Download or read book Search for the Rare Leptonic Decay B Tau Nubar written by and published by . This book was released on 2004 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for the decay B− →?− {bar {nu}}{sub?} in a sample of 88.9 x 106 B{bar B}pairs recorded with the BABAR detector at the SLAC B-Factory. One of the two B mesons from the?(4S) is reconstructed in a hadronic or a semileptonic final state and the decay products of the other B in the event are analyzed for consistency with a B− →?− {bar {nu}}{sub {tau}} decay. We find no evidence of a signal and set an upper limit on the branching fraction of?(B− → {tau}− {bar {nu}}{sub {tau}})
Download or read book A Search for the Rare Leptonic B Decay B to Tau Nu Recoiling Against B to Dstar zero 1 Nu written by Mousumi Datta and published by . This book was released on 2005 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Search for the Rare Leptonic B to Tau Anti neutrino Recoiling Against B to Decays to Anti D 0 L Lepton neutrino written by Mousumi Datta and published by . This book was released on 2006 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes a search for the decay B{sup -} {yields} {tau}{sup -}{bar {nu}}{sub {tau}} in 231.8 x 10{sup 6} {Upsilon}(4S) decays recorded with the BABAR detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B{sup +} {yields} {bar D}*{sup 0} {ell}{sup +}{nu}{sub {ell}}) is selected, and in the recoil a search for B{sup -} {yields} {tau}{sup -} {bar {nu}}{sub {tau}} signal is performed in the following {tau} decay modes: {tau}{sup -} {yields} e{sup -}{bar {nu}}{sub e}{nu}{sub {tau}}, {tau}{sup -} {yields} {mu}{sup -}{bar {nu}}{sub {mu}}{nu}{sub {tau}}, {tau}{sup -} {yields} {pi}{sup -}{nu}{sub {tau}}, {tau}{sup -} {yields} {pi}{sup -}{pi}{sup 0}{nu}{sub {tau}}, and {tau}{sup -} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup -}{nu}{sub {tau}}. They find no evidence of signal, and they set a preliminary upper limit on the branching fraction of {beta}(B{sup -} {yields} {tau}{sup -}{bar {nu}}{sub {tau}})
Download or read book Search for the Rare Decay B K Nu Nubar written by and published by . This book was released on 2010 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for the rare decays B → K+?{bar?} and B° → K°?{bar?} using 459 million B{bar B} pairs collected with the BABAR detector at the SLAC National Accelerator Laboratory. Flavor-changing neutral-current decays such as these are forbidden at tree level but can occur through one-loop diagrams in the Standard Model (SM), with possible contributions from new physics at the same order. The presence of two neutrinos in the final state makes identification of signal events challenging, so reconstruction in the semileptonic decay channels B → D{sup (*)}l? of the B meson recoiling from the signal B is used to suppress backgrounds. We set an upper limit at the 90% confidence level of 1.3 x 10−5 on the total branching fraction for B+ → K+?{bar {nu}}, and 5.6 x 10−5 for B° → K°{nu}{bar {nu}}. We additionally report partial branching fractions in two ranges of di-neutrino mass squared for B+ → K+{nu}{bar {nu}}.
Download or read book Search for the Rare Leptonic Decay B Mu Nu sub Mu written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have performed a search for the rare leptonic decay B[sup +] [yields] [mu][sup +][nu][sub [mu]] with data collected at the [Upsilon](4S) resonance by the BABAR experiment at the PEP-II storage ring. In a sample of 88.4 million B[bar B] pairs, we find no significant evidence for a signal and set an upper limit on the branching fraction [Beta](B[sup +] [yields] [mu][sup +] [nu][sub [mu]])
Download or read book A Search for the Decay B to Tau Nu tau written by and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We search for the rare leptonic decay B →?+?{sub?} in a sample of 232 x 106 B{bar B} pairs collected with the BABAR detector at the SLAC PEP-II B-Factory. Signal events are selected by examining the properties of the B meson recoiling against the semileptonic decay B− → D*°l{bar?}{sub {ell}}. We find no evidence for a signal and set an upper limit on the branching fraction of?(B+ →?+?{sub?})
Download or read book A Search for the Decay of a B Meson Into a Kaon and a Tau Lepton Pair at the BaBar Experiment written by and published by . This book was released on 2016 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flavour changing neutral current (FCNC) process, $B^+$ → $K^+ [tau]^+ [tau]^-$ highly suppressed in the Standard Model (SM). This decay is forbidden at tree level and only occurs at lowest order via one-loop diagrams.$B^+$ → $K^+ [tau]^+ [tau]^-$ thus has the potential to provide a stringent test of the SM and a fertile ground for new physics searches. Contributions due to virtual particles in the loop allow one to probe, at relatively low energies, new physics at large mass scales. We search for the rare FCNC process $B^+$ → $K^+ [tau]^+ [tau]^-$ using data collected by the BaBaR detector at the SLAC National Accelerator Laboratory. The BaBaR data sample corresponds to a total integrated luminosity, at the energy of the [Tau](4S) resonance, of 424.4 $fb^-1$ and 471 million $B\bar{B}$ pairs. For this search, hadronic $B_{tag}$ reconstruction is employed, where one B is exclusively reconstructed via one of many possible hadronic modes. The remaining decay products in an event are then attributed to the signal B, on which the search for $B^+$ → $K^+ [tau]^+ [tau]^-$ is performed. Each [tau] is required to decay leptonically, into either an electron or a muon and the lepton neutrinos. Furthermore, a multi-variate analysis technique (neural network) is used to select for signal events and suppress dominant background modes. No significant signal is observed. The resulting branching fraction is measured to be $\beta(B^+$ → $K^+ [tau]^+)$ = $1.31^{0:66}_{-0:61}$(stat.) $^{+0:35}_{-0:25}$(sys.) x 10$^{-3}$, which is consistent with zero at the 1.9[sigma] level, with an upper limit of 2.25 x 10$^{-3}$, at the 90% confidence level.
