ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Searches for heavy long-lived sleptons and R-hadrons with the ATLAS detector in pp collisions at root s=7 TeV. Phys. Lett. B, 720(4-5), 277–308.
Abstract: A search for long-lived particles is performed using a data sample of 4.7 fb(-1) from proton-proton collisions at a centre-of-mass energy. root s = 7 TeV collected by the ATLAS detector at the LHC. No excess is observed above the estimated background and lower limits, at 95% confidence level, are set on the mass of the long-lived particles in different scenarios, based on their possible interactions in the inner detector, the calorimeters and the muon spectrometer. Long-lived staus in gauge-mediated SUSY-breaking models are excluded up to a mass of 300 GeV for tan beta = 5-20. Directly produced long-lived sleptons are excluded up to a mass of 278 GeV. R-hadrons, composites of gluino (stop, sbottom) and light quarks, are excluded up to a mass of 985 GeV (683 GeV, 612 GeV) when using a generic interaction model. Additionally two sets of limits on R-hadrons are obtained that are less sensitive to the interaction model for R-hadrons. One set of limits is obtained using only the inner detector and calorimeter observables, and a second set of limits is obtained based on the inner detector alone.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Search for single b*-quark production with the ATLAS detector at root s=7 TeV. Phys. Lett. B, 721(4-5), 171–189.
Abstract: The results of a search for an excited bottom-quark b* in pp collisions at root s = 7 TeV, using 4.7 fb(-1) of data collected by the ATLAS detector at the LHC are presented. In the model studied, a single b*-quark is produced through a chromomagnetic interaction and subsequently decays to a W boson and a top quark. The search is performed in the dilepton and lepton + jets final states, which are combined to set limits on b*-quark couplings for a range of b*-quark masses. For a benchmark with unit size chromomagnetic and Standard Model-like electroweak b* couplings, b* quarks with masses less than 870 GeV are excluded at the 95% credibility level.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Search for displaced muonic lepton jets from light Higgs boson decay in proton-proton collisions at root s=7 TeV with the ATLAS detector. Phys. Lett. B, 721(1-3), 32–50.
Abstract: A search is performed for collimated muon pairs displaced from the primary vertex produced in the decay of long-lived neutral particles in proton-proton collisions at root s = 7 TeV centre-of-mass energy, with the ATLAS detector at the LHC. In a 1.9 fb(-1) event sample collected during 2011, the observed data are consistent with the Standard Model background expectations. Limits on the product of the production cross section and the branching ratio of a Higgs boson decaying to hidden-sector neutral long-lived particles are derived as a function of the particles' mean lifetime.
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Nieves, J., Ruiz Simo, I., & Vicente Vacas, M. J. (2013). Two particle-hole excitations in charged current quasielastic antineutrino-nucleus scattering. Phys. Lett. B, 721(1-3), 90–93.
Abstract: We evaluate the quasielastic and multinucleon contributions to the antineutrino-nucleus scattering cross section and compare our results with the recent MiniBooNE data. We use a local Fermi gas model that includes RPA correlations and gets the multinucleon part from a systematic many body expansion of the W boson selfenergy in the nuclear medium. The same model had been quite successful for the neutrino cross section and contains no new parameters. We have also analyzed the relevance of 2p2h events for the antineutrino energy reconstruction.
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Botella, F. J., Branco, G. C., & Rebelo, M. N. (2013). Invariants and flavour in the general Two Higgs Doublet Model. Phys. Lett. B, 722(1-3), 76–82.
Abstract: The flavour structure of the general Two Higgs Doublet Model (2HDM) is analysed and a detailed study of the parameter space is presented, showing that flavour mixing in the 2HDM can be parametrized by various unitary matrices which arise from the misalignment in flavour space between pairs of various Hermitian flavour matrices which can be constructed within the model. This is entirely analogous to the generation of the CKM matrix in the Standard Model (SM). We construct weak basis invariants which can give insight into the physical implications of any flavour model, written in an arbitrary weak basis (WB) in the context of 2HDM. We apply this technique to two special cases, models with MFV and models with NNI structures. In both cases non-trivial CP-odd WB invariants arise in a mass power order much smaller than what one encounters in the SM, which can have important implications for baryogenesis in the framework of the general 2HDM.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Search for a heavy narrow resonance decaying to e mu, e tau, or μtau with the ATLAS detector in root s=7 TeV pp collisions at the LHC. Phys. Lett. B, 723(1-3), 15–32.
