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AGATA Collaboration(Soderstrom, P. A. et al), & Gadea, A. (2012). High-spin structure in K-40. Phys. Rev. C, 86(5), 054320–9pp.
Abstract: High-spin states of K-40 have been populated in the fusion-evaporation reaction C-12(Si-30,np)K-40 and studied by means of gamma-ray spectroscopy techniques using one triple-cluster detector of the Advanced Gamma Tracking Array at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. Several states with excitation energy up to 8 MeV and spin up to 10(-) have been discovered. These states are discussed in terms of J = 3 and T = 0 neutron-proton hole pairs. Shell-model calculations in a large model space have shown good agreement with the experimental data for most of the energy levels. The evolution of the structure of this nucleus is here studied as a function of excitation energy and angular momentum.
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Sekihara, T., Yamagata-Sekihara, J., Jido, D., & Kanada-En'yo, Y. (2012). Branching ratios of mesonic and nonmesonic antikaon absorptions in the nuclear medium. Phys. Rev. C, 86(6), 065205–17pp.
Abstract: The branching ratios of K- absorption in nuclear matter are theoretically investigated in order to understand the mechanism of K- absorption into nuclei. For this purpose mesonic and nonmesonic absorption potentials are evaluated as functions of nuclear density, the kaon momentum, and energy from one- and two-body K- self-energy, respectively. By using a chiral unitary approach for the s-wave (K) over bar N amplitude we find that both the mesonic and nonmesonic absorption potentials are dominated by the Lambda(1405) contributions. The fraction of the mesonic and nonmesonic absorptions are evaluated to be respectively about 70% and 30% at the saturation density almost independently of the kaon momentum. We also observe different behavior of the branching ratios to pi(+)Sigma(-) and pi(-)Sigma(+) channels in mesonic absorption due to the interference between Lambda(1405) and the I = 1 nonresonant background, which is consistent with experimental results. The nonmesonic absorption ratios [Lambda p]/[Sigma(0)p] and [Lambda n]/[Sigma(0)n] are about unity while [Sigma(+)n]/[Sigma(0)p] and [Sigma(-) p]/[Sigma(0)n] are about 2 due to the Lambda(1405) dominance in absorption. Taking into account the kaon momenta and energies, the absorption potentials become weaker due to the downward shift of the initial K- N two-body energy, but this does not drastirally change the nonmesonic fraction. The Sigma(1385) contribution in the p-wave (K) over bar N amplitude is examined and found to be very small compared to the Lambda(1