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LHCb-Babar Meeting 8 April 2005.

A first look at B s → J/ YF in LHCb. Paul Soler University of Glasgow and Rutherford Appleton Laboratory. LHCb-Babar Meeting 8 April 2005. Contents. Motivation Physics aims Angle c from B s → J/ Yf LHCb Experiment Analysis of B s → J/ Yf Toy Monte Carlo Sensitivity New Physics

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LHCb-Babar Meeting 8 April 2005.

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  1. A first look at Bs→J/YF in LHCb Paul Soler University of Glasgow and Rutherford Appleton Laboratory LHCb-Babar Meeting 8 April 2005.

  2. Contents • Motivation • Physics aims • Angle c from Bs→J/Yf • LHCb Experiment • Analysis of Bs→J/Yf • Toy Monte Carlo • Sensitivity • New Physics • Conclusions Work carried out in collaboration with: Stuart Paterson (Glasgow) Andrew Pickford (Glasgow) Borrowed from: G. Raven’s analysis in 2003 LHCb-Babar Meeting, 4 April 2005

  3. Motivation • Bs → J/Yf is the “gold plated” decay mode in the Bs system, similar to theBd → J/YKs in the Bd system • This mode is theoretically clean (very small penguin contributions). • It provides a measurement of the unitarity angle cdg, which is predicted to be very small (~0.02) in the SM. • Sensitive to new physics • Exploits the production capabilities of Bs mesons at the LHC (not available at B-factories) • Exploits UK investment in the RICH and VELO detectors LHCb-Babar Meeting, 4 April 2005

  4. Physics aims • CKM matrix: CKM matrix provides link between mass eigenstates and weak eigenstates Experimentally: LHCb-Babar Meeting, 4 April 2005

  5. Physics aims CKM matrix in Wolfenstein parametrization ~O(l5): _ b: Bd-Bd Mixing Phase g: Weak Decay Phase _ cdg : Bs-Bs Mixing Phase (From CKM-fit hep-ph/0406184) Standard Model: a=p-b-g LHCb-Babar Meeting, 4 April 2005

  6. (db) (ut) Im Im  a a      c Re 1 Re  c c Physics aims • Two main unitarity triangles: LHCb-Babar Meeting, 4 April 2005

  7. Physics aims • Channels to be used to extract unitarity triangles: LHCb-Babar Meeting, 4 April 2005

  8. c from Bs→J/Yf (Diagrams) Decay Mixing (This l is not Wolfenstein parameter!) LHCb-Babar Meeting, 4 April 2005

  9. c from Bs→J/Yf (Asymmetry) • Asymmetry: (if J/YF is eigenstate) • But J/Y F is not pure CP eigenstate: CP even CP odd CP even LHCb-Babar Meeting, 4 April 2005

  10. c from Bs→ J/Yf (Non-CP) • Change due to mixed eigenstate: The effect of the CP admixture is to dilute extraction of c and to add a small coefficient in front of cos(Dms) since: LHCb-Babar Meeting, 4 April 2005

  11. c from Bs→ J/Yf (Transversity) • Extraction of CP eigenstates (transversity analysis): Three polarization states • Bs→J/Y(l+l-)F(K+K-) has three angles but can be put into J/Y reference frame with only one angle (the transversity qtrq) that comes out of F(K+K-) decay plane . J/Y rest frame LHCb-Babar Meeting, 4 April 2005

  12. c from Bs → J/Yf (Transversity) • Angular distribution in transversity: • Once CP eigenstates established, the analysis proceeds in the same manner to establish CP asymmetries. • References: • Durham workshop CERN-TH/2001-034 (hep-ph/0102159) • LHCb notes: LHCb 98-067 & G. Raven, LHCb 2003-118 and LHCb 2003-119 • “B decays at the LHC”: CERN-TH/2000-101 LHCb-Babar Meeting, 4 April 2005

