B c mass, lifetime and BR’s at CDF Masato Aoki University of Tsukuba For the CDF Collaboration International Workshop on Heavy Quarkonium BNL

Masato AokiInternational Workshop on Heavy Quarkonium BNL2 Outline 1.Introduction a.The B c meson b.Tevatron and CDF 2.  (B c )B(B c  J/  l )/  (B u )B(B u  J/  K) measurement 3.Lifetime measurement 4.Mass measurement 5.Summary

Masato AokiInternational Workshop on Heavy Quarkonium BNL3 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  B c has measurable lifetime B c provides unique features of heavy quark bound states In the future…  As a B s generator  CP asymmetry measurement in D 0 D s decay mode The B c Meson

Masato AokiInternational Workshop on Heavy Quarkonium BNL4 B c in CDF Run I (1991~1996) B c signal search using B c  J/  l  (l=e,  ) channel ~20 B c signal events were observed in 0.11 fb -1 of J/    data [PRL 81, 2432 (1998) and PRD 58, (1998)] M=6.4±0.39±0.13 GeV/c 2  =0.46 ±0.03 ps –0.16 =0.132 ± – –0.020  (B c )  B(B c  J/  l )  (B u )  B(B u  J/  K) * harder p T (B c ) was assumed

Masato AokiInternational Workshop on Heavy Quarkonium BNL5 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  cm -2 s -1

Masato AokiInternational Workshop on Heavy Quarkonium BNL6 B field : 1.4 T HAD calorimeter Muon system Drift chamber Silicon microstrip detector EM calorimeter The CDF II detector

Masato AokiInternational Workshop on Heavy Quarkonium BNL7 Heavy Flavor Physics at CDF Huge production cross sections at Tevatron   b ~30  b Large backgrounds as well qb q b b g g b q q b g b b g g g b B triggers  lepton trigger  displaced track trigger  and combined trigger Trigger requirements  large bandwidth  background suppression  deadtimeless primary vertex secondary vertex d0 B J/    Used for current B c analysis

Masato AokiInternational Workshop on Heavy Quarkonium BNL8 B c Production and Decay B c has differently flavored heavy quarks  Much smaller production rate  Unique decay (b  c,c  s,annihilation…)  Rich decay modes SpeciesProd. Fraction B+B+ 40% B0B0 BsBs 10% b-baryons10% BcBc ~0.05% Theoretical calculation : 7.4nb Phys. Lett. B605, 311(2005) DecayBR bcbc B c  J/  e ~1.9% B c  J/  ~0.13% cscs B c  B s  ~16.4% BcBs*BcBs* ~20.2% ann. BcBc ~1.6% B c  cs ~4.9% hep-ph/ (2003)

Masato AokiInternational Workshop on Heavy Quarkonium BNL9 Production Rate Measurement B c  J/  e and J/  semileptonic decays  Use J/    trigger data (0.36 fb -1 )  Large BR  statistical advantage  No narrow mass peak due to missing neutrino (4~6GeV/c 2 )  Need to understand all of backgrounds  fake J/  …………………..J/  mass sideband  fake e,  and DIF………...J/  +track & fake rate  bb (b  J/  X,b  l X)….....PYTHIA Monte Carlo  photon conversion e……...tagged conv. e & its efficiency  prompt J/  ……………….require to have a displaced vertex Use B u  J/  K as a normalization mode  Topologically similar  Measure  (B c )B(B c  J/  l )/  (B u )B(B u  J/  K)  Cancel out most of uncertainties

Masato AokiInternational Workshop on Heavy Quarkonium BNL10  (B c )B(B c  J/  l )/  (B u )B(B u  J/  K) Measurement : 0.36 fb -1 electron mode : ± 0.038(stat.) ± 0.035(yield) ± 0.065(acceptance) (p T (B)>4GeV/c) ± 0.036(stat.) ± 0.031(yield) ± 0.051(acceptance) (p T (B)>6GeV/c) muon mode : ± 0.045(stat.) ± 0.066(syst.) /-0.032(life.) (p T (B)>6GeV/c) J/  e J/  5.9  5.2  * softer p T (B c ) was assumed

Masato AokiInternational Workshop on Heavy Quarkonium BNL11 Lifetime Three major decay diagrams Lifetime should be  B c   1/( )  0.5 ps if all the three diagrams contribute to the decay

Masato AokiInternational Workshop on Heavy Quarkonium BNL12 Lifetime Measurement B c  J/  e semileptonic decay Perform a maximum likelihood fit to J/  e decay length Correct neutrino’s momentum using Monte Carlo Background shapes Estimate # of BKGs fake J/  conversion fake e bb Constrained during the fitting (same way as  B ratio measurement)

Masato AokiInternational Workshop on Heavy Quarkonium BNL13 Lifetime Measurement  (B c ) = /-0.065(stat.) ± 0.036(syst.) ps B c  J/  e channel Data : ~  fb -1 accepted by PRL

Masato AokiInternational Workshop on Heavy Quarkonium BNL14 Mass Theoretical calculations predict M(B c )  6.3GeV/c 2 B c full reconstruction is necessary for precise mass measurement CDF searches for the B c  J/  decay : (BR~0.1%) PRL94,172001(2005)

Masato AokiInternational Workshop on Heavy Quarkonium BNL15 Observation of the B c  J/  decay and Mass Measurement Data : ~1.1 fb -1 J/  selection is optimized using B u  J/  K events 7.5  M(B c ) = ± 4.0(stat.) ± 2.7(syst.) MeV/c 2 N(B c )  50 Close up

Masato AokiInternational Workshop on Heavy Quarkonium BNL16 Summary The B c signal has been observed in B c  J/  e  modes with >5  significance in CDF Run II Measured B c meson properties   (B c )B(B c  J/  l )/  (B u )B(B u  J/  K)  e : ± ± ± (p T (B)>4GeV/c)   : ± ± / (p T (B)>6GeV/c)  Lifetime  / ± ps  Mass  ± 4.0 ± 2.7 MeV/c 2 Other studies are to follow soon… Lifetime measurements from J/ , J/ 

Masato AokiInternational Workshop on Heavy Quarkonium BNL17 Backup slides

Masato AokiInternational Workshop on Heavy Quarkonium BNL18 Residual photon conversions Electrons coming from photon conversion event are removed from the J/  e candidate list Find colinear partner track miss-tracking in low p T region not 100% finding efficiency  residual photon conversion electrons Estimate using found conversions and its efficiency