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Albertus, C., Hernandez, E., & Nieves, J. (2012). Exclusive c -> s, d semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy cb baryons. Phys. Rev. D, 85(9), 094035–21pp.
Abstract: We evaluate exclusive semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy cb baryons driven by a c --> s, d transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil. Based on those constraints we make model-independent, though approximate, predictions for ratios of decay widths.
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Bertolini, S., Di Luzio, L., & Malinsky, M. (2012). Seesaw scale in the minimal renormalizable SO(10) grand unification. Phys. Rev. D, 85(9), 095014–22pp.
Abstract: Simple SO(10) Higgs models with the adjoint representation triggering the grand unified symmetry breaking, discarded long ago due to inherent tree-level tachyonic instabilities in the physically interesting scenarios, have been recently brought back to life by quantum effects. In this work we focus on the variant with 45(H) circle plus 126(H) in the Higgs sector and show that there are several regions in the parameter space of this model that can support stable unifying configurations with the B – L-breaking scale as high as 10(14) GeV, well above the previous generic estimates based on the minimal survival hypothesis. This admits for a renormalizable implementation of the canonical seesaw and makes the simplest potentially realistic scenario of this kind a good candidate for a minimal SO(10) grand unification. Last, but not least, this setting is likely to be extensively testable at future large-volume facilities such as Hyper-Kamiokande.
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BABAR Collaboration(Lees, J. P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2012). Search for the decay D-0 -> gamma gamma and measurement of the branching fraction for D-0 -> pi(0)pi(0). Phys. Rev. D, 85(9), 091107–8pp.
Abstract: We search for the rare decay of the D-0 meson to two photons, D-0 -> gamma gamma, and present a measurement of the branching fraction for a D-0 meson decaying to two neutral pions, B(D-0 -> pi(0)pi(0)). The data sample analyzed corresponds to an integrated luminosity of 470.5 fb(-1) collected by the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at SLAC. We place an upper limit on the branching fraction, B(D-0 -> gamma gamma) < 2.2 x 10(-6), at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B(D-0 -> pi(0)pi(0)) = (8.4 +/- 0.1 +/- 0.4 +/- 0.3 +/-) x 10(-4).
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Aguilar-Saavedra, J. A., Deppisch, F., Kittel, O., & Valle, J. W. F. (2012). Flavor in heavy neutrino searches at the LHC. Phys. Rev. D, 85(9), 091301–4pp.
Abstract: Heavy neutrinos at the TeV scale have been searched for at the LHC in the context of left-right models, under the assumption that they couple to the electron, the muon, or both. We show that current searches are also sensitive to heavy neutrinos coupling predominantly to the tau lepton, and present limits can significantly constrain the parameter space of general flavor mixing.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions at root s=7 TeV with the ATLAS detector. Phys. Rev. D, 85(9), 092014–30pp.
Abstract: A measurement of the cross section for the production of an isolated photon in association with jets in proton-proton collisions at a center-of-mass energy root s = 7 TeV is presented. Photons are reconstructed in the pseudorapidity range vertical bar eta(gamma)vertical bar < 1.37 and with a transverse energy E-T(gamma) > 25 GeV. Jets are reconstructed in the rapidity range vertical bar y(jet)vertical bar < 4.4 and with a transverse momentum p(T)(jet) > 20 GeV. The differential cross section d sigma/dE(T)(gamma) is measured, as a function of the photon transverse energy, for three different rapidity ranges of the leading-p(T) jet: vertical bar y(jet)vertical bar < 1.2, 1.2 <= vertical bar y(jet)vertical bar < 2.8 and 2.8 <= vertical bar y(jet)vertical bar < 4.4. For each rapidity configuration the same-sign (eta(gamma)y(jet) >= 0) and opposite-sign (eta(gamma) y(jet) < 0) cases are studied separately. The results are based on an integrated luminosity of 37 pb(-1), collected with the ATLAS detector at the LHC. Next-to-leading order perturbative QCD calculations are found to be in fair agreement with the data, except for E-T(gamma) <= 45 GeV, where the theoretical predictions overestimate the measured cross sections.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2012). Branching fraction and form-factor shape measurements of exclusive charmless semileptonic B decays, and determination of vertical bar V-ub vertical bar. Phys. Rev. D, 86(9), 092004–31pp.
Abstract: We report the results of a study of the exclusive charmless semileptonic decays, B-0 -> pi(-)l(+)nu, B+ -> pi(0)l(+)nu, B+ -> omega l(+)nu, B+ -> eta l(+)nu, and B+ -> eta'l(+)nu (l = e or mu) undertaken with approximately 462 X 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q(2), the square of the momentum transferred to the lepton-neutrino pair, for B-0 -> pi(-)l(+)nu, B+ -> pi(0)l(+)nu, B+ -> omega l(+)nu, and B+ -> eta l(+)nu. From these distributions, we extract the form-factor shapes f(+)(q(2)) and the total branching fractions B(B-0 -> pi(-)l(+)nu) = (1.45 +/- 0.04(stat) +/- 0.06(syst)) X 10(-4) (combined pi(-) and pi(0) decay channels assuming isospin symmetry), B(B+ -> omega l(+)nu) = (1.19 +/- 016(stat) +/- 0.09(syst)) X 10(-4) and B(B+ -> eta l(+)nu) = (0.38 +/- 0.05(stat) +/- 0.05(syst)) X 10(-4). We also measure B(B+ -> eta'l(+)nu) = (0.24 +/- 0.08(stat) +/- 0.03(syst)) X 10(-4). We obtain values for the magnitude of the Cabibbo-Kobayashi-Maskawa (KM) matrix element vertical bar V-ub vertical bar by direct comparison with three different QCD calculations in restricted q(2) ranges of B -> pi l(+)nu decays. From a simultaneous fit to the experimental data over the full q(2) range and the FNAL/MILC lattice QCD predictions, we obtain vertical bar V-ub vertical bar = (3.25 +/- 0.31) X 10(-3), where the error is the combined experimental and theoretical uncertainty.
