Time Dependent Analysis of B⁰ →ρ⁰ρ⁰ Decays

Thesis/Dissertation · Thu Oct 01 00:00:00 EDT 2009

DOI:https://doi.org/10.2172/969249· OSTI ID:969249

Osipenkov, Ilya Leonidovich ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The BABAR detector at the PEP-II asymmetric-energy e⁺e^- collider is located at the Stanford Linear Accelerator Center. It has been gathering data on the Υ(4S) resonance from 2000 until 2007 with the primary objective of studying CP violation in B-meson decays. In this thesis they provide a theoretical overview of how CP violation arises in the context of the Standard Model, why B decays are relevant, and how BABAR gathers the necessary data. Specifically, they present the analysis of B⁰ →ρ⁰ρ⁰ decays in a sample of 465 x 10⁶ Υ(4S) → B$$\bar{B}$$. They measure the corresponding branching fraction β = (0.92 ± 0.32(stat.) ± 0.14(syst.)) x 10^-6 and the longitudinal polarization fraction f_L = 0.75_-0.14^+0.11(stat.) ± 0.04(syst.). The evidence for the B⁰→ ρ⁰ρ⁰ signal has a significance of 3.1 standard deviations (σ), when the systematic uncertainties are included. There is insufficient evidence for B decays into similar modes and the corresponding upper limits are determined to be β_ρ⁰f₀ < 0.34 x 10^-6, β_f0f0 < 0.16 x 10^-6, β_{ρ⁰π⁺π^-} < 8.7 x 10^-6, B _{π⁺π^-π⁺π^-} < 21.1 x 10^-6 at the 90% Confidence Level (CL). They also investigate the proper-time dependence of the longitudinal component in the decay and measure the Cp-violating coefficients S_L = 0.3± 0.7(stat.) ± 0.2(syst.) and C_L = 0.2 ± 0.8(stat.) ± 0.3(syst.). By combining these results with other measurements from the B → ρρ processes and performing an Isospin Analysis, they are able to restrict the unitarity angle α as well as its uncertainty due to penguin contributions, Δα. Namely, α = (92.4_-6.5^+6.0)° with -1.8° < Δα < 6.7° at 1σ CL.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 969249
• Report Number(s): SLAC-R-935; TRN: US1000221
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
DECAY
ISOSPIN
POLARIZATION
RESONANCE
STANDARD MODEL
STANFORD LINEAR ACCELERATOR CENTER
UNITARITY
Experiment-HEP
ACCPHY
HEPEX