Initial results from the LHCb Vertex Locator Hutchcroft, D.E.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2011, Volume:
648
Journal Article
Peer reviewed
The design and initial performance of the LHCb Vertex Locator is presented; including the construction tolerances, metrology measurements and the track resolution performance in the LHC proton–proton ...collision data.
A study of the two-body decays B±→Xcc¯K±, where Xcc¯ refers to one charmonium state, is reported by the BABAR Collaboration using a data sample of 424 fb−1. The absolute determination of branching ...fractions for these decays are significantly improved compared to previous BABAR measurements. Evidence is found for the decay B+→X(3872)K+ at the 3σ level. The absolute branching fraction BB+→X(3872)K+=2.1±0.6(stat)±0.3(syst)×10−4 is measured for the first time. It follows that BX(3872)→J/ψπ+π−=(4.1±1.3)%, supporting the hypothesis of a molecular component for this resonance.
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The hadronic final states observed with the ALEPH detector at LEP in e+e- annihilation are analysed using 730 pb-1 of data collected between 91 and 209 GeV in the framework of QCD. In particular ...event-shape variables and inclusive charged particle spectra are measured. The energy evolution of quantities derived from these measurements is compared to analytic QCD predictions. The mean charged particle multiplicity, the charged particle momentum spectrum and its peak position are compared to predictions of the modified-leading-logarithmic approximation. The strong coupling constant alpha_s is determined from a fit of the QCD prediction to distributions of six event-shape variables at eight centre-of-mass energies. A study of non-perturbative power law corrections is presented
We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay Υ(3S)→e±μ∓ in a sample of 118 million ...Υ(3S) mesons from 27 fb-1 of data collected with the BABAR detector at the SLAC PEP-II e+e- collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction BΥ(3S)→e±μ∓<3.6×10-7 at 90% C. L. This result can be interpreted as a limit ΛNP/gNP2>80 TeV on the energy scale ΛNP divided by the coupling-squared gNP2 of relevant new physics (NP).
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Exotic hadrons made of five quarks (pentaquarks) are searched for in hadronic Z decays collected by the ALEPH detector at LEP. No significant signal is observed. At 95% C.L., upper limits are set on ...the production rates N of such particles and their charge-conjugate state per Z decay: NΘ(1535)+⋅BR(Θ(1535)+→pKS0)<6.2×10−4,NΞ(1862)−−⋅BR(Ξ(1862)−−→Ξ−π−)<4.5×10−4,NΞ(1862)0⋅BR(Ξ(1862)0→Ξ−π+)<8.9×10−4,NΘc(3100)0⋅BR(Θc(3100)0→D*−p)<6.3×10−4,NΘc(3100)0⋅BR(Θc(3100)0→D−p)<31×10−4.
Triple gauge-boson couplings γWW and ZWW involving single-photon, single-W and W-pair production are determined using data samples collected at LEP with the ALEPH detector at centre-of-mass energies ...between 183 and 209 GeV. The integrated luminosity used is 700 pb−1 for the single-photon measurement and 683 pb−1 for the W channels. Restricting the measurement to C- and P-conserving terms and applying local SU(2)L×U(1)Y gauge invariance, the measured values of the parameters g1Z, κγ and λγ are: g1Z=1.001±0.027(stat)±0.013(syst),κγ=0.971±0.055(stat)±0.030(syst),λγ=−0.012±0.027(stat)±0.011(syst) for single-parameter fits, where the two other parameters are fixed to their Standard Model values. Results are also presented for the cases where two or all three couplings are allowed to vary.
An additional analysis using W-pair events is performed to measure the unconstrained real and imaginary parts of all 14 triple gauge-boson couplings and to perform an indirect search for a techni-ρ resonance. No deviations from the Standard Model expectations are observed and the lower limit on the techni-ρ mass is set to 600 GeV/c2 at 95% confidence level.
Aging studies for a multi-wire proportional chamber of the LHCb muon system have been performed using the CERN Gamma Irradiation Facility. The irradiated four-gap chamber corresponds to a full-size ...prototype with
1500
cm
2
sensitive area and has been operated with an Ar/CO
2/CF
4 (40:50:10) gas mixture. A linear charge of
∼0.25
C/cm
for
100
m
anode wire length has been accumulated over a period of 6 months, which corresponds to the charge collected in
5
LHCb
years. The observed aging effects do not prohibit the use of these chambers in the LHCb experiment.
Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the ...first search for a stable, doubly strange six-quark state in ϒ→SΛover ¯Λover ¯ decays based on a sample of 90×10^{6}ϒ(2S) and 110×10^{6}ϒ(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined ϒ(2S,3S)→SΛover ¯Λover ¯ branching fraction in the range (1.2-1.4)×10^{-7} are derived for m_{S}<2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.
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