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Aranda, A., Bonilla, C., Morisi, S., Peinado, E., & Valle, J. W. F. (2014). Dirac neutrinos from flavor symmetry. Phys. Rev. D, 89(3), 033001–5pp.
Abstract: We present a model where Majorana neutrino mass terms are forbidden by the flavor symmetry group Delta(27). Neutrinos are Dirac fermions and their masses arise in the same way as those of the charged fermions, due to very small Yukawa couplings. The model fits current neutrino oscillation data and correlates the octant of the atmospheric angle theta(23) with the magnitude of the lightest neutrino mass, with maximal mixing excluded for any neutrino mass hierarchy.
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Langer, C. et al, & Domingo-Pardo, C. (2014). Determining the rp-Process Flow through Ni-56: Resonances in Cu-57(p,gamma)Zn-58 Identified with GRETINA. Phys. Rev. Lett., 113(3), 032502–5pp.
Abstract: An approach is presented to experimentally constrain previously unreachable (p,gamma) reaction rates on nuclei far from stability in the astrophysical rp process. Energies of all critical resonances in the Cu-57(p,gamma)Zn-58 reaction are deduced by populating states in Zn-58 with a (d, n) reaction in inverse kinematics at 75 MeV/u, and detecting.-ray-recoil coincidences with the state-of-the-art gamma-ray tracking array GRETINA and the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The results reduce the uncertainty in the Cu-57(p,gamma) reaction rate by several orders of magnitude. The effective lifetime of Ni-56, an important waiting point in the rp process in x-ray bursts, can now be determined entirely from experimentally constrained reaction rates.
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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 ratio of B-c(+) branching fractions to J/psi pi(+) and J/psi mu(+)nu(mu) final states. Phys. Rev. D, 90(3), 032009–11pp.
Abstract: The first measurement that relates semileptonic and hadronic decay rates of the B-c(+) meson is performed using proton-proton collision data corresponding to 1.0 fb(-1) of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, B(B-c(+) -> J/psi pi(+))/B(B-c(+) -> J/psi mu(+)nu(mu)) = 0.0469 +/- 0.0028(stat) +/- 0.0046(syst), is at the lower end of available theoretical predictions.
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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 a multi-Higgs-boson cascade in W(+)W(-)b(b)over-bar events with the ATLAS detector in pp collisions at root s=8 TeV. Phys. Rev. D, 89(3), 032002–23pp.
Abstract: A search is presented for new particles in an extension to the Standard Model that includes a heavy Higgs boson (H-0), an intermediate charged Higgs-boson pair (H-+/-), and a light Higgs boson (h(0)). The analysis searches for events involving the production of a single heavy neutral Higgs boson which decays to the charged Higgs boson and a W boson, where the charged Higgs boson subsequently decays into a W boson and the lightest neutral Higgs boson decaying to a bottom-antibottom-quark pair. Such a cascade results in a W-boson pair and a bottom-antibottom-quark pair in the final state. Events with exactly one lepton, missing transverse momentum, and at least four jets are selected from a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in proton-proton collisions at root s = 8 TeV at the LHC. The data are found to be consistent with Standard Model predictions, and 95% confidence-level upper limits are set on the product of cross section and branching ratio. These limits range from 0.065 to 43 pb as a function of H-0 and H-+/- masses, with m(h)o fixed at 125 GeV.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Precision Measurement of the Mass and Lifetime of the Xi(0)(b) Baryon. Phys. Rev. Lett., 113(3), 032001–10pp.
Abstract: Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb(-1) collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 Xi(0)(b) -> Xi(+)(c)pi(-), Xi(+)(c) -> pK(-)pi(+) signal decays are reconstructed. From this sample, the first measurement of the Xi(0)(b) baryon lifetime is made, relative to that of the Lambda(0)(b) baryon. The mass differences M(Xi(0)(b)) – M(Lambda(0)(b)) and M(Xi(+)(c)) – M(Lambda(+)(c)) are also measured with precision more than 4 times better than the current world averages. The resulting values are tau(Xi b0)/tau(Lambda b0) = 1.006 +/- 0.018 +/- 0.010, M(Xi(0)(b)) – M(Lambda(0)(b)) = 172.44 +/- 0.39 +/- 0.17 MeV/c(2), M(Xi(+)(c)) – M(Lambda(+)(c)) = 181.51 +/- 0.14 +/- 0.10 MeV/c(2), where the first uncertainty is statistical and the second is systematic. The relative rate of Xi(0)(b) to Lambda(0)(b) baryon production is measured to be f(Xi b0) B(Xi(0)(b) -> Xi(+)(c)pi(-)) B(Xi(+)(c) -> pK(-)pi(+))/f(Lambda b0) B(Lambda(0)(b) -> Lambda(+)(c)pi(-)) B(Lambda(+)(c) -> pK(-)pi(+)) = (1.88 +/- 0.04 +/- 0.03) x 10(-2), where the first factor is the ratio of fragmentation fractions, b -> Xi(0)(b) relative to b -> Lambda(0)(b). Relative production rates as functions of transverse momentum and pseudorapidity are also presented.
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