Studies of Inclusive Semileptonic B Meson Decays with the BABAR Detector PDF Download

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 6

View

Book Description
This is a brief report on the measurement of the inclusive branching fraction [Beta]({bar B} → X{sub c}l−{bar {nu}}) and the preliminary measurement of the first moment of the hadron mass M{sub X} in such decays. The implications of these results on.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5

View

Book Description
We present measurements of the inclusive semileptonic branching fractions of charged and neutral B mesons using 20.6 fb−1 of data measured at the [Upsilon](4S) with the BABAR detector. Events are tagged with a fully reconstructed hadronic decay of a B meson. The correlation between the flavor of the tag B meson and the electron charge allows the separation of prompt semileptonic B decays and cascade semileptonic charm decays. We obtain the preliminary inclusive semileptonic branching fraction of charged B mesons b+ = 0.103 ± 0.006 ± 0.005, neutral B mesons b0 = 0.104 ± 0.008 ± 0.005, their average b = 0.104 ± 0.005 ± 0.004, and their ratio b+/b0 = 0.99 ± 0.10 ± 0.03.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
We present results on semileptonic B decays obtained with the BABAR detector. The large data set accumulated at the PEP-II asymmetric-energy B-Factory allows a new measurement technique, where the hadronic decay of one B meson is fully reconstructed and the semileptonic decay of the recoiling B meson is studied. Traditional analysis techniques of inclusive and exclusive B decays complement this approach with very high statistics data samples. These measurements play an important role in the tests of the description of CP violation in the Standard Model: The determinations of the Cabibbo-Kobayashi-Maskawa matrix elements V[sub cb] and V[sub ub] provide constraints on the unitarity of the CKM triangle. Furthermore, the experimental measurement of parameters of Heavy Quark Effective Theory test the consistency of the theoretical description of semileptonic B decays.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

View

Book Description
A largely model-independent measurement of the inclusive electron momentum spectrum and branching fraction for semileptonic decays of B mesons is presented based on data recorded at the [Upsilon](4S) resonance with the BABAR detector. Backgrounds from secondary charm decays are separated from prompt B decays using charge and angular correlations between the electron from one B meson and a high momentum electron tag from the second B meson. The resulting branching fraction is [Beta](B → Xe[nu]) = (10.87 ± 0.18(stat) ± 0.30(syst))%. Based on this measurement we determine the CKM matrix element.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
The authors present a preliminary determination of the CKM matrix element V[sub ub] based on the analysis of semileptonic B decays from a sample of 88 million [Upsilon](4S) decays collected with the BaBar detector at the e[sup +]e[sup -] storage ring. Charmless semileptonic B decays are selected using the electron energy E-e and the invariant mass q[sup 2] of the electron-neutrino pair. The neutrino meomentum is inferred from a measurement of the visible energy and momentum in the detector and knowledge of the e[sup +]e[sup -] beam momenta. The partial branching fraction is determined in a region of the q[sup 2]-E-e plane where semileptonic B decays to charm are highly suppressed. The total charmless semileptonic branching fraction is extracted using a theoretical calculation based on the heavy quark expansion. Preliminary results yield V[sub ub] = (4.57 [+-] 0.21 [+-] 0.25 [+-] 0.34 + 0.59 - 0.29 [+-] 0.22) x 10[sup -3] where the uncertainties are from statistics (data and MC), detector modeling, background modeling, the shape function, and the heavy quark operator product expansion, respectively.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 7

View

Book Description
We report a measurement of the inclusive charmless semileptonic branching fraction of B mesons in a sample of 89 million B{bar B} events recorded with the BABAR detector at the [Upsilon](4S) resonance. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson. The number of signal events is extracted from the hadronic mass distribution and is used to determine the ratio of branching fractions [Beta]({bar B} → X{sub u}l{bar {nu}})/[Beta]({bar B} → Xl{bar {nu}}) = (2.06 ± 0.25(stat) ± 0.23(syst) ± 0.36(theo)) x 10−2. Using the measured branching fraction for inclusive semileptonic B decays, we find [Beta]({bar B} → X{sub u}l{bar {nu}}) = (2.24 ± 0.27(stat) ± 0.26(syst) ± 0.39(theo)) x 10−3 and derive the CKM matrix element.

