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B c mass, lifetime and BR’s at CDF

B c mass, lifetime and BR’s at CDF. Masato Aoki University of Tsukuba For the CDF Collaboration International Workshop on Heavy Quarkonium 2006 @ BNL. Outline. Introduction The B c meson Tevatron and CDF s (B c )B(B c  J/ y l n )/ s (B u )B(B u g J/ y K) measurement

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B c mass, lifetime and BR’s at CDF

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  1. Bc mass, lifetime and BR’s at CDF Masato Aoki University of Tsukuba For the CDF Collaboration International Workshop on Heavy Quarkonium 2006 @ BNL

  2. Outline • Introduction • The Bc meson • Tevatron and CDF • s(Bc)B(BcJ/yln)/s(Bu)B(BugJ/yK) measurement • Lifetime measurement • Mass measurement • Summary International Workshop on Heavy Quarkonium 2006 @ BNL

  3. 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 • Bcprovides unique features of heavy quark bound states • In the future… • As a Bs generator • CP asymmetry measurement in D0Ds decay mode International Workshop on Heavy Quarkonium 2006 @ BNL

  4. M=6.4±0.39±0.13 GeV/c2 +0.18 –0.16 t=0.46 ±0.03 ps s(Bc)B(BcgJ/yln) =0.132 ±0.031 +0.041 –0.037 +0.032 –0.020 s(Bu)B(BugJ/yK) 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)] * harder pT(Bc) was assumed International Workshop on Heavy Quarkonium 2006 @ BNL

  5. 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 International Workshop on Heavy Quarkonium 2006 @ BNL

  6. The CDF II detector B field : 1.4 T Muon system HAD calorimeter EM calorimeter Drift chamber Silicon microstrip detector International Workshop on Heavy Quarkonium 2006 @ BNL

  7. b g q b b g b g g g q g q q b b b b secondary vertex B d0 primary vertex Heavy Flavor Physics at CDF • Huge production cross sections at Tevatron • sb~30 mb • Large backgrounds as well J/ygmm • B triggers • lepton trigger • displaced track trigger • and combined trigger • Trigger requirements • large bandwidth • background suppression • deadtimeless Used for current Bc analysis International Workshop on Heavy Quarkonium 2006 @ BNL

  8. Bc Production and Decay • Bc has differently flavoredheavy quarks • Much smaller production rate • Unique decay (bgc,cgs,annihilation…)  Rich decay modes Theoretical calculation : 7.4nb Phys. Lett. B605, 311(2005) hep-ph/0308214(2003) International Workshop on Heavy Quarkonium 2006 @ BNL

  9. 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(BcJ/yln)/s(Bu)B(BugJ/yK) • Cancel out most of uncertainties International Workshop on Heavy Quarkonium 2006 @ BNL

  10. s(Bc)B(BcJ/yln)/s(Bu)B(BugJ/yK) Measurement : 0.36 fb-1 • electron mode : • 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.) (pT(B)>6GeV/c) J/y e J/y m 5.9s 5.2s * softer pT(Bc) was assumed International Workshop on Heavy Quarkonium 2006 @ BNL

  11. Lifetime • Three major decay diagrams • Lifetime should be t(Bc) 1/(0.6+1.2+0.1)  0.5 psif all the three diagrams contribute to the decay International Workshop on Heavy Quarkonium 2006 @ BNL

  12. 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 • Estimate # of BKGs fake J/y bb conversion fake e (same way as sB ratio measurement) Constrained during the fitting International Workshop on Heavy Quarkonium 2006 @ BNL

  13. Lifetime Measurement • BcgJ/yen channel • Data : ~0.36 fb-1 t(Bc) = 0.463 +0.073/-0.065(stat.) ± 0.036(syst.) ps accepted by PRL International Workshop on Heavy Quarkonium 2006 @ BNL

  14. 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) International Workshop on Heavy Quarkonium 2006 @ BNL

  15. 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 International Workshop on Heavy Quarkonium 2006 @ BNL

  16. 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(BcJ/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… • Lifetime measurements from J/ymn, J/yp International Workshop on Heavy Quarkonium 2006 @ BNL

  17. Backup slides International Workshop on Heavy Quarkonium 2006 @ BNL

  18. 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 International Workshop on Heavy Quarkonium 2006 @ BNL

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