Measurement of the Branching Fraction And Search for Direct CP-Violation in the B+- --> J/Psi Pi+- Decay Mode at BaBar
The phenomenon of CP-violation in weak interactions, discovered in 1964 in decays of neutral kaons, receives a simple and elegant explanation in the Standard Model with three generations of quarks. Indeed, in this model the common source of CP-asymmetry phenomena is represented by a simple complex phase in the unitary matrix (the Cabibbo-Kobayashi-Maskawa matrix) describing the charged weak couplings of the quarks. This simple scheme has never received an accurate validation, because the phenomenological parameters determined from measurements of CP-violation in kaons decays are related to the fundamental parameters of the theory in a complex way, sensitive to large theoretical uncertainties. On the contrary, decays of neutral B mesons like B{sup 0} {yields} J/{psi} K{sub S}{sup 0} represent a unique laboratory to test the predictions of the theory because they are expected to show significant CP-violation effects, the magnitude of which is cleanly related to the Standard Model parameters. Thus experimental facilities have been built with the purpose of performing extensive studies of B decays. The BABAR experiment is operating at one of these facilities, at the Stanford Linear Accelerator Center. It is collecting data at the PEP-II asymmetric e{sup +}e{sup -} collider (E{sub e{sup -}} = 9.0 GeV; E{sub e{sup +}} = 3.1 GeV), a high-luminosity accelerator machine (L = 3 x 10{sup 33} cm{sup -2}s{sup -1}). The center-of-mass energy (10.58 GeV) of the e{sup +}e{sup -} system at PEP-II allows resonant production of the {Upsilon}(4S), a b{bar b} bound state, which decays almost exclusively in a B{sup 0}{bar B}{sup 0} or a B{sup +}B{sup -} pair. A high-acceptance detector, projected and built by a wide international collaboration, detects and characterizes the decay products of the B mesons. From the analysis of the data collected during the first two years of operation, the BABAR collaboration has established CP-violation in decays of neutral B mesons at the 4.1{sigma} level. Besides the primary goal of CP-violation studies, the high luminosity of PEP-II, coupled with the high acceptance of the BABAR detector, allows competitive studies of the properties of a wide set of B decay modes. In particular, measurements of non-leptonic decays are extremely useful to understand the dynamics of the non-perturbative strong interactions involved in these processes. In this thesis a study of the non-leptonic decay mode B{sup {+-}} {yields} J/{psi}{pi}{sup {+-}} is presented.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 890245
- Report Number(s):
- SLAC-R-837; TRN: US0604787
- Country of Publication:
- United States
- Language:
- English
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