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Cottin, G., Helo, J. C., & Hirsch, M. (2018). Searches for light sterile neutrinos with multitrack displaced vertices. Phys. Rev. D, 97(5), 055025–6pp.
Abstract: We study discovery prospects for long-lived sterile neutrinos at the LHC with multitrack displaced vertices, with masses below the electroweak scale. We reinterpret current displaced vertex searches making use of publicly available, parametrized selection efficiencies for modeling the detector response to displaced vertices. We focus on the production of right-handed WR bosons and neutrinos N in a left-right symmetric model, and find poor sensitivity. After proposing a different trigger strategy ( considering the prompt lepton accompanying the neutrino displaced vertex) and optimized cuts in the invariant mass and track multiplicity of the vertex, we find that the LHC with root s = 13 TeV and 300 fb(-1) is able to probe sterile neutrino masses between 10 GeV < m(N) < 20 GeV ( for a right-handed gauge boson mass of 2 TeV < m(WR) < 3.5 TeV). To probe higher masses up to m(N) similar to 30 GeV and m(WR) < 5 TeV, 3000 fb(-1) will be needed. This work joins other efforts in motivating dedicated experimental searches to target this low sterile neutrino mass region.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2018). Searches for heavy ZZ and ZW resonances in the llqq and vvqq final states in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 03(3), 009–53pp.
Abstract: This paper reports searches for heavy resonances decaying into ZZ or ZW using data from proton-proton collisions at a centre-of-mass energy of root s – 13 TeV. The data, corresponding to an integrated luminosity of 36.1 fb(-1), were recorded with the ATLAS detector in 2015 and 2016 at the Large Hadron Collider. The searches are performed in final states in which one Z boson decays into either a pair of light charged leptons (electrons and muons) or a pair of neutrinos, and the associated W boson or the other Z boson decays hadronically. No evidence of the production of heavy resonances is observed. Upper bounds on the production cross sections of heavy resonances times their decay branching ratios to ZZ or ZW are derived in the mass range 300-5000 GeV within the context of Standard Model extensions with additional Higgs bosons, a heavy vector triplet or warped extra dimensions. Production through gluon-gluon fusion, Drell-Yan or vector-boson fusion are considered, depending on the assumed model.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2018). Searches for exclusive Higgs and Z boson decays into J/psi gamma, psi (2S) gamma, and Upsilon(nS) gamma at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 786, 134–155.
Abstract: Searches for the exclusive decays of the Higgs and Z bosons into a J/psi, psi(2S), or Upsilon(nS) (n = 1, 2, 3) meson and a photon are performed with a pp collision data sample corresponding to an integrated luminosity of 36.1 fb(-1) collected at root s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above the expected backgrounds, and 95% confidence- level upper limits on the branching fractions of the Higgs boson decays to J/psi gamma, psi(2S) gamma and Upsilon(nS) gamma of 3.5 x 10(-4), 2.0 x 10(-3), and (4.9, 5.9, 5.7) x 10(-4), respectively, are obtained assuming Standard Model production. The corresponding 95% confidence-level upper limits for the branching fractions of the Z boson decays are 2.3 x 10(-6), 4.5 x 10(-6) and (2.8, 1.7, 4.8) 10(-6), respectively.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2018). Search for WW/WZ resonance production in lvqq final states in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 03(3), 042–45pp.
Abstract: A search is conducted for new resonances decaying into a WW or WZ boson pair, where one W boson decays leptonically and the other W or Z boson decays hadronically. It is based on proton-proton collision data with an integrated luminosity of 36.1 fb(-1) collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of root s = 13 TeV in 2015 and 2016. The search is sensitive to diboson resonance production via vector-boson fusion as well as quark-antiquark annihilation and gluon-gluon fusion mechanisms. No significant excess of events is observed with respect to the Standard Model backgrounds. Several benchmark models are used to interpret the results. Limits on the production cross section are set for a new narrow scalar resonance, a new heavy vector-boson and a spin-2 Kaluza-Klein graviton.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Search for weakly decaying b-flavored pentaquarks. Phys. Rev. D, 97(3), 032010–11pp.
Abstract: Investigations of the existence of pentaquark states containing a single b (anti) quark decaying weakly into four specific final states J/psi K+pi(-)p, J/psi K-pi(-)p, J/psi K-pi(+)p, and J/psi phi(1020)p are reported. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) in 7 and 8 TeV pp collisions acquired with the LHCb detector. Signals are not observed and upper limits are set on the product of the production cross section times branching fraction with respect to that of the A(b)(0).
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