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Background Suppression in the Study of the Rare Decay B->Xs̳ll− Using Multi-variable Data Analysis

Background Suppression in the Study of the Rare Decay B->Xs̳ll− Using Multi-variable Data Analysis PDF Author: Dion C. McIntosh
Publisher:
ISBN:
Category : B mesons
Languages : en
Pages : 86

Book Description

Background Suppression in the Study of the Rare Decay B->Xs̳ll− Using Multi-variable Data Analysis

Background Suppression in the Study of the Rare Decay B->Xs̳ll− Using Multi-variable Data Analysis PDF Author: Dion C. McIntosh
Publisher:
ISBN:
Category : B mesons
Languages : en
Pages : 86

Book Description

Search for the Rare Decay $B_s^0 \to \mu^+\mu^-$ at

Search for the Rare Decay $B_s^0 \to \mu^+\mu^-$ at PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 110

Book Description

Study of the Rare Decay B --> Xs L L− at BaBar

Study of the Rare Decay B --> Xs L L− at BaBar PDF Author: Ventzislav B. Koptchev
Publisher:
ISBN:
Category : Beta decay
Languages : en
Pages : 368

Book Description

Study of the Rare Decay B0 to Pi0 Pi0 at BaBar

Study of the Rare Decay B0 to Pi0 Pi0 at BaBar PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5

Book Description
The BABAR experiment operating at the PEP-II ee− collider is designed to study CP violation effects in the B-meson system. From May 1999 to June 2002 approximately 81 fb−1 of data have been collected at the [Upsilon](4S) resonance, containing (87.9 ± 1.4) Million BB pairs. From this data sample the branching fraction for the decay B° 2![pi]°[pi]° has been extracted using a multi-dimensional maximum likelihood technique. With an efficiency of 20.4%, we find 3614−1{sup +15+1} B° 2![pi]°[pi]° events and measure the branching fraction to be [Beta](B° 2![pi]°[pi]°) = (2.0{sub -0.8-0.2}{sup +0.9+0.3}) x 10−6 where the first error is statistical and the second systematic. The statistical significance is 3.1[sigma] and we report an upper limit of [Beta](B° 2![pi]°[pi]°)

Analysis of B {u2192} ?l? Decays With BaBar

Analysis of B {u2192} ?l? Decays With BaBar PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

Book Description
As part of the BaBar project at SLAC to study the properties of B mesons, we have carried out a study of the exclusive charmless semileptonic decay mode B → ?l?, which can be used to determine the magnitude of the Cabbibo- Kobayashi-Maskawa matrix element Vub. Using simulated event samples, this study focuses on determining criteria on variables for selection of B → ?l? signal and suppression of background from other types of BB events and continuum processes. In addition, we determine optimal cuts on variables to ensure a good neutrino reconstruction. With these selection cuts, we were able to achieve a signal-to-background ratio of 0.68 and a signal efficiency of the order of 1%. Applying these cuts to a sample of 83 million BB events recorded by BaBar in e+e– collisions at the (4S) resonance, we obtain a yield of 115 ± 19 B → ?l? decays.

A Search for the Rare Decay [B Meson to Two Photons]

A Search for the Rare Decay [B Meson to Two Photons] PDF Author: Andrew Michael Ruland
Publisher:
ISBN:
Category :
Languages : en
Pages : 362

Book Description
This thesis describes a search for the rare radiative decay of a B meson to two photons. where the charged congugate mode is implied throughout. These decays are highly suppressed in the Standard Model where the branching fraction is expected to be of order 10^-8. In some new physics scenarios this could be enhanced by up to an order of magnitude to 10^-7. Therefore an observation of a significant signal above the Standard Model prediction could be a sign of new physics. The search for this rare decay was performed using the data collected with the BaBar detector at the SLAC National Accelerator Laboratory PEP-II storage ring operating at the Upsilon(4S) resonance. The analysis uses a dataset with an integrated luminosity of 425.7 fb-1 corresponding to 467 million BB pairs. A signal yield of 21.3 +12.8 -11.8 events with a significance of 1.88 sigma was measured using an unbinned extended maximum likelihood fit. An upper limit on the branching fraction is set at the 90% confidence level of less than 3.2 times 10^-7. This is about two times more stringent than the best upper limit of less than 6.2 times 10^-7 published by the Belle collaboration.

