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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). Combined search for the Standard Model Higgs boson in pp collisions at root s=7 TeV with the ATLAS detector. Phys. Rev. D, 86(3), 032003–31pp.
Abstract: A combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC is presented. The data sets used correspond to integrated luminosities from 4.6 fb(-1) to 4.9 fb(-1) of proton-proton collisions collected at root s = 7 TeV in 2011. The Higgs boson mass ranges of 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV to 541 GeV are excluded at the 95% confidence level, while the range 120 GeV to 560 GeV is expected to be excluded in the absence of a signal. An excess of events is observed at Higgs boson mass hypotheses around 126 GeV with a local significance of 2.9 standard deviations (sigma). The global probability for the background to produce an excess at least as significant anywhere in the entire explored Higgs boson mass range of 110-600 GeV is estimated to be similar to 15%, corresponding to a significance of approximately 1 sigma.
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Lee, J. S., & Pilaftsis, A. (2012). Radiative corrections to scalar masses and mixing in a scale invariant two Higgs doublet model. Phys. Rev. D, 86(3), 035004–14pp.
Abstract: We study the Higgs boson mass spectrum of a classical scale invariant realization of the two Higgs doublet model (SI-2HDM). The classical scale symmetry of the theory is explicitly broken by quantum loop effects due to gauge interactions, Higgs self-couplings and top quark Yukawa couplings. We determine the allowed parameter space compatible with perturbative unitarity and electroweak precision data. Taking into account the LEP and the recent LHC exclusion limits on a standard-model-like Higgs boson HSM, we obtain rather strict constraints on the mass spectrum of the heavy Higgs sector of the SI-2HDM. In particular, if MHSM 125 GeV, the SI-2HDM strongly favors scenarios in which at least one of the nonstandard neutral Higgs bosons has a mass close to 400 GeV and is generically degenerate with the charged Higgs boson, whilst the third neutral Higgs scalar is lighter than 500 GeV.
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BABAR Collaboration(Lees, J. P. et al), Azzolini, V., Martinez-Vidal, F., & Oyanguren, A. (2012). Study of (B)over-bar -> X(u)l(v)over-bar decays in B(B)over-bar events tagged by a fully reconstructed B-meson decay and determination of vertical bar V-ub vertical bar. Phys. Rev. D, 86(3), 032004–23pp.
Abstract: We report measurements of partial branching fractions for inclusive charmless semileptonic B decays (B) over bar -> X(u)l (v) over bar and the determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V-ub vertical bar. The analysis is based on a sample of 467 x 10(6) Y(4S) -> B (B) over bar decays recorded with the BABAR detector at the PEP- II e(+)e(-) storage rings. We select events in which the decay of one of the B mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other B meson. We measure partial branching fractions Delta B in several restricted regions of phase space and determine the CKM element vertical bar V-ub vertical bar based on different QCD predictions. For decays with a charged lepton momentum p(l)* > 1.0 GeV in the B meson rest frame, we obtain Delta B = (1.80 +/- 0.13(stat) +/- 0.15(sys) +/- 0.02(theo)) x 10(-3) from a fit to the two-dimensional M-X – q(2) distribution. Here, M-X refers to the invariant mass of the final state hadron X and q(2) is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract vertical bar V-ub vertical bar = (4.33 +/- 0.24(exp) +/- 0.15(theo)) x 10(-3) as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for (B) over bar (0) and B- decays and derive a limit on the isospin breaking in (B) over bar -> X(u)l (v) over bar decays.
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Olmo, G. J., & Rubiera-Garcia, D. (2012). Reissner-Nordstrom black holes in extended Palatini theories. Phys. Rev. D, 86(4), 044014–15pp.
Abstract: We study static, spherically symmetric solutions with an electric field in an extension of general relativity containing a Ricci-squared term and formulated in the Palatini formalism. We find that all the solutions present a central core whose area is proportional to the Planck area times the number of charges. Far from the core, curvature invariants quickly tend to those of the usual Reissner-Nordstrom solution, though the structure of horizons may be different. In fact, besides the structures found in the Reissner-Nordstrom solution of general relativity, we find black hole solutions with just one nondegenerate horizon (Schwarzschild-like) and nonsingular black holes and naked cores. The charge-to-mass ratio of the nonsingular solutions implies that the core matter density is independent of the specific amounts of charge and mass and of order the Planck density. We discuss the physical implications of these results for astrophysical and microscopic black holes, construct the Penrose diagrams of some illustrative cases, and show that the maximal analytical extension of the nonsingular solutions implies a bounce of the radial coordinate.
