The "τ\to 3πην" decay with the "η\to γγ" mode is studied using 384 fb^-1 of data collected by the BaBar detector. The branching fraction is measured to be (1.60+/-0.05+/-0.11)x10^-4. It is found that "τ\to f1 πνto 3πην" is the dominant decay mode with a branching fraction of (1.11+/-0.06+/-0.05)x10^-4. The first error on the branching fractions is statistical and the second systematic. In addition, a 90% confidence level upper limit on the branching fraction of the "τ\to η'(958) πν" decay is measured to be 7.2x10^-6. This last decay proceeds through a second-class current and is expected to be forbidden in the limit of isospin symmetry.
We have searched for lepton flavor violating semileptonic tau decays using a data sample of 153.8/fb accumulated with the Belle detector at the KEKB e+e- collider. For the six decay modes studied, the observed yield is compatible with the estimated background and the following upper limits are set at the 90% confidence level: B(tau- -> e- eta) < 2.3 x 10^-7, B(tau- -> mu- eta) < 1.5 x 10^-7, B(tau- -> e- pi0) < 1.9 x 10^-7, B(tau- -> mu- pi0) < 4.1 x 10^-7, B(tau- -> e- eta') < 10 x 10^-7, and B(tau- -> mu- eta') < 4.7 x 10^-7. These results are 10 to 64 times more restrictive than previous li…
We have studied hadronic tau decay modes involving an eta meson using 490 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The following branching fractions have been measured: B(tau- -> K- eta nu)=(1.58 +- 0.05 +- 0.09)x 10^{-4}, B(tau- -> K- pi0 eta nu)=(4.6 +- 1.1 +- 0.4)x 10^{-5}, B(tau- -> pi- pi0 eta nu)=(1.35 +- 0.03 +- 0.07)x 10^{-3}, B(tau- -> pi- KS eta nu)=(4.4 +- 0.7 +- 0.2)x 10^{-5}, and B(tau- -> K^{*-} eta nu)=(1.34 +- 0.12 +- 0.09)x 10^{-4}. These results are substantially more precise than previous measurements. The new measurement…
We present measurements of the branching fractions for B0 meson decays to eta'K0 and omegaK0, and of the branching fractions and CP-violation charge asymmetries for B+ meson decays to etapi+, etaK+, eta'pi+, eta'K+, omegapi+, and omegaK+. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 383 million BBbar pairs produced in e+e- annihilation. The measurements agree with previous results; we find no evidence for direct CP violation.
We report on analyses of tau lepton decays $τ^- \to ηK^- ν_τ$ and $τ^- \to ηπ^- ν_τ$, with $η\to π^+ π^- π^0$, using 470 fb$^{-1}$ of data from the Babar experiment at PEP-II, collected at center-of-mass energies at and near the $Υ(4S)$ resonance. We measure the branching fraction for the $τ^- \to ηK^- ν_τ$ decay mode, $\Br(τ^- \to ηK^- ν_τ) = (1.42\pm0.11\text{(stat)}\pm0.07\text{(syst)})\times10^{-4}$, and report a 95% confidence level upper limit for the second-class current process $τ^- \to ηπ^- ν_τ$, $\Br(τ^- \to ηπ^- ν_τ) < 9.9\times10^{-5}$.
We describe searches for decays to two-body charmless final states eta' eta, eta' pi0 and eta pi0 of B0 mesons produced in e+e- annihilation. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent 232 million produced B-anti-B pairs. The results for branching fractions are, in units of 10^-6 (upper limits at 90% C.L.): BF(B0 -> eta' eta) = 0.2 +0.7 -0.5 +/- 0.4 (<1.7), BF(B0 -> eta pi0) = 0.6 +0.5 -0.4 +/- 0.1 (<1.3), and BF(B0 -> eta' pi0) = 0.8 +0.8 -0.6 +/- 0.1 (<2.1). The first error quoted is statistical and the second systematic.
