Rare B decays in ATLAS and CMS

CKM2006 at Nagoya UniversityDec. 14th 2006 Makoto Tomoto Nagoya Universityon behalf of CMS and ATLAS collaborationsRare B decays in ATLAS and CMS

Makoto Tomoto (Nagoya University)CKM2006 at Nagoya

Outline

B physics in ATLAS and CMSATLAS and CMS detectorsBmmbXsmmConclusion


B physics in ATLAS and CMSATLAS and CMS p-p collision at s = 14TeV s(bb) = 500 mb BdBd : B+B- : BsBs : b-barions = 4:4:1:1105 bb pairs/s @ L=1033 cm-2s-1B-factory as well as New particle-factoryDetector design is dedicated to high-pT physicsMajority of B-events is low-pT particlesTrigger and analysis are a challenge B-decays to ms are promisingStrategy on B-physics in ATLAS and CMSCP violation (Low luminosity run)Bs oscillation (Low luminosity run)Rare B decay (Even in High lumi.) (Bmm, BK*mm, LbLmm)


Bm+m- and bsllSensitive to new physicsSUSY etc.FCNC transitionForbidden at tree diagram

SM: Br(bsll) ~ 10-6 ~ 10-7

|Vts| and |Vtd| determinationWilson coefficient C7, C9, C10BsllBsm+m-tanb=5010-910-8BdmmBsmmBr(BdK*mm) measurementsRare B decays

Br(Bmm)Bs mmBd mmSM 3.510-90.910-10CDF (780 pb-1)1.010-7 95%CL 3.010-7 95%CLD (700 pb-1)2.010-7 95%CL 11.110-7 95%CLBelle 78 fb-1-1.610-7 90% CLBaBar 111 fb-1-0.610-7 90% CL


LHCATLASCMS 27Km ring, proton-proton collider, s=14TeV

4 experiments in LHC LHCb dedicated B-physics ALICE dedicated heavy ion Two general purpose detectors: CMS and ATLAS

Operation plan - End of 2007: 900 GeV commissioning run

- After summer 2008: 14TeV, Low luminosity run (L = 1033cm-2s-1)

- Design: 14TeV, High luminosity run (L = 1034cm-2s-1)LHC 27Km tunnel


DetectorsCompact Muon Solenoid A Toroidal LHC ApparatuSTotal weight : 12500 TOverall diameter : 15.0 m Overall length : 21.5 mMagnetic Field : 4 TeslaTotal weight : 7000 TOverall diameter : 22.0 m Overall length : 46.0 mMagnetic Field : 2 Tesla (solenoid) 0.5 Tesla (toroid)


Inner DetectorsTo reconstruct vertex of B decays Used in HLT, better b-ID Impact parameter significance Di muon mass resolutionATLAS:Pixel, SCT, TRT in 2 T solenoid fieldCMS: Pixel, Silicon tracker in 4 T solenoid field


CMSATLASh< 0.25Tracker PerformanceImpact parameterMmm Mass ResolutionCMSATLASCMS pT>3-6GeV 50-90mms=36MeV(4Tesla)s=84MeV(2Tesla)All h|h|1.2ATLAS pT>6GeV 25-70mm|h||h|


Muon detectorsFor trigger and offline selection to get pure rare B-decay samples ATLAS: RPC (barrel) and TGC (endcap) for LVL1 trigger CSC and MDT for precise tracking in 0.5 T toroid fieldCMS: RPC (barrel) for LVL1 trigger CSC and DT for precise tracking in 2 T solenoid field


Muon detectorsATLAS Barrel muonATLAS Endcap muonCMS Endcap muonCMS Barrel muonATLAS CMSCosmic ray run with real muon detectors!


ATLAS/CMS Trigger SystemHardwareSoftware40MHz~100kHz~150HzFor rare B-decays, di-muon trigger is used Region of Interest (RoI ):HLT reconstruct b-decays using partial reconstructionin RoI around L1 muon


ATLAS LVL2:Confirm each m RoI from LVL1Mass cut Bmm : 4 GeV < M(mm)< 6 GeVATLAS EF: Refit ID tracks in Level-2 RoIDecay vertex reconstructionTransverse Decay length cut:Lxy > 200mmdi-muon triggerpT>3GeV1/2singlemdimrate ~900HzpT (GeV)CMS HLT:Primary vertex reconstruction - use three most probable verticesRegional track reconstruction - partial reconstruction with 6hits - Pt > 4 GeV Track pairs - mass windows for signal - (un)like sign chargeVertex fit - c2 150mmCMS LVL1:


CMS offline analysis : Bmmc2COSaisolationlxy/sxyAfter selections 6.1 events/10fb-1 v.s. mmX background 13.8 +22.0 -13.8lxyapT(Bs)m+m-


ATLAS offline analysis : Bsmm

pT>6GeV, Rmm 0.8 GeV in cone q < 15 degreesvertex fit with pointing to primary vertex constrainttransverse decay length Lxy/s(Lxy) > 11Exected signal v.s. inclusive bbmmX bkgL=10fb-1(can be collected in a year)Br(Bsmm) = 3.5x10-9

B0s signalBG (bbmmX)pT>6 GeV, Rmm11, c2

Documents

Rare B decays in ATLAS and CMS