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La misura di  : status e prospettive per le B factories

La misura di  : status e prospettive per le B factories. Marco Zito DAPNIA CEA-Saclay. Outline. Introduction sin(2 +) with BD (*)  B->DK Conclusions. IFAE 04, 14-16 Aprile 2004, Torino. *. V td V tb. *. V ud V ub. *. V cd V cb. CP Violation in Standard Model.

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La misura di  : status e prospettive per le B factories

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  1. La misura di  : status e prospettiveper le B factories Marco Zito DAPNIA CEA-Saclay Outline • Introduction • sin(2+) with BD(*) • B->DK • Conclusions IFAE 04, 14-16 Aprile 2004, Torino Marco Zito IFAE 04, Torino

  2. * VtdVtb * VudVub * VcdVcb CP Violation in Standard Model Standard Model with 3 generations accommodates CP violation through a phase in CKM matrix Unitarity of the CKM Matrix Aim of B factories : Measure precisely the angles and the sides to overconstrain the unitarity triangle. Test of the SM in the CP violating sector a/f2 g/f3 b/f1 Marco Zito IFAE 04, Torino

  3. Current Constraints on the CKM Angles World Averagesin2b = 0.736 ± 0.049 95% CL intervals with CKM Fitter: Direct measurement of g is a crucial step in the B factory program! Method in A. Hoecker et al, Eur. Phys. Jour. C21 (2001) 225, [hep-ph/0104062] Marco Zito IFAE 04, Torino

  4. * VtdVtb * VudVub * VcdVcb Why measuring  is difficult ? In the Wolfenstein phase convention,  is the angle between Vub and Vcb. The ratio Vub/Vcb enters all interference terms sensitive to  : small asymmetry or few events ! a/f2 g/f3 b/f1 • Strategies : • BD(*) Small asymmetry : partial + full reconstruction • B->DK : (GLW) Small asymmetry : many modes • B->DK (ADS) Large asymmetry : few events • B->DK Dalitz plot analysis • B->K difficult theory uncertainties ! (not covered in this talk) Marco Zito IFAE 04, Torino

  5. Measurement of sin(2b+g) in B0D(*)p Favored amplitude Suppressed amplitude through b  u transition Strong phase difference • CP violation from interference of mixing (weak phase= 2b) and decay (weak phase )  interference terms measures sin(2b+g) • Theoretically clean : no penguin contribution, strong phase measurable • Small time dependentasymmetry (o(4%)) • r is an external input CKM angle B0 mixing f B0 Marco Zito IFAE 04, Torino

  6. B0D(*)p Time-dependent decay rate distributions - K+ -s Tag B K+ U(4s) Reco B z + Dt @Dz/gbc Dz • Measurement of S and S determine 2b+g and d • Using Dp and D*p removes some ambiguities Marco Zito IFAE 04, Torino 4 ambiguities on 2b+g

  7. D*- +f B0 D0 -s X B0D(*)p :partial reconstruction (BaBar) • Use only the fast and soft pion tracks : no D° reconstruction ! F E(F)~.5 mB • Combine the fast pion (2.1<p<2.4 GeV/c) with a slow pion (p<250 MeV). • Compute the mass Mmiss of the recoiling object (r.m.s. 3 MeV) 1 rad S P(s-)<250 MeV D0 The unreconstructed D0 complicates vertexing and tagging Most of the D0 decay product inside this cone Marco Zito IFAE 04, Torino

  8. B0D(*)p :the BaBar event sample B invariant mass Exclusive reconstruction(ER) : N(D)=5200 N(D*)=4700 BaBar Based on a 81 fb-1 sample Partial reconstruction(PR) : N(D*)=6400 (lepton tag) N(D*)=25100 (kaon tag) Kaon tagged Lepton tagged signal combinatoric BaBar Continuum Marco Zito IFAE 04, Torino