We present measurements of the B->eta K gamma branching fractions and upper limits for the B->eta' K gamma branching fractions. For B->eta K+ gamma we also measure the time-integrated charge asymmetry. The data sample, collected with the BaBar detector at the Stanford Linear Accelerator Center, represents 232 million produced B B-bar pairs. The results for branching fractions and upper limits at 90% C.L. in units of 10^{-6} are: Br(B0->eta K0 gamma)=11.3+2.8-2.6+/-0.6, Br(B+->eta K+gamma)=10.0+/-1.3+/-0.5, Br(B0->eta' K0 gamma)<6.6, Br(B+->eta' K+ gamma)<4.2. The charge asymmetry in the decay …
We study the decays B+ -> etac K+ and B0 -> etac K0, where the etac is reconstructed in the Ks K+ pi- and K+ K- pi0 decay modes. Results are based on a sample of 86 million BBbar pairs collected with the BaBar detector at the SLAC e+e- B Factory. We measure the branching fractions BR(B+ -> etac K+) = (1.34 +/- 0.09 +/- 0.13 +/- 0.41) x 10^{-3} and BR(B0 -> etac K0) = (1.18 +/- 0.16 +/- 0.13 +/- 0.37) x 10^{-3}, where the first error is statistical, the second is systematic, and the third reflects the etac branching fraction uncertainty. In addition, we search for B -> etac K events with etac -…
In this report, we present the observation of the exclusive decays B0 -> EtaC K0 and B+ -> EtaC K+, and the measurement of the related branching fractions. Using a sample of 22.7x10^6 Upsilon(4S) -> BBbar decays collected with the BABAR detector at the SLAC PEP-II asymmetric B Factory during 1999-2000, we have observed statistically significant signals in the EtaC -> KsK+Pi- and K+K-Pi0 channels and set upper limits in the EtaC -> K+K-K+K- channels. All the results presented are preliminary. We have measured BF(B+ -> EtaC K+) = (1.50 +/- 0.19 +/- 0.15 +/- 0.46)x10^{-3} BF(B0 -> Etac K0) = (1.0…
We report preliminary measurements of the exclusive charmless semileptonic branching fractions of the B+ --> eta l+ nu and B+ --> eta' l+ nu decays. These measurements are based on 316 fb-1 of data collected at the Y(4S) resonance by the BABAR detector. In events in which the decay of one B meson to a hadronic final state is fully reconstructed, the semileptonic decay of the recoiling B meson is identified by the detection of a charged lepton and an eta or eta'. We measure the branching fraction BR(B+ --> eta l+ nu) = (0.84 +/- 0.27 +/- 0.21) x 10-4, where the first error is statistical and th…
We present measurements of branching fractions and charge asymmetries for six B-meson decay modes with an eta or eta' meson in the final state. The data sample corresponds to 232 million BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- B Factory at SLAC. We measure the branching fractions (in units of 10^-6): B(B->etapi+)=5.1+/-0.6+/-0.3, B(B->etaK+)=3.3+/-0.6+/-0.3, B(B->etaK0)=1.5+/-0.7+/-0.1 (<2.5 at 90% C.L.), B(B->etarho+)=8.4+/-1.9+/-1.1, B(B->etaomega)=1.0+/-0.5+/-0.2 (<1.9 at 90% C.L.), and B(B->eta'pi+)=4.0+/-0.8+/-0.4, where the first uncertainty is …
We present the results of searches for B decays to the two charmless two-body final states B^0 --> eta K^{*0} and B^+ --> eta K^{*+}, based on 20.7 fb-1 of data collected in 1999 and 2000 with the BABAR detector at PEP-II. We find the branching fractions BF(B^0 --> eta K^{*0}) = (19.8^{+6.5}_{-5.6} +/- 1.7) x 10^{-6} and BF(B^+ --> eta K^{*+}) = (22.1^{+11.1}_{-9.2} +/- 3.3) x 10^{-6}, where the first error quoted is the statistical and the second systematic.
