Wouter Verkerke (UC Santa Barbara) for the BaBar collaboration

1. Limits onthe Lifetime Difference DG of Neutral B Mesons andCP, T, and CPT Violation in B0B0 mixing Wouter Verkerke (UC Santa Barbara) for the BaBar collaboration EPS2003 July 17-23 Aachen, Germany Wouter Verkerke, UCSB

2. -1 0 1 E (ps-1) Introduction: Flavor mixing in the Bd system • Mass states BL, BH superposition of B0 and B0 flavor states • Properties of the system: IfCPT holds Oscillation frequency Well measured Average life time Well measured NOT well measured Life time difference Wouter Verkerke, UCSB

3. Introduction: CP,T,CPT violation in B0B0 mixing • Increasing statistics of B factories  precision measurements: look at correction to ‘naïve’ mixing picture: CP/T/CPT violation in B0B0 mixing 1) CPT violation CP and CPT violation  0 Violated in mixing if Locality  CPT invariance (e.g SM: 0) 2) CP/T violation CP and T violation Violated in mixing if SM:small 3) SM: small  Life time difference DG Usually assumed to be 0.. Best limit sofar: DG/G < 18% (90% CL) Eur. Phys. J. C 28 (2003) 155-173 Effect and magnitude on B decay rate measurement similar • Need combined analysis to disentangle effects Wouter Verkerke, UCSB

4. Coherent Time Evolution at the Y(4S) PEP-II (SLAC) B-Flavor Tagging Exclusive B Meson Reconstruction Vertexing &Time DifferenceDetermination Wouter Verkerke, UCSB

5. Time dependent B decay rates: naïve mixing picture Differential event rate, as a function of the difference between the proper decay times of the two B mesons in the final state Assume DG = 0, no CP/T/CPT violation Oscillations with frequency Dm Exp. Decay Decay time distributions Mixed – Unmixed Mixed + Unmixed ftag frec (unmixed) ftag= frec (mixed) Asymmetry Decay rate Decay rate Wouter Verkerke, UCSB -15 0 15Dt (ps) -15 0 15Dt (ps) -15 0 15Dt (ps)

6. with and Time dependent B decay rates allowing DG0, CP/T/CPT violation Full expression much more complicated… Allow DG 0  =1 if DG=0 Allow CP/CPTviolation =1 w/o CP/CPT violation Absent w/o CP/CPT violation If z  0 Prob(B0  B0,t) Prob(B0  B0,t) New parameterization allows to test conventional assumptions on CP/T/CPT violation in mixing Wouter Verkerke, UCSB

7. Variation: B decay into CP eigenstates Allow DG 0  Different expression for coefficients C and S complex CP-parametercharacterizes interferencebetween mixing & decay Wouter Verkerke, UCSB

8. Effect of DG0, CP/T/CPT violation on B decay rate Flavor eigenstate sample Sensitive to:|p/q| Im(z)Dm DG (2nd order) t-parityevenoddeven unmixed mixed Effect of |q/p| opposite for B0/B0 Naïve model & DG/G = 20% & |q/p| = 0.9 & Im(z) = 0.1 CP eigenstate sample t-parityevenoddodd Sensitive to:Re(z)lCP DG (1st order) Naïve model & Re(z) = 0.2 & DG/G = 20% & |q/p| = 0.9 (Untagged eventsalso sensitive to DG/G) Clearly a precision measurement, effects of detector performance not even yet included… Wouter Verkerke, UCSB

9. before tagging and vertexing cuts The measurement – Data Samples Nov 1999- June 2002 data 82 fb-1 on-peak – 88 million BB pairs Samples of B decays to flavor-specific final states (31000 events) charge conjugate decays are implied, unless specified Samples of B decays to CP-eigenstates with charmonium . (2600 events) CP = -1 CP = +1 Wouter Verkerke, UCSB

10. The measurement – Fit Procedure • Effects of (DG0, CPT violation) small  be precise • Take %-level physics effects that can fake CP/CPT/DG into account • Accurate detector response modelling • Simultaneous fit for |q/p|, DG/G, Dm, Im(z), Re(z) and lCPto time-dependence of CP and flavor eigenstates, including tagged and untagged events FitModel Detector response(Dt, ftag, frec) • Account for • Possible direct CP violation in the CP eigenstate sample (lCP) • Correlation between reco B and tag B via interference between CKM-allowed and doubly-CKM suppressed decays • Account for • Incorrect assignments of the flavour tagging algorithm (separate mistag fractions for B0 and B0bar) • Dt resolution that is comparable to the B life time and asymmetric for positive and negative dt (triple Gaussian Dt resolution model) • Account for possible asymmetries in detector response for positive and negative particles Wouter Verkerke, UCSB

11. Results – Limits on DG, search for CP,T,CPT violation in mixing Preliminary result SM: -0.003 Mixing Best limit so far DG/G<20%, big improvement Eur. Phys. J. C 28 (2003) 155-173 SM: |q/p|-1  510-4 CP & T violation S i m u l t a n e o u s f i t SM: 0 CPT & CP violation SM: 0 90% CL intervals Physics parameter correlations O(5%), largest correlation 17% (Assuming CPT invariance – Consistent with above results) Mixing CP & T violation Wouter Verkerke, UCSB

12. Preliminary result Also represented: constraint on indirect CPV using dilepton sample Phys. Rev. Lett. 89 (2002) 201802 Results – Limits on DG, search for CP,T,CPT violation in mixing (CP/CPT violation) (CP/T violation) Wouter Verkerke, UCSB

13. Summary • First simultaneous measurement of DG/G, CP, T and CPT violation in the B0 system • Hadronic data sample Nov 1999 – June 2002 (82 fb-1) • Much improved limit on DG/G • DG/G < 20 % (90% C.L., PDG 2003 (DELPHI))  DG/G < 8% (90% C.L. this analysis) • Measurement of CP and T violation (|q/p|) consistentwith Standard Model expectation • Also consistent with previous BaBar measurement using di-lepton events • Strongest test of CPT invariance outside K0 system to date • BaBar (2003): Im(z) = 0.038  0.029  0.025 Re(z) = 0.014  0.035  0.034 • Belle di-Lepton (2002) Im(z) = -0.03  0.01  0.03 Re(z) = 0.00  0.12  0.02 • OPAL Z  bb (1997) Im(z) = 0.040  0.032  0.012 Wouter Verkerke, UCSB

14. (Backup slides) Wouter Verkerke, UCSB

15. Correlations between physics parameters Wouter Verkerke, UCSB

16. Summary of systematic uncertainties Wouter Verkerke, UCSB