Download or read book A Search for the Decay of a B Meson Into a Kaon and a Tau Lepton Pair at the BaBar Experiment written by Racha Cheaib and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The flavour changing neutral current (FCNC) process , B+ → K+ [tau]+[tau]−, is highly sup-pressed in the Standard Model (SM). This decay is forbidden at tree level and only occursat lowest order via one-loop diagrams. B+ → K+ [tau]+[tau]− thus has the potential to providea stringent test of the SM and a fertile ground for new physics searches. Contributions dueto virtual particles in the loop allow one to probe, at relatively low energies, new physicsat large mass scales. We search for the rare FCNC process B+ → K+ [tau]+[tau]− using datacollected by the BABAR detector at the SLAC National Accelerator Laboratory. The BABARdata sample corresponds to a total integrated luminosity, at the energy of the [UPSILON](4S) reso-nance, of 424.4 fb−1 and 471 million BB pairs. For this search, hadronic Btag reconstructionis employed, where one B is exclusively reconstructed via one of many possible hadronicmodes. The remaining decay products in an event are then attributed to the signal B, onwhich the search for B+ → K+ [tau]+[tau]− is performed. Each [tau] is required to decay leptonically,into either an electron or a muon and the lepton neutrinos. Furthermore, a multi-variateanalysis technique (neural network) is used to select for signal events and suppress dominantbackground modes. No significant signal is observed. The resulting branching fraction ismeasured to be B(B+ → K+[tau]+[tau]−) = 1.310.66 (stat.)+0.35(sys.) × 10−3, which is consistent −0.61 −0.25with zero at the 1.9[sigma] level, with an upper limit of 2.25 ×10−3 at the 90% confidence level." --
Download or read book A Search for the Decay Modes B to H Tau L written by and published by . This book was released on 2012 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for the lepton flavor violating decay modes B{sup ±} → h{sup ±} [tau]l (h = K, [pi]; l = e, [mu]) using the BABAR data sample, which corresponds to 472 million B{bar B} pairs. The search uses events where one B meson is fully reconstructed in one of several hadronic final states. Using the momenta of the reconstructed B, h, and l candidates, we are able to fully determine the [tau] four-momentum. The resulting [tau] candidate mass is our main discriminant against combinatorial background. We see no evidence for B{sup ±} → h{sup ±} [tau]l decays and set a 90% confidence level upper limit on each branching fraction at the level of a few times 10−5.
Download or read book Leptonic Decays of the Charged B Meson written by Luke Andrew Corwin and published by . This book was released on 2008 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: We present a search for the decay of the charged B meson into a charged lepton and a neutrino 458.9 million Upsilon(4S) decays recorded with the Babar detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed exclusive semileptonic B decay is selected, and in the recoil a search for the signal decay is performed. The tau lepton is identified in decays to an electron and two neutrinos; a muon and two neutrinos; a charged pion and a neutrino; or a charged pion, a neutral pion, and a neutrino. The analysis strategy and the statistical procedure is set up for branching fraction extraction or upper limit determination. We determine from the data set a preliminary measurement of the branching fraction a charged B decaying to a tau lepton and a neutrino = (1.8 " 0.8 " 0.1)E-4, which excludes zero at 2.4 standard deviations. We extract the B meson decay constant = 255 " 58 MeV. Combination with the hadronically tagged measurement yields (1.8 " 0.6)E-4. We also set preliminary limits on the branching fraction of charged B decaying to an electron and a neutrino at 7.7E-6 and the charged B decaying to a muon and a neutrino at 11E-6. The limits are at the 90% confidence level.