  9. Lepton tags B0D(*)p :BaBar results BaBar CP asymmetry  2 r* sin(2β+γ) cos(δ*)sin(m t) Lepton tagged Kaon tagged BaBar t(ps) t(ps) t(ps) PRELIMINARY hep-ex/0309017 hep-ex/0310037 Mixing asymmetry 2.3  significance ! 2 r* sin(2β+γ) cos(δ*) = -0.063 ± 0.024 (stat.) ± 0.014 (syst.) PR 2 r* sin(2β+γ) cos(δ*) = -0.068 ± 0.038 (stat.) ± 0.020 (syst.) ER 2 r sin(2β+γ) cos(δ) = -0.022 ± 0.038 (stat.) ± 0.020 (syst.) ER Used as a cross-check There is also a Belle result with excl. Reco. hep-ex/0308048 Marco Zito IFAE 04, Torino

  10. B0D(*)p :Interpretation • Need the value of r(*) to interpret the results in terms of sin(2β+γ) • Use (I. Dunietz, PLB 427,179 (1988)) the measured (BaBar+Belle) Br(BD(*)s) + SU(3) + decays constants to get • r=0.019 0.004 and r*=0.017+0.005 -0.007 • Derive the combined confidence level as a function of sin(2β+γ) using the Feldman-Cousins method with toy MC • |sin(2β+γ)|>0.87 (68% CL) • |sin(2β+γ)|>0.58 (95% CL) • With a similar method limits on |sin(2β+γ)| versus r* are produced CL(%) |sin(2β+γ)| Marco Zito IFAE 04, Torino

  11. Constraints on the Unitarity Triangle from BaBar • Despite limited statistics already interesting constraint ! • Complementary to  • Excludes two sin(2) branches • Start constraining the triangle only with CP violation in the B sector ! Using sin(2), sin(2+) and cos(2) Thanks to Ch. Yeche Marco Zito IFAE 04, Torino

  12. g b u D0 c B+ s K+ u u g with B- D0K- decays Suppressed amplitude: b  u transition Color suppression Favored amplitude s K+ u b c B+ D0 u u • Interference (and direct CP violation) may occur if D° and D° decay in the same final state f : • f can be CP eigenstate (+-, K+K-, Ks° …)Gronau, London, Wyler (GWL) method • f =DCSD for D° (K+-) and CFD for D° (K+-) Atwood, Dunietz, Soni (ADS) • or f=3 body final state : Dalitz plot analysis (Giri, Grossman, Soffer, Zupan) DCSD : Doubly Cabibbo Suppressed Decay CFD : Cabibbo Favoured Decay Marco Zito IFAE 04, Torino

  13. GLW method Hep-ex/0311032 82 fb-1 BaBar Flavor modes (K,K3,K°) D°K D° • Measure A and R and solve for r,, • Four observables and three unknowns • Based on o(20) ev. for the CP eigenstate modes • Analysis of CP=- modes by BaBar in progress • No constraint on  yet CP=+ modes (K+K-,+-) D°K D° E(GeV) Marco Zito IFAE 04, Torino

  14. ADS method BaBar • ADS method : Measure B+ [K-+]DK+ • Only O(5-20) DCSD events expected • Requires powerful background rejection • Use favored modes as control sample • N (B+ [K-+]DK+) = 1.13.0 (DCSD) • vs 261 22 (CFD) • rB<0.22 (90% CL) • Excludes most favorable scenario for the sensitivity of this method DCSD 109 fb-1 CFD Ratio DCS/CF Marco Zito IFAE 04, Torino rB

  15. GLW-ADS method : expected sensitivity GLW +ADS(K) +CLEO-c GLW GLW +ADS(K) 2 • Toy MC with 500 fb-1 • Strong dependence on r • Prospect not so bright for r=0.1 rb=0.1 1  2 3 rb=0.2 2  Study by C. Campagnari et al. Marco Zito IFAE 04, Torino

  16. Belle: Dalitz plot method-1 Hep-ex/0308043 Belle • Proposed by Giri et al. (hep-ph/0303187) • Uses Cabibbo-allowed mode Ks+ - • The Dalitz plot amplitude can be written as • Where |f|2 can be fitted in D* tagged D° decays (57800 evt !!) and r, and  are fitted in the Dalitz plot of B- D0K- decays • B- D0- is used as a control sample m2(Ks-) NB: this is data ! m2(Ks+) m2(Ks+) m2(+-) MC: Slices of Dalitz plot B invariant mass B+ B- Marco Zito IFAE 04, Torino 107 signal ev. are selected on 140 fb-1 m2(Ks-) m2(Ks+)