The decay psi(2S) --> eta J/psi is used to measure, for the first time, all prominent eta-meson branching fractions with the same experiment in the same dataset, thereby providing a consistent treatment of systematics across branching fractions. We present results for eta decays to gamma gamma, pi+pi-pi0, 3 pi0, pi+ pi- gamma, and e+ e- gamma, accounting for 99.9% of all eta decays. The precisions for several of the branching fractions and their ratios are improved. Two channels, pi+ pi- gamma and e+ e- gamma, show results that differ at the level of three standard deviations from those previo…
We report measurements of B to pseudoscalar-pseudoscalar decays with at least one eta meson in the final state using 140 fb^{-1} of data collected by the Belle detector at KEKB e^+ e^- collider. We observe the decay B^+-> eta pi^+ and find evidence of B^+-> eta K+; the measured branching fractions are B(B^+-> eta pi^+)=(4.8^{+0.8}_{-0.7}(stat) +- 0.3(sys))*10^{-6} and B(B^+-> eta K^+)=(2.1 +- 0.6(stat)+- 0.2(sys))*10^{-6}. Their corresponding CP violating asymmetries are measured to be 0.07+- 0.15 (stat) +- 0.03(sys) for eta pi^+- and -0.49+- 0.31 (stat) +- 0.07(sys) for eta K^+-. No significa…
We report improved measurements of B decays with an eta meson in the final state using 357 fb^-1 of data collected by the Belle detector at the KEKB e^+ e^- collider. We observe the decays B^+- ->eta pi^+- and B^+- -> eta K^+-; the measured branching fractions are Br(B^+- -> eta pi^+-) = (3.9 +- 0.5(stat.)+-0.2(sys.))*10^-6 and Br(B^+- -> eta K^+-) = (2.2+-0.4(stat.)+-0.1(sys.))*10^-6, respectively. Their corresponding CP-violating asymmetries are measured to be -0.10+-0.11(stat.)+-0.02(sys.) for eta pi^+- and -0.55+-0.19(stat.)+0.04-0.03(sys.) for eta K^+-. No significant signal is found for …
We report measurements of $B$ to pseudoscalar-pseudoscalar decays with at least one eta meson in the final state using 140 fb^{-1} of data collected by the Belle detector at KEKB e^+ e^- collider. We observe the decays of B^+-> eta pi^+ and B^+-> eta K^+; the measured branching fractions are Br(B^+-> eta pi^+) = (4.8^{+0.8}_{-0.7}(stat) +- 0.3 (sys)) * 10^-6 and Br(B^+-> eta K^+) = (2.1 +- 0.6 (stat) +- 0.2 (sys)) * 10^-6. Their corresponding CP violating asymmetries are measured to be 0.07 +- 0.15 +- 0.03 for eta pi^+- and -0.49 +- 0.31 +- 0.07 for eta K^+-. No significant signals are found f…
We present a search for tau sneutrino production using the Tevatron ppbar collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb^-1. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which tau sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set the upper limits on sigma(ppbar -> tau sneutrino)*BR(tau sneutrino ->emu,mutau,etau) and use these results to constrain the RPV couplings as a function of tau sneutrino mass.
We have searched with the KLOE detector for the P and CP violating decay eta -> pi^+pi^- in a sample of 1.55 x 10^7 eta's from the decay phi -> eta gamma of phi mesons produced in e+e- annihilations at DAFNE. No signal is found. We obtain the upper limit BR(eta -> pi^+pi^-) < 1.3 x 10^-5 at 90% confidence level.
We report measurements of branching fractions for the decays B --> P l nu, where P are the pseudoscalar charmless mesons pi-, pi0, eta and eta', based on 348 fb-1 of data collected with the BABAR detector, using B0 and B+ mesons found in the recoil of a second B meson decaying as B --> D(*) l nu. Assuming isospin symmetry, we combine pionic branching fractions to obtain B(B0 --> pi- l+ nu) = (1.54 +/- 0.17(stat) +/- 0.09(syst)) x 10-4; we find 3.2 sigma evidence of the decay B+ --> eta l+ nu and measure its branching fraction to be (0.64 +/- 0.20 (stat) +/- 0.03 (syst)) x 10-4, and determine B…
Using CLEO-c data, we confirm the observation of D0 ->omega eta by BESIII. In the Dalitz Plot of D0 -> Kshort eta pi0, we find a background in the Kshort(->pipi)pi0 projection with a m(pipipi0) equal to the omega(782) mass. In a direct search for D0 -> (omega eta) we find a clear signal and measure BF(D0 ->omega eta) = (1.78+/-0.19+/-0.14) x 10**(-3), in good agreement with BESIII.
