Investigation of the decays B0d,s-> J/yh in the ATLAS experiment at the LHC C. D
Galli, Michael, Founder;Editor; President has reference to this Academic Journal, PHwiki organized this Journal Investigation of the decays B0d,s-> J/yh in the ATLAS experiment at the LHC C. Driouichi, P.Eerola, Lund M. Melcher, F. Ohlsson-Malek, S. Viret, Grenoble Physics background Decays B0s->J/yf, B0s ->J/yh(), B0s ->D+sD-s are analogous, but up to now, only the first one has been studied Advantages of B0s->J/yh: no angular analysis needed since the final state is a CP eigenstate (V-PS) Cross-check of the decay mode B0s->J/yf CP asymmetry: in the St in addition to ard Model, the CP asymmetry is predicted to be theoretically clean, but very small, where l=sinqC, qC is the Cabibbo angle, h is the heigth of the Unitarity Triangle, in addition to g is one of the angles of the UT. Measurements Branching ratio Decay is not yet observed, exp. upper limit BR<3.8 10-3 Bs lifetime in addition to other parameters If large CP violation is observed => New Physics! For example, LR-symmetric models with spontaneous CP violation predict CP asymmetry O(40%)[Ball, Fleischer] (SM: 4%) BR predictions: BR=(8.3-9.5) 10-4 [Sk in addition to s]. Uncertainty from h-h mixing. Direct measurement of angle g using Bs in addition to Bd decays to J/yh
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J/y reconstruction J/y->m+m- selected with pT(m1)>5 GeV, pT(m2)>3 GeV => passes level-1 in addition to level-2 triggers efficiency: 85% as long as m1 (incl. level-1 in addition to reconstruction in muon spectrometer), 78% as long as m2 (incl. Reconstruction in muon spectrometer in addition to tilecal). Fake rate is very small. J/y reconstruction: vertexing with c2/NDF<6, transverse decay length > 250 mm => mass res. 39 MeV, rec. eff. 79%. h reconstruction h->gg reconstruction in the ATLAS LAr calorimeter: cell size 0.025×0.025 (DhxDf) in the second sampling layer further selection: cuts on energy sharing in the 3 ECAL layers in addition to HCAL cluster width energy containment in the 3×3 window => mass resolution 35 MeV, efficiency 2.3%, background 28% energy resolution (s(E)/E)2=(0.10/sqrt(E))2 + (0.01)2 (E in GeV) clusterization of 3×3 cells with 1 GeV threshold => if E(g)< 1 GeV => photon lost => if gg opening angle < 5o => two clusters merge to 1 => rejected 20% of h->gg retained B0s,(d) reconstruction J/y in addition to h c in addition to idates combined, using mass constraints. s(B0s,d)= 67 MeV.
Results as long as 30 fb-1 Background considered: b->J/yX Clear Bs signal Bd CANNOT be observed CP asymmetry Events need to be tagged as B or anti-B Use jet-charge tagging with 57% efficiency, 37% wrong-tag fraction Fit: where D is dilution from background in addition to wrong tags. d(sinfM) = 0.27 (xs = Dms/Gs=19), 0.31 (xs=30) Only very large asymmetries can be observed Comparisons in addition to conclusions Simple estimates: B-factories PEPII, KEKB cannot produce Bs Tevatron 2 fb-1: CDF 190 Bs->J/yh LHC ATLAS 30 fb-1: 9700 Bs->J/yh LHC LHCb 10 fb-1: 260 000 Bs ->J/yh, 2150 Bd->J/yh ATLAS can see a clear signal of Bs->J/yh, measure BR in addition to other parameters: measurement in addition to cross-check. Note ISN-01.68, LUNDF6/(NFFL-7198)2001 submitted as long as publication. Improve statistics by investigating h->p+p-p0 (BR=23%) improve h efficiency by better use of the fine granularity of the first ECAL sampling (cluster fine structure)
Galli, Michael Founder;Editor; President
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