1. B c Results from CDF II Satyajit Behari (For the CDF Collab.) Johns Hopkins Univ., Baltimore,USA 23 rd Jul. 2005 HEP2005 Europhysics Conference, Lisboa, Portugal

2. S.Behari, Bc Results from CDF II, HEP2005 2 23rd July 2005 Contents Introduction Interests in B c Meson Measurements π Mass in fully reconstructed B c  J/Ψ π decay μ Cross-section × BR ratio in B c  J/Ψ μν  decay e Cross-section × BR ratio in B c  J/Ψ eν e decay Summary

3. S.Behari, Bc Results from CDF II, HEP2005 3 23rd July 2005 Heavy Flavor Physics at Tevatron Since  (bb) <<  (pp)  Events have to be selected with specific triggers Trigger requirements: large bandwidth, background suppression, deadtimeless Flavor Creation (annihilation) qb q b Flavor Creation (gluon fusion) b g g b Flavor Excitation q q b g b Gluon Splitting b g g g b Tevatron is a source of all B-hadron species, B d, B u, B c, B s and Λ b  b = 29.4 ± 0.6 ± 6.2  b (|η| < 1) ( CDF ) Huge cross-sections compared to the the B-factories but proportionally large backgrounds as well

4. S.Behari, Bc Results from CDF II, HEP2005 4 23rd July 2005 Di-muon trigger p T >1.5GeV,  p T >2GeV, 0.6<  1  < 2.5 o and Muon ID cuts Yields higher than Run I (low p T threshold, increased acceptance) Triggers for B c Analyses Two track trigger 2 opposite charged displaced tracks p T > 2 GeV, 120  m < |IP| < 1mm D*  D 0 ,   p  For Signal and Control Sample For particle ID studies Single electron trigger A track matched to a central electron cluster p T > 8 GeV   e e

5. S.Behari, Bc Results from CDF II, HEP2005 5 23rd July 2005 The B c is a ground state bc meson, first experimentally observed by CDF I ( PRL 81, 1998 ). The measured mass is less precise than theoretical prediction. Test of lattice QCD and potential models  Test of lattice QCD and potential models Unlike quarkonia it carries flavor Probes heavy quark dynamics in new territories  Probes heavy quark dynamics in new territories Spectroscopy of excited states Possible observation, test of models  Possible observation, test of models What is interesting about B c ‾ Production rate can shed light on fragmentation mechanism Gluon fusion diagram dominant 7.4 nb Recent cross-section calculation 7.4 nb [Saleev et al, Phys. Lett. B605, 311 (2005)] BCBC b g c g

6. S.Behari, Bc Results from CDF II, HEP2005 6 23rd July 2005 Interests in B c Continued.. B S produced from B C decays Estimate B C contribution to B S lifetime and mixing  Estimate B C contribution to B S lifetime and mixing B S mixing B C as a source of (lepton) tagged B S  B S mixing CP asymmetry CP asymmetry measurement in D 0 D S + decay mode ‾ c J/   l  l  b c Bs*Bs* b b c W+W+ No annihilation decay channel for B C  hadrons via gluons  Only weak decays, large lifetime lifetime Long term…

7. S.Behari, Bc Results from CDF II, HEP2005 7 23rd July 2005 Lifetime: (0.46 ± 0.03) ps +0.18 -0.16 CDF Run I B c Measurements 20.4 signal events 10.6 ± 2.3 background events L = 110 pb -1 pT(B c ) > 6 GeV/c, |  | < 0.6 + 6.2 - 5.5 PRL 81 n.12 (1998) Mass: (6.4 ± 0.39 ± 0.13) GeV/c 2

8. S.Behari, Bc Results from CDF II, HEP2005 8 23rd July 2005 B c  J/    Search Pros: Exclusive mode; Precise mass measurement possible Same topology well known normalization mode: B +  J/  K +Cons: B c lifetime is shorter than light b- mesons (charm decay dominates)  Need aggressive secondary vertex resolution Expected signal > 10 times smaller than the signal in the semileptonic decay. Primary vertex    ±,K ± B c,B + Analysis method: Analysis method: Reconstruct     vertex, Constrain     to J/  mass Attach a third track w/ p T threshold Event-by-event primary vertex

9. S.Behari, Bc Results from CDF II, HEP2005 9 23rd July 2005 Cut Optimization Blind analysis: Search range: 6.4 ± 2  = [5.6 to 7.2] GeV/c 2 Use MC for: optimizing cuts, estimate sensitivity, relative to B + Cut optimization: Score function: (for 3  search) Signal from MC and background from data Tight vertex requirements using 3D  2, 2D decay length significance, pointing angle, impact parameter etc.   B+B+ B0B0   Backgrounds (Prompt J/Ψ + track from PV) (bb production from gluon splitting) -

10. S.Behari, Bc Results from CDF II, HEP2005 10 23rd July 2005 Peak Search Criteria 390 390 data events within mass range Expected signal: Use Toy MC to determine criteria for seeing a significant peak: Yellow: Toy MC with no signal, corresponding to 0.1% prob. of background fluctuation Blue: Toy MC for N sig =30 events  Score function threshold: Σ > 3.5