Download or read book Rare Leptonic Decays of the D Meson and Tau Lepton written by Ilya Narsky and published by . This book was released on 2001 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for the Rare Decay B u2192 l l in the BaBar Experiment written by and published by . This book was released on 2006 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rare decay B → ?ll- is the simplest manifestation of a b → dl+l- flavor-changing neutral current (FCNC) process. This type of process only proceeds through penguin loop or box diagrams and is sensitive to physics at the electroweak scale. It can be used to constrain parameters of the Standard Model and its extensions. B → ?l+l- events have not yet been observed; the branching fraction is expected to be an order of magnitude smaller than the measured branching fraction for the similar B → Kl+l- decay. Using 230 million B$ar{B}$ meson pairs collected with the BABAR detector, we have done a search for the rare decay B →?l+l- . The data was produced in e+e- collision at the Y(4S) resonance in the PEP-II collider between 1999 and 2004. Four exclusive B-meson decay modes have been reconstructed: B+ → ?+l+l- and B0 → ?0l+l- , where l+ l- is either an electron pair (e+e-) or a muon pair (?+?-). We find no evidence for a signal, and we obtain upper limits on the branching fractions ?. Assuming the isospin relation ?(B+ → ?+l+l- ) 2 x ?B+/?B0 ?(B0 → ?0l+l-), we obtain an upper limit at 90% confidence level on the lepton-flavor-averaged branching fraction of B → ?l+l- to be ?(B → ?e?) 9.2 x 10sup-8 /supat 90% C.L. We have also reconstructed two control modes Bsup+/sup→ ?sup+/supesup±/sup?sup±/sup and Bsup0/sup → ?sup0/supesup±/sup?sup±/sup and we also obtain an upper limit at 90% confidence level on the lepton-flavor-violating decay B → ?e? of ?(B → ?e?) 9.2 x 10
Download or read book Search for the Rare Leptonic Decays B to L nu l l written by and published by . This book was released on 2009 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have performed a search for the rare leptonic decays B → l+?{sub l}({ell} = e,?), using data collected at the?(4S) resonance by the BABAR detector at the PEP-II storage ring. In a sample of 468 x 106 B{bar B} pairs we find no evidence for a signal and set an upper limit on the branching fractions B(B+ → e+?{sub e})
Download or read book A Search for the Rare Decay B tau tau at the BaBar Experiment written by Christopher Thomas Potter and published by . This book was released on 2006 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Standard Model of particle physics predicts that the branching ratio for the rare decay B{sup 0} {yields} {tau}{sup +}{tau}{sup -} is 3.1 x 10{sup -8}, though untested models which could supersede it predict large enhancements. This dissertation describes the search for this rare decay in 210.4 fb{sup -1} of B{sup 0}{bar B}{sup 0} data collected at the {Upsilon}(4S) resonance in the Babar detector at the Stanford Linear Accelerator Center. In the analysis, one neutral B meson is fully reconstructed in a hadronic mode and recoil events which are consistent with each tau decaying in a mode {tau} {yields} {pi}{nu}, {rho}{nu}, or l{nu}{bar {nu}} are selected. There is no evidence for signal. The result is consistent with a downward fluctuation by 1.1 statistical standard deviations of the expected Standard Model background. Taking the expected background, the number of observed events and the expected statistical and systematic errors into account yields 2.7 x 10{sup -3} as the upper limit for B{sup 0} {yields} {tau}{sup +}{tau}{sup -} at the 90% confidence level.
Download or read book Search for the Rare Decay B to Pi L L written by B. Aubert and published by . This book was released on 2006 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present results of a search for the rare flavor-changing neutral-current decay B {yields} {pi}{ell}{sup +}{ell}{sup -}, based on a data sample corresponding to 209 fb{sup -1} of integrated luminosity collected with the BABAR detector at the PEP-II B Factory. They reconstruct the four exclusive B decay modes B{sup +} {yields} {pi}{sup +}{ell}{sup +}{ell}{sup -} and B{sup 0} {yields} {pi}{sup 0}{ell}{sup +}{ell}{sup -}, where {ell} is either an e or {mu}. They find no evidence for a signal, and they obtain the upper limit at 90% confidence level on the lepton-flavor-averaged branching fraction to be {Beta}(B{sup +} {yields} {pi}{sup +}{ell}{sup +}{ell}{sup -}) = 2 x {tau}B{sup +}/{tau}B{sup 0} {Beta}(B{sup 0} {yields} {pi}{sup 0}{ell}{sup +}{ell}{sup -})
Download or read book Search for Rare Multi pion Decays of the Tau Lepton Using the BABAR Detector written by Ruben Ter-Antonyan and published by . This book was released on 2006 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A search for the decay of the tau lepton to rare multi-pion final states is performed using the BABAR detector at the PEP-II asymmetric-energy ee− collider. The analysis uses 232 fb−1 of data at center-of-mass energies on or near the Upsilon(4S) resonance. In the search for the tau− -> 5pi−2pi2pi0nu[tau] decay, we observe 10 events with an expected background of 6.5+2̇0−1.4 events. In the absence of a signal, we calculate the decay branching ratio upper limit B(tau− -> 5pi−2pi+2pi0nu[tau]) 3.4x10−6 at 90% confidence level. This is more than a factor of 30 improvement over the previously established limit. In addition, we search for the exclusive decay mode tau− - 2omega.pi−nu[tau] with the further decay of omega -> pi−pi+pi0. We observe 1 event, expecting 0.4+1̇0−0.4 background events, and calculate the upper limit B(tau− -> 2omega.pi−nu[tau])
Download or read book A Search for the Rare Decay B Meson to Two Photons written by Andrew Michael Ruland and published by . This book was released on 2010 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
