L. Perera LPC physics meeting 11/17/ Search for H/A → Lalith Perera Rutgers University for Rutgers CMS Group Amit Lath, Keith Rose, Sunil Somalvar, Steve Schnetzer, Bob Stone, Alik McPerson, Dimity Hits, (Eva Halkiadakis)
L. Perera LPC physics meeting 11/17/ Why H→ At LHC MSSM higgs are expected to produced by gg →bbH, gg →H qq→ H Dominant decay modes of H: B(H→ ) ~ 8%, B(H→ bb) ~90% bb channel is affected by large dijet background could tag associative b to lower backgrounds Dominant back ground to from Z/ *: can be estimated ( # of Zs from Z→e e,..) channel could be equally promising
L. Perera LPC physics meeting 11/17/ →e →e 3 High DY → ee BG → → 3 High DY → BG →e → 6 low QCD BG →e →h 23 promising → →h 23 promising →h →h 41 multi jet BG modefraction %comments H→ Decay Modes
L. Perera LPC physics meeting 11/17/ CDF results on H Rutgers CDF group did CDF run II, H analysis
L. Perera LPC physics meeting 11/17/ B/ group (and others) already working on this channel Rutgers group plan to concentrate on low mass higgs low mass higgs search is challenging due to overlap with Z
L. Perera LPC physics meeting 11/17/ CMS hadronic taus Level 1: narrow hadronic jet with E T cut Level2 (HLT): Localized energy in ECAL – isolation 0.4 Level 25: isolation in tracker (Calo+pixel, Si) signal cone 0.07, isolation cone, 0.4, E T, P T Offline taged tau jets: Isolation using fully reconstructed tracks
L. Perera LPC physics meeting 11/17/ tau jet E T > 93 GeV (104 high L) 2 tau jets E T > 66 GeV (76 high L) …. This is good at rejecting Z back ground 22 11 E T of from Z → GeV L1 tau trigger:
L. Perera LPC physics meeting 11/17/ But also rejects low mass higgs M(H) = 120GeVM(H)= 140GeV 22 11 22 11 ET
L. Perera LPC physics meeting 11/17/ L1 efficiency for H→ 1 or 2 tau bit L1 global efficiencyAny L1 tau bit Any: tau 1, tau 2, tau+gamma
L. Perera LPC physics meeting 11/17/ L1 Trigger rates DataL1 Accept1 or 2 Tau“Any” Tau Z->ee 16.8%0.2%8.0% Z-> 55.8%0.9%3.7% Z-> 65.9%0.1%3.0% H(120)-> 38.1%0.8%11% H(140)-> 44.0%1.0%15% H(180)-> 53.2%2.8%25% H(250)-> 67.7%15%41%
L. Perera LPC physics meeting 11/17/ Possible ways to improve sensitivity to low mass higgs Understanding/estimating back grounds Tau reconstruction: to reject jet backgrounds, improve energy resolution Use tau Impact parameter Any other signatures of → –angular distributions. H scaler, Z-vector
L. Perera LPC physics meeting 11/17/ Number of tracks in tagged tau jets. (from H→ m(H) =140) (fewer 3 prong taus likely a bug in Exroot) Tau mass reconstruction → h % →h 11.8% → 3 h 10% →h 2 0 9.4% → h3 0 4.5%
L. Perera LPC physics meeting 11/17/ Tau mass Calculation Case study with 140GeV → Use tau tagged jets with a single track ( → n 0 ) Add energy in ECAL and HCAL cells within 0.25 of jet axis exclude cells 0.04 (ECAL)/0.15 (HCAL) from track Calculate the momentum of photons and take the sum Add track momentum and energy Calculate invariant mass
L. Perera LPC physics meeting 11/17/ Angle between pion and gammas in the tau decay (from MC)
L. Perera LPC physics meeting 11/17/ Visible tau mass from generator e/p of tau decay particles except neutrinos. (what is possible with an ideal detector ) Reconstructed Tagged tau jet Invariant mass (for single track tau jets)
L. Perera LPC physics meeting 11/17/ Improving tau mass reconstruction Is it track energy In ECAL MIP or more? Can we identify? Opposite form what is expected ? CAL CAL
L. Perera LPC physics meeting 11/17/ fraction of energy in HCAL, f <0.05 f > 0.05 Again, does not look right ? Investigating! Reconstructed visible tau mass single track tau jets
L. Perera LPC physics meeting 11/17/ Reconstructing higgs mass Calculate energy, momentum in collinear approx. add to to the visible e-p to get mass. Method used by CERN (Higgs PRS) group:
L. Perera LPC physics meeting 11/17/ H/A mass generator level Reconstructed 2 mass from MC parameters of t decay products Use energies of s to get E T Use e-p of tau decay particles as jet/track energy A 30% minimum loss for 140 GeV H Testing Collinear approximation
L. Perera LPC physics meeting 11/17/ Alternate method ( CDF ) Use missing E T (Ex, Ey) from calorimeter and Take neutrino E =E T Px=Ex; Py=Ey; Pz= 0 GeV For m(H)=140 GeV Generater level p-E from tau decays particles E T from neutrinos No loss of efficiency, Lower reconstructed mass
L. Perera LPC physics meeting 11/17/ Future Plans More trigger and background studies (more MC) Improvements to tau mass reconstruction Looking at other possible parameters, …
L. Perera LPC physics meeting 11/17/ Back up slides
L. Perera LPC physics meeting 11/17/
L. Perera LPC physics meeting 11/17/