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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of forward J/psi production cross-sections in pp collisions at root s=13 TeV. J. High Energy Phys., 10(10), 172–29pp.
Abstract: The production of J/psi mesons in proton-proton collisions at a centre-of-mass energy of root s = 13 TeV is studied with the LHCb detector. Cross-section measurements are performed as a function of the transverse momentum p(T) and the rapidity y of the J/psi meson in the region p(T) < 14 GeV/c and 2.0 < y < 4.5, for both prompt J/psi mesons and J/psi mesons from b-hadron decays. The production cross-sections integrated over the kinematic coverage are 15.30 +/- 0.03 +/- 0.86 μb for prompt J/psi and 2.34 +/- 0.01 +/- 0.13 μb for J/psi from b-hadron decays, assuming zero polarization of the J/psi meson. The first uncertainties are statistical and the second systematic. The cross-section reported for J/psi mesons from b-hadron decays is used to extrapolate to a total b<(b)over bar> cross-section. The ratios of the cross-sections with respect to root s = 8 TeV are also determined.
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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). Constraints on new phenomena via Higgs boson couplings and invisible decays with the ATLAS detector. J. High Energy Phys., 11(11), 206–52pp.
Abstract: The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb(-1) of pp collision data at root S = 7 TeV and 20.3 fb(-1) at root s = 8 TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the gamma gamma, ZZ, WW, Z gamma, bb, tau tau, and μμdecay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the gamma gamma and ZZ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of m(A) > 370 GeV in the “hMSSM” simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with W/Z (Z -> ll, W/Z -> jj) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter.
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Helo, J. C., & Hirsch, M. (2015). LHC dijet constraints on double beta decay. Phys. Rev. D, 92(7), 073017–7pp.
Abstract: We use LHC dijet data to derive constraints on neutrinoless double beta decay. Upper limits on cross sections for the production of “exotic” resonances, such as a right-handed W boson or a diquark, can be converted into lower limits on the double beta decay half-life for fixed choices of other parameters. Constraints derived from run-I data are already surprisingly strong and complementary to results from searches using same-sign dileptons plus jets. For the case of the left-right symmetric model, in case no new resonance is found in future runs of the LHC and assuming g(L) = g(R), we estimate a lower limit on the double beta decay half-life larger than 10(27) yr can be derived from future dijet data, except in the window of relatively light right-handed neutrino masses in the range 0.5 MeV to 50 GeV. Part of this mass window will be tested in the upcoming SHiP experiment. We also discuss current and future limits on possible scalar diquark contributions to double beta decay that can be derived from dijet data.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). First measurement of the differential branching fraction and CP asymmetry of the B-+/- -> pi(+/-)mu(+/-)mu(-) decay. J. High Energy Phys., 10(10), 034–21pp.
Abstract: The differential branching fraction with respect to the dimuon invariant mass squared, and the CP asymmetry of the B-+/- -> pi(+/-)mu(+/-)mu(-) decay are measured for the first time. The CKM matrix elements vertical bar V-td vertical bar, and vertical bar V-ts vertical bar, and the ratio vertical bar V-td/V-ts vertical bar are determined. The analysis is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The total branching fraction and CP asymmetry of B-+/- -> pi(+/-)mu(+/-)mu(-) decays are measured to be B(B-+/- -> pi(+/-)mu(+/-)mu(-)) = (1.83 +/- 0.24 +/- 0.05) x 10(-8) and A(cp)(B-+/- -> pi(+/-)mu(+/-)mu(-)) = -0.11 +/- 0.12 +/- 0.01, where the first uncertainties are statistical and the second are systematic. These are the most precise measurements of these observables to date, and they are compatible with the predictions of the Standard Model.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of CP violation parameters and polarisation fractions in B-s(0) -> J/psi(K)over-bar*(0) decays. J. High Energy Phys., 11(11), 082–38pp.
Abstract: The first measurement of CP asymmetries in the decay B-s(0) -> J/psi(K) over bar*(892)(0) and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb (-1) of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Together with constraints from B-0 -> J/psi rho(0), the results are used to constrain additional contributions due to penguin diagrams in the CP-violating phase phi(s), measured through B-s(0) decays to charmonium.
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