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Prospects for g at LHCb

Prospects for g at LHCb. Val Gibson (University of Cambridge) On behalf of the LHCb collaboration. Physics at the LHC Split, October 3 rd 2008. g plays a unique role in flavour physics Can be measured via both tree and loop processes Trees Benchmark Standard Model reference point

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Prospects for g at LHCb

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  1. Prospects for g at LHCb Val Gibson (University of Cambridge) On behalf of the LHCb collaboration Physics at the LHC Split, October 3rd 2008

  2. g plays a unique role in flavour physics Can be measured via both tree and loop processes Trees Benchmark Standard Model reference point Loops Sensitive to New Physics Very impressive measurements from the B factories To fully test SM and unitarity need sg ~ few % precision measurements in B, B0 and Bs systems Introduction K.Trabelsi CKM 2008 V.Sordini CKM 2008 Prospects for gamma at LHCb

  3. High statistics sbb ~ 500 mb at 14 TeV ℒ ~ 2 x 1032 cm-2s-1 1012 bb per 2 fb-1 (1 year) All B species (B0, Bs, Bc, Lb …) Excellent tracking system VELO and tracking detectors Mass resolution, sB(D)~15 (7) MeV B vertex resolution, sz~ 200 mm Proper time resolution, st~ 40 fs Excellent particle identification 2 RICH detectors p/K separation over p ~2-100 GeV Trigger High pT hadron trigger at L0 RICH HPDs VELO First real tracks LHCb Prospects for gamma at LHCb

  4. g with trees B  DK Strategies Time integrated analyses based on: “ADS”: Atwood, Dunietz, Soni; Phys. Rev. Lett. 78 (1997) 3257; Phys Rev. D63 (2001) 036005. “GLW”: Gronau, London, Wyler; Phys. Lett. B253 (1991) 483; Phys. Lett. B265 (1991)172. “Dalitz” or “GGSZ”: Giri, Grossman, Soffer, Zupan, Phys. Rev. D68 054018 (2003)

  5. colour-allowed colour-suppressed colour-suppressed colour-suppressed B  DK Strategies • Measureg through interference in decays • Provided and decay to common final state • Common parameters CKM angle g Amplitude ratio, rB Strong phase difference, dB Prospects for gamma at LHCb

  6. ICHEP 2008 BD(hh)K (ADS+GLW) LHCb-2008-011 LHCb-2008-031 • 6 rates, 5 parameters g = 60o rB= 0.10 dB = 130o (PDG) D decay parameters: rKp = 0.0616 (PDG) dKp = -158o (ADS formalism requires -180o phase shift w.r.t published result) • Constraints from CLEO-c PRL 100(2008) 221801 *All signal yields presented are for 2 fb-1 Sensitivity 2 fb-1 Prospects for gamma at LHCb

  7. ICHEP 2008 B0 D(hh)K*0 (ADS+GLW) LHCb-2007-050 LHCb-2008-031 • 6 rates, 5 parameters g = 60o rB0= 0.40 dB0 (scan) D decay parameters: rKp = 0.0616 (PDG) dKp = -158o (ADS formalism requires -180o phase shift w.r.t published result) • Constraints from CLEO-c PRL 100(2008) 221801 68% 95% Sensitivity 2 fb-1 Prospects for gamma at LHCb

  8. Br(DK3p) = 8.1% c.f. Br(D Kp)=3.89% 4 rates Multi-body final state Integrate over ALL phase space “Coherence factor” RK3p rK3p = 0.0568 (PDG) Constraints δK3π (o) RK3π BD(K3p)K (ADS) LHCb-2007-004 LHCb-2008-031 Atwood and Soni, PRD 68 033003(2003) Prelim: arXiv:0805.1722 CLEO-c Sensitivity 2 fb-1 Prospects for gamma at LHCb

  9. BD(Ksp+p-)K (“Dalitz”) • Ksp+p- Dalitz plots contain a CP-violating contribution from the B+ and B- interference which is sensitive to g. • Two analysis methods: • Unbinned fit based on amplitude model • Model independent binned fit using results from (3770) on D decays Giri et. al., PRD 68 (2003) 054018; Bondar and Poluektov, EPJ C47 (2006) 347; hep-ph/0703267;arXiv:0801.0840 LHCb 2 fb-1 Prospects for gamma at LHCb

  10. BD(Ksp+p-)K (“Dalitz”) LHCb-2008-028 • Signal yield ~ 5k (total) per year • BD(Ksp+p-) p background suppressed with max. momentum cut (good for RICH pid) • Dominant physics background BD(Ksp+p-) X plus random “K” ~16% prob. of picking up “K” from underlying event or other B. 2 fb-1 Loose K pid Prospects for gamma at LHCb

  11. Amplitude fit, model error 7o Binned fit, CLEO-c error 2o BD(Ksp+p-)K (“Dalitz”) LHCb-2007-048 LHCb-2007-141 • Amplitude Fit: Generate and fit events assuming isobar model. • Models of BaBar [PRL 95 (2005) 121802] and Belle [hep-ex/0411049] give consistent results. • Total error will include model uncertainty, currently ~ 7o[BaBar PRD 78 (2008) 034023] • Binned Fit: Removes model dependence by relating bins of Dalitz plot to experimental observables • Slight degradation in statistical precision • Residual error on g from CLEO-c statistics ~1-2o[Asner, ICHEP 08] Sensitivity 2 fb-1 Fit assumes pure combinatorial background same level as DK-random Prospects for gamma at LHCb

  12. g with trees Time DependentB  DhStrategies Bs DsK: Aleskan, Dunietz and Kayser, Z. Phys. C54 (1992) 653. B0  Dp and Bs DsK “Uspin Approach”: Fleischer, Nuc. Phys. B671 (2003) 459.

