETj5    4 b: b-discriminator: b from H+, spectator-bExploited difference signal/ttbar+X:- mH+ invariant mass- up to 4 b-jets10M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007gg/gb→tH+[b], H+→tb (2)CMS NOTE 2006/109, Lowette/D'Hondt/Vanlaer[SN-ATLAS-2004-042, Assamagan/Gollub]CMS3 b­tagsCMS4 b­tagsMA (GeV)MA (GeV)ATLAS 10%5%1%MA (GeV)Conclusion: Even assuming very low systematic background uncertainties:No sensitivity in the MSSM space.(Similar conclusions for ATLAS froma fast simulation-based study)MSSM Discovery Contour11M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007gg/gb→tH+[b], H+→τhadν , W→qq (1)ATL-PHYS-PUB-2007-006, Mohn/Flechl/Alwall   [CMS NOTE 2006/100, Kinnunen, see slide 19]               Signature:- hard tau-jet- large missing ET- hadronic W, top- 1-2 b-jetsMain Backgrounds:- ttbar- W+jets- QCDEvent Selection:(mass range: low/medium/high)- one hard -jet (pT>65/80/100 GeV)- Etmiss > 120/135/165 GeV- ≥ 3 more jets (=1 b-tagged)- Veto on isolated leptons- W/top-Reco (25 GeV-mass window)- pT  pTadd. Jet > 6.0/5.5/5.0- azimuthal angle (pT  pTmissExploited difference signal/ttbar:- mH+ invariant mass- => hard -jet, high missing ET12M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007gg/gb→tH+[b], H+→τhadν , W→qq (2)ATL-PHYS-PUB-2007-006, Mohn/Flechl/Alwall                       [CMS NOTE 2006/100, Kinnunen]                       After all selection cuts (tan =35):Signal Bkg57 5.437 5.411 1.17 1.1Events/30fb-1mH+= 165 GeVmH+= 175 GeVmH+= 300 GeVmH+= 400 GeVEvent Generator MATCHIG allows for the 1st time a matched production gg/gb and thus a consistent treatment of the transition region mH+ ≈ mtop CMS30 fb­1ATLAS30/100 fb­1w/o systematicsw/o systematicsw/ systematicsDiscovery Channel for a heavy H+ at the LHCMH+ (GeV)High S/B ratio makes the channel less sensitive to systematics than H+→tb 13Backgrounds: Fast SimulationCMS: Fullsim Backgrounds, Trigger Simulation,no MATCHIG,some difference in cuts - see slide 19M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007More H+ channels...● H+→ci+cj0CMS-NOTE-2003-004, SN-ATLAS-2005-050sensitive at the uncovered region tan ≈4-20(of course heavily dependend on the SUSY scenario, and a previous understanding of the SUSY background and parameters)● H+→Wh0, H+→WH0ATL-PHYS-99-025, ATL-PHYS-PUB-2005-017- significant cross section only for very small tan .- current studies show that even with known mh0 and high luminosity, no discovery reach is given● H+ sensitivity in ttbar andsingle top cross section measurements14M2 = 210 GeV, μ = 135 GeV, mlr = 110 GeVmτr = 210 GeV, mg = 800 GeV, mq = 1 TeVM. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Discovery ReachN.B.: The currently approved discovery contours cannot be compared.ATLAS update expected for end of this year.CMS and ATLAS Discovery Contours: MSSM, mh-max scenarioThe current studies suggest:mH+ < ≈mtop: will be covered at the LHC (in worst case at high luminosity)mH+ > mtop: sensitive only for high tan 15note: for heavy H+→tn, for consistency, the plot contains results from an ATLFAST study [10] and not the recent fullsim study presented hereCMS ATLASwith without systematics systematics  Fullsim Fastsim30 fb-1 300 fb-1M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Conclusions and Outlook● Implications of current studies:- H+→τν is the prime LHC H+ discovery channel in the MSSM space    (and could be the first BSM-signal and SUSY-glimpse we see)- H+→tb does not have any MSSM discovery sensitivity- light mH+: the LHC experiments are sensitive to an MSSM H+ up to mH+ values close to mtop- heavy H+: high luminosity runs are needed. The medium tan      region is not covered (might be accessible after a SUSY discovery)● The future:- refine studies, understand systematics, identify control samples / sidebands, improve tools (b/t-tagging, ...)- first studies on H+→τν with τ→lνν are arriving- all presented channels+some more: currently investigated with Full Simulation for ATLAS, too => results end of this year- data!!!16M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Backup Slides17The mh-max scenario of the MSSM: M2 = 200 GeV μ = 200 GeV XT = 2 TeVMSUSY = 1 TeV mgluino= 800 GeVmH+ and tan b are free parametersM. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Differences between ATLAS and CMS Studies (1)gg/gb→tH+[b], H+→tbIn SN-ATLAS-2004-042, as compared to CMS NOTE 2006/109:● based on Fast Simulation● no pile-up● mass range mH+ = 200-800 GeV investigated● only investigates gg→tbH+● looks at muon and electron decays of one of the Ws● Likelihood to decrease combinatorial background, but no kinematic fit to the particle four-momentauses reconstructed angles, momenta and invariant mass● different variables for background suppression:mb0b2 cos(b0,b2) cos(b0 + b2) cos(b0,b2) cos(tH+,H+)              18M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007Differences between ATLAS and CMS Studies (2)gg/gb→tH+[b], H+→τhadν, W→qqIn CMS NOTE 2006/100, as compared to ATL-PHYS-PUB-2007-006:● Full Simulation used for backgrounds● only gg→tH+b simulated (scaled to gg/gb→tH+[b] cross section)● Simulation includes pile-up for low luminosity runs● Poisson significance estimator used● same optimisation for whole mass range (mH+ = 170-600 GeV)● cut on p (leading track) / E (t-jet) > 0.8 (exploit t helicity correlations)● Veto on additional central jets [instead of cut on pT(additional jet)/pT(t-jet)]● no cut on the pseudorapidity of the t-jet● trigger simulation applied● differences in t-jet/b-jet/lepton reconstruction and tagging              19M. Flechl: Search for Charged Higgs Bosons at the LHC SUSY 2007References[1] LHWG-note-2001-05, The LEP EW Working Group[2] CMS NOTE 2006/056, Baarmand, Hashemi, Nikitenko[3] Prog.Part.Nucl.Phys.50:63-152,2003, M. Carena, H. Haber[4] Phys. Rev., D67 (2003) 014018, T. Plehn[5] ATL-PHYS-2003-038, Biscarat, Dosil[6] CMS NOTE 2006/109, Lowette, D'Hondt, Vanlaer[7] SN-ATLAS-2004-042, Assamagan, Gollub[8] ATL-PHYS-PUB-2007-006, Mohn, Flechl, Alwall[9] CMS NOTE 2006/100, Kinnunen[10] Acta Physica Polonica B 33 (2002) 707-720, Assamagan, Coadou20

The discovery potential for charged Higgs bosons at the ATLAS and CMS experiments is discussed with focus on the MSSM. Studies for several decay channels for the charged Higgs boson are presented both for production in top quark decays and gluon-gluon/gluon-bottom fusion.The discovery potential for charged Higgs bosons at the ATLAS and CMS experiments is discussed with focus on the MSSM. Studies for several decay channels for the charged Higgs boson are presented both for production in top quark decays and gluon-gluon/gluon-bottom fusion

Search for Charged Higgs Bosons at the LHC

Abstract

Similar works

Full text

Available Versions

CERN Document Server

CERN Document Server

CERN Document Server