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Information about chargedHiggsSB

Published on January 3, 2008

Author: Jancis


Slide1:  Search for Charged Higgs at the LHC Ashfaq Ahmad (Stony Brook) Contents:  Contents Introduction Charged Higgs studies in ATLAS and CMS Search for the light charged Higgs bosons with H± ->  in top quark decays Search for heavy charged Higgs bosons with: H± ->  decay channel H± -> tb decay channel Discovery reach LHC experiments:  LHC experiments ATLAS and CMS Detectors:  ATLAS and CMS Detectors ATLAS as of July 2007 CMS as of Jan 2007 Charged Higgs Boson:  Charged Higgs Boson MSSM, the minimal supersymmetric extension to SM requires two Higgs doublets Give masses to the up and down type quarks and leptons Corresponds to 8 degrees of freedom 3 of which are absorbed as Goldstone bosons to give mass and longitudinal components to the W± and Z Leaves five physical states (Higgs particles) Two neutral scalars, h0, H0, a pseudo scalar A0 and a pair of scalar charged Higgs H± At tree level all masses and couplings can be expressed as a function of two parameters: The pseudo scalar Higgs boson mass mA and tan  the ratio of the vacuum expectation values of the two Higgs doublets Charged Higgs at the LHC:  Charged Higgs at the LHC Production modes for heavy charged Higgs: Below top mass: tH+b LHC is a top factory, NLO ttbar cross section ~833pb  over 8M ttbar pair in one year (10fb-1) Above top mass: Via gluon fusion, ggtbH+ And gbtH+ Decay modes: H+, H+tb, H+cs Search for Charged Higgs below Mtop (1):  Search for Charged Higgs below Mtop (1) In MSSM charged Higgs may be produced in top decay if kinematically allowed via ttbar→W+bH-b If MH+ < (Mtop – Mb) the decay t→W+b together with t→H+b saturates the top decay width in the MSSM BR is large at SMALL and LARGE tanβ (for a given MH) but it has a pronounced minimum at tanβ ~√mtop/mb ~7.5 BR(tH±b)~mtop2 cotan2β+mb2 tan2β LEP excludes 0.5 < tan  < 2.4 Search for Charged Higgs below Mtop (2):  Search for Charged Higgs below Mtop (2) Assuming a heavy SUSY spectrum a charged Higgs will decay exclusively into SM particles and below Mtop the braching ratio H+ is~100% Main channels of interest: H± decay BR. into different final states for tan  = 20 ttbar → H-bW+bbar, H-→ had, W→qq (1):  ttbar → H-bW+bbar, H-→ had, W→qq (1) Exploited the difference between signal and ttbar mH+ > mW so diff in pT and ET miss Spin (helicity effect): scalar H+, vector W Event Selection Tau+MET ot Jet+MET trigger Tau jet pT > 25 GeV 2 b jets, pTj1 >35GeV, pTj2 >20GeV isolated lepton veto ET miss > 45 GeV W/top reco. in 20/40 GeV mass window ttbar event pattern: cuts on  between two reco tops and the ratio between their pT(< 2) pT /pTb > 0.8 transverse mass (MT) + tau pT > 30 GeV Main background ttbar, QCD ATL-PHYS-2003-038 ttbar → H-bW+bbar, H-→ had, W→qq (2):  ttbar → H-bW+bbar, H-→ had, W→qq (2) Expected events @ 10fb-1, tan = 30 significant ttbar background with standard cuts Masses above 113 GeV are passed through a final event selection on the charged Higgs transverse mass, and tightening of the tau pT cut ttbar → H-bW+bbar, H-→ had, W→qq (3):  ttbar → H-bW+bbar, H-→ had, W→qq (3) The dip between tanβ ~ 5 and tanβ ~10 is covered by hadronic channel A high significance is obtainable for all tan and mH+ < 150 Leptonic channel (Wl) was studied long time ago(ATL-PHYS-94-053). This channel features a high Pt lepton for triggering, but the presence of two neutrinoes exludes any mass extraction possibilities. 