  13. Bs→Ds-K+ Bs→Ds-K+ BsDsK LHCb-2007-017 LHCb-2007-041 • Measure g+fsfrom interference between mixing and decay amplitudes. • Large interference effects • fsinput from Bs J/f (sfs~ 0.03 mrad for 2 fb-1 see A.Satta talk) • Include Bs Dsp (20x Br) to determine Dmsand tagging dilution • Simultaneous fit to Bs Dsp and Bs DsK decay time distributions (tagged and untagged) Input parameters: g = 60o, Dms = 17.5 ps-1 Prospects for gamma at LHCb

  14. 2 fb-1  30% Uspin breaking g (o) B0 Dp LHCb-2008-035 LHCb-2007-044 • Measure g+fdanalogous to Bs DsK • fdinput from B0 J/Ks(sfd = 0.02 mrad for 2 fb-1 see ? talk) • Problems • Interference small • 8 fold ambiguity (DG small) • Potential solutions • “Conventional approach”: compare with other channels e.g. B0 D*p • “Uspin approach”: B0 Dp and Bs DsK Uspin approach shows very promising results. Input : g = 60o (stat.  30% Upsin breaking) Prospects for gamma at LHCb

  15. Parameters (input value): • BD0K • g (60o) • rB – ratio of magnitude of diagrams (0.1) • dB – strong phase difference (130o) • B0D0K*0analogues: rB0 (0.4), dB0 (scan) • D0 decay parameters for Kp, Kppp: • rKp , rK3p well known (PDG) • dKp(-158o), dK3p (144o) • RK3p – coherence factor Constrained by CLEO-c gwith trees : Global Sensitivity LHCb-2008-031 Perform global fit to B DKwith common parameters. Include results from B0 and Bs time dependent analyses. • Input measurements: • BD0K • D0Kp, KK, pp(LHCb-2008-011) • D0Kppp(LHCb-2007-004) • D0Kspp(LHCb-2007-048) • B0D0K*0 • D0Kp, KK, pp(LHCb-2007-050) • Time dependent measurements: • B0  Dp (LHCb-2008-035) • Bs  DsK (LHCb-2007-041) “Conventional” approach used for B0  Dp (sg=20o with 2 fb-1) to avoid large correlations with Bs  DsK. Prospects for gamma at LHCb

  16. g with loops New physics in B  hh and B  hhh modes B0  pp and Bs  KK : “Uspin Approach”, Fleischer, Phys. Lett B458 (1999) 306. B+  K+p-p+and B0  Ksp-p+: “Dalitz Approach”, Bediaga, Guerrer and Miranda, Phys Rev D76 073011 (2007).

  17. W pp hypothesis KK hypothesis mhh (GeV/c2) mhh (GeV/c2) B0 pp and Bs  KK LHCb-2007-059 • Measure g from interference between mixing and tree and penguin decay diagrams • Demonstrates excellence of RICH pid Prospects for gamma at LHCb

  18. 2 fb-1 BsKK t (ps) B0 pp and Bs  KK LHCb-2007-059 • Fit CP asymmetries of B0pp and BsKK events • 4 observables: • Parameters • g • penguin to tree amplitude ratio dppeiqpp, dKKeiqKK • Input fd and fs • Weak Uspin constraint • dpp= dKK 20%,qpp , qKK indep. Measures g and tests Uspin symmetry Prospects for gamma at LHCb

  19. W m2KK II IV I III m2pp III no-CP CP I B+ K+p+p- and B0 Ksp+p- G.Guerrer CKM 2008 • Measure g from a Dalitz analysis of B+ K+p+ p- and B0Ksp+p- decays • K* resonance (dominant contributions) • Extract penguin contribution from B+ K+p+ p- • Use Dalitz anistropy to measure CP asymmetry including phase differences • Dalitz analysis of B0/ B0Ksp+p- • Untagged analysis possible since B0 and B0 interference regions do not overlap • Promising results: sg~5o with 2 fb-1 Prospects for gamma at LHCb

  20. Summary LHCb offers exciting prospects for a precision measurement of g • g with trees • Standard Model benchmark • External input from CLEO-c of upmost importance • A combined sensitivity of sg~2-3o is expected with 10 fb-1 of data • Many channels still to be investigated DKpp0, DKsKK, DKsKp, BD(*)K (*), BsDs(*)K1etc • g with loops • Sensitive to New Physics • B hh analysis can measure g (sg ~ 5o with 10 fb-1) and test Upsin symmetry • B hhh very promising first studies • Other channels to investigate: Bd KK, Bs pp, Bs Kpp0etc First challenge: reconstruct hadronic final states with real data….. coming soon Prospects for gamma at LHCb

  21. Backup Slides Prospects for gamma at LHCb

  22. B Tagging Prospects for gamma at LHCb

  23. gwith trees : Global Sensitivity LHCb-2008-031 Weight (in %) of each contributing analysis with 2 fb-1 for two values of dB0 Sensitivity of B0D0K*0improves by a factor of two in going from dB0 =45 180o. Residual dependence remains in global fit, but diluted due to other measurements. Prospects for gamma at LHCb

  24. B+ K+p+p- and B0 Ksp+p- G.Guerrer CKM 2008 Prospects for gamma at LHCb

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