skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment

Abstract

This study reports the observation of the decays B 0→D$$*+\atop{s}$$π - and B 0→D (*)-K + in a sample of 230 x 10 6 Y(4S) → B$$\bar{B}$$ events collected with the BABAR detector at the PEP-II asymmetric-energy e +e - storage ring, located at the Stanford Linear Accelerator Center. The branching fractions β(B 0 → D$$+\atop{S}$$π -) = (1.3 ± 0.3 (stat) ± 0.2 (syst)) x 10 -5, β(B 0 → D$$+\atop{S}$$K +) = (2.5 ± 0.4 (stat) ± 0.4 (syst)) x 10 -5, β(B 0→D$$*+\atop{s}$$π -) = (2.8 ± 0.6 (stat) ± 0.5 (syst)) x 10 -5, and β(B 0→D (*)-K +) = (2.0 ± 0.5 (stat) ± 0.4 (syst)) x 10 -5 are measured. The significance of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is a first observation of the decaysB +→D$$*+\atop{s}$$π - and B 0→D (*)-K +. These results may potentially be useful in determining the CP asymmetry parameter sin(2β + γ) in the decays B 0→D$$*+\atop{s}$$π -.

Authors:
 [1]
  1. Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
915388
Report Number(s):
SLAC-R-845
TRN: US0804976
DOE Contract Number:
AC02-76SF00515
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; MESONS; DECAY; STANFORD LINEAR ACCELERATOR CENTER; Experiment-HEP; HEPEX; HEPPH

Citation Formats

Orimoto, Toyoko Jennifer. Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment. United States: N. p., 2006. Web. doi:10.2172/915388.
Orimoto, Toyoko Jennifer. Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment. United States. doi:10.2172/915388.
Orimoto, Toyoko Jennifer. Sun . "Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment". United States. doi:10.2172/915388. https://www.osti.gov/servlets/purl/915388.
@article{osti_915388,
title = {Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment},
author = {Orimoto, Toyoko Jennifer},
abstractNote = {This study reports the observation of the decays B0→D$*+\atop{s}$π- and B0→D(*)-K+ in a sample of 230 x 106 Y(4S) → B$\bar{B}$ events collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring, located at the Stanford Linear Accelerator Center. The branching fractions β(B0 → D$+\atop{S}$π-) = (1.3 ± 0.3 (stat) ± 0.2 (syst)) x 10-5, β(B0 → D$+\atop{S}$K+) = (2.5 ± 0.4 (stat) ± 0.4 (syst)) x 10-5, β(B0→D$*+\atop{s}$π-) = (2.8 ± 0.6 (stat) ± 0.5 (syst)) x 10-5, and β(B0→D(*)-K+) = (2.0 ± 0.5 (stat) ± 0.4 (syst)) x 10-5 are measured. The significance of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is a first observation of the decaysB+→D$*+\atop{s}$π- and B0→D(*)-K+. These results may potentially be useful in determining the CP asymmetry parameter sin(2β + γ) in the decays B0→D$*+\atop{s}$π-.},
doi = {10.2172/915388},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Thesis/Dissertation:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this thesis or dissertation.

