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Fornengo, N., Lineros, R. A., Regis, M., & Taoso, M. (2011). Possibility of a Dark Matter Interpretation for the Excess in Isotropic Radio Emission Reported by ARCADE. Phys. Rev. Lett., 107(27), 271302–5pp.
Abstract: The ARCADE 2 Collaboration has recently measured an isotropic radio emission which is significantly brighter than the expected contributions from known extra-galactic sources. The simplest explanation of such excess involves a "new'' population of unresolved sources which become the most numerous at very low (observationally unreached) brightness. We investigate this scenario in terms of synchrotron radiation induced by weakly interacting massive particle (WIMP) annihilations or decays in extra-galactic halos. Intriguingly, for light-mass WIMPs with a thermal annihilation cross section, the level of expected radio emission matches the ARCADE observations.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for Dilepton Resonances in pp Collisions at sqrt(s) = 7 TeV with the ATLAS Detector. Phys. Rev. Lett., 107(27), 272002–19pp.
Abstract: This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at sqrt(s) = 7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21) fb(-1) in the e(+)e(-) (mu(+)mu(-)) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C. L. on the cross section times branching fraction of Z' resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z' boson is set. A Randall-Sundrum graviton with coupling k/(M) over bar Pl = 0.1 is excluded at 95% C. L. for masses below 1.63 TeV.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Measurement of the ZZ Production Cross Section and Limits on Anomalous Neutral Triple Gauge Couplings in Proton-Proton Collisions at root s=7 TeV with the ATLAS Detector. Phys. Rev. Lett., 108(4), 041804–18pp.
Abstract: A measurement of the ZZ production cross section in proton-proton collisions at root s = 7 TeV using data corresponding to an integrated luminosity of 1.02 fb(-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 +/- 0.3(stat)(-0.3)(+0.4)(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 sigma(fid)(ZZ -> l+l-l+l-) = 19.4(-5.2)(+6.3)(stat)(-0.7)(+0.9)(syst) +/- 0.7(lumi) fb. The resulting total cross section for on-shell ZZ production, sigma(tot)(ZZ) = 8.5(-2.3)(+2.7)(stat)(-0.3)(+0.4)(syst) +/- 0.3(lumi) pb, is consistent with the standard model expectation of 6.5(-0.2)(+0.3) pb calculated at the next-to-leading order in QCD. Limits on anomalous neutral triple gauge boson couplings are derived.
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Iocco, F., Taoso, M., Leclercq, F., & Meynet, G. (2012). Main Sequence Stars with Asymmetric Dark Matter. Phys. Rev. Lett., 108(6), 061301–5pp.
Abstract: We study the effects of feebly or nonannihilating weakly interacting dark matter (DM) particles on stars that live in DM environments denser than that of our Sun. We find that the energy transport mechanism induced by DM particles can produce unusual conditions in the cores of main sequence stars, with effects which can potentially be used to probe DM properties. We find that solar mass stars placed in DM densities of rho(chi) >= 10(2) GeV/cm(3) are sensitive to spin-dependent scattering cross section sigma(SD) >= 10(-37) cm(2) and a DM particle mass as low as m(chi) = 5 GeV, accessing a parameter range weakly constrained by current direct detection experiments.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for New Phenomena in t(t)overbar Events with Large Missing Transverse Momentum in Proton-Proton Collisions at root s=7 TeV with the ATLAS Detector. Phys. Rev. Lett., 108(4), 041805–18pp.
Abstract: A search for new phenomena in t (t) over bar events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1: 04 fb(-1) of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb for a top-partner mass of 420 GeVand a neutral particle mass less than 10 GeV. In a model of exotic fourth generation quarks, toppartner masses are excluded up to 420 GeV and neutral particle masses up to 140 GeV.
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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2012). Measurements of the Angular Distributions in the Decays B -> K-(*)mu(+)mu(-) at CDF. Phys. Rev. Lett., 108(8), 081807–8pp.
