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Lifetime Difference ( = 1/ ) in the B s System

Lifetime Difference ( = 1/ ) in the B s System. Avdhesh Chandra, UCR Kin Yip, BNL Daria Zieminska, IU D  Winter Physics Workshop February 21, 2006. PRL 95, 171801 (2005) ~0.45 fb -1 Triggers v13 and lower 1- and 2-muon triggers unbiased in c t Reco p14 1-angle (q) analysis

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Lifetime Difference ( = 1/ ) in the B s System

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  1. Lifetime Difference ( = 1/ ) in the Bs System Avdhesh Chandra, UCR Kin Yip, BNL Daria Zieminska, IU D Winter Physics Workshop February 21, 2006 Kin Yip

  2. PRL 95, 171801 (2005) ~0.45 fb-1 Triggers v13 and lower 1- and 2-muon triggers unbiased in ct Reco p14 1-angle (q) analysis ~500 signal events Winter 2006 ~0.9 fb-1 (?) [ D Note 4810 ] Triggers v14 and lower 1- and 2-muon triggers, unbiased in ct and track pT (173 trigger names) Data sample: CSskim p17fix + p17.09 (4%) (SKIM_2MU) Compared to 2005 PRL Improved track energy loss Rematched muons “adaptive” vertexing Same kinematic cuts, slightly tigther quality cuts 3-angle (q,,) analysis ~1000 signal events Old (PRL 2005) and New Analyses Kin Yip

  3. (r, h) a g b (0,0) (1,0) CKM Matrix and Unitarity triangle Relates quark mass and weak eigenstates SM: CP-violating processes solely related to one phase in CKM. ’bs’ (A ‘squashed’ unitary triangle) ‘bd’ (THE unitary triangle) Large effort in B physics Mainly at B factories • bbs, small in SM Interesting to check how small/big bs really is. Currently: Tevatron domain

  4. Bs System and CP violation c CP violating weak phase 2bs df (SM) • In Standard Model,   2λ2η(0.03), very small. • Much larger measurement of   a striking signal of new physics in Bs – Bs mixing. • m = MH ML >0;  = L -H (> 0 in Standard Model) • Any dependence on mt cancels in untagged samples. Kin Yip

  5. Untagged Bs Decay  Bs  J/y f, Pseudoscalar  Vector Vector decay Three waves: S, P, D, orA0, A||, A┴ Both CP-even and CP-odd present, but separated in angular distributions S, D (Parity, CP even) : linear combination ofA0, A|| P (Parity, CP odd) :A┴ R┴  |A┴(t=0)|2 Kin Yip

  6. Bs Lifetime Difference D0 p17fix/p17.09 • We measure TWO distinct lifetimes (or, equivalently, DG and t) by fitting time evolution and angular distributions in untagged Bs J/y f decays. • If CP is conserved, they can be interpreted as the lifetimes of the two Bsmass eigenstates. • We discuss the sensitivity to a free CP violating angle df Nsignals = 978  45 History: CDF (PRL 2004) fit used 3 angles, q, f, y 203 events D0 (PRL 2005) used 1 angle, θ, 513 events Kin Yip

  7. Some selection cuts CSG p17fix + p17.09 Total number of BsJ/y fcandidates: 21380 (PRL 2005: 9699) Kin Yip

  8. Data Kin Yip

  9. Untagged Bs Decay Rate in Time & Angles correction for acceptances, kinematic cuts • d1Arg[A||(0)*A┴(0)]and d2Arg[A0(0)*A┴(0)] are CP-conserving strong phases • No dependence on mt Kin Yip

  10. H(cos y) flat distribution Detector Acceptance (MC & data) F() = 1 + J cos(2) + K cos2(2) G(cos ) = 1 + Bcos2 + Ccos4

  11. Maximum Likelihood Fit Simultaneous fit to mass, proper decay length and 3 angles using an unbinned maximum log-likelihood method 30 parameters: 1 fsig = signal fraction 2 signal mass, width 3 A , |A0|2-|A|||2, 1 strong phase 1 c = c / ,  = (L+ H) /2 1  =  L-H 3 bkg mass (1 prompt, 2 long-lived) 1 (ct ) scale 6 bkg ct shape 4 bkg transversity (2 prmpt + 2 long-lived) 4 bkg angle φ (2 prompt + 2 long-lived) 2 bkg angle ψ (1 prompt + 1 long-lived) 2 bkg “interference” (1 prompt + 1 bkg) set df = 0 Kin Yip

  12. Full (chain) MC Test Input:(close to PRL 2005 results) cL = 370 µm cH = 460 µm |A┴| = 0.4 with ~9K events(~10  current stats) Kin Yip

  13. Data:Fit projections in signal regions   q (transversity) Kin Yip

  14. Background mass region Fit projection (lifetime) All events • Signal mass region  Kin Yip

  15. Results (3-angle fit) Kin Yip

  16. Cross-check: 1-angle fit This analysis PRL (2005) Kin Yip

  17. 1.580.09 0.220.13 0.140.06 Comparisons: D ’06 – errors statistical only Kin Yip

  18. 1 - 2 Systematics • One “outlyer”  treat its effect as systematic uncertainty • Event Run #: 210344 Event #:23385781 • unlikely signal or background • Signal: mass 2.3  from peak, lifetime 8.5 x mean • Bkg: 10.2 x mean for “right slope long” Kin Yip

  19. Sensitivity to CP violation So far, we have assumed CP to be conserved, i.e.  = 0,no interference between CP-even and CP-odd terms, and the two physical Bs states, L and H, are orthogonal CKM (Standard Model) :  = 2λ2η = 0.03 Allowing for a freedfrequires an assumption on strong phasesd1&d2, our fit does not converge with all 3 phases free Withd1 freeandd2 = 0, we obtain= -0.9 ± 0.7 CP-violating angledfconsistent within statistical uncertainty of ± 0.7. Kin Yip

  20. NNewew results based on X2 Summary • New analysis based on ~1 fb-1 data • Statistical uncertainty on the CP-violating angle  0.7 • Bd  J/ K analysis is in progress Kin Yip

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