ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., Ferrer, A., et al. (2015). Measurement of differential J/psi production cross sections and forward-backward ratios in p plus Pb collisions with the ATLAS detector. Phys. Rev. C, 92(3), 034904–23pp.
Abstract: Measurements of differential cross sections for J/psi production in p + Pb collisions at root S-NN= 5.02 TeV at the CERN Large Hadron Collider with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb(-1). The J/psi mesons are reconstructed in the dimuon decay channel over the transverse momentum range 8 < PT < 30 GeV and over the center-of-mass rapidity range -2.87 < y* < 1.94. Prompt J/psi are separated from J/psi resulting from b-hadron decays through an analysis of the distance between the J/psi decay vertex and the event primary vertex. The differential cross section for production of nonprompt J/psi is compared to a FONLL calculation that does not include nuclear effects. Forward-backward production ratios are presented and compared to theoretical predictions. These results complement previously published results by covering a region of higher transverse momentum and more central rapidity. They thus constrain the kinematic dependence of nuclear modifications of charmonium and b-quark production in p + Pb collisions.
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XENON Collaboration(Aprile, E. et al), & Orrigo, S. E. A. (2015). Search for Event Rate Modulation in XENON100 Electronic Recoil Data. Phys. Rev. Lett., 115(9), 091302–6pp.
Abstract: We have searched for periodic variations of the electronic recoil event rate in the (2-6) keVenergy range recorded between February 2011 and March 2012 with the XENON100 detector, adding up to 224.6 live days in total. Following a detailed study to establish the stability of the detector and its background contributions during this run, we performed an unbinned profile likelihood analysis to identify any periodicity up to 500 days. We find a global significance of less than 1 sigma for all periods, suggesting no statistically significant modulation in the data. While the local significance for an annual modulation is 2.8 sigma, the analysis of a multiple-scatter control sample and the phase of the modulation disfavor a dark matter interpretation. The DAMA/LIBRA annual modulation interpreted as a dark matter signature with axial-vector coupling of weakly interacting massive particles to electrons is excluded at 4.8 sigma.
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Sekihara, T., & Oset, E. (2015). Investigating the nature of light scalar mesons with semileptonic decays of D mesons. Phys. Rev. D, 92(5), 054038–17pp.
Abstract: We study the semileptonic decays of D-s(+), D+, and D-0 mesons into the light scalar mesons [f(0)(500), K-0(*)(800), f(0)(980), and a(0)(980)] and the light vector mesons [rho(770), omega(782), K-*(892), and phi(1020)]. With the help of a chiral unitarity approach in coupled channels, we compute the branching fractions for scalar meson processes of the semileptonic D decays in a simple way. Using current known values of the branching fractions, we make predictions for the branching fractions of the semileptonic decay modes with other scalar and vector mesons. Furthermore, we calculate the pi(+)pi(-), pi eta, pi K, and K+K- invariant mass distributions in the semileptonic decays of D mesons, which will help us clarify the nature of the light scalar mesons.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Search for photonic signatures of gauge-mediated supersymmetry in 8 TeV pp collisions with the ATLAS detector. Phys. Rev. D, 92(7), 072001–35pp.
Abstract: A search is presented for photonic signatures motivated by generalized models of gauge-mediated supersymmetry breaking. This search makes use of 20.3 fb(-1) of proton-proton collision data at root s = 8 TeV recorded by the ATLAS detector at the LHC, and explores models dominated by both strong and electroweak production of supersymmetric partner states. Four experimental signatures incorporating an isolated photon and significant missing transverse momentum are explored. These signatures include events with an additional photon, lepton, b-quark jet, or jet activity not associated with any specific underlying quark flavor. No significant excess of events is observed above the Standard Model prediction and model-dependent 95% confidence-level exclusion limits are set.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of the branching fraction ratio B(B-c(+) -> psi(2S)pi(+))/B(B-c(+) -> J/psi pi(+)). Phys. Rev. D, 92(7), 072007–10pp.
Abstract: Using pp collision data collected by LHCb at center-of-mass energies root s = 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1), the ratio of the branching fraction of the B-c(+) -> psi(2S)pi(+) decay relative to that of the B-c(+) -> J/psi pi(+) decay is measured to be 0.268 +/- 0.032(stat) +/- 0.007(syst) +/- 0.006(BF). The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainties on the branching fractions of the J/psi -> mu(+)mu(-) and psi(2S) -> mu(+)mu(-) decays. This measurement is consistent with the previous LHCb result, and the statistical uncertainty is halved.
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