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Calabrese, E., de Putter, R., Huterer, D., Linder, E. V., & Melchiorri, A. (2011). Future CMB constraints on early, cold, or stressed dark energy. Phys. Rev. D, 83(2), 023011–11pp.
Abstract: We investigate future constraints on early dark energy (EDE) achievable by the Planck and CMBPol experiments, including cosmic microwave background (CMB) lensing. For the dark energy, we include the possibility of clustering through a sound speed c(s)(2) < 1 (cold dark energy) and anisotropic stresses parametrized with a viscosity parameter c(vis)(2). We discuss the degeneracies between cosmological parameters and EDE parameters. In particular we show that the presence of anisotropic stresses in EDE models can substantially undermine the determination of the EDE sound speed parameter c(s)(2). The constraints on EDE primordial energy density are however unaffected. We also calculate the future CMB constraints on neutrino masses and find that they are weakened by a factor of 2 when allowing for the presence of EDE, and highly biased if it is incorrectly ignored.
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Borja, E. F., Freidel, L., Garay, I., & Livine, E. R. (2011). U(N) tools for loop quantum gravity: the return of the spinor. Class. Quantum Gravity, 28(5), 055005–28pp.
Abstract: We explore the classical setting for the U(N) framework for SU(2) intertwiners for loop quantum gravity and describe the corresponding phase space in terms of spinors with the appropriate constraints. We show how its quantization leads back to the standard Hilbert space of intertwiner states defined as holomorphic functionals. We then explain how to glue these intertwiners states in order to construct spin network states as wavefunctions on the spinor phase space. In particular, we translate the usual loop gravity holonomy observables to our classical framework. Finally, we propose how to derive our phase space structure from an action principle which induces non-trivial dynamics for the spin network states. We conclude by applying explicitly our framework to states living on the simple 2-vertex graph and discuss the properties of the resulting Hamiltonian.
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Das, S. P., & Drees, M. (2011). CP-violating supersymmetric Higgs boson at the Tevatron and LHC. Phys. Rev. D, 83(3), 035003–17pp.
Abstract: We analyze the prospect for observing the intermediate neutral Higgs boson (h(2))in its decay to two lighter Higgs bosons (h(1)) at the presently operating hadron colliders in the framework of the CP-violating minimal supersymmetric standard model using the PYTHIA event generator. We consider the lepton + 4-jets + E-T channel from associate Wh(2) production, with Wh(2) -> Wh(1)h(1) -> l -> l nu lb (b) over barb (b) over bar. We require two, three or four tagged b jets. We explicitly consider all relevant standard model backgrounds, treating c jets separately from light flavor and gluon jets and allowing for mistagging. We find that it is very hard to observe this signature at the Tevatron, even with 20 fb(-1) of data, in the LEP-allowed region of parameter space due to the small signal efficiency, even though the background is manageable. At the LHC, a priori huge standard model backgrounds can be suppressed by applying judiciously chosen kinematical selections. After all cuts, we are left with a signal cross section of around 0.5 fb, and a signal to background ratio between 1.2 and 2.9. According to our analysis this Higgs signal should be viable at the LHC in the vicinity of present LEP exclusion once 20 to 50 fb(-1) of data have been accumulated at root s = 14 TeV.
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MiniBooNE Collaboration(Aguilar-Arevalo, A. A. et al), & Sorel, M. (2011). Measurement of nu(mu)-induced charged-current neutral pion production cross sections on mineral oil at E-nu is an element of 0.5-2.0 GeV. Phys. Rev. D, 83(5), 052009–17pp.
Abstract: Using a custom 3-Cerenkov ring fitter, we report cross sections for nu(mu)-induced charged-current single pi(0) production on mineral oil (CH2) from a sample of 5810 candidate events with 57% signal purity over an energy range of 0.5-2.0 GeV. This includes measurements of the absolute total cross section as a function of neutrino energy, and flux-averaged differential cross sections measured in terms of Q(2), mu(-) kinematics, and pi(0) kinematics. The sample yields a flux-averaged total cross section of (9.2 +/- 0.3(stat) +/- 1.5(syst)) X 10(-39) cm(2)/CH2 at mean neutrino energy of 0.965 GeV.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2011). Search for the decay B-0 -> gamma gamma. Phys. Rev. D, 83(4), 032006–11pp.
Abstract: We report the result of a search for the rare decay B-0 -> gamma gamma in 426 fb(-1) of data, corresponding to 226 x 10(6) B-0(B) over bar (0) pairs, collected on the Y(4S) resonance at the PEP-II asymmetric-energy e(+)e(-) collider using the BABAR detector. We use a maximum likelihood fit to extract the signal yield and observe 21(-12)(+13) signal events with a statistical significance of 1.8 sigma. This corresponds to a branching fraction B(B-0 -> gamma gamma) = (1.7 +/- 1.1(stat.) +/- 0.2(syst.)) X 10(-7). Based on this result, we set a 90% confidence level upper limit of B(B-0 -> gamma gamma) < 3.2 X 10(-7).
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