  17. Belle: Dalitz plot method-2 Dalitz plot projection • B+→D0K+and B+→D*°K+, D°→Ksπ+π- • =φ3=81°±19°±13°(syst)±11°(model) from combined fit, r=0.31±0.11 • 95% CL interval from combined fit: 35°<φ3<127° • Caveat : • model dependence of Dalitz amplitude • Unexpectedly large value of r (r=0.13 exp.) r=0 m2(Ks-) m2(Ks+)  Belle 95% CL  r    A. Poluektov at Moriond EW 2004 Marco Zito IFAE 04, Torino

  18. Outlook • BaBar : 200 fb-1 expected by summer 2004, 500 fb-1 by 2006 • sin(2+) : add new modes like D, D* • B- D°K : add many modes : drops in the bucket concept • Dalitz plot analysis : r value ? Model independent approach Marco Zito IFAE 04, Torino

  19. Conclusions • First measurements of sin(2+) and  are available for CKM fitters ! • Many more methods and modes currently explored mainly B DK • Already interesting constraints in the - plane • The rapid increase of luminosity will be extremely beneficial to these difficult measurements • Improved and complementary measurements of  in 2004-2005 at the B-factories experiments Marco Zito IFAE 04, Torino

  20. B0D(*)p : Full result list 2 r* sin(2β+γ) cos(δ*) = -0.063 ± 0.024 (stat.) ± 0.014 (syst.) PR 2 r* cos(2β+γ) sin(δ*) = -0.004 ± 0.037 (stat.) ± 0.020 (syst.) PR 2 r* sin(2β+γ) cos(δ*) = -0.068 ± 0.038 (stat.) ± 0.020 (syst.) ER 2 r* sin(2β+γ) cos(δ*) = 0.031 ± 0.070 (stat.) ± 0.033 (syst.) ER 2 r sin(2β+γ) cos(δ) = -0.022 ± 0.038 (stat.) ± 0.020 (syst.) ER 2 r cos(2β+γ) sin(δ) = -0.025 ± 0.068 (stat.) ± 0.033 (syst.) ER Marco Zito IFAE 04, Torino

  21. B0D(*)p :CP violation on the tag side for kaon tagged events Due to presence of Doubly Cabibbo Suppressed Decays on the tag side  We introduce r’ and δ’ in the coefficients relevant to the sin(Δm.t) term ABC parametrization* to restrict the set of fit variables to 3 a = 2 r sin(2β+γ) cos(δ) b = 2 r’ sin(2β+γ) cos(δ’) c = 2 cos(2β+γ) (r sin(δ) – r’ sin(δ’) * : O. Long, M. Baak, R.N. Cahn, and D. Kirkby, SLAC-PUB-9687, hep-ex/0303030 Marco Zito IFAE 04, Torino

  22. d sin(2b+g) in B0 D(*)0K(*)0 Al3(r-ih)e-ig Al2 c u b b D(*)0 u c B0 B0 l s s K(*)0 d d d Strong phase difference • Similar to D(*)p: interference between decay and mixing, but… • Advantages: • Much larger asymmetries: • CP violation from tag-side not significant • Disadvantages: • Color suppressed decays: Smaller branching fractions • Possible competing effects from Doubly-Cabibbo-suppressed D0 decays • Requires tagging for time-dependent studies: 70% tagging efficiency Measure r with K*0K-p+ Marco Zito IFAE 04, Torino Kayser, London, PRD 61, 116013 Atwood, Soni, hep-ph/0206045

  23. D0K0 D0K*0 Current measurements and limits in B0 D(*)0K(*)0 81 fb-1 78 fb-1 Peaking background D0 sideband Combinatoric Vub Vub contribution necessary for measurement of g not observed yet! Marco Zito IFAE 04, Torino

  24. g in Charmless B  PP,PV decays g P T • Tree amplitude suppressed in Standard Model • Penguin contributions large: • Interference between Tree and Penguin • Main Challenges • Background suppression • Contribution of EW penguins • Effects of Final State Interaction • Requires estimate of |P/T| Possible window on New Physics 5% if neglecting penguins Branching fractions and CPasymmetries sensitive to g ACP alone not sufficient Need also BF to have ahandle on d Marco Zito IFAE 04, Torino

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