Abstract: We report an indirect search for nonstandard model physics using the flavor-changing neutral current decays B -> K-(*)mu(+)mu(-). We reconstruct the decays and measure their angular distributions, as a function of q(2) = M(mu mu)(2)c(2), where M-mu μis the dimuon mass, in p (P) over bar collisions at root s = 1.96 Tev using a data sample corresponding to an integrated luminosity of 6.8 fb(-1). The transverse polarization asymmetry A(T)((2)) and the time-reversal-odd charge-and-parity asymmetry A(im) are measured for the first time, together with the K* longitudinal polarization fraction F-L and the muon forward-backward asymmetry A(FB) for the decays B-0 -> K*(0)mu(+)mu(-) and B -> K*(+)mu(+)mu(-). The B -> K*mu(+)mu(-) forward-backward asymmetry in the most sensitive kinematic regime, 1 <= q(2) < 6 GeV2/c(2), is measured to be A(FB) 0.29(-0.23)(+0.20) (stat) +/- 0.07 (syst), the most precise result to date. No deviations from the standard model predictions are observed.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for the Standard Model Higgs Boson in the Diphoton Decay Channel with 4.9 fb(-1) of pp Collision Data at root s=7 TeV with ATLAS. Phys. Rev. Lett., 108(11), 111803–19pp.
Abstract: A search for the standard model Higgs boson is performed in the diphoton decay channel. The data used correspond to an integrated luminosity of 4.9 fb(-1) collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of root s = 7 TeV. In the diphoton mass range 110-150 GeV, the largest excess with respect to the background-only hypothesis is observed at 126.5 GeV, with a local significance of 2.8 standard deviations. Taking the look-elsewhere effect into account in the range 110-150 GeV, this significance becomes 1.5 standard deviations. The standard model Higgs boson is excluded at 95% confidence level in the mass ranges of 113-115 GeV and 134.5-136 GeV.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for the Higgs Boson in the H -> WW(*()) -> l(+)vl(-)(v)over-bar Decay Channel in pp Collisions at root s=7 TeV with the ATLAS Detector. Phys. Rev. Lett., 108(11), 111802–19pp.
Abstract: A search for the Higgs boson has been performed in the H -> WW(*()) -> l+vl-(v) over bar channel (l = e/mu) with an integrated luminosity of 2.05 fb(-1) of pp collisions at root s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 110 GeV< m(H) < 300 GeV. The observations exclude the presence of a standard model Higgs boson with a mass 145 < m(H) < 206 GeV at 95% confidence level.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Observation of a New chi(b) State in Radiative Transitions to Y(1S) and Y(2S) at ATLAS. Phys. Rev. Lett., 108(15), 152001–17pp.
Abstract: The chi(b)(np) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at root s=7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb(-1), these states are reconstructed through their radiative decays to Y(1S,2S) with Y ->mu(+)mu(-). In addition to the mass peaks corresponding to the decay modes chi(b)(1P,2P)-> Y(1S)gamma, a new structure centered at a mass of 10.530 +/- 0.005(stat)+/- 0.009(syst) GeV is also observed, in both the Y(1S)gamma and Y(2S)gamma decay modes. This structure is interpreted as the chi(b)(3P) system.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for Scalar Bottom Quark Pair Production with the ATLAS Detector in pp Collisions at root s=7 TeV. Phys. Rev. Lett., 108(18), 181802–18pp.
Abstract: The results of a search for pair production of the scalar partners of bottom quarks in 2: 05 fb(-1) of pp collisions at root s = 7 TeV using the ATLAS experiment are reported. Scalar bottom quarks are searched for in events with large missing transverse momentum and two jets in the final state, where both jets are identified as originating from a bottom quark. In an R-parity conserving minimal supersymmetric scenario, assuming that the scalar bottom quark decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits are obtained in the (b) over tilde (1) – (chi) over tilde (0)(1) mass plane such that for neutralino masses below 60 GeV scalar bottom masses up to 390 GeV are excluded.
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