  13. LHCb Experiment • LHCb Detector: forward single arm spectrometer at LHC • Acceptance: 10-300 mrad bending 10-250 mrad non-bending LHCb-Babar Meeting, 4 April 2005

  14. LHCb Experiment • Exploit VELO for Bs proper time measurement (Bs oscillations) • Proper time resolution: ~40 fs • Dms sensitivity: 68 ps-1(Standard Model ~ 20 ps-1) • Exploit RICH for particle identification: F(K+K-) • PID: p-K separation 1-100 GeV RICH1 LHCb-Babar Meeting, 4 April 2005 RICH2

  15. Select J/ψ Calculate Transversity Combine to select Bs Real MC Data SelectФ Write Histos & NTuples Bs → J/Yf (Da Vinci Analysis) • Work flow of Bs → J/Yfanalysis using Da Vinci (LHCb analysis package) • First ever LHCb analysis run on the Grid (GLite) by S Paterson LHCb-Babar Meeting, 4 April 2005

  16. Bs → J/Yf (Da Vinci Analysis) • Ran with 100,000 Bs → J/Yfsignal events Efficiency F(K+K-): 9.8% Energy resolution: 9 MeV Efficiency J/Y(m+m-):14.4% Energy resolution: 13 MeV LHCb-Babar Meeting, 4 April 2005

  17. Bs → J/Yf (Da Vinci Analysis) • Transversity distribution looks promising • Contributions from CP odd (ℓ=1) & CP even (ℓ=0,2) states • Bs Efficiency ~ 8.2% • Energy resolution: 17 MeV • Event selection quite clean LHCb-Babar Meeting, 4 April 2005

  18. Bs → J/Yf (Da Vinci Analysis) • LHCb 2003-119 by Gerhard Raven, used a toy MC for re-optimization TDR (20% CP odd; 80% CP even) Very similar to distribution extracted. Need to fit to CP-odd versus CP-even LHCb-Babar Meeting, 4 April 2005

  19. Bs → J/Yf (G. Raven toy MC) • Proper time resolution: 38 fs (G Raven LHCb 2003-118) • Annual yield: Assume Lint=2 fb-1(107 s at 2x1032 cm-2s-1); sbb=500mb; fB=10% for Bs hadronization; BRvis=3.1x10-5 • Implies: 113 k events per year (with 8.2% efficiency) LHCb-Babar Meeting, 4 April 2005

  20. Bs → J/Yf (G. Raven toy MC) • G. Raven’s toy Monte Carlo varied a number of parameters to extract sensitivities _ q=+1(-1) for events tagged as Bs (Bs) w=wrong tag fraction (=0.5 for untagged) Assumed Q=etag(1-2w)2=4.5% (w=35%, etag =50%). Untagged sample can be used to extract lifetime difference: • One can fit for 5 parameters: LHCb-Babar Meeting, 4 April 2005

  21. Bs → J/Yf (G. Raven toy MC) • Results: LHCb-Babar Meeting, 4 April 2005

  22. Sensitivity Bs→ J/Yf • In one year expect ~ 113 k events (negligible background) • s(sin 2c) ~ 0.064 (depending on ) • In five years:s(sin 2c) ~ 0.03 (Standard Model:sin 2c ~ 0.04) One year LHCb-Babar Meeting, 4 April 2005

  23. New Physics • Left-Right symmetric models (eg. SB-LR) LHCb-Babar Meeting, 4 April 2005

  24. Conclusions • Bs→J/Yf is a very promising channel to study at LHCb • Not accessible at B factories or Tevatron • Standard Model prediction for cis very small (~ 0.02) • New Physics could make c significantly larger than SM • Started analysis of Bs→J/Yf and can achieve yields of ~100k events per year • Using Toy Monte Carlo (G Raven), LHCb can probe c to values very close to SM predictions, s(sin 2c) ~ 0.064 within 1 year. LHCb-Babar Meeting, 4 April 2005

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