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Title: Evidence for B+ {yields} {tau}+{nu}{tau} decays and measurement of fB from Belle

Abstract

We present the first evidence for B+ {yields} {tau}+{nu}{tau} decay, using 414 fb-1 of B meson decay event sample collected with the Belle detector at the KEKB e+e- collider. To cope with large missing energy due to multiple neutrinos in the final state, events are tagged by fully reconstructing one of the B mesons. We find the evidence for signal with a significance of 3.5 {sigma} including systematic uncertainties. The branching fraction is measured to be B(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) (1.79{sub -0.49-0.51}{sup +0.56+0.46}) x 10{sup -4}. From this we obtain f{sub B} = 0.229{sub -0.031-0.037}{sup +0.036+0.034} GeV, the first direct determination of the B meson decay constant.

Authors:
 [1]
  1. Dept. of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)
Publication Date:
OSTI Identifier:
21056844
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 892; Journal Issue: 1; Conference: QCHS7: 7. conference on quark confinement and the hadron spectrum, Ponta Delgada, Acores (Portugal), 2-7 Sep 2006; Other Information: DOI: 10.1063/1.2714406; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA). Belle Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; B PLUS MESONS; BRANCHING RATIO; DECAY AMPLITUDES; ELECTRON-POSITRON INTERACTIONS; GEV RANGE; LEPTONIC DECAY; MULTIPARTICLE SPECTROMETERS; PARTICLE IDENTIFICATION; TAU NEUTRINOS; TAU PARTICLES

