Wouter Verkerke, UCSB Limits on the Lifetime Difference  of Neutral B Mesons and CP, T, and CPT Violation in B 0 B 0 mixing Wouter Verkerke (UC Santa Barbara) for the BaBar collaboration EPS2003 July Aachen, Germany

Wouter Verkerke, UCSB E (ps -1 ) Introduction: Flavor mixing in the B d system Mass states B L, B H superposition of B 0 and B 0 flavor states Properties of the system: Oscillation frequency Well measured Average life time Well measured Life time difference NOT well measured If CPT holds

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

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

Wouter Verkerke, UCSB Time dependent B decay rates: naïve mixing picture Exp. Decay Oscillations with frequency m Differential event rate, as a function of the difference between the proper decay times of the two B mesons in the final state Assume  = 0, no CP/T/CPT violation f tag  f rec (unmixed) f tag = f rec (mixed) Mixed – Unmixed Mixed + Unmixed Decay time distributions Decay rate Asymmetry t (ps)

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

Wouter Verkerke, UCSB Variation: B decay into CP eigenstates Allow   0 complex CP-parameter characterizes interference between mixing & decay Different expression for coefficients C and S 

Wouter Verkerke, UCSB Effect of 0, CP/T/CPT violation on B decay rate unmixedmixed Flavor eigenstate sample CP eigenstate sample Sensitive to: |p/q| Im(z) m  (2 nd order) Sensitive to: Re(z) CP  (1 st order) Naïve model & / = 20% & |q/p| = 0.9 & Im(z) = 0.1 Naïve model & Re(z) = 0.2 & / = 20% & |q/p| = 0.9 Effect of |q/p| opposite for B 0 /B 0 Clearly a precision measurement, effects of detector performance not even yet included… t-parity even odd even t-parity even odd odd (Untagged events also sensitive to /)

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

Wouter Verkerke, UCSB The measurement – Fit Procedure Effects of (0, CPT violation) small  be precise –Take %-level physics effects that can fake CP/CPT/ into account –Accurate detector response modelling –Simultaneous fit for |q/p|, /, m, Im(z), Re(z) and CP to time-dependence of CP and flavor eigenstates, including tagged and untagged events Account for – Possible direct CP violation in the CP eigenstate sample ( CP ) – 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 B 0 and B 0 bar) – t resolution that is comparable to the B life time and asymmetric for positive and negative dt (triple Gaussian t resolution model) – Account for possible asymmetries in detector response for positive and negative particles Fit Model  Detector response(  t, f tag, f rec )

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

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

Wouter Verkerke, UCSB Summary First simultaneous measurement of /, CP, T and CPT violation in the B 0 system –Hadronic data sample Nov 1999 – June 2002 (82 fb -1 ) Much improved limit on / – / < 20 % (90% C.L., PDG 2003 (DELPHI))  / < 8% (90% C.L. this analysis) Measurement of CP and T violation (|q/p|) consistent with Standard Model expectation –Also consistent with previous BaBar measurement using di-lepton events Strongest test of CPT invariance outside K 0 system to date –BaBar (2003): Im(z) =   Re(z) =   –Belle di-Lepton (2002)Im(z) =  0.01  0.03 Re(z) = 0.00  0.12  0.02 –OPAL Z  bb (1997)Im(z) =   0.012

Wouter Verkerke, UCSB (Backup slides)

Wouter Verkerke, UCSB Correlations between physics parameters

Wouter Verkerke, UCSB Summary of systematic uncertainties