5 line @30fb-1 is also shown. Results given here are from ATLAS fast simulation. Full simulation studies are in progress ttbar → H+bW-bbar, H+→ had, W→l (1):  ttbar → H+bW-bbar, H+→ had, W→l (1) Enhanced tau-lepton rate in ttbar decays mass of H± cannot be directly reconstructed because several neutrinos are produced in the final state Excellent -ID is a must! Measurement of significance of the event excess with an isolated  with respect to rate foreseen by SM BACKGROUNDS intrinsic Due to fake tau’s W+jets SIGNAL ttbar → H+bW-bbar, H+→ had, W→l (2):  ttbar → H+bW-bbar, H+→ had, W→l (2) Exploited difference between signal and ttbar mH+ > mW, diff in pT and ET miss Spin: scalar H+, vector W Event Selection Triggered lepton 3 jets with ET > 40GeV At least one b-tagged jet Q(l)+Q()=0 Tau jet ET > 40GeV Plead track/ E > 0.8, to exploit opposite helicity correlations in the taus coming from H+ and W ET miss > 70GeV CMS Note 2006/056 Discovery potential (3):  Discovery potential (3) 5 contour in mH± , tan plane for the light Charged Higgs with and without systematic uncertainties tan > 50, covered up to top mass Due to systematic uncertainties there is a decrease of 5-10GeV in the observable charged Higgs mass for tan < 50 Charged Higgs mass of 170GeV observable at tan~ 100 CMS Note 2006/056 I am working on this channel for ATLAS. Preliminary results expected in few weeks. Search for Charged Higgs above Mtop :  Search for Charged Higgs above Mtop Above top mass: Via gluon fusion, ggtbH+ And gbtH+ BR(H+tb)~0.8-1 H+tb results in complex final states Having 3 or 4 b jets Crucial to supress very large kinematically similar ttbar+jets background xBR (pb) Channels of interest: gb/gg → t(b)H+ → Wb(b) tb → lυb (b) jjbb (1):  gb/gg → t(b)H+ → Wb(b) tb → lυb (b) jjbb (1) Event Selection Isolated muon, pT > 20GeV At least 3(4) b jets At least 5(6) jets with pT > 25GeV Kinematic fit imposing mass constraints on both W,s and top quarks LH to suppress combinatorial background 3(4)b-tags, with LH based secondary vertex algorithm Background ttbar+b, ttbar+jets High combinatorics CMS Note 2006/109 SN-ATLAS-2004-042 CMS: S/B ratio after selection ~1% for mH+ = 300 GeV Discovery potenial (2):  Discovery potenial (2) CMS 3 b-tags CMS 4 b-tags No sensitivity in MSSM space even with very low systematic uncertainties Similar conclusions from ATLAS FAST simulation studies 30 fb-1 30 fb-1 gb/gg → t(b)H+ → qqb(b) had (1) :  gb/gg → t(b)H+ → qqb(b) had (1) Event Selection One -jet, PT > 100 GeV At least three non -jets(at least one b-tag) No more than one hard b-jet (|η| < 2.0, PT > 50 GeV) Reconstruct W/top in 25 GeV mass window ET miss > 100 GeV cut on the azimuthal opening angle (Δφ) between the -jet and missing Pt. Require Δφ > 1.1 Veto on isolated leptons Plead track/ E > 0.8 Main background ttbar, QCD, W+jets Discovery potenial (2):  Discovery potenial (2) with systematics without systematics Background: FAST simul. without systematics ATLAS CMS systematics included Background: Full simul. promising channel for heavy charged Higgs CMS and ATLAS Discovery Potential …:  CMS and ATLAS Discovery Potential … Fast simulation ATLAS full simulation studies in progress. Results by the end of 2007 Charged Higgs covered at LHC for mH+ < mtop Heavy Charged Higgs sensitive at high tan ATLAS CMS Full simulation 300 fb-1 30 fb-1 Conclusions:  Conclusions Both ATLAS and CMS are sensitive to light charged Higgs below top mass Discovery potential @ 30fb-1 Heavier charged Higgs would have to wait for the high luminosity mode Accessible at high tan The intermediate tan region in MSSM space is not covered by any SM decay H+ is the best H+ discovery channel at the LHC backup:  backup

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