Citation Formats

Kwon, Youngjoon. Evidence for B+ {yields} {tau}+{nu}{tau} decays and measurement of fB from Belle. United States: N. p., 2007. Web. doi:10.1063/1.2714406.
Kwon, Youngjoon. Evidence for B+ {yields} {tau}+{nu}{tau} decays and measurement of fB from Belle. United States. doi:10.1063/1.2714406.
Kwon, Youngjoon. Tue . "Evidence for B+ {yields} {tau}+{nu}{tau} decays and measurement of fB from Belle". United States. doi:10.1063/1.2714406.
@article{osti_21056844,
title = {Evidence for B+ {yields} {tau}+{nu}{tau} decays and measurement of fB from Belle},
author = {Kwon, Youngjoon},
abstractNote = {We present the first evidence for B+ {yields} {tau}+{nu}{tau} decay, using 414 fb-1 of B meson decay event sample collected with the Belle detector at the KEKB e+e- collider. To cope with large missing energy due to multiple neutrinos in the final state, events are tagged by fully reconstructing one of the B mesons. We find the evidence for signal with a significance of 3.5 {sigma} including systematic uncertainties. The branching fraction is measured to be B(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) (1.79{sub -0.49-0.51}{sup +0.56+0.46}) x 10{sup -4}. From this we obtain f{sub B} = 0.229{sub -0.031-0.037}{sup +0.036+0.034} GeV, the first direct determination of the B meson decay constant.},
doi = {10.1063/1.2714406},
journal = {AIP Conference Proceedings},
number = 1,
volume = 892,
place = {United States},
year = {Tue Feb 27 00:00:00 EST 2007},
month = {Tue Feb 27 00:00:00 EST 2007}
}
  • We present measurements of B{sup +{yields}}D*{sup 0{tau}+{nu}}{sub {tau}}and B{sup +{yields}}D{sup 0{tau}+{nu}}{sub {tau}}decays in a data sample of 657x10{sup 6} BB pairs collected with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. We find 446{sub -56}{sup +58} B{sup +{yields}}D*{sup 0{tau}+{nu}}{sub {tau}}events with a significance of 8.1 standard deviations, and 146{sub -41}{sup +42} B{sup +{yields}}D{sup 0{tau}+{nu}}{sub {tau}}events with a significance of 3.5 standard deviations. The latter signal provides the first evidence for this decay mode. The measured branching fractions are B(B{sup +{yields}}D*{sup 0{tau}+{nu}}{sub {tau}})=(2.12{sub -0.27}{sup +0.28}(stat){+-}0.29(syst))% and B(B{sup +{yields}}D{sup 0{tau}+{nu}}{sub {tau}})=(0.77{+-}0.22(stat){+-}0.12(syst))%.
  • We present measurements of the semileptonic decays B{sup -}{yields}D{sup 0}{tau}{sup -}{nu}{sub {tau}}, B{sup -}{yields}D*{sup 0}{tau}{sup -}{nu}{sub {tau}}, B{sup 0}{yields}D{sup +}{tau}{sup -}{nu}{sub {tau}}, and B{sup 0}{yields}D*{sup +}{tau}{sup -}{nu}{sub {tau}}, which are potentially sensitive to non-standard model amplitudes. The data sample comprises 232x10{sup 6} {upsilon}(4S){yields}BB decays collected with the BABAR detector. From a combined fit to B{sup -} and B{sup 0} channels, we obtain the branching fractions B(B{yields}D{tau}{sup -}{nu}{sub {tau}})=(0.86{+-}0.24{+-}0.11{+-}0.06)% and B(B{yields}D*{tau}{sup -}{nu}{sub {tau}})=(1.62{+-}0.31{+-}0.10{+-}0.05)% (normalized for the B{sup 0}), where the uncertainties are statistical, systematic, and normalization-mode-related.
  • We present measurements of the semileptonic decays B{sup -}{yields}D{sup 0}{tau}{sup -}{nu}{sub {tau}}, B{sup -}{yields}D*{sup 0}{tau}{sup -}{nu}{sub {tau}}, B{sup 0}{yields}D{sup +}{tau}{sup -}{nu}{sub {tau}}, and B{sup 0}{yields}D*{sup +}{tau}{sup -}{nu}{sub {tau}}, which are sensitive to non-standard model amplitudes in certain scenarios. The data sample consists of 232x10{sup 6} {upsilon}(4S){yields}BB decays collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider. We select events with a D or D* meson and a light lepton (l=e or {mu}) recoiling against a fully reconstructed B meson. We perform a fit to the joint distribution of lepton momentum and missing mass squared to distinguish signalmore » B{yields}D{sup (*)}{tau}{sup -}{nu}{sub {tau}}({tau}{sup -}{yields}l{sup -}{nu}{sub l}{nu}{sub {tau}}) events from the backgrounds, predominantly B{yields}D{sup (*)}l{sup -}{nu}{sub l}. We measure the branching-fraction ratios R(D){identical_to}B(B{yields}D{tau}{sup -}{nu}{sub {tau}})/B(B{yields}Dl{sup -}{nu}{sub l}) and R(D{sup *}){identical_to}B(B{yields}D*{tau}{sup -}{nu}{sub {tau}})/B(B{yields}D*l{sup -}{nu}{sub l}) and, from a combined fit to B{sup -} and B{sup 0} channels, obtain the results R(D)=(41.6{+-}11.7{+-}5.2)% and R(D*)=(29.7{+-}5.6{+-}1.8)%, where the uncertainties are statistical and systematic. Normalizing to measured B{sup -}{yields}D{sup (*)0}l{sup -}{nu}{sub l} branching fractions, we obtain B(B{yields}D{tau}{sup -}{nu}{sub {tau}})=(0.86{+-}0.24{+-}0.11{+-}0.06)% and B(B{yields}D*{tau}{sup -}{nu}{sub {tau}})=(1.62{+-}0.31{+-}0.10{+-}0.05)%, where the additional third uncertainty is from the normalization mode. We also present, for the first time, distributions of the lepton momentum, |p{sub l}{sup *}|, and the squared momentum transfer, q{sup 2}.« less
  • We report on a search for CP violation in {tau}{sup {+-}}{yields}K{sub S}{sup 0}{pi}{sup {+-}}{nu}{sub {tau}} decays using a data sample of 699 fb{sup -1} collected by the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K{sub S}{sup 0}{pi}{sup {+-}} system and found to be compatible with zero with a precision of O(10{sup -3}) in each mass bin. Limits for the CP violation parameter Im({eta}{sub S}) are given at the 90% confidence level. These limits are |Im({eta}{sub S})|<0.026 or better, depending on the parametrization used to describemore » the hadronic form factors, and improve upon previous limits by 1 order of magnitude.« less
  • The purely leptonic decays of heavy mesons D{sub s}{yields}{tau}{nu}{sub {tau}} and B{yields}{tau}{nu}{sub {tau}} are studied in a sample of 1.5M Z{yields}qq-bar({gamma}) events collected in 1994 by the L3 detector at LEP. A signal for the decay chain D{sub s}{sup 0}{yields}{gamma}D{sub s}, D{sub s}{yields}{tau}{nu}{sub {tau}}, {tau}{yields}l{nu}{sub l}{nu}{sub {tau}} is observed in the invariant mass distribution M({gamma}D{sub s}). From this signal, a branching ration of B(D{sub s}{yields}{tau}{nu}{sub {tau}})=0.074{+-}0.028(stat){+-}0.016(syst){+-}0.018(norm) is derived, corresponding to a decay constant f{sub D{sub s}}=309{+-}58(stat){+-}33(syst){+-}38(norm) GeV. No signal is observed for the decay B{yields}{tau}{nu}{sub {tau}}, and an upper limit of B(B{yields}{tau}{nu}{sub {tau}})<5.7x10{sup -4} at 90% CL is set. Thesemore » results have been published in [1].« less