A bstract An upperlim itforthe {neutrino m asshasbeen determ ined from thedecay ! 5 using data collected with the OPAL detectorfrom 1991 to 1995 in e e collisionsat p s M Z. A lim itof43.2 M eV at95% CL isobtained using a two{dim ensionalm ethod in the5 invariant m ass and energy distribution from 22 selected events. Com bining this result with OPAL’s previously published m easurem entusing + ! 3h  + 3h decays,anew com bined lim it ofm < 27.6M eV (95% CL)isobtained.

A search for doubly charged Higgs bosons decaying to pairs of electrons and/or muons is presented. The search is performed using a data sample corresponding to an integrated luminosity of 4.7 fb−1 of pp collisions at \(\sqrt{s}\) = 7 TeV collected by the ATLAS detector at the LHC. Pairs of prompt, isolated, high-p T leptons with the same electric charge (e ± e ±, e ± μ ±, μ ± μ ±) are selected, and their invariant mass distribution is searched for a narrow resonance. No significant excess over Standard Model background expectations is observed, and limits are placed on the cross section times branching ratio for pair production of doubly charged Higgs bosons. The masses of doubly charged Higgs bosons are constrained depending on the branching ratio into these leptonic final states. Assuming pair production, coupling to left-handed fermions, and a branching ratio of 100 % for each final state, masses below 409 GeV, 375 GeV, and 398 GeV are excluded for e ± e ±, e ± μ ±, and μ ± μ ±, respectively.

AbstractA search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at $\sqrt{s}=189\mbox{--}209\ \mbox{GeV}$, corresponding to an integrated luminosity of approximately 600 pb−1. Charged Higgs bosons are assumed to be pair-produced and to decay into $\mathrm{q} \bar{\mathrm{q}}$, τντ or AW±. No signal is observed. Model-independent limits on the charged Higgs-boson production cross section are derived by combining these results with previous searches at lower energies. Under the assumption $\mathrm{BR} (\mathrm{H}^{\pm} \to \tau\nu_{\tau}) + \mathrm{BR} (\mathrm{H}^{\pm} \to \mathrm{q} \bar{\mathrm{q}}) = 1$, motivated by general 2HDM type II models, excluded areas on the $[m_{\mathrm{H}^{\pm}} , \mathrm{BR} (\mathrm {H}^{\pm} \to \tau\nu_{\tau})]$ plane are presented and charged Higgs bosons are excluded up to a mass of 76.3 GeV at 95 % confidence level, independent of the branching ratio BR(H±→τντ). A scan of the 2HDM type I model parameter space is performed and limits on the Higgs-boson masses $m_{\mathrm{H}^{\pm}}$ and mA are presented for different choices of tanβ.

A blind analysis searching for the decay B-s(0) -> mu(+)mu(-) has been performed using proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. With an integrated luminosity of 2.4 fb(-1) no excess of events over the background expectation is found and an upper limit is set on the branching fraction BR(B-s(0) -> mu(+)mu(-)) <2.2(1.9) x 10(-8) at 95% (90%) confidence level. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

A measurement of the $ZZ$ production cross section in proton-proton collisions at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ using data corresponding to an integrated luminosity of $1.02\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ recorded by the ATLAS experiment at the LHC is presented. Twelve events containing two $Z$ boson candidates decaying to electrons and/or muons are observed, with an expected background of $0.3\ifmmode\pm\else\textpm\fi{}0.3(\mathrm{stat}{)}_{\ensuremath{-}0.3}^{+0.4}(\mathrm{syst})$ events. The cross section measured in a phase-space region with good detector acceptance and for dilepton masses within the range 66 to 116 GeV is ${\ensuremath{\sigma}}_{ZZ\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}}^{\mathrm{fid}}={19.4}_{\ensuremath{-}5.2}^{+6.3}(\mathrm{stat}{)}_{\ensuremath{-}0.7}^{+0.9}(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.7(\mathrm{lumi})\text{ }\text{ }\mathrm{fb}$. The resulting total cross section for on-shell $ZZ$ production, ${\ensuremath{\sigma}}_{ZZ}^{\mathrm{tot}}={8.5}_{\ensuremath{-}2.3}^{+2.7}(\mathrm{stat}{)}_{\ensuremath{-}0.3}^{+0.4}(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.3(\mathrm{lumi})\text{ }\text{ }\mathrm{pb}$, is consistent with the standard model expectation of ${6.5}_{\ensuremath{-}0.2}^{+0.3}\text{ }\text{ }\mathrm{pb}$ calculated at the next-to-leading order in QCD. Limits on anomalous neutral triple gauge boson couplings are derived.