We present a search for the lepton-flavor-violating decays \(B{}^0_s \rightarrow \ell^{\mp}\tau^{\pm}\), where \(\ell = e, \mu\), using the full data sample of \(121~\mathrm{fb}^{-1}\) collected at ...the \(\Upsilon(5S)\) resonance with the Belle detector at the KEKB asymmetric-energy \(e^+e^-\) collider. We use \(B{}^0_s \overline{B}{}^0_s\) events in which one \(B{}^0_s\) meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for \(B{}^0_s \rightarrow \ell^{\mp}\tau^{\pm}\) decays and set upper limits on their branching fractions at \(90\%\) confidence level as \(\mathcal{B}(B{}^0_s \rightarrow e^{\mp}\tau^{\pm}) < 14 \times 10^{-4}\) and \(\mathcal{B}(B{}^0_s \rightarrow \mu^{\mp}\tau^{\pm}) < 7.3 \times 10^{-4}\). Our result represents the first upper limit on the \(B{}^0_s \rightarrow e^{\mp}\tau^{\pm}\) decay rate.
Searches for charginos, neutralinos and sleptons at LEP2 centre-of-mass energies from 130 GeV to 189 GeV have been used to set lower limits on the mass of the Lightest Supersymmetric Particle and ...other supersymmetric particles within the MSSM framework. R
A test of the benchmark QED process e(+) e(-) -->gammagamma(gamma) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ...ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb(-1). The Born cross-section for the process e(+) e(-)-->gammagamma(gamma) was determined, confirming the validity of QED at the highest energies ever attained in electron-positron collisions. Lower limits on the parameters of a number of possible deviations from QED, predicted within theoretical frameworks expressing physics beyond the Standard Model, were derived.
Data from Z decays in DELPHI have been searched for <(B-d(o))over bar> --> D*+ l(-) (ν) over bar (l) with the D*+ decaying to D(0)pi(+) and D-0 --> K(-)pi(+), K(-)pi(+)pi(+)pi(-) or K- pi(+)(pi(0)). ...These events are used to measure the CKM matrix element V-cb and the form factor slope, rho(A1)(2): F-D*(1) V-cb = 0.0392 +/- 0.0018 +/- 0.0023; rho(A1)(2) = 1.32 +/- 0.15 +/- 0.33 corresponding to a branching fraction: BR(<(B-d(0))over bar> --> D(*+)l(-)(ν) over bar (l)) = (5.90 +/- 0.22 +/- 0.50)%. Combining these and previous DELPHI measurements gives: FD*(1)V-cb = 0.0377 +/- 0.0011 +/- 0.0019, rho(A1)(2) = 1.39 +/- 0.10 +/- 0.33 and BR(<(B-d(0))over bar> --> D(*+)l(-)(ν) over bar (l)) = (5.39 +/- 0.11 +/- 0.34)% Using F-D*(1) = 0.91 +/- 0.04, yields: V-cb = 0.0414 +/- 0.0012(stat.) +/- 0.0021(syst.) +/- 0.0018 (theory). The b-quark semileptonic branching fraction into a D*+ emitted from higher mass charmed excited states has also been measured to be: BR(b --> D*+ Xl(-)(ν) over bar (l)) = (0.67 +/- 0.08 +/- 0.10)%.
The forward-backward asymmetries of the processes e(+) e(-) --> Z --> b (b) over bar and e(+)e(-) --> Z --> c (c) over bar were measured from a sample of hadronic Z decays collected by the DELPHI ...experiment between 1993 and 1995. Enriched samples of b (b) over bar and c (c) over bar events were obtained using lifetime information. The tagging of b and c quarks in these samples was based on the semileptonic decay channels b/c --> X + mu and b/c --> X + e combined with charge flow information from the hemisphere opposite to the lepton. Combining the A(FB)(b (b) over bar) and A(FB)(c (c) over bar) measurements presented in this paper with published results based on 1991 and 1992 DELPHI data samples, the following pole asymmetries were obtained: A(FB)(0,b) = 0.1021 +/- 0.0052 (stat) +/- 0.0024 (syst) A(FB)(0,c) = 0.0728 +/- 0.0086 (stat) +/- 0.0063 (syst) The effective value of the weak mixing angle derived from these measurements is sin(2) theta(W,eff)(lept) = 0.23170 +/- 0.00097.
We report the first measurement of the inclusive \(e^+e^- \to b\bar{b} \to D_s^{\pm}X\) and \(e^+e^- \to b\bar{b} \to D^0/\bar{D}^0X\) cross sections in the energy range from \(10.63\) to \(11.02\). ...Based on these results, we determine \(\sigma(e^+ e^- \to B_s^0 \bar{B}_s^0 X)\) and \(\sigma(e^+ e^- \to B\bar{B}X)\) in the same energy range. We measure the fraction of \(B_s^0\) events at \(\Upsilon(10860)\) to be \(f_{\rm s}=(22.0^{+2.0}_{-2.1})\%\). We determine also the ratio of the \(B_s^0\) inclusive branching fractions \(\mathcal{B}(B_s^0 \to D^0/\bar{D}^0X)/\mathcal{B}(B_s^0 \to D_s^{\pm} X)=0.416 \pm 0.018 \pm 0.092\). The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy \(e^+e^-\) collider.