Save / Share:
  • This study reports measurements of the branching fractions of B meson decays to {eta}{prime}K{sup +}, {eta}{prime}K{sup 0}, {omega}{pi}{sup +}, {omega}K{sup +}, and {omega}K{sup 0}. Charge asymmetries are measured for the charged modes and the time-dependent CP-violation parameters S and C are measured for the neutral modes. The results are based on a data sample of 347 fb{sup -1} containing 383 million B{bar B} pairs recorded by the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring located at the Stanford Linear Accelerator Center. Statistically significant signals are observed for all channels with the following results: B(B{sup +} {yields} {eta}{prime}K{sup +})more » = (70.0{+-}1.5{+-}2.8)x10{sup -6}, B(B{sup 0} {yields} {eta}{prime}K{sup 0}) = (66.6{+-}2.6{+-}2.8)x10{sup -6}, B(B{sup +} {yields} {omega}{pi}{sup +}) = (6.7{+-}0.5{+-}0.4)x10{sup -6}, B(B{sup +} {yields} {omega}K{sup +}) = (6.3{+-}0.5{+-}0.3)x10-6, and B(B{sup 0} {yields} ?K0) = (5.6{+-}0.8{+-}0.3)x10-6, where the first uncertainty is statistical and the second is systematic. We measure A{sub ch}({eta}{prime}K{sup +}) = +0.010{+-}0.022{+-}0.006, A{sub ch}({omega}{pi}{sup +}) = -0.02{+-}0.08{+-}0.01, A{sub ch}({omega}K{sup +}) = -0.01{+-}0.07{+-}0.01, S{sub {eta}{prime}K{sup 0}{sub S}} = 0.56{+-}0.12{+-}0.02, C{sub {eta}{prime}K{sup 0}{sub S}} = -0.24 {+-} 0.08 {+-} 0.03, S{sub {omega}{prime}K{sup 0}{sub S}} = 0.62+0.25 -0.29 {+-} 0.02, and C{sub {omega}{prime}K{sup 0}{sub S}} = -0.39+0.25 -0.24 {+-} 0.03. The result in S{sub {eta}{prime}K{sup 0}{sub S}} contributes to the published measurement from BABAR, which differs from zero by 5.5 standard deviations and is the first observation of mixing-induced CP-violation in a charmless B decay.« less
  • In this thesis work we have measured the following upper limits at 90% of confidence level, for B meson decays (in units of 10 -6), using a statistics of 465.0 x 10 6 Bmore » $$\bar{B}$$ pairs: β(B 0 → ηK 0) < 1.6 β(B 0 → ηη) < 1.4 β(B 0 → η'η') < 2.1 β(B 0 → ηΦ) < 0.52 β(B 0 → ηω) < 1.6 β(B 0 → η'Φ) < 1.2 β(B 0 → η'ω) < 1.7 We have no observation of any decay mode, statistical significance for our measurements is in the range 1.3-3.5 standard deviation. We have a 3.5σ evidence for B → ηω and a 3.1 σ evidence for B → η'ω. The absence of observation of the B 0 → ηK 0 open an issue related to the large difference compared to the charged mode B + → ηK + branching fraction, which is measured to be 3.7 ± 0.4 ± 0.1 [118]. Our results represent substantial improvements of the previous ones [109, 110, 111] and are consistent with theoretical predictions. All these results were presented at Flavor Physics and CP Violation (FPCP) 2008 Conference, that took place in Taipei, Taiwan. They will be soon included into a paper to be submitted to Physical Review D. For time-dependent analysis, we have reconstructed 1820 ± 48 flavor-tagged B 0 → η'K 0 events, using the final BABAR statistic of 467.4 x 10 6 B$$\bar{B}$$ pairs. We use these events to measure the time-dependent asymmetry parameters S and C. We find S = 0.59 ± 0.08 ± 0.02, and C = -0.06 ± 0.06 ± 0.02. A non-zero value of C would represent a directly CP non-conserving component in B 0 → η'K 0, while S would be equal to sin2β measured in B 0 → J/ΨK s 0 [108], a mixing-decay interference effect, provided the decay is dominated by amplitudes of a single weak phase. The new measured value of S can be considered in agreement with the expectations of the 'Standard Model', inside the experimental and theoretical uncertainties. Inconsistency of our result for S with CP conservation (S = 0) has a significance of 7.1 standard deviations (statistical and systematics included). Our result for the direct-CP violation parameter C is 0.9 standard deviations from zero (statistical and systematics included). Our results are in agreement with the previous ones [18]. Despite the statistics is only 20% larger than the one used in previous measurement, we improved of 20% the error on S and of 14% the error on C. This error is the smaller ever achieved, by both BABAR and Belle, in Time-Dependent CP Violation Parameters measurement is a b → s transition.« less
  • Note that the main goal of this thesis work is the measurement of the branching fractions, charge asymmetry, and Time-Dependent CP Violation in η'K 0 mode. All other measurements are reported here for completion because they are connected by similar physics arguments. They are part of the Milan analysis activity, done by undergraduate students. They should not be considered as done in this thesis work. The measurements of the two body-modes ηη, ηΦ, and η'Φare used to determine a theoretical bound based on SU(3) flavor symmetry for the difference between SM prediction and the experimental measurements of CP violation parametersmore » in b → s loop-dominated modes. In general for this estimation we need to measure the branching fractions (or upper limits) of neutral B decays to two-body