11. S.Behari, Bc Results from CDF II, HEP2005 11 23rd July 2005 Peak Evaluation Σ max = 3.6 A sliding fit is performed in the search region and the score function is estimated. Σ max = 3.6 Probability for the background to give a peak at Σ max = 3.6 is estimated from Toy MC as 0.27%. As a consistency check compare partially reconstructed B c yield with that for B + Study impact parameter of the pion with J/Ψ vertex Yield difference between upper and lower sidebands consistent with B + LSB USB

12. S.Behari, Bc Results from CDF II, HEP2005 12 23rd July 2005 B c Mass Measurement Unbinned likelihood fit w/ width fixed in 6.180 < M < 6.480 Sources of systematics: Background shape 0.8 MeV/c 2 Momentum scale 0.6  /K dE/dx 0.2 Tracking 0.2  p T 0.5 Total 1.1 MeV/c 2 M(B c ) = (6287.0 ± 4.8 stat. ± 1.1 syst. ) MeV/c 2

13. S.Behari, Bc Results from CDF II, HEP2005 13 23rd July 2005 σ×BR Ratio in B c  J/ψ μ Analysed ~360 pb -1 Normalization mode: B +  J/ψ K + Basic cuts: Good muons:    |M(μμ) – M(J/ψ)| < 50 MeV J/ψ mass constrained, Prob(   )> 1%, c  > 60  m Third muon p T > 3 GeV Remove B +  J/ψ K + within M B ± 50 MeVBackgrounds: Fake muons from decay-in-flight of K, ,p Estimated by assigning muon probabilities to the third track, obtained from PID quantities, dE/dx and ToF Predicted background: 16.3±2.9 events

14. S.Behari, Bc Results from CDF II, HEP2005 14 23rd July 2005 Background Predictions From bb fragmentation Estimated relative contribution of QCD processes from a Pythia MC and compared to data Predicted background: 12.7 ± 1.7 ± 5.7 events Fake J/ψ + a third muon Estimated by matching a third muon with events in J/ψ sidebands Predicted background: 19.0 ± 3.0 events ‾

15. S.Behari, Bc Results from CDF II, HEP2005 15 23rd July 2005 σ×BR Ratio Results 60.0 ± 12.6 Signal events: 60.0 ± 12.6 46.0 ± 7.3 Background: 46.0 ± 7.3 5.2σ Significance: 5.2σ For p T (B c ) > 4 GeV, |  (B c )| < 1

16. S.Behari, Bc Results from CDF II, HEP2005 16 23rd July 2005 σ×BR Ratio in B c  J/ψ e 360 pb-1 data, Normalization mode: B +  J/ψ K + Basic cuts: Similar J/ψ selection as muon mode Soft electron identification: Good quality tracks, p T > 1 GeV, matched to central strip chambers and EM calorimeter likelihood ratio P e < 0.7 Cut on a likelihood ratio variable constructed from 10 electromagnetic and tracking variables P e < 0.7 dE/dx Additional cut on specific ionization, dE/dx: Z e /σ z > -1.3

17. S.Behari, Bc Results from CDF II, HEP2005 17 23rd July 2005 Backgrounds Fake electrons from decay-in- flight of K, ,p From bb fragmentation From fake J/ψ Conversion electrons: Removed during J/ψ e sample selection Residual conversion electrons are found by pairing electron candidates with tracks, w/o electron requirement ‾

18. S.Behari, Bc Results from CDF II, HEP2005 18 23rd July 2005 σ×BR Ratio Result 114.9 ± 15.5 ± 13.6 Signal: 114.9 ± 15.5 ± 13.6 63.6 ± 4.9 ± 13.6 Background: 63.6 ± 4.9 ± 13.6 5.9σ Significance: 5.9σ For p T (B c ) > 4 GeV, |  (B c )| < 1

19. S.Behari, Bc Results from CDF II, HEP2005 19 23rd July 2005 Summary A precise B c mass measurement in B c  J/Ψ π decay is in agreement with lattice QCD. σ*BR ratios of B c measured in Bc  J/Ψ μ,e ν decays improve upon CDF Run I measurements. Update of mass and BR ratio measurements using high statistics (~ 1 fb -1 ) are underway. Lifetime and other studies to follow..

20. S.Behari, Bc Results from CDF II, HEP2005 20 23rd July 2005 B c  J/ψ μ ν: 95 ± 12 ± 11 signal events L = 210 pb -1 Lifetime: (0.45  ps Mass: (5.95  GeV/c 2     Backup-1 DØ Run II (ICHEP2004)

21. S.Behari, Bc Results from CDF II, HEP2005 21 23rd July 2005 We know From CDF Run-1 All theoretical uncertainties are in the value of R 2 define R = To evaluate the expected signal we use CDF Run I measurement and one ratio of BR. Ratio of efficiencies Number of events in B +  J/   data “R” in MC Backup-2 Expected B c Signal w.r.t B + data