208 research outputs found

    Measurement of Mass and Width of the W Boson at LEP

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    We report on measurements of the mass and total decay width of the W boson with the L3 detector at LEP. W-pair events produced in e+e−\mathrm{e^+e^-} interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of 76.7 pb−1^{-1}. Combining all final states in W-pair production, the mass and total decay width of the W boson are determined to be MW=80.61±0.15\mathrm{M_W}=80.61\pm0.15 GeV and ΓW=1.97±0.38\Gamma_{\mathrm{W}}=1.97\pm0.38 GeV, respectively

    Search for Heavy Neutral and Charged Leptons in e+^+e−^- Annihilation at s\sqrt{s} = 183 and 189 GeV

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    A search for unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed at center-of-mass energies s\sqrt{s} = 183 and 189 GeV with the L3 detector at LEP. No evidence for their existence is found. We exclude neutral heavy leptons which couple to the electron, muon or tau family, of the Dirac type for masses below 92.4, 93.3 and 83.3 GeV, and of the Majorana type for masses below 81.8, 84.1 and 73.5 GeV, respectively. We exclude unstable charged heavy leptons for masses below 93.9 GeV for a wide range of the associated neutral heavy lepton mass. If the unstable charged heavy lepton decays to a light neutrino, we exclude masses below 92.4 GeV. The production of stable charged heavy leptons with mass less than 93.5 GeV is also excluded

    Measurement of an Elongation of the Pion Source in Z Decays

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    We measure Bose-Einstein correlations between like-sign charged pion pairs in hadronic Z decays with the L3 detector at LEP. The analysis is performed in three dimensions in the longitudinal center-of-mass system. The pion source is found to be elongated along the thrust axis with a ratio of transverse to longitudinal radius of 0.81±0.02−0.19+0.030.81\pm 0.02 ^{+0.03}_{-0.19}

    2q36.3 is associated with prognosis for oestrogen receptor-negative breast cancer patients treated with chemotherapy

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    Large population-based registry studies have shown that breast cancer prognosis is inherited. Here we analyse single-nucleotide polymorphisms (SNPs) of genes implicated in human immunology and inflammation as candidates for prognostic markers of breast cancer survival involving 1,804 oestrogen receptor (ER)-negative patients treated with chemotherapy (279 events) from 14 European studies in a prior large-scale genotyping experiment, which is part of the Collaborative Oncological Gene-environment Study (COGS) initiative. We carry out replication using Asian COGS samples (n=522, 53 events) and the Prospective Study of Outcomes in Sporadic versus Hereditary breast cancer (POSH) study (n=315, 108 events). Rs4458204-A near CCL20 (2q36.3) is found to be associated with breast cancer-specific death at a genome-wide significant level (n=2,641, 440 events, combined allelic hazard ratio (HR)=1.81 (1.49-2.19); P for trend=1.90 × 10 Ăą ̂'9). Such survival-associated variants can represent ideal targets for tailored therapeutics, and may also enhance our current prognostic prediction capabilities

    Search for Heavy Isosinglet Neutrinos in e+^+e−^- Annihilation at 130<s<<\sqrt{s}<189 GeV

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    A search for heavy neutrinos that are isosinglets under the standard SU(2)LSU(2)_L gauge group is made at center-of-mass energies 130 <s<< \sqrt{s} < 189 GeV with the L3 detector at LEP. Such heavy neutrinos are expected in many extensions of the Standard Model. The search is performed for the first generation heavy singlet neutrino, Ne\mathrm{N}_e, through the decay mode Ne→e+W\mathrm{N}_e \to \mathrm{e} + \mathrm{W}. We set upper limits on the mixing parameter between the heavy and light neutrino for the heavy neutrino mass range from 80 GeV to 185 GeV

    Inclusive Sigma+ and Sigma0 Production in Hadronic Z Decays

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    We report on measurements of the inclusive production rate of Sigma+ and Sigma0 baryons in hadronic Z decays collected with the L3 detector at LEP. The Sigma+ baryons are detected through the decay Sigma+ -> p pi0, while the Sigma0 baryons are detected via the decay mode Sigma0 -> Lambda gamma. The average numbers of Sigma+ and Sigma0 per hadronic Z decay are measured to be: < N_Sigma+ > + = 0.114 +/- 0.011 (stat) +/- 0.009 (syst), < N_Sigma0 > + = 0.095 +/- 0.015 (stat) +/- 0.013 (syst). These rates are found to be higher than the predictions from Monte Carlo hadronization models and analytical parameterizations of strange baryon production

    Galaxy Clusters Associated with Short GRBs. II. Predictions for the Rate of Short GRBs in Field and Cluster Early-Type Galaxies

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    We determine the relative rates of short GRBs in cluster and field early-type galaxies as a function of the age probability distribution of their progenitors, P(\tau) \propto \tau^n. This analysis takes advantage of the difference in the growth of stellar mass in clusters and in the field, which arises from the combined effects of the galaxy stellar mass function, the early-type fraction, and the dependence of star formation history on mass and environment. This approach complements the use of the early- to late-type host galaxy ratio, with the added benefit that the star formation histories of early-type galaxies are simpler than those of late-type galaxies, and any systematic differences between progenitors in early- and late-type galaxies are removed. We find that the ratio varies from R(cluster)/R(field) ~ 0.5 for n = -2 to ~ 3 for n = 2. Current observations indicate a ratio of about 2, corresponding to n ~ 0 - 1. This is similar to the value inferred from the ratio of short GRBs in early- and late-type hosts, but it differs from the value of n ~ -1 for NS binaries in the Milky Way. We stress that this general approach can be easily modified with improved knowledge of the effects of environment and mass on the build-up of stellar mass, as well as the effect of globular clusters on the short GRB rate. It can also be used to assess the age distribution of Type Ia supernova progenitors.Comment: ApJ accepted versio

    High mass photon pairs in ℓ+ℓ−γγ events at LEP

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    A determination of electroweak parameters from Z0→Ό+ÎŒ- (Îł)

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