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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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