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Register a new userSearch for decays of neutral beauty mesons into four muons
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A search for the non-resonant decays $B^0_s rightarrow mu^{+}mu^{-}mu^{+}mu^{-}$ and $B^0 rightarrow mu^{+}mu^{-}mu^{+}mu^{-}$ is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of $1$ and $2~mathrm{fb}^{-1}$ collected at centre-of-mass energies of $7$ and $8~mathrm{TeV}$, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at $95%$ confidence level are determined to be mathcal{B}(B^0_s rightarrow mu^{+}mu^{-}mu^{+}mu^{-}) & < 2.5 times 10^{-9} mathcal{B}(B^0 rightarrow mu^{+}mu^{-}mu^{+}mu^{-}) & < 6.9 times 10^{-10}.
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A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb-1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, xi^2 = sigma(e+e- --> Zh)/sigma_{SM}(e+e- --> Zh) x B(h --> aa)x B(a --> tau^+tau^-)^2. For mh < 107 GeV/c2 and 4 < ma < 10 GeV/c2, xi^2 > 1 is excluded at the 95% confidence level.
First observations of the decays $Lambda_b^0 to Lambda_c^+ D_{(s)}^-$ are reported using data corresponding to an integrated luminosity of $3,{rm fb}^{-1}$ collected at 7 and 8 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction ${mathcal{B}(B_s^0 to D^+D_s^-)}$ is made and a search is performed for the decays $B^0_{(s)} to Lambda_c^+ Lambda_c^-$. The results obtained are begin{eqnarray*} mathcal{B}(Lambda_b^0 to Lambda_c^+ D^-)/mathcal{B}(Lambda_b^0 to Lambda_c^+ D_{s}^-) &=& 0.042 pm 0.003({rm stat}) pm 0.003({rm syst}), left[frac{mathcal{B}(Lambda_b^0 to Lambda_c^+ D_{s}^-)}{mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+D_s^-)}right]big/left[frac{mathcal{B}(Lambda_b^0 to Lambda_c^+pi^-)}{mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+pi^-)}right] &=& 0.96 pm 0.02({rm stat}) pm 0.06({rm syst}), mathcal{B}(B_s^0 to D^+D_s^-)/mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+D_s^-) &=& 0.038pm0.004({rm stat})pm0.003({rm syst}), mathcal{B}({kern 0.2em}overline{kern -0.2em B}^0 to Lambda_c^+ Lambda_c^-)/mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+D_s^-) & < & 0.0022; [95% ; {rm C.L.}], mathcal{B}(B^0_{s} to Lambda_c^+ Lambda_c^-)/mathcal{B}(B_s^0 to D^+D_s^-) & < & 0.30; [95% ; {rm C.L.}]. end{eqnarray*} Measurement of the mass of the $Lambda_b^0$ baryon relative to the $B^0$ meson gives ${M(Lambda_b^0) -M(B^0) = 339.72pm 0.24({rm stat}) pm 0.18({rm syst})}$ MeV$/c^2$. This result provides the most precise measurement of the mass of the $Lambda_b^0$ baryon to date.
Using a data sample of $e^+e^-$ collision data with an integrated luminosity of 2.93 fb$^{-1}$ taken at the center-of-mass energy $sqrt s= 3.773$~GeV with the BESIII detector operating at the BEPCII storage rings, we measure the absolute branching fractions of the two-body hadronic decays $D^+to pi^+pi^0$, $K^+ pi^0$, $pi^+ eta$, $K^+eta$, $pi^+eta^prime$, $K^+eta^prime$, $K_S^0 pi^+$, $K_S^0 K^+$, and $D^0to pi^+ pi^-$, $K^+ K^-$, $K^mp pi^pm$, $K_S^0 pi^0$, $K_S^0 eta$, $K_S^0 eta^prime$. Our results are consistent with previous measurements within uncertainties. Among them, the branching fractions for $D^+topi^+pi^0$, $K^+pi^0$, $pi^+eta$, $pi^+eta^prime$, $K_S^0 pi^+$, $K_S^0 K^+$ and $D^0 to K_S^0 pi^0$, $K_S^0 eta$, $K_S^0 eta^prime$ are determined with improved precision compared to the world average values.
We report the results of a search for the rare baryonic decay modes B -> Lambda Lambdabar, B -> Lambdabar p, B -> Lambdabar p pi, and B -> p pbar using 5.8M BBbar pairs collected with the CLEO detector. We see no statistically significant signals in any of these modes and set 90% confidence level upper limits on their branching fractions, B(B -> Lambda Lambdabar) < 3.9 times 10^{-6}, B(B -> Lambdabar p) < 2.6 times 10^{-6}, B(B -> Lambdabar p pi) < 1.3 times 10^{-5}, and B(B -> p pbar) < 7.0 times 10^{-6}.
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