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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2014). Dalitz plot analysis of eta(c) -> K+K-eta and eta(c) -> K+K-pi(0) in two-photon interactions. Phys. Rev. D, 89(11), 112004–16pp.
Abstract: We study the processes gamma gamma -> K+K-eta and gamma gamma -> K+K-pi(0) using a data sample of 519 fb(-1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies at and near the Upsilon(nS) (n = 2, 3, 4) resonances. We observe eta(c) -> K+K-pi(0) and eta(c) -> K+K-eta decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K*(0)(1430) -> K eta decay and measure its branching fraction relative to the K pi decay mode to be R(K*(0)(1430)) = B(K*(0)(1430)-> K eta)/B(K*(0)(1430)-> K pi) = 0.092 +/- 0.025(- 0.025)(+0.010). The eta(c) -> K+K-eta and K*(0)(1430) -> K eta results correspond to the first observations of these channels. The data also show evidence for eta(c)(2S) -> K+K-pi(0) and first evidence for eta(c)(2S) -> K+K-eta.
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Barenboim, G., Bosch, C., Lopez-Ibañez, M. L., & Vives, O. (2014). Improved tau-lepton tools for Higgs boson hunting. Phys. Rev. D, 90(1), 015003–14pp.
Abstract: In this work, we use the results from Higgs searches in the gamma gamma and tau tau decay channels at LHC and indirect bounds as BR (B -> X-s gamma) to constrain the parameter space of a generic minimal supersymmetric standard model (MSSM) Higgs sector. In particular, we include the latest CMS results that look for additional Higgs states with masses up to 1 TeV. We show that the tau tau channel is the best and most accurate tool in the hunt for new Higgs states beyond the standard model. We obtain that present experimental results rule out additional neutral Higgs bosons in a generic MSSM below 300 GeV for any value of tan beta and, for instance, values of tan beta above 30 are only possible for Higgs masses above 600 GeV. ATLAS stored data have the potential to render this bound obsolete in the near future.
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Carrasco, N., Ciuchini, M., Dimopoulos, P., Frezzotti, R., Gimenez, V., Lubicz, V., et al. (2014). D-0-(D)over-bar(0) mixing in the standard model and beyond from N-f=2 twisted mass QCD. Phys. Rev. D, 90(1), 014502–9pp.
Abstract: We present the first unquenched lattice QCD results for the bag parameters controlling the short distance contribution to D meson oscillations in the standard model and beyond. We have used the gauge configurations produced by the European Twisted Mass collaboration with N-f = 2 dynamical quarks, at four lattice spacings and light meson masses in the range 280-500 MeV. Renormalization is carried out nonperturbatively with the regularization-independent momentum subtraction method. The bag-parameter results have been used to constrain new physics effects in D-0 – (D) over bar (0) mixing, to put a lower bound to the generic new physics scale and to constrain off-diagonal squark mass terms for TeV-scale supersymmetry.
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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. (2014). Search for dark matter in events with a Z boson and missing transverse momentum in pp collisions at root s=8 TeV with the ATLAS detector. Phys. Rev. D, 90(1), 012004–21pp.
Abstract: A search is presented for production of dark-matter particles recoiling against a leptonically decaying Z boson in 20.3 fb(-1) of pp collisions at root s = 8 TeV with the ATLAS detector at the Large Hadron Collider. Events with large missing transverse momentum and two oppositely charged electrons or muons consistent with the decay of a Z boson are analyzed. No excess above the Standard Model prediction is observed. Limits are set on the mass scale of the contact interaction as a function of the dark-matter particle mass using an effective field theory description of the interaction of dark matter with quarks or with Z bosons. Limits are also set on the coupling and mediator mass of a model in which the interaction is mediated by a scalar particle.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of the resonant and CP components in (B)over-bar(0) -> J/psi pi(+)pi(-) decays. Phys. Rev. D, 90(1), 012003–21pp.
Abstract: The resonant structure of the reaction (B) over bar (0) --> J/psi pi(+)pi(-) is studied using data from 3 fb(-1) of integrated luminosity collected by the LHCb experiment, one third at 7 TeV center-of-mass energy and the remainder at 8 TeV. The invariant mass of the pi(+)pi(-) pair and three decay angular distributions are used to determine the fractions of the resonant and nonresonant components. Six interfering pi(+)pi(-) states, rho(770), f(0)(500), f(2)(1270), rho(1450), omega(782) and rho(1700), are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative charge parity fractions of each of the resonant final states are determined. The f(0)(980) meson is not seen and the upper limit on its presence, compared with the observed f(0)(500) rate, is inconsistent with a model where these scalar mesons are formed from two quarks and two antiquarks (tetraquarks) at the eight standard deviation level. In the q (q) over bar model, the absolute value of the mixing angle between the f(0)(980) and the f(0)(500) scalar mesons is limited to be less than 17 degrees at 90% confidence level.
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