Search for the Rare Decay B0 - J/[psi]γ in the BABAR Experiment

Search for the Rare Decay B0 - J/[psi]γ in the BABAR Experiment PDF Author: Sheila McLachlin
Publisher:
ISBN:
Category :
Languages : en
Pages :

Book Description

Inclusive Rare B Decays Using Effective Field Theories

Inclusive Rare B Decays Using Effective Field Theories PDF Author: Christian Bauer
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Book Description
In this thesis we will discuss several properties of rare decays of ' B' mesons. First we discuss properties of the inclusive radiative decay 'B¢' [right arrow] 'Xs'ã, where 'Xs' stands for any hadronic state containing an 's' quark. We extend previous studies of this decay, which included perturbative corrections to order Ã's' and nonperturbative contributions up to order ([Lambda]QCD/' mb')2 and calculate the O ([Lambda]QCD/'mb')3 contributions to this decay. The values of the nonperturbative parameters entering at this order are unknown, leading to uncertainties in the standard model prediction of this decay. We estimate the size of these nonperturbative uncertainties by varying these parameters in the range suggested by dimensional analysis. We also estimate uncertainties arising from a cut on the photon energy which is required experimentally. Another decay mode investigated is 'B¢' [right arrow] ' Xs'3⁄4+3⁄4-. We study the O ([Lambda]QCD/'mb')3 contributions to the leptonic invariant mass spectrum, the forward-backward asymmetry and hadronic invariant mass moments and estimate the resulting uncertainties. We calculate how the size of these uncertainties depend on the value of an experimental cut that has to be applied to eliminate the large background from other 'B' decays. A model independent way to determinate the CKM matrix element @' Vub'@ from the dilepton invariant mass spectrum of the inclusive decay B[right arrow]Xu3⁄4+ n is presented next. We show that cuts required to eliminate the charm background still allow for a theoretically clean way to determine the CKM matrix element @'Vub'@. We also discuss the utility of the 'B¢' [right arrow] 'Xs'3⁄4 +3⁄4- decay rate above the y (2'S') resonance to reduce the resulting uncertainties. Finally, we introduce a novel effective theory valid for highly energetic particles. In decays where the phase space is sufficiently restricted such that final state particles have very high energies compared to their mass, the perturbative as well as nonperturbative series diverge. The effective theory presented allows to sum perturbative Sudakov logarithms in a framework that also incorporates the nonperturbative physics in such limits of phase space.

A Study of the Rare Decays B0 -]Ds(*)+pi- and B0 -] Ds(*)-K

A Study of the Rare Decays B0 -]Ds(*)+pi- and B0 -] Ds(*)-K PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

Book Description
The authors report on the evidence for the decays B[sup 0][yields] D[sub s][sup+][pi][sup -] and B[sup 0][yields] D[sub s][sup -] K[sup+] and the results of a search for the decays B[sup 0][yields] D*[sub s][sup+][pi][sup -] and B[sup 0][yields] D*[sub s][sup -] K[sup+] from a sample of 84 million[Upsilon](4S) decays into B meson pairs collected with the BaBar detector at the PEP II asymmetric-energy e[sup+]e[sup -] collider. The measured B[sup 0][yields] D[sub s][sup+][pi][sup -] yield has a probability of less than 10[sup -3] to be a fluctuation of the background and they measure the branching fraction[Beta](B[sup 0][yields] D[sub s][sup+][pi][sup -])= (3.2[+-] 0.9(stat.)[+-] 1.0 (syst.)) x 10[sup -5]. The measured B[sup 0][yields] D[sub s][sup -] K[sup+] yield has a probability of less than 5 x 10[sup -4] to be a fluctuation of the background and they measure the branching fraction[Beta](B[sup 0][yields] D[sub s][sup -] K[sup+])= (3.2[+-] 1.0(stat.)[+-] 1.0(syst.)) x 10[sup -5]. They also set 90% C.L. limits[Beta](B[sup 0][yields] D*[sub s][sup+][pi][sup -])

Search for B°--]a{_}0(980)pi−

Search for B°--]a{_}0(980)pi− PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 19

Book Description
We present preliminary results of a search for the decay B° → a0(980)?− among 22.7 million?(4S) → B{bar B} pairs collected by the BABAR detector at PEP-II. Using improved background suppression techniques and optimal signal extraction for rare decay searches, an excess of events over expected background is observed at the level of 3.7 standard deviations. This corresponds to the branching fraction B(B° → a0+(a0+ →??+)?−) = (6.2−2{sup +0} ± 1.1) x 10−6, where the first error is statistical and the second is systematic. The 90% confidence level upper limit is 11.5 x 10−6.
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