A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb{sup -1} recorded at the {Upsilon}(4S) resonance and 3.9 fb{sup -1} off-resonance. One of the neutral B mesons, which are produced in pairs at the {Upsilon}(4S), is fully reconstructed in the CP decay modes J/{psi} K{sub S}{sup 0}, {psi}(2S) K{sub S}{sup 0}, {chi}{sub c1} K{sub S}{sup 0}, J/{psi} K*{sup 0} (K*{sup 0} {yields} K{sub S}{sup 0}{pi}{sup 0}) and J/{psi} K{sub L}{sup 0}, or in flavor-eigenstate modes involving D(*){pi}/{rho}/{sub 1} and J/{psi} K*{sup 0} (K*{sup 0} {yields} K{sup +}{pi}{sup -}). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural network tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the B{sup 0}-{bar B}{sup 0} oscillation frequency {Delta}m{sub d}are measured with a sample of about 6350 fully-reconstructed B{sup 0} decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds {Delta}m{sub d} = 0.516 {+-} 0.016 (stat) {+-} 0.010 (syst) ps{sup -1}. The value of the asymmetry amplitude sin2{beta} is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B{sup 0} decays in the CP-eigenstate modes. We find sin2{beta} = 0.59 {+-} 0.14 (stat) {+-} 0.05 (syst), demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter |{lambda}| = 0.93 {+-} 0.09 (stat) {+-} 0.03 (syst), which is consistent with the expectation of |{lambda}| = 1 for no direct CP violation.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 798946
- Report Number(s):
- SLAC-PUB-9060; TRN: US0205107
- Resource Relation:
- Other Information: PBD: 10 Jan 2002
- Country of Publication:
- United States
- Language:
- English
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