modes with η', η, Φ, ω, π 0, K 0, K* 0 [13, 14, 15, 16]. There is an important issue related to the branching fractions of η'K (charged and neutral) modes. Since the discover of B → η'K in 1997 [17] with high branching fraction (higher than expected), it was found that the corresponding mode with η is suppressed. This fact was pointed out by Lipkin in 1991 [18]. In particular, using arguments concerning the η-η' mixing angle and the parity of K or K* we can say that η'K and vK* are enhanced, while ηK and η'K* are suppressed. This scheme is experimentally verified. The branching fraction of all these modes are already measured, but the B 0 → ηK 0. So it is important to measure also this mode to complete the scenario. Finally we report on the measurements of the radiative modes B → η'Kγ and of the three-body mode B → η'η'K. Both cases are good candidates to manifest effects due to NP in CP violations [19, 20]. For all measurements we use an unbinned maximum likelihood fit to extract the number of signal yields and CP parameters. To perform these fits we have developed a flexible program in C++ language, called MiFit, which has taken a consistent part of the work described in this thesis. This program is used in all Milan analyses. All these measurements have been presented in conferences and published in Physical Review Letters or Physics Review D (Rapid Communication). These measurements are official BABAR results, approved by the Collaboration. The thesis is structured in eight chapters. In the first chapter we describe the CP violation and how it is explained in the SM. We give the theoretical description of the modes studied in this thesis. We report also the latest main results for the CP violation. In the second chapter we describe the BABAR detector with a description of each sub-detector. In the third chapter we describe the software used by the collaboration, in particular the code used in the events reconstruction, which is described in the fourth chapter. In the fifth chapter we describe the software used to selected the events and the MiFit program. After that, in the sixth chapter we show the discriminating variables used for the events selection and how the selection is done. In the last two chapters we report the analyses and results of the branching fractions and charge asymmetries measurements and the time-dependent CP asymmetries analysis of the mode B 0 → η'K 0, respectively.« less
  • This document presents the searches for the flavour-changing neutral current decays Bmore » $$0\atop{s}$$ → μ +μ - and B$$0\atop{s}$$s → φμ +μ - . A data set with integrated luminosity of 300 pb -1 of proton-antiproton collisions at √ s = 1 . 96 TeV collected with the DØ detector in Run II of the FERMILAB Tevatron collider is used. The former decay mode is particularly sensitive to supersymmetric extensions of the Standard Model. For the latter mode, a measurement of the branching ratio could validate the prediction of the Standard Model. In the absence of an apparent signal, a limit on the branching fraction B(B$$0\atop{s}$$ → μ +μ -) can be computed by normalising the upper limit on the number of events in the B$$0\atop{s}$$ signal region to the number of reconstructed B ± → J/ψ K ± events. An upper limit on the branching fraction of B(B$$0\atop{s}$$ → μ + μ - ) ≤ 3.7 × 10 -7 at a 95% CL is obtained. This limit can be used to constrain models beyond the Standard Model. In models where the lightest supersymmetric particle is considered to be a dark matter candidate the limit aids in restricting the dark matter scattering cross section on nucleons. For the decay B$$0\atop{s}$$ → φμ +μ - also no signal has been observed and an upper limit on the branching ratio normalised to B$$0\atop{s}$$ → J/ψ φ events of B$$0\atop{s}$$ B(B$$0\atop{s}$$ → φ μ + μ -)/B(B$$0\atop{s}$$→J/ψφ) < 4 . 4 × 10 -3 at a 95% CL is obtained. In addition, the rare decay B$$0\atop{s}$$ → ψ (2 S ) φ has been observed. To measure a branching ratio, the B$$0\atop{s}$$ → J/ψ φ mode was used for normalisation, while B ± → ψ (2S) K ± and B ± → J/ψ K ± modes were used as control samples. The relative branching ratio has been measured to be B(B$$0\atop{s}$$ → ψ (2S) φ)/ B(B$$0\atop{s}$$ → J/ψ φ ) = 0 . 58 ± 0 . 24 (stat) ± 0 . 09 (sys).« less
  • We describe studies of the decays of B mesons to final states ηK*(892), ηK* 0(S-wave), ηK* 2(1430), and η'K based on data collected with the BABAR detector at the PEP-II asymmetric-energy e +e - collier at the Stanford Linear Accelerator Center. We measure branching fractions and charge asymmetries for the decays B → ηK*, where K* indicates a spin 0, 1, or 2 Kπ system, making first observations of decays to final states ηK 0* 0(S-wave), ηK +* 0 (S-wave), and ηK 0* 2(1430). We measure the time-dependent CP-violation parameters S and C for the decays B 0 → η'Kmore » 0, observing CP violation in a charmless B decay with 5σ significance considering both statistical and systematic uncertainties.« less