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Studies of b- hadron decays to charming final states at LHCb

DPF, APS Meeting of the Division of Particles and Fields of the American Physical Society August 9-13, 2011 , Brown University, Providence, Rhode Island. Studies of b- hadron decays to charming final states at LHCb. Stefania Ricciardi STFC, Rutherford Appleton Laboratory

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Studies of b- hadron decays to charming final states at LHCb

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  1. DPF, APS Meeting of the Division of Particles and Fields of the American Physical Society August 9-13, 2011 , Brown University, Providence, Rhode Island Studies of b-hadron decays to charming final states at LHCb Stefania Ricciardi STFC, Rutherford Appleton Laboratory on behalf of the LHCb Collaboration

  2. Which “charming” final states? b-hadron decays to open charm: Hb→HcX • B+→D0K+ and B+→D0p+ • ratio of branching fractions [LHCb-CONF-2011-031] • R_CP+ , A_CP • R_ADS, A_ADS [LHCb-CONF-2011-044] Bu • Bs→Dsp, B0→D+p-, B0→D+K- , arXiv: 1106.4435 • Rates and fs/fd production fractions Bs • fs/fd Average • [LHCb-CONF-2011-034] Bd Bu Bs Lb Semileptonic decays Production fractions from Hb→HcXmn [LHCb-CONF-2011-028] Lb→D0pK- and Lb→D0pp- [LHCb-CONF-2011-036] Observation of new decay modes and hints of Xb Lb LHCb Summer 2011 results Stefania Ricciardi

  3. b-hadron decays to open charm for CP violation studies CKM precision tests Super-clean measurement of g • y • Least well-measured CKM UT angle • Measurements of g via interference of b→c and b→utree-level transitions • Essentially no theoretical uncertainties • Several decays suitable, e.g., • B+ →DK+ • B0 →DK*0 • Bs →DsK+ • Lb →Dl g = ( 68 +13 -14 )⁰ CKMFitter g = ( 76±11 )⁰ UTFit Stefania Ricciardi

  4. b-hadron decays to open charm: physics potential CP Violation Super-clean measurement of g • QCD • Factorisation • Hadronisation models • Fragmentation fractions Baryons: a largely unexplored land g = (68 +13 -14 )⁰ CKMFitter g = (76 ± 11 )⁰ UTFit G.Tonelli@ EPS2011 Stefania Ricciardi

  5. Crucial experimental ingredients Precision @VERTEX LHCB Vertex detector and tracking s(p)/p ~ 0.5-0.8% [3-100 GeV/c] s(IP)~ 16mm + 30mm/pT Excellent invariant mass resolution Excellent vertex resolution Mass resolution and displaced vertices for separation from low-mass background and rejection of combinatorial background • Large b-DATA SAMPLE • High Integrated Luminosity at LHCb • 2010: 37 pb-1 • 2011: 630 pb-1 (11 Aug) • Large b-production cross-section at s=7TeV • ~125 mb (in acceptance) 2010 data PID : 2 RICH detectors @LHCb kaon-pion separation over 2—100GeV/c Dedicated TRIGGER L0 (Hardware) “high pT” (>2-3GeV) m and hadrons HLT (Software) output 3 kHz Efficient selection of key B and D decays Effectively separate B→DK from 10x more abundant B→Dp Stefania Ricciardi

  6. On the g heritage trail: ADS and GLW results from B+->D0K+ (and B+->D0p+) Charged B decays Stefania Ricciardi

  7. g from direct CPV in B± decays b → u (suppressed) g extraction from measurements of time-integrated decay rates of B+ and B- to DK± b → c (favoured) Interference if D0 and D0 decay to common final state f Several strategies to extract g: GLW : f =CP eigenstate Gronau & London, PLB 253, 483 (1991); Gronau & Wyler, PLB 265, 172 (1991) ADS: f =Flavour state Atwood, Dunietz, & Soni, PRL 78, 3257 (1997), Atwood, Dunietz, & Soni, PRD 63, 036005 (2001) GGSZ: f =3-body decays Giri, Grossman, Soffer, & Zupan, PRD 68, 054018 (2003) Bondar, PRD 70, 072003 (2004) Other parameters measured from data: dB=B-decay strong phase difference rB = relative magnitude of suppressed B-decay amplitude Stefania Ricciardi