Using a data sample with integrated luminosity of about 3.9 fb^{-1} collected in e+ e- annihilation with the CLEO-II detector at the Cornell Electron Storage Ring, we have measured the branching ratios for the decay modes Ds -> (eta, eta') pi and Ds -> (eta, eta') rho relative to Ds -> phi pi. These decay modes are among the most common hadronic decays of the Ds's and can be related by factorization to the semileptonic decays Ds -> (eta,eta') l nu. The results obtained are compared with previous CLEO results and with the branching ratios measured for the related semileptonic decays. We also re…
We present measurements of branching fractions and charge asymmetries for the decays etaK*, where K* indicates a spin 0, 1, or 2 Kpi system. The data sample corresponds to 344x10^6 BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the branching fractions (in units of 10^-6): BR(B0->etaK*0)=16.5\pm1.1\pm0.8, BR(B+->etaK*+)=18.9\pm1.8\pm1.3, BR(B0->eta(Kpi)_0*0)=11.0\pm1.6\pm1.5, BR(B+->eta(Kpi)_0*+)=18.2\pm2.6\pm 2.6, BR(B0->etaK_2*0(1430))=9.6\pm1.8\pm1.1, and BR(B+->etaK_2*+(1430))=9.1\pm2.7\pm 1.4. We also determine the charge asy…
We have searched for the C-violating decay eta to gamma gamma gamma in a sample of ~ 18 million eta mesons produced in phi to eta gamma decays, collected with the KLOE detector at the Frascati phi-factory DAFNE. No signal is observed and we obtain the upper limit BR(eta to gamma gamma gamma) less equal than 1.6x10^(-5) at 90 % C.L.
We report improved measurements of B decays with an eta meson in the final state using 492 fb^{-1} of data collected by the Belle detector at the KEKB e^+ e^- collider. We observe the decays B^{+-}-> eta pi^{+-} and B^{+-}-> eta K^{+-}; the measured branching fractions are Br(B^{+-}-> eta pi^{+-}) = (4.2+- 0.4(stat)+- 0.2(sys))x10^{-6} and Br(B^{+-}-> eta K^{+-}) = (1.9+-0.3(stat)^{+0.2}_{-0.1}(sys))x10^{-6}. The corresponding CP-violating asymmetries are measured to be -0.23+- 0.09(stat) +-0.02(sys) for eta pi^{+-} and -0.39+-0.16(stat)+-0.03(sys) for eta K^{+-}. We also search for B^0-> eta …
We present preliminary measurements of branching fractions and charge asymmetries for the B meson decays B -> eta(')K*, B -> eta(')rho, and B+ -> eta' pi+. The data were recorded with the BaBar detector at PEP-II and correspond to 89 x 10^6 B B-bar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We find the branching fractions B(B0 -> eta K*0) = (19.0 +2.2 -2.1 +/- 1.3) x 10^-6, B(B+ -> eta K*+) = (25.7 +3.8 -3.6 +/- 1.8) x 10^-6, B(B+ -> eta rho+) = (10.5 +3.1 -2.8 +/- 1.3) x 10^-6, B(B+ -> eta' rho+) = (14.0 +5.1 -4.6 +/- 1.9) x 10^-6 (< 22 x 10^-6 with 90% confidence)…
We report measurements for two-body charmless B decays with an eta' meson in the final state. Using 11.1X10^6 BBbar pairs collected with the Belle detector, we find BF(B^+ ->eta'K^+)=(79^+12_-11 +-9)x10^-6 and BF(B^0 -> eta'K^0)=(55^+19_-16 +-8)x10^-6, where the first and second errors are statistical and systematic, respectively. No signal is observed in the mode B^+ -> eta' pi^+, and we set a 90% confidence level upper limit of BF(B^+-> eta'pi^+) < 7x10^-6. The CP asymmetry in B^+- -> eta'K^+- decays is investigated and a limit at 90% confidence level of -0.20<Acp<0.32 is obtained.
We present a study of the charmless semileptonic B-meson decays B+ -> omega l+ nu and B+ -> eta l+ nu. The analysis is based on 383 million BBbar pairs recorded at the Upsilon(4S) resonance with the BABAR detector. The omega mesons are reconstructed in the channel omega -> pi+ pi- pi0 and the eta mesons in the channels eta -> pi+ pi- pi0 and eta -> gamma gamma. We measure the branching fractions B(B+ -> omega l+ nu) = (1.14 +- 0.16 (stat) +- 0.08 (syst)) x 10^-4 and B(B+ -> eta l+ nu) = (0.31 +- 0.06 (stat) +- 0.08 (syst)) x 10^-4.
We present measurements of the B -> eta' K branching fractions;for B+ -> eta' K+ we measure also the time-integrated charge asymmetry Ach, and for B0 -> eta' K0S the time dependent CP-violation parameters S and C. The data sample corresponds to 232 million B Bbar pairs produced by e+ e- annihilation at the Upsilon(4S). The results are BF(B+ -> eta' K+) = (68.9 +- 2.0 +- 3.2) * 10^-6, BF(B0 -> eta' K0) = (67.4 +- 3.3 +- 3.2) * 10^-6, Ach = 0.033 +- 0.028 +- 0.005, S=0.30 +- 0.14 +- 0.02, C=-0.21 +- 0.10 +- 0.02, where the first error is statistical and the second systematic.