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Archidiacono, M., Giusarma, E., Melchiorri, A., & Mena, O. (2012). Dark radiation in extended cosmological scenarios. Phys. Rev. D, 86(4), 043509–7pp.
Abstract: Recent cosmological data have provided evidence for a “dark” relativistic background at high statistical significance. Parameterized in terms of the number of relativistic degrees of freedom N-eff, however, the current data seem to indicate a higher value than the one expected in the standard scenario based on three active neutrinos. This dark radiation component can be characterized not only by its abundance but also by its clustering properties, as its effective sound speed and its viscosity parameter. It is therefore crucial to study the correlations among the dark radiation properties and key cosmological parameters, as the dark energy equation of state or the running of the scalar spectral index, with current and future cosmic microwave background data. We find that dark radiation with viscosity parameters different from their standard values may be misinterpreted as an evolving dark energy component or as a running spectral index in the power spectrum of primordial fluctuations.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Measurement of branching fractions and rate asymmetries in the rare decays B -> K((*))l(+)l(-). Phys. Rev. D, 86(3), 032012–15pp.
Abstract: In a sample of 471 x 10(6) B (B) over bar events collected with the BABAR detector at the PEP-II e(+)e(-) collider we study the rare decays B -> K((*))l(+)l(-), where l(+)l(-) is either e(+)e(-) or mu(+)mu(-). We report results on partial branching fractions and isospin asymmetries in seven bins of dilepton mass-squared. We further present CP and lepton-flavor asymmetries for dilepton masses below and above the J/psi resonance. We find no evidence for CP or lepton-flavor violation. The partial branching fractions and isospin asymmetries are consistent with the Standard Model predictions and with results from other experiments.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Precise measurement of the e(+)e(-) -> pi(+)pi(-)(gamma) cross section with the initial-state radiation method at BABAR. Phys. Rev. D, 86(3), 032013–49pp.
Abstract: A precise measurement of the cross section of the process e(+)e(-) -> pi(+)pi(-) (gamma) from threshold to an energy of 3 GeV is obtained with the initial-state radiation (ISR) method using 232 fb(-1) of data collected with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e(+)e(-) -> mu(+)mu(-) (gamma)gamma(ISR), which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process e(+)e(-) -> pi(+)pi(-) (gamma) is obtained with a systematic uncertainty of 0.5% in the dominant rho resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured pi pi cross section from threshold to 1.8 GeV is (514.1 +/- 2.2(stat) +/- 3.1(sys)) x 10(-10).
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Mazumdar, A., & Morisi, S. (2012). Split neutrinos, two Majorana and one Dirac, and implications for leptogenesis, dark matter, and inflation. Phys. Rev. D, 86(4), 045031–6pp.
Abstract: We propose a simple framework to split neutrinos with a slight departure from tribimaximal-where two of the neutrinos are Majorana type which provide thermal leptogenesis. We propose a model based on S-3 flavor symmetry. The Dirac neutrino with a tiny Yukawa coupling explains primordial inflation and the cosmic microwave background radiation, where the inflaton is the gauge invariant flat direction. The observed baryon asymmetry, and the scale of inflation are intimately tied to the observed reactor angle sin theta(13), which can be further constrained by the LHC and the 0 nu beta beta experiments. The model also provides the lightest right-handed sneutrino as a part of the inflaton to be the dark matter candidate.
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Dorame, L., Morisi, S., Peinado, E., Valle, J. W. F., & Rojas, A. D. (2012). New neutrino mass sum rule from the inverse seesaw mechanism. Phys. Rev. D, 86(5), 056001–9pp.
Abstract: A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum rules. One of these implies a lower bound on the effective neutrinoless double beta mass parameter, even for normal hierarchy neutrinos. Here we propose a new model based on the S-4 flavor symmetry that leads to the new neutrino mass sum rule and discuss how to generate a nonzero value for the reactor angle theta(13) indicated by recent experiments, and the resulting correlation with the solar angle theta(12).
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Das, S. P., Deppisch, F. F., Kittel, O., & Valle, J. W. F. (2012). Heavy neutrinos and lepton flavor violation in left-right symmetric models at the LHC. Phys. Rev. D, 86(5), 055006–20pp.
Abstract: We discuss lepton flavor violating processes induced in the production and decay of heavy right-handed neutrinos at the LHC. Such particles appear in left-right symmetrical extensions of the standard model as the messengers of neutrino mass generation, and can have masses at the TeV scale. We determine the expected sensitivity on the right-handed neutrino mixing matrix, as well as on the right-handed gauge boson and heavy neutrino masses. By comparing the sensitivity of the LHC with that of searches for low energy lepton flavor violating processes, we identify favorable areas of the parameter space to explore the complementarity between lepton flavor violating at low and high energies.
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