LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Search for long-lived scalar particles in B+-> K+chi(mu(+) mu(-)) decays. Phys. Rev. D, 95(7), 071101–9pp.
Abstract: A search for a long-lived scalar particle. is performed, looking for the decay B+ -> K+chi with chi ->mu(+)mu(-) pp collision data corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment at center-of-mass energies of root s = 7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250 < m(chi) < 4700 MeV/c(2) and lifetime 0.1 < tau(chi) < 1000 ps. Upper limits on the branching fraction B(B-broken vertical bar -> K-broken vertical bar chi(mu(vertical bar) mu(-))) at 95% confidence level are set as a function of m(chi) and tau(chi), varying between 2 x 10(-10) and 10(-7). These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.
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T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Izmaylov, A., Novella, P., & Sorel, M. (2017). Combined Analysis of Neutrino and Antineutrino Oscillations at T2K. Phys. Rev. Lett., 118(15), 151801–9pp.
Abstract: T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino-and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482 x 10(20) protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 mu-like events, and 7.471 x 10(20) protons on target in antineutrino mode, which yielded 4 e-like and 66 mu-like events. Reactor measurements of sin(2) 2 theta(13) have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase delta(CP) spans the range (-3.13,-0.39) for normal mass ordering. The CP conservation hypothesis (delta(CP) = 0, pi) is excluded at 90% C.L.
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FLAG Working Group(Aoki, S. et al), & Della Morte, M. (2017). Review of lattice results concerning low-energy particle physics. Eur. Phys. J. C, 77(2), 112–228pp.
Abstract: We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle-physics community. More specifically, we report on the determination of the light-quark masses, the form factor f(+)(0), arising in the semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK / f pi and its consequences for the CKM matrix elements V-us and V-ud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2) L x SU(2) R and SU(3) L x SU(3) R Chiral Perturbation Theory. We review the determination of the B-K parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the StandardModel. The latter quantities are an addition compared to the previous review. For the heavy-quark sector, we provide results for m(c) and m(b) (also new compared to the previous review), as well as those for D- and B-meson-decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. Finally, we review the status of lattice determinations of the strong coupling constant alpha(s).
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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. (2017). Measurement of the prompt J/psi pair production cross-section in pp collisions at root s=8 TeV with the ATLAS detector. Eur. Phys. J. C, 77(2), 76–34pp.
Abstract: The production of two prompt J/psi mesons, each with transverse momenta p(T) > 8.5 GeV and rapidity vertical bar y vertical bar < 2.1, is studied using a sample of proton-proton collisions at root s = 8 TeV, corresponding to an integrated luminosity of 11.4 fb(-1) collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised J/psi production, is measured as a function of the transverse momentum of the lower-p(T) J/psi meson, di-J/psi p(T) and mass, the difference in rapidity between the two J/psi mesons, and the azimuthal angle between the two J/psi mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two J/psi mesons. The total and double parton scattering cross-sections are compared with predictions. The effective cross-section of double parton scattering is measured to be sigma(eff) = 6.3 +/- 1.6(stat) +/- 1.0(syst) mb.
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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. (2017). Search for triboson (WWW -/+)-W-+/-W-+/- production in pp collisions at root s=8 TeV with the ATLAS detector. Eur. Phys. J. C, 77(3), 141–28pp.
Abstract: This paper reports a search for triboson (WWW -/+)-W-+/--W-+/- production in two decay channels ((WWW -/+)-W-+/--W-+/- -> l(+/-)vl(+/-)vl(-/+) v and (WWW -/+)-W-+/--W-+/- -> l(+/-)vl(+/-)vjj with l = e, mu) in proton-proton collision data corresponding to an integrated luminosity of 20.3 fb(-1) at a centre-of-mass energy of 8 TeV with the ATLAS detector at the Large Hadron Collider. Events with exactly three charged leptons, or two leptons with the same electric charge in association with two jets, are selected. The total number of events observed in data is consistent with the Standard Model (SM) predictions. The observed 95% confidence level upper limit on the (WWW -/+)-W-+/--W-+/- production cross section is found to be 730 fb with an expected limit of 560 fb in the absence of SM (WWW -/+)-W-+/--W-+/- production. Limits are also set on WWWW anomalous quartic gauge couplings.
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