We report results on the branching fraction ($\mathcal{BF}$) measurement of the color-suppressed decays $\bar{B}^0\to D^0 π^0$, $D^{*0}π^0$, $D^0η$, $D^{*0}η$, $D^0ω$, $D^{*0}ω$, $D^0η^{\prime}$, and $D^{*0}η^{\prime}$. The result is based on a sample of $(454\pm 5)\times 10^{6} B\bar{B}$ pairs collected at the $Υ(4S)$ resonance from 1999 to 2007, with the $\babar$ detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. The measurements are compared to theoretical predictions by factorization, SCET and pQCD.
Recent data on branching ratios for ψ(2S) decays to J/ψπ^+π^-, J/ψπ^0π^0 and J/ψηare reviewed. An alternative treatment of data is proposed to get rid of the logical inconsistency which occurs in original computational procedure.
We present an improved measurement of the eta' meson energy spectrum in Upsilon(1S) decays, using 1.2 fb^{-1}} of data taken at the Upsilon(1S) center-of-mass energy with the CLEO III detector. We compare our results with models of eta' gluonic form factor that have been suggested to explain the unexpectedly large B to eta' X_s rate. Models based on perturbative QCD fail to fit the data for large eta' energies, showing that Standard Model strong interaction dynamics is not likely to provide an explanation for the large rate of high energy eta' observed in B decays.
Using a sample of 88.8 10**6 BBbar events collected with the BaBar detector at the PEP-II storage rings at the Stanford Linear Accelerator Center, we measure the branching fractions of seven color-suppressed B-meson decays: BF(B0bar to D0 pi0)=(2.9 +/- 0.2(stat.)+/- 0.3(syst.))*10**-4, BF(B0bar to D*0 pi0)=(2.9 +/- 0.4(stat.)+/- 0.5(syst.))*10**-4, BF(B0bar to D0 eta)=(2.5 +/- 0.2(stat.)+/- 0.3(syst.))*10**-4, BF(B0bar to D*0 eta)=(2.6 +/- 0.4(stat.)+/- 0.4(syst.))*10**-4, BF(B0bar to D0 omega)=(3.0 +/- 0.3(stat.)+/- 0.4(syst.))*10**-4, BF(B0bar to D*0 omega)=(4.2 +/- 0.7(stat.)+/- 0.9(syst.))…
We present measurements of the branching fractions of the decays B+ -> eta' K+ and B0 -> eta' K0. For B0 -> eta' K0s we also measure the time dependent CP-violation parameters S and C, and for B+ ->eta' K+ the time-integrated charge asymmetry Ach. The data sample corresponds to 88.9 million BBbar pairs produced by e+e- annihilation at the Upsillon(4S). The results are B(B+->eta'K+) = (76.9 +/- 3.5 +/- 4.4)*10^-6, B(B0->eta'K0) = (60.6 +/- 5.6 +/- 4.6)*10^-6, S = 0.02+/-0.34 +/- 0.03, C = 0.10+/-0.22 +/- 0.04, and Ach = 0.037 +/- 0.045+/- 0.011.
We present measurements of the CP-violation parameters S and C for the radiative decay B0 -> eta K0s gamma; for B -> eta K gamma we also measure the branching fractions and for B+ -> eta K+ gamma the time-integrated charge asymmetry Ach. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent $465 \times 10^6$ BBbar pairs produced in $e^{+} e^{-}$ annihilation. The results are $S = -0.18^{+0.49}_{-0.46} \pm 0.12$, $C = -0.32^{+0.40}_{-0.39} \pm 0.07$, BF(B0 -> eta K0 gamma) = $(7.1^{+2.1}_{-2.0} \pm 0.4) \times 10^{-6}$, BF(B+ -> eta K+ gamma) = $(7.7+-…
We report on a study of the isospin-violating and conserving decays of the J/psi and psi(2S) charmonium state to Lambda Lambdabar pi0 and Lambda Lambdabar eta, respectively. The data are based on 225 million J/psi and 106 million psi(2S) events that were collected with the BESIII detector. The most accurate measurement of the branching fraction of the isospin-violating process J/psi ->Lambda Lambdabar pi0 is obtained, and the isospin-conserving processes J/psi ->Lambda Lambdabar eta and psi(2S) ->Lambda Lambdabar eta are observed for the first time. The branching fractions are measured to be B…
A measurement of the tau- --> K- pi0 nu_tau branching fraction has been made using 230.2 fb-1 of data recorded by the BABAR detector at the PEP-II e+ e- collider, located at the Stanford Linear Accelerator Center (SLAC), at a center of mass energy sqrt{s} close to 10.58 GeV. We measure BF(tau- --> K- pi0 nu_tau) = (0.416 +/- 0.003 (stat) +/- 0.018 (syst)) %.
