1 / 29

Exploring B-Hadron Decays to Charming Final States at LHCb: Physics Potential and Results

This study at the Meeting of the Division of Particles and Fields of the American Physical Society in 2011 explores b-hadron decays to charming final states at LHCb, focusing on open charm decays like B+→D0K+ and B+→D0p+. The research investigates CP violation, CKM precision tests, and the measurement of the g angle, with negligible theoretical uncertainties. Key results include the observation of new decay modes and hints of Xb states. The study utilizes advanced experimental techniques with precise detection instruments and efficient data processing. The analysis aims to enhance our understanding of CP violation, with a focus on g extraction and the use of various strategies like GLW and ADS methods. The research presents significant findings on B decays, CP asymmetries, and branching fractions. Notably, innovative techniques like Boosted Decision Trees are employed to analyze complex decay patterns and distinguish signal from background in the data.

boone
Download Presentation

Exploring B-Hadron Decays to Charming Final States at LHCb: Physics Potential and Results

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

  27. Stefania Ricciardi

  28. Stefania Ricciardi

More Related