Abstract: This Letter presents the results of a search for a heavy particle decaying into an e(+/-)mu(+/-), e(+/-)tau(+/-), or mu(+/-)tau(+/-) final state in pp collisions at root s = 7 TeV. The data were recorded with the ATLAS detector at the LHC during 2011 and correspond to an integrated luminosity of 4.6 fb(-1). No significant excess above the Standard Model expectation is observed, and exclusions at 95% confidence level are placed on the cross section times branching ratio for the production of an R-parity-violating supersymmetric tau sneutrino. For a sneutrino mass of 500 (2000) GeV, the observed limits on the production cross section times branching ratio are 3.2 (1.4) fb, 42 (17) fb, and 40 (18) fb for the e mu, e tau, and μtau modes, respectively. These results considerably extend constraints from Tevatron experiments.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Search for direct CP violation in D-0 -> h(-)h(+) modes using semileptonic B decays. Phys. Lett. B, 723(1-3), 33–43.
Abstract: A search for direct CP violation in D-0 -> h(-)h(+) (where h = K or pi) is presented using data corresponding to an integrated luminosity of 1.0 fb(-1) collected in 2011 by LHCb in pp collisions at a centre-of-mass energy of 7 TeV. The analysis uses D-0 mesons produced in inclusive semileptonic b-hadron decays to the D-0 μX final state, where the charge of the accompanying muon is used to tag the flavour of the D-0 meson. The difference in the CP-violating asymmetries between the two decay channels is measured to be Delta A(CP) = A(CP)(K-K+) – A(CP)(pi(-)pi(+)) = (0.49 +/- 0.30 (stat) +/- 0.14 (syst))%. This result does not confirm the evidence for direct CP violation in the charm sector reported in other analyses.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Observation of the suppressed ADS modes B-+/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)K-+/- and B-+/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)pi(+/-). Phys. Lett. B, 723(1-3), 44–53.
Abstract: An analysis of and B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays is presented where the D meson is reconstructed in the four-body final state K-+/-pi(-/+)pi(+)pi(-). Using LHCb data corresponding to an integrated luminosity of 1.0 fb(-1), first observations are made of the suppressed ADS modes B-+/- ->[pi K-+/-(-/+)pi(+)pi(-)](D)K-+/- and B +/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)pi(+/-) with a significance of 5.1 sigma and greater than 10 sigma, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B-+/- -> DK +/- amplitudes is determined to be r(B)(K) = 0.097 +/- 0.011.
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Bernal, N., Boehm, C., Palomares-Ruiz, S., Silk, J., & Toma, T. (2013). Observing Higgs boson production through its decay into gamma-rays: A messenger for dark matter candidates. Phys. Lett. B, 723(1-3), 100–106.
Abstract: In this Letter, we study the gamma-ray signatures subsequent to the production of a Higgs boson in space by dark matter annihilations. We investigate the cases where the Higgs boson is produced at rest or slightly boosted and show that such configurations can produce characteristic bumps in the gamma-ray data. These results are relevant in the case of the Standard Model-like Higgs boson provided that the dark matter mass is about 63 GeV, 109 GeV or 126 GeV, but can be generalized to any other Higgs boson masses. Here, we point out that it may be worth looking for a 63 GeV line since it could be the signature of the decay of a Standard Model-like Higgs boson produced in space, as in the case of a di-Higgs final state if m chi similar or equal to 126 GeV. We show that one can set generic constraints on the Higgs boson production rates using its decay properties. In particular, using the Fermi-LAT data from the galactic center, we find that the dark matter annihilation cross section into gamma+ a Standard Model-like Higgs boson produced at rest or near rest cannot exceed (sigma nu) similar to a few 10(-25) cm(3)/s or (sigma-nu) similar to a few 10(-27) cm(3)/s respectively, providing us with information on the Higgs coupling to the dark matter particle. We conclude that Higgs bosons can indeed be used as messengers to explore the dark matter mass range.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Search for long-lived, multi-charged particles in pp collisions at root s=7 TeV using the ATLAS detector. Phys. Lett. B, 722(4-5), 305–323.
Abstract: A search for highly ionising, penetrating particles with electric charges from vertical bar q vertical bar = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at root s = 7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb(-1), are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell-Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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