We have searched for lepton flavor violating $τ$ decays with a pseudoscalar meson ($η$, $η'$ and $π^0$) using a data sample of 401 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No evidence for these decays is found and we set the following upper limits on the branching fractions: ${\cal{B}}(τ^-\to e^-η) < 9.2\times 10^{-8}$, ${\cal{B}}(τ^-\to μ^-η) < 6.5\times 10^{-8}$, ${\cal{B}}(τ^-\to e^-η') < 1.6\times 10^{-7}$, ${\cal{B}}(τ^-\to μ^-η') < 1.3\times 10^{-7}$ ${\cal{B}}(τ^-\to e^-π^0) < 8.0\times 10^{-8}$ and ${\cal{B}}(τ^-\to μ^-π^0) < 1.2\time…
We report preliminary results of an experimental investigation of the color-suppressed decays bar{B^0} --> D^0 pi^0, D^0 eta, and D^0 omega. We measure the branching fractions B (bar{B^0} --> D^0 pi^0) = (2.89 +/- 0.29 (stat.) +/- 0.38 (syst.)) times 10^{-4}, B (\bar{B^0} \to D^0 η) = (2.41 \pm 0.39 (stat.) +/- 0.32 (syst.)) times 10^{-4}, and B (bar{B^0} --> D^0 omega) = (2.48 +/- 0.40 (stat.) +/- 0.32 (syst.)) times 10^{-4}. The results are based on (48.8 +/- 0.5) times 10^6 B B-bar pairs collected with the BaBar detector. The branching fractions of these color-suppressed decays are signific…
Using about 3.9 million hadronic Z decays from e+e- collisions recorded by the OPAL detector at LEP at centre-of-mass energies near MZ the branching ratio for the decay D_s -> tau nu_tau has been measured to be (7.0 +/- 2.1(stat) +/- 2.0 (syst))%. This result can be used to derive the decay constant of the D_s meson: f(D_s) = 286 +/- 44(stat) +/- 41(syst) MeV.
The reaction pd->3He eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta->pi+pi-e+e- is measured to be (4.3+/-1.3+/-0.4)x10^-4.
We perform a measurement of the tau -> l gamma nu anti-nu (l = e, mu) branching fractions for a minimum photon energy of 10 MeV in the tau rest frame, using 431fb^-1 of e^+e^- collisions collected at the center-of-mass energy of the Upsilon(4S) resonance with the BaBar detector at the PEP-II storage rings. We find B(tau -> mu gamma nu anti-nu ) = (3.69pm0.03pm0.10)x10^-3, and B(tau -> e gamma nu anti-nu ) = (1.847pm0.015pm0.052)x10^-2, where the first quoted error is statistical, and the second is systematic. These results are substantially more precise than previous measurements.
We present a study of tau- --> pi- K0S K0S (pi0) nu and tau- --> K- K0S K0S (pi0) nu decays using a dataset of 430 million tau lepton pairs, corresponding to an integrated luminosity of 468 fb-1, collected with the BaBar detector at the PEP-II asymmetric energy e+e- storage rings. We measure branching fractions of (2.31 +/- 0.04 +/- 0.08)x10^{-4} and (1.60 +/- 0.20 +/- 0.22)x10^{-5} for the tau- --> pi- K0S K0S nu and tau- --> pi- K0S K0S pi0 nu decays, respectively. We find no evidence for tau- --> K- K0S K0S nu and tau- --> K- K0S K0S pi0 nu decays and place upper limits on the branching fra…
The branching fraction of the psi(2S) decay into tau pair has been measured for the first time using the BES detector at the Beijing Electron-Positron Collider. The result is $B_{ττ}=(2.71\pm 0.43 \pm 0.55) \times 10^{-3}$, where the first error is statistical and the second is systematic. This value, along with those for the branching fractions into e+e- and mu+mu of this resonance, satisfy well the relation predicted by the sequential lepton hypothesis. Combining all these values with the leptonic width of the resonance the total width of the psi(2S) is determined to be $(252 \pm 37)$ keV.
