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Bc mass, lifetime and BR’s at CDF Masato Aoki University of Tsukuba For the CDF Collaboration International Workshop on Heavy Quarkonium 2006 @ BNL Outline 1. Introduction a. The Bc meson b. Tevatron and CDF s(Bc)B(BcJ/yln)/s(Bu)B(BugJ/yK) measurement 3. Lifetime measurement 4. Mass measurement 5. Summary 2. Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 2 The Bc Meson • Ground state of bottom-charm quark bound system Both quarks are heavy Similar to cc and bb families But the two quarks have different flavor Only weak decay is possible Bc has measurable lifetime • Bc provides unique features of heavy quark bound • states In the future… As a Bs generator CP asymmetry measurement in D0Ds decay mode Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 3 Bc in CDF Run I (1991~1996) • Bc signal search using BcgJ/yln (l=e,m) channel • ~20 Bc signal events were observed in 0.11 fb-1 of J/ygmm data [PRL 81, 2432 (1998) and PRD 58, 112004 (1998)] M=6.4±0.39±0.13 GeV/c2 +0.18 t=0.46 –0.16 ±0.03 ps s(Bc)B(BcgJ/yln) +0.041 ±0.031+0.032 =0.132 –0.037 –0.020 s(Bu)B(BugJ/yK) Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL * harder pT(Bc) was assumed 4 The Tevatron Collider • √s=1.98 TeV proton-antiproton collider • Tevatron has already delivered 1.6 fb-1 • CDF has ~1 fb-1 available for analysis We anticipate 4~8 fb-1 by the end of Run II Record peak luminosity : 1.82 1032 cm-2 s-1 Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 5 The CDF II detector Muon system HAD calorimeter EM calorimeter Drift chamber B field : 1.4 T Masato Aoki Silicon microstrip detector International Workshop on Heavy Quarkonium 2006 @ BNL 6 Heavy Flavor Physics at CDF q b g b q b g b b g b q q b g •Huge production cross sections at Tevatron sb~30 mb •Large backgrounds as well b g g J/ygmm •B triggers lepton trigger secondary displaced track trigger vertex and combined trigger B •Trigger requirements d0 large bandwidth primary vertex background suppression deadtimeless Used for current Bc analysis Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 7 Bc Production and Decay • Bc has differently flavored heavy quarks Much smaller production rate Unique decay (bgc,cgs,annihilation…) Rich decay modes Species B+ B0 Bs Prod. Fraction 40% 40% 10% b-baryons 10% Bc ~0.05% Theoretical calculation : 7.4nb Phys. Lett. B605, 311(2005) Masato Aoki Decay BR BcgJ/y en ~1.9% bgc BcgJ/y p ~0.13% BcgBs p ~16.4% cgs BcgBs*r ~20.2% ~1.6% Bcgtn ann. ~4.9% Bcgcs hep-ph/0308214(2003) International Workshop on Heavy Quarkonium 2006 @ BNL 8 Production Rate Measurement • BcgJ/yen and J/ymn semileptonic decays Use J/ygmm trigger data (0.36 fb-1) Large BR statistical advantage No narrow mass peak due to missing neutrino (4~6GeV/c2) Need to understand all of backgrounds fake J/y…………………..J/y mass sideband fake e, m and DIF………...J/y+track & fake rate bb (bgJ/yX,bglnX)….....PYTHIA Monte Carlo photon conversion e……...tagged conv. e & its efficiency prompt J/y……………….require to have a displaced vertex • Use BugJ/yK as a normalization mode Topologically similar Measure s(Bc)B(BcJ/yln)/s(Bu)B(BugJ/yK) Cancel out most of uncertainties Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 9 s(Bc)B(BcJ/yln)/s(Bu)B(BugJ/yK) Measurement : 0.36 fb-1 J/y m J/y e 5.9s • electron mode : 5.2s * softer pT(Bc) was assumed 0.282 ± 0.038(stat.) ± 0.035(yield) ± 0.065(acceptance) (pT(B)>4GeV/c) • 0.242 ± 0.036(stat.) ± 0.031(yield) ± 0.051(acceptance) (pT(B)>6GeV/c) • • muon mode : • 0.245 ± 0.045(stat.) ± 0.066(syst.) +0.080/-0.032(life.) Masato Aoki (pT(B)>6GeV/c) International Workshop on Heavy Quarkonium 2006 @ BNL 10 Lifetime • Three major decay diagrams • Lifetime should be t(Bc) 1/(0.6+1.2+0.1) 0.5 ps if all the three diagrams contribute to the decay Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 11 Lifetime Measurement •BcgJ/yen semileptonic decay •Perform a maximum likelihood fit to J/ye decay length •Correct neutrino’s momentum using Monte Carlo •Background shapes bb fake J/y •Estimate # of BKGs (same way as sB ratio fake e conversion measurement) Constrained during the fitting Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 12 Lifetime Measurement • BcgJ/yen channel • Data : ~0.36 fb-1 accepted by PRL t(Bc) = 0.463 +0.073/-0.065(stat.) ± 0.036(syst.) ps Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 13 Mass • Theoretical calculations predict M(Bc) 6.3GeV/c2 • Bc full reconstruction is necessary for precise mass • measurement CDF searches for the BcgJ/yp decay : (BR~0.1%) PRL94,172001(2005) Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 14 Observation of the BcgJ/yp decay and Mass Measurement • Data : ~1.1 fb-1 • J/yp selection is optimized using BugJ/yK events Close up N(Bc)50 7.5s M(Bc) = 6276.5 ± 4.0(stat.) ± 2.7(syst.) MeV/c2 Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 15 Summary The Bc signal has been observed in BcgJ/y p,en,mn modes with >5s significance in CDF Run II Measured Bc meson properties s(Bc)B(BcJ/yln)/s(Bu)B(BugJ/yK) e : 0.282 ± 0.038 ± 0.035 ± 0.065 (pT(B)>4GeV/c) m : 0.245 ± 0.045 ± 0.066 +0.080/-0.032 (pT(B)>6GeV/c) Lifetime 0.463 +0.073/-0.065 ± 0.036 ps Mass 6276.5 ± 4.0 ± 2.7 MeV/c2 Other studies are to follow soon… International Workshop Heavy Quarkonium Lifetime measurements from onJ/ymn, J/yp 2006 @ BNL Masato Aoki 16 Backup slides Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 17 Residual photon conversions • Electrons coming from photon conversion event are removed from the J/ye candidate list • • • • Find colinear partner track miss-tracking in low pT region not 100% finding efficiency residual photon conversion electrons Estimate using found conversions and its efficiency Masato Aoki International Workshop on Heavy Quarkonium 2006 @ BNL 18