1. 1 Rare Decays of B Hadrons at CDF Matthew Jones October 3, 2005

2. 2 Oh my!

3. 3 Rare Decays of B Hadrons at CDF Search B s,B d  μ + μ - Charmless B decays –B d,B s,Λ b  hh’ –B +  φK +, B s  φφ Not covered –B masses –B s  D s π, Λ b  Λ c π and kin –D 0  K - π +,K - K +,π - π + In this talk, “rare” means branching fractions ≲ 10 -6.

4. 4 The CDF Detector Muon systems: Tracking systems: SVX-II COT CMP CMX CMU

5. 5 Heavily suppressed in Standard Model: Approximately 2 orders of magnitude below current experimental sensitivity Significant enhancements from contributions of new physics processes Search for B s  μ + μ -

6. 6 B s  μ + μ - enhancement by SUSY: Correlation between Br(B s  μ + μ - ) and (g-2) μ measurement – BNL result could imply a10-100 enhancement compared with SM. Different behavior for B s /B d  μ + μ - possible ~ (tan β) 6  up to 3 orders of magnitude enhancement

7. 7 Search for B s  μ + μ - Di-muon trigger, p T >1.5 or 2 GeV/c Limit normalized to B +  J/ψK + signal Significant backgrounds from –Sequential semileptonic –Double semileptonic decays –Fake leptons Discriminate using multivariate likelihood (isolation, 3D vertex quantities)

8. 8 Search for B s,B d  μ + μ - Good mass resolution allows separation of B s  μ + μ - and B d  μ + μ - : No events observed in either mass window 90% C.L. limits: Expected background: hep-ex/0508036 hep-ex/0508036 submitted to PRL 1.5  0.2 events

9. 9 Example of Constraints on Models R. Dermíšek, et al., hep-ph/0507233 hep-ph/0507233 Minimal SO 10 SUSY

10. 10 Hadronic Decays B  ππ/Kπ/KK: original motivation for Secondary Vertex Trigger in CDF-II –Level 1 trigger: require two tracks with requirements on p T and ΔΦ Dominates level 1 trigger rate! –Level 2 trigger: vertex displaced with respect to beam axis  heavy flavor trigger. Applications at CDF: –Two-body B-decays, B 0  π + π -, B 0  K + π -,... –Non-leptonic B-decays (eg., B s  D - s  + ) –Semi-leptonic decays (eg. Lepton + displaced track) –Charm physics

11. 11 Charmless B  hh’ Decays CDF observes overlapping contributions from B 0  π + π -, B 0  K + π -, B s 0  K + K - : Update of result from Summer 2004: Same data sample, uncertainties reduced. Separate individual decays using kinematics and particle identification. ~ 900 candidates Wider than expected for a single channel

12. 12 Charmless B  hh’ Decays Discriminating variables: –Invariant mass, m(π + π - ), –“Signed momentum imbalance”, α=Q 1 (1-p 1 /p 2 ) –Energy loss in tracking chamber, dE/dx –Total momentum Corrections applied for relative efficiencies Measure relative branching fractions and A CP in B 0  K + π - Time-dependent asymmetries possible: already demonstrated In 1 fb -1 we expect of order 50 tagged events Γ(B s  KK)/Γ(B d  ππ) needed for extraction of  (hep-ph/0404009)hep-ph/0404009

13. 13 Charmless B  hh’ Decays f(B d  Kπ) = 0.600  0.034 f(B s  KK) = 0.262  0.035 f(B d  ππ) = 0.134  0.030 f(B s  Kπ) = 0.003  0.028

14. 14 Search for Λ b  pπ - /pK - Charmless Λ b decays yet to be observed Large A CP expected in baryons Branching fraction could be 1-2 x10 -6 Count excess over background in distribution of m(π + π - ):

15. 15 Search for Λ b  pπ - /pK - Normalize with respect to B 0  K + π - signal: No events observed, set upper limit: Significant improvements possible with particle identification and larger data sample. (90% C.L.)

16. 16 B +  φK + and B s  φφ More examples of charmless B decays selected using secondary vertex trigger Pure penguin transitions may differ from SM expectations A CP can be measured in B +  φK + In principle, CP composition in B s  VV obtained from angular analysis B +  φK + already seen but this is the first observation of B s  φφ

17. 17 B +  φK + Analysis Candidates are 3-track vertices containing two trigger tracks Discriminating variables: –M(K + K - K + ): signal and physics backgrounds –M(K + K - ): φ  K + K - signal –φ decay helicity angle, H φ –dE/dx: kaon identification Likelihood fit to determine yield of B +  φK + and CP asymmetry.

18. 18 B +  φK + Analysis Physics backgrounds: B +  K + K - K + X B +  f 0 K + B +  K *0  + B +  K + K - K + B +  K +  +  - Signal: B+ φK+B+ φK+

19. 19 B +  φK + CP Asymmetry Br(B +  φK + ) x 10 -6 A CP (B +  φK + )

20. 20 Observation of B s  φφ Angular analysis possible with 1 fb -1. 179 pb -1 hep-ex/0502044hep-ex/0502044 and PRL 95, 031801 (2005) 8 events in search window 0.75  0.41 BG expected

21. 21 2005 2004 2003 2002 Bsμ+μ-Bsμ+μ- B  hh’, B +  φK +, B s  φφ 1 fb -1 of data for analysis by 2006 spring shutdown.

22. 22 What to do with 1 fb -1 Expected limit on Br(B s  μ + μ - ): <10 -7 Ultimate sensitivity in Run-II could reach 3x10 -8 Resolution on A CP (B 0  K + π - ) should approach  0.025 with 1 fb -1 Ultimate precision of ~1% B s  φφ background free – 120 events in 1 fb -1  angular analysis. Good prospects for observing Λ b  pπ/pK

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24. 24 CDF Triggers for B Physics Beam crossings every 396 ns Level 1 trigger: –Axial tracks from segments found in COT –Association with hits in muon chambers Level 2 trigger: –Silicon hits added to tracks found at level 1 –Finer granularity in muon systems Level 3 trigger: –Full event reconstruction

25. 25 CDF Detector Performance J/ψ trigger: –8x10 6 J/ψ with hits in SVX-II in 1 fb -1 B +  J/ψK + : Includes c  >60 μm

26. 26 J/ψ Trigger at CDF Level 1 – Two muons with p T >1.5 GeV Level 2 – Opposite charge Level 3 – Full event reconstruction

27. 27 Charmless B  hh’ Decays Contributions to systematic uncertainty: –m(π + π - ) resolution from Monte Carlo –Shapes of dE/dx p.d.f.’s, dE/dx correlations –Electron/proton backgrounds –B meson masses –Background shape, momentum spectrum –  (B),  s through decay length requirements –Isolation requirement used in reconstruction –Track trigger K/π bias –Proton/anti-proton asymmetry in background –Correlations between discriminating variables –Final state radiation (Cirigliano, et al.)Cirigliano, et al. not fundamental limitations

28. 28 B  hh’ systematics

29. 29 dE/dx Calibration at CDF High statistics calibration samples: –D *+  D 0  + –   p  - –K 0 S   +  - –J/ψ  μ + μ - 1.4σ K/π separation for p>2 GeV/c

30. 30 The Future