We present new measurements of the six largest branching fractions of the KL using data collected in 1997 by the KTeV experiment (E832) at Fermilab. The results are B(KL -> pi e nu) = 0.4067 +- 0.0011 B(KL -> pi mu nu) = 0.2701 +- 0.0009 B(KL -> pi+ pi- pi0) = 0.1252 +- 0.0007 B(KL -> pi0 pi0 pi0) = 0.1945 +- 0.0018 B(KL -> pi+ pi-) = (1.975 +- 0.012)E-3, and B(KL -> pi0 pi0) = (0.865 +- 0.010)E-3, where statistical and systematic errors have been summed in quadrature. We also determine the CP violation parameter |eta+-| to be (2.228 +- 0.010)E-3. Several of these results are not in good agree…
Using data collected with the L3 detector at LEP from 1992 to 1995 on the Z peak, we determine the branching fractions of the tau lepton into one, three and five charged particles to be: B(tau->(1-prong)) = 85.274 +- 0.105 +- 0.073 %, B(tau->(3-prong)) = 14.556 +- 0.105 +- 0.076 %, B(tau->(5-prong)) = 0.170 +- 0.022 +- 0.026 %. The first uncertainties are statistical and the second systematic. The accuracy of these measurements alone is similar to that of the current world average.
The branching ratios of the decay of the tau lepton to five charged hadrons have been measured with the OPAL detector at LEP using data collected between 1991 and 1995 at e+e- centre-of-mass energies close to the Z resonance. The branching ratios are measured to be BR(tau- to 3h-2h+nutau) = 0.091+-0.014+-0.005% BR(tau- to 3h-2h+pi0nutau) = 0.027+-0.018+-0.007% where the first error is statistical and the second systematic.
We present a study of tau->pipipinu, tau->Kpipinu, tau->KKpinu, and tau->KKKnu decays using a 666 fb-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider at and near a center-of-mass energy of 10.58 GeV. The branching fractions are measured to be: B(tau->pipipinu) = (8.42+-0.01+0.26-0.25) x 10^-2, B(tau->Kpipinu) = (3.30+-0.01+0.16-0.17) x 10^-3, B(tau->KKpinu) = (1.55+-0.01+0.06-0.05) x 10^-3, and B(tau->KKKnu) = (3.29+-0.17+0.19-0.20) x 10^-5, where the first uncertainty is statistical and the second is systematic. These branching fractions do not inclu…
The inclusive production of the omega(782) vector meson in hadronic Z decays is measured and compared to model predictions. The analysis is based on 4 million hadronic Z decays recorded by the ALEPH detector between 1991 and 1995. The production rate for x_p = p_meson/p_beam > 0.05 is measured in the omega -> pi^+ pi^- pi^0 decay mode and found to be 0.585 +- 0.019_stat +- 0.033_sys per event. Inclusive eta meson production is also measured in the same decay channel for x_p > 0.10, obtaining 0.355 +- 0.011_stat +- 0.024_sys per event. The branching ratio for omega -> mu^+ mu^- is investigated.…
The branching ratio for the decay tau->e nue nutau has been measured using Z0 decay data collected by the OPAL experiment at LEP. In total 33073 tau->e nue nutau candidates were identified from a sample of 186197 selected tau decays, giving a branching ratio of 17.81 +- 0.09(stat) +_ 0.06(sys)%. This result is combined with other measurements to test e-mu and mu-tau universality in charged-current weak interactions. Additionally, the strong coupling constant alpha_s has been extracted and evolved to the Z0 mass scale, giving alpha_s = 0.1204 +- 0.0011(exp) +- 0.0019(theory).
We present measurements of branching fraction, polarization and charge asymmetry in charmless hadronic B decays with eta, eta', omega, and b_1 in the final state. All the results use the final BABAR dataset.
In a sample of 19 million produced B mesons, we have observed the decays B -> eta K* and improved our previous measurements of B -> eta'K. The branching fractions we measure for these decay modes are BR(B+ -> eta K*+) = (26.4 +9.6-8.2 +- 3.3) x $10^{-6}$, BR(B0 -> eta K*0) = (13.8 +5.5-4.6 +- 1.6) x $10^{-6}$, BR(B+ -> eta' K+) = (80 +10-9 +- 7) x $10^{-6}$ and BR(B0 -> eta' K0) = (89 +18-16 +- 9) x $10^{-6}$. We have searched with comparable sensitivity for related decays and report upper limits for these branching fractions.
