The Measurement of CP Asymmetries in the Three-Body Charmless Decay Neutral B Meson Decays to Neutral Kaon(S) Neutral Kaon(S) Neutral Kaon(S)

Hadavand, Haleh K. ; /UC, San Diego

Stanford Linear Accelerator Center

关键词: Daughter Products;    Maximum-Likelihood Fit;    Decay;    Amplitudes;    B Mesons;   

DOI  :  10.2172/878354
RP-ID  :  SLAC-R-812
RP-ID  :  AC02-76SF00515
RP-ID  :  878354

美国|英语

来源: UNT Digital Library

【 摘 要 】

In this dissertation, a measurement of CP-violating effects in decays of neutral B mesons is presented. The data sample for this measurement consists of about 272 million {Upsilon}(4S) {yields} B{bar B} decays collected between 1999 and 2004 with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider, located at the Stanford Linear Accelerator Center. One neutral B meson is fully reconstructed in the CP eigenstate B{sup 0} {yields} K{sub S}{sup 0} K{sub S}{sup 0} K{sub S}{sup 0}. The other B meson is determined to be either a B{sup 0} or a {bar B}{sup 0}, at the time of its decay, from the properties of its decay products. The proper time {Delta}t elapsed between the decay of the two mesons is determined by reconstructing their decay vertices, and by measuring the distance between them. A novel technique for determining the B vertex of the decay to the CP eigenstate B{sup 0} {yields} K{sub S}{sup 0} K{sub S}{sup 0} K{sub S}{sup 0} has been applied since the tracks in the final state do not originate from the B decay vertex. The time-dependent CP asymmetry amplitudes are determined by the distributions of {Delta}t in events with a reconstructed B meson in the CP eigenstate. The detector resolution and the b flavor tagging parameters are constrained by the {Delta}t distributions of events with a fully reconstructed flavor eigenstate. Because of the special topology of this decay, the detector resolution on {Delta}t must be checked for consistency with decays with tracks which originate from the B decay. From a maximum likelihood fit to the {Delta}t distributions of all selected events, the value of the CP violating asymmetries are measured to be S{sub 3K{sub S}{sup 0}} = -0.71{sub -0.32}{sup +0.38} {+-} 0.04 and C{sub 3K{sub S}{sup 0}} = -0.34{sub -0.25}{sup +0.28} {+-} 0.05. Fixing C = 0 we measure the time-dependent CP asymmetry amplitude sin 2{beta} = -S{sub 3K{sub S}{sup 0}} = 0.79{sub -0.36}{sup +0.39} {+-} 0.04. The value of sin 2{beta} is in agreement with Standard Model predictions.