Author: S. Bentvelsen
Publisher: Elsevier
ISBN: 0444599169
Category : Science
Languages : en
Pages : 1004

View

Book Description
The first precision measurements on CP violation in the B system are reported. Both the BELLE and the BABAR collaboration presented, among others, results for sin 2ß with much improved accuracy. Results from the Sudbury Neutrino Observatory, SNO, also deserve to be mentioned. The convincing evidence of solar neutrino oscillations had been presented by SNO prior to the conference; a full presentation was given at the conference. An incredibly precise measurement of the anomalous magnetic moment of the muon is reported, a fresh result from the Brookhaven National Laboratory. Apart from these distinct physics highlights, there are also the first results from the new Tevatron run and from the relativistic heavy ion collider RHIC. Theorists write of our ever better understanding of the Standard Model and of what might lie beyond. Risky as it is to highlight only a couple of exciting subjects, it is merely meantto whet the appetite for further reading.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 4

View

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
The BABAR experiment at SLAC provides an opportunity for measurement of the Standard Model parameters describing CP violation. A method of measuring the CKM matrix element V[sub cb] using Inclusive Semileptonic B decays in events tagged by a fully reconstructed decay of one of the B mesons is presented here. This mode is considered to be one of the most powerful approaches due to its large branching fraction, simplicity of the theoretical description and very clean experimental signatures. Using fully reconstructed B mesons to flag B[bar B] event we were able to produce the spectrum and branching fraction for electron momenta P[sub C.M.S.]> 0.5 GeV/c. Extrapolation to the lower momenta has been carried out with Heavy Quark Effective Theory. The branching fractions are measured separately for charged and neutral B mesons. For 82 fb[sup -1] of data collected at BABAR we obtain: BR(B[sup [+-]] [yields] X e[bar [nu]]) = 10.63 [+-] 0.24 [+-] 0.29%, BR(B[sup 0] [yields] X e[bar [nu]]) = 10.68 [+-] 0.34 [+-] 0.31%, averaged BR(B [yields] X e[bar [nu]]) = 10.65 [+-] 0.19 [+-] 0.27%, ratio of Branching fractions BR(B[sup [+-]])/BR(B[sup 0]) = 0.996 [+-] 0.039 [+-] 0.015 (errors are statistical and systematic, respectively). They also obtain V[sub cb] = 0.0409 [+-] 0.00074 [+-] 0.0010 [+-] 0.000858 (errors are: statistical, systematic and theoretical).

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
The neutral B meson, consisting of a b quark and an anti-d quark, can mix (oscillate) to its own anti-particle through second-order weak interactions. The measurement of the mixing frequency can constrain the quark mixing matrix in the Standard Model of particle physics. The PEP-II B-factory at the Stanford Linear Accelerator Center provides a very large data sample that enables us to make measurements with much higher precisions than previous measurements, and to probe physics beyond the Standard Model. The lifetime of the neutral B meson[tau][sub B0] and the B[sup 0]-[bar B][sup 0] mixing frequency[Delta]m[sub d] are measured with a sample of approximately 14,000 exclusively reconstructed B[sup 0][yields] D*[sup -][ell][sup+][nu][sub[ell]] signal events, selected from 23 million B[bar B] pairs recorded at the[Upsilon](4S)resonance with the BABAR detector at the asymmetric-energy e[sup+]e[sup -] collider, PEP-II. The decay position of the exclusively reconstructed B is determined by the charged tracks in the final state, and its b-quark flavor at the time of decay is known unambiguously from the charge of the lepton. The decay position of the other B is determined inclusively, and its b-quark flavor at the time of decay is determined (tagged) with the charge of tracks in the final state, where identified leptons or kaons give the most information. The decay time difference of two B mesons in the event is calculated from the distance between their decay vertices and the Lorentz boost of the center of mass. Additional samples of approximately 50,000 events are selected for studies of background events. The lifetime and mixing frequency, along with wrong-tag probabilities and the time-difference resolution function, are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in B decay times ([Delta]t), the calculated uncertainty on[Delta]t, the signal and background probabilities, and b-quark tagging for the other B meson. The results are[tau][sub B[sup 0]]= (1.523[sub -0.023][sup+0.024][+-] 0.022) ps and[Delta]m[sub d]= (0.492[+-] 0.018[+-] 0.013) ps[sup -1], where the first error is statistical and the second is systematic. The statistical correlation coefficient between[tau][sub B[sup 0]] and[Delta]m[sub d] is -0.22. This result is consistent with the current world average values, the total errors are comparable with other most-precise measurements.