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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. (2012). Further search for supersymmetry at root s=7 TeV in final states with jets, missing transverse momentum, and isolated leptons with the ATLAS detector. Phys. Rev. D, 86(9), 092002–35pp.
Abstract: This work presents a new inclusive search for supersymmetry (SUSY) by the ATLAS experiment at the LHC in proton-proton collisions at a center-of-mass energy root s = 7 TeV in final states with jets, missing transverse momentum and one or more isolated electrons and/or muons. The search is based on data from the full 2011 data-taking period, corresponding to an integrated luminosity of 4.7 fb(-1). Single-lepton and multilepton channels are treated together in one analysis. An increase in sensitivity is obtained by simultaneously fitting the number of events in statistically independent signal regions, and the shapes of distributions within those regions. A dedicated signal region is introduced to be sensitive to decay cascades of SUSY particles with small mass differences (“compressed SUSY”). Background uncertainties are constrained by fitting to the jet-multiplicity distribution in background control regions. Observations are consistent with Standard Model expectations, and limits are set or extended on a number of SUSY models.
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Abbate, R., Fickinger, M., Hoang, A. H., Mateu, V., & Stewart, I. W. (2012). Precision thrust cumulant moments at N^3LL. Phys. Rev. D, 86(9), 094002–22pp.
Abstract: We consider cumulant moments (cumulants) of the thrust distribution using predictions of the full spectrum for thrust including O(alpha(3)(s)) fixed order results, resummation of singular (NLL)-L-3 logarithmic contributions, and a class of leading power corrections in a renormalon-free scheme. From a global fit to the first thrust moment we extract the strong coupling and the leading power correction matrix element Omega(1). We obtain alpha(s)(m(Z)) = 0.1140 +/- (0.0004)(exp) +/- (0.0013)(hadr) +/- (0.0007)(pert), where the 1-sigma uncertainties are experimental, from hadronization (related to Omega(1)) and perturbative, respectively, and Omega(1) = 0.377 +/- (0.044)(exp) +/- (0.039)(pert) GeV. The nth thrust cumulants for n >= 2 are completely insensitive to Omega(1), and therefore a good instrument for extracting information on higher order power corrections, Omega'(n)/Q(n), from moment data. We find ((Omega) over tilde '2)(1/2) = 0.74 +/- (0.11)(exp) +/- (0.09)(pert) GeV.
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Hirsch, M., Reichert, L., Porod, W., & Staub, F. (2012). Phenomenology of a supersymmetric U(1)(B-L) x U(1)(R) extension of the standard model with inverse seesaw mechanism. Phys. Rev. D, 86(9), 093018–26pp.
Abstract: We discuss the minimal supersymmetric U(1)(B-L) X U(1)(R) extension of the standard model. Gauge couplings unify as in the minimal supersymmetric standard model (MSSM), even if the scale of U(1)(B-L) X U(1)(R) breaking is as low as order TeV and the model can be embedded into a SO(10) grand unified theory. The phenomenology of the model differs in some important aspects from the MSSM, leading potentially to rich phenomenology at the LHC. It predicts more light Higgs states and the mostly left CP-even Higgs having a mass that easily reaches 125 GeV, with no constraints on the supersymmetry spectrum. Right sneutrinos can be the lightest supersymmetric particle, changing all dark matter constraints on supersymmetry parameter space. The model has seven neutralinos, and squark/gluino decay chains involve more complicated cascades than in the MSSM. We also briefly discuss low-energy and accelerator constraints on the model, where the most important limits come from recent Z' searches at the LHC and upper limits on lepton flavor violation.
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Xiao, C. W., Bayar, M., & Oset, E. (2012). Prediction of D*-multi-rho states. Phys. Rev. D, 86(9), 094019–10pp.
Abstract: We present a study of the many-body interaction between a D* and multi-rho. We use an extrapolation to SU(4) of the hidden gauge formalism, which produced dynamically the resonances f(2)(1270) in the rho rho interaction and D-2* (2460) in the rho D* interaction. We then let a third particle, rho, D*, or a resonance, collide with them, evaluating the scattering amplitudes in terms of the fixed center approximation of the Faddeev equations. We find several clear resonant structures above 2800 MeV in the multibody scattering amplitudes. They would correspond to new charmed resonances, D-3*, D-4*, D-5*, and D-6*, which are not yet listed in the Particle Data Group, which would be analogous to the rho(3)(1690), f(4)(2050), rho(5)(2350), f(6)(2510) and K-3*(1780), K-4*(2045), K-5*(2380) described before as multi-rho and K*-multi-rho states, respectively.
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