We observe the process \(\Upsilon(2S)\to D_s^{(*)+} D_{sJ}^{-}\) and continuum production \(e^+e^- \to D_s^{(*)+} D_{sJ}^- \) at \(\sqrt{s} = 10.52\) GeV (and their charge conjugates) using the data ...samples collected by the Belle detector at KEKB, where \(D_{sJ}^-\) is \(D_{s1}(2536)^-\) or \(D^{*}_{s2}(2573)^-\). Both \(D_{sJ}^-\) states are identified through their decay into \(\bar{K}\bar{D}^{(*)}\). We measure the products of branching fractions \({\cal B}(\Upsilon(2S) \to D_{s}^{(*)+} D_{sJ}^-) {\cal B}(D_{sJ}^-\to \bar{K} \bar{D}^{(*)})\) and the Born cross sections \(\sigma^{\rm Born}(e^+e^- \to D_{s}^{(*)+} D_{sJ}^-) {\cal B}(D_{sJ}^-\to \bar{K} \bar{D}^{(*)})\), and then compare the ratios \(R_1 \equiv {\cal B}(\Upsilon(2S)\to D_{s}^{(*)+} D_{sJ}^-)/{\cal B}(\Upsilon(2S)\to\mu^{+}\mu^-)\) for \(\Upsilon(2S)\) decays and \(R_2 \equiv \sigma^{\rm Born}(e^+e^-\to D_{s}^{(*)+}D_{sJ}^-)/\sigma^{\rm Born}(e^+e^-\to \mu^{+}\mu^-)\) for continuum production. We obtain \(R_1/R_2 = 9.7\pm 2.3 \pm 1.1\), \(6.8 \pm 2.1 \pm 0.8\), \(10.2 \pm 3.3 \pm 2.5\), and \(3.4 \pm 2.1 \pm 0.5\) for the \(D_s^+ D_{s1}(2536)^-\), \(D_s^{*+} D_{s1}(2536)^-\), \(D_s^+ D_{s2}^{*}(2573)^{-}\), and \(D_s^{*+} D_{s2}^{*}(2573)^{-}\) final states in the \(D_{sJ}^-\to K^{-} \bar{D}^{(*)0}\) modes, respectively. Therefore, the strong decay is expected to dominate in the \(\Upsilon(2S)\to D_{s}^{(*)+}D_{sJ}^-\) processes. We also measure the ratios of branching fractions \({\cal B}(D_{s1}(2536)^-\to K_S^0 D^{*}(2010)^{-})/{\cal B}(D_{s1}(2536)^-\to K^{-} D^{*}(2007)^0) = 0.48 \pm 0.07 \pm 0.02\) and \({\cal B}(D_{s2}^{*}(2573)^- \to K_S^0 D^-)/{\cal B}(D_{s2}^{*}(2573)^- \to K^{-}D^0) = 0.49 \pm 0.10 \pm 0.02\), which are consistent with isospin symmetry. The second ratio is the first measurement of this quantity. Here, the first uncertainties are statistical and the second are systematic.
We search for the \(B^0\to p\bar{\Sigma}^0\pi^-\) decay with \(\bar{\Sigma}^0 \to \bar{\Lambda}\gamma\), where the \(\gamma\) is not measured, using a data sample corresponding to an integrated ...luminosity of 711 \(\rm{fb^{-1}}\) which contains 772 \(\times\) \(10^{6}\) \(B\bar{B}\) pairs, collected around the \(\Upsilon\)(4S) resonance with the Belle detector at the KEKB asymmetric-energy \(e^{+}e^{-}\) collider. We measure for the first time the \(B^0\to p\bar{\Sigma}^0\pi^-\) branching fraction to be \(\mathcal{B}(B^0 \to p \bar\Sigma^0 \pi^-) = (1.17^{+0.43}_{-0.40}(\text{stat})\pm 0.07(\text{syst})) \times 10^{-6}\) with a significance of \(3.0\sigma\). We simultaneously measure the branching fraction for the related channel \(B^{0}\to p\bar{\Lambda}\pi^{-}\) with much improved precision.
The first simultaneous determination of the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element \(V_{ub}\) using inclusive and exclusive decays is performed with the full Belle data set at ...the \(\Upsilon(4S)\) resonance, corresponding to an integrated luminosity of 711 fb\({}^{-1}\). We analyze collision events in which one \(B\) meson is fully reconstructed in hadronic modes. This allows for the reconstruction of the hadronic \(X_u\) system of the semileptonic \(b \to u \ell \bar \nu_\ell\) decay. We separate exclusive \(B \to \pi \, \ell\, \bar \nu_{\ell}\) decays from other inclusive \(B \to X_u \, \ell\, \bar \nu_{\ell}\) and backgrounds with a two-dimensional fit, that utilizes the number of charged pions in the \(X_u\) system and the four-momentum transfer \(q^2\) between the \(B\) and \(X_u\) system. Combining our measurement with information from lattice QCD and QCD calculations of the inclusive partial rate as well as external experimental information on the shape of the \(B \to \pi \, \ell\, \bar \nu_{\ell}\) form factor, we determine \(\left|V_{ub}^{\mathrm{excl.}} \right| = (3.78 \pm 0.23 \pm 0.16 \pm 0.14)\times 10^{-3}\) and \(\left|V_{ub}^{\mathrm{incl.}} \right| = (3.88 \pm 0.20 \pm 0.31 \pm 0.09)\times 10^{-3}\), respectively, with the uncertainties being the statistical error, systematic errors, and theory errors. The ratio of \(\left|V_{ub}^{\mathrm{excl.}} \right| / \left|V_{ub}^{\mathrm{incl.}} \right| = 0.97 \pm 0.12\) is compatible with unity.
PDF