  8. GLW: B+ → D(KK)K+ and B+ → D(KK)p+ 2010 data 36.5 pb-1 B- → D(KK)K- B+ → D(KK)K+ PRELIMINARY Nsig=44 Nsig=40 Time-integrated CP asymmetry: B- → D(KK)p- B+ → D(KK)p+ Nsig=405 Nsig=419 Branching fractions ratio BF(B→DK)/BF(B→Dp) Negative Positive Stefania Ricciardi

  9. GLW analysis: Cabibbo favoured modesB+ → DK+, B+ → Dp+ (D → Kp, D→ Kppp) B- → D(Kp)K- B+ → D(Kp)K+ 2010 data 36.5 pb-1 PRELIMINARY Time-integrated CP asymmetry: Nsig=235 Nsig=272 B- → D(Kp)p- B+ → D(Kp)p+ Branching fractions ratio BF(B→DK)/BF(B→Dp) Nsig=3486 Nsig=3545 Negative B Positive B Stefania Ricciardi

  10. GLW results 2010 data 36.5 pb-1 PRELIMINARY New HFAG averages including LHCb results Stefania Ricciardi

  11. Towards GGSZ analysis: B±→D(KSpp)K± 2010 data 36.5 pb-1 B→D(KSpp)K B→D(KSpp)p Nsig=12 Nsig=95 Branching fractions ratio BF(B→DK)/BF(B→Dp) PRELIMINARY Stefania Ricciardi

  12. ADS: B±→D(Kp)K ± • D flavdecays to K+p-andK-p+ • Experimentally we distinguish • SS: Same sign kaons (favoured) • OS: Opposite side kaons (suppressed, 10-7 branching fractions) CP asymmetry enhanced by interfering amplitudes with similar size • 4 decay rates to be measured : (B+,B-) x (SS,OS) • Yields extracted from simultaneous fit to B±→DK± and B±→Dp± ADS Observables: OS/SS rate CP asymmetry Stefania Ricciardi

  13. ADS fit and yields 343 pb-1 2011 data sample B→DK B→Dp SS OS B- B+ B+ B- • Boosted Decision Tree reduces combinatorial background • Peaking backgrounds: • charmless: suppressed with D0 vertex separation cuts • Double MISID: veto candidates which satisfy SS AND OS selection criteria at the same time Signal in the suppressed modes Hint of charged CP asymmetry Stefania Ricciardi

  14. ADS Results B- and B+ Results consistent and competitive with B-factories and CDF results. Suppressed ADS signal: 4s significance Belle: 4.1s PRELIMINARY Hint of direct CPV • Dominant systematic uncertainties: • Low mass background model • PID efficiency Stefania Ricciardi

  15. Entering the hadron-colliders specific realm: studies with strange Beautiful mesons and baryons Stefania Ricciardi

  16. BS→ Ds-p+ 2010 data, 35 pb-1 BS→ Ds-p+, Interesting for several reasons: 1. World-class measurement of oscillation frequency Dms [Daan van Eijk for LHCb @DPF] 2. B-Tagging calibration 3. First step to reconstruction and time-dependent measurements of BS→ Ds-K+ which is sensitive tog+fs Fleischer, Serra, Tuning Phys.Rev.D82:034038,2010 Phys.Rev D83: 014017,2011 4. Relative abundance to U-spin related B0 modes can be used to measure fs/fdratio of Bs and Bd production fractions Necessary for absolute B.F. measurements of Bs decays, e.g. important for Bs→ mm [Marc Olivier Bettler for LHCb @DPF] Stefania Ricciardi