Using data acquired with the CLEO-c detector at the CESR e+e- collider, we measure branching fractions for J/psi, psi(2S), and psi(3770) decays to gamma pi0, gamma eta, and gamma eta'. Defining R_n = B[ psi(nS)-->gamma eta ]/B[ psi(nS)-->gamma eta' ], we obtain R_1 = (21.1 +- 0.9)% and, unexpectedly, an order of magnitude smaller limit, R_2 < 1.8% at 90% C.L. We also use J/psi-->gamma eta' events to determine branching fractions of improved precision for the five most copious eta' decay modes.
Using a sample of tagged D_s decays collected near the D^*_s D_s peak production energy in e+e- collisions with the CLEO-c detector, we study the leptonic decay D^+_s to tau^+ nu_tau via the decay channel tau^+ to e^+ nu_e bar{nu}_tau. We measure B(D^+_s to tau^+ nu_tau) = (6.17 +- 0.71 +- 0.34) %, where the first error is statistical and the second systematic. Combining this result with our measurements of D^+_s to mu^+ nu_mu and D^+_s to tau^+ nu_tau (via tau^+ to pi^+ bar{nu}_tau), we determine f_{D_s} = (274 +- 10 +- 5) MeV.
Inclusive branching ratios involving b to tau transitions are measured in approximately four million hadronic Z decays collected by the ALEPH detector at LEP. The fully-inclusive branching ratio b -> tau nu X and the semi-inclusive branching ratio b -> tau nu D*+/- X are measured to be (2.43 +/- 0.20 +/- 0.25)% and (0.88 +/- 0.31 +/- 0.28)%, in agreement with the standard model predictions. Upper limits on the branching fractions b -> tau nu and b -> s nu nubar are set to 8.3 10**-4 and 6.4 10**-4 at the 90% C.L. These results allow a 90% C.L. lower limit of 0.40 (GeV/c**2)**-1 to be set on th…
The decay modes $\jpsi\arγπ^0, γη$ and $γ\etap$ are analyzed using a data sample of 58 million $\jpsi$ decays collected with the BESII detector at BEPC. The branching fractions are determined to be: $Br(\jpsi\arγπ^0)=(3.13^{+0.65}_{-0.44})\times10^{-5}$, $Br(\jpsi\arγη)=(11.23\pm0.89)\times10^{-4}$, and $Br(\jpsi\arγ\etap)=(5.55\pm0.44)\times10^{-3}$, where the errors are combined statistical and systematic errors. The ratio of partial widths $Γ(\jpsi\arγ\etap)/Γ(\jpsi\arγη)$ is measured to be $4.94\pm0.40$, and the singlet-octet pseudoscalar mixing angle of $η-\etap$ system is determined to b…
A preliminary measurement of the branching fraction B(tau- --> K0 pi- nu) is made using 384.6 fb-1 of e+e- collision data provided by the PEP-II collider, operating primarily at sqrt(s)=10.58 GeV, and recorded using the BaBar detector. From this we measure: B(tau- --> K0 pi- nu) = (0.840 +/- 0.004 (stat) +/- 0.023 (syst)) %. This result is the most precise measurement to date and is consistent with the world average.
We have studied the leptonic decay D^+_s to tau^+ nu_tau, via the decay channel tau^+ to e^+ nu_e anti-nu_tau, using a sample of tagged D_s^+ decays collected near the D^*_s D_s peak production energy in e^+ e^- collisions with the CLEO-c detector. We obtain B(D^+_s to tau^+ nu_tau) = (5.30 +- 0.47 +- 0.22) % and determine the decay constant f_Ds = (252.5 +- 11.1 +- 5.2) MeV, where the first uncertainties are statistical and the second are systematic.
The inclusive branching ratio for the process b -> tau nu X has been measured using hadronic Z decays collected by the OPAL experiment at LEP in the years 1992-2000. The result is: BR(b -> tau nu X) = (2.78 +/- 0.18 +/- 0.51)% This measurement is consistent with the Standard Model expectation and puts a constraint of tan(beta) / M(H+/-) < 0.53 GeV-1 at the 95% confidence level on Type II Two Higgs Doublet Models.
We have searched for decays of the tau lepton into seven or more charged particles, using data collected with the OPAL detector from 1990 to 1995 in e^+e^- collisions at sqrt(s) ~ M_Z. No candidate events were found and an upper limit on the branching ratio for tau decays into seven charged particles of 1.8 x 10^-5 at the 95% confidence level was determined.