  17. Bs production fraction from fully hadronic decays: BS→ Ds-p+, B0→ D-K+,B0→ D-p+ 2010 data, 35 pb-1 B0→ D-K+, [arXiv:1106.4435] B0→ D-K+dominated by colour-allowed tree diagram theoretically well-understood From B.F. (BS→ Ds-p+)/B.F. (B0→ D-K+) B0→ D-p+, B0→ D-p+larger yield: smaller statistical uncertainty but additional theoretical uncertainty contribution from W exchange From B.F. (BS→ Ds-p+)/B.F. (B0→ D-p+) Stefania Ricciardi

  18. Semileptonic decays: b-hadron production fractions [LHCb-CONF-2011-028] m(Hc) GeV ln(IP/mm) PRELIMINARY D0mnX • D0mnX + D+mnX dominant for B0 + B+ • DsmnX dominant for Bs • LcmnX dominant for Lb • Yields from 2D ML fit to m(Hc)-ln(IP/mm) • to separate prompt charm • Cross-feed contributions corrected for • D0,± Kmn (B0,B+,Bs) • DsKmn (B0,B+,Bs) • D0)±)p(n)mn (B0,B+,Lb) D+mnX DsmnX LcmnX Main systematic: charm and Bs B.F. Stefania Ricciardi

  19. LHCb fs/fd average [LHCb-CONF-2011-034] No dependence on pT nor h Hadronic and semileptonic results consistent PRELIMINARY More precise than LEP/Tevatron average <fs/fd> =0.271 ± 0.027 (remarkable agreement, despite not a priori a “universal” number) Stefania Ricciardi

  20. More news on BAryons Stefania Ricciardi

  21. Lb→D0ph- (h=p,K) 2011 Data set (330 pb-1) Also colour-suppressed transitions sensitive to g Lb→Lcp Lb→D0pp • Lb→D0pK • Enhances sensitivity of • Lb→D0L • No long-lived V0 • Full 3-body phase space PRELIMINARY Stefania Ricciardi

  22. [LHCb-CONF-2011-036] Lb →D0pK and Xb→D0pK Lb →D0pK: 6.3s significance PRELIMINARY First observation • Xb→D0pK: 2.6s Stefania Ricciardi

  23. Conclusions • LHCb on a fast track for precise measurement of CKM angle g using b-hadron decays to open charm, with both • traditional modes: • GLW and ADS results competitive with previous measurements • 4s observation of the suppressed ADS modes • GGSZ analysis also on the way • and innovative ways: • Lb→DpK (first observation) • Important by-product: fs/fdworld best measurement (average of results with semileptonic and hadronic modes) • Present results obtained with 2010 (~35 pb-1) or early 2011(<350 pb-1) data, i.e., just a fraction of total expected by end of this year (1 fb-1) A new blossoming season for charming tree level decays has started at LHCb! Stefania Ricciardi

  24. Additional Material Stefania Ricciardi

  25. Measurements of Hb→Hch+h-h+[LHCb-CONF-2011-007; LHCb-CONF-2011-018] Hb: B0, B-,Lb h= p or K First observation of B- →D0Kpp Sensitive to CKM-angle g. Relatively large B.F. [> B.F. (B-→D0K)] In addition First observation of B0 →D+K-pp: First measurement of Lb→Lcppp: Stefania Ricciardi

  26. First observation of Bs→D0K*0[LHCB-CONF-2011-008] Bd →D0K*0 Bs →D0K*0 • Previously unobserved decay • Interesting probe of SU(3)F breaking in colour-suppressed modes • BF predicted to be 3-9 10-4 • [Colangelo, Ferrandes, PLB 627,1(2005);Chiang, Senaha, PRD75,074021(2007);Chua, Hou, PRD77,116001(2008)] • Together with Bs →D*0K*0, potentially large background to Bd→D0K*0 modes sensitive to g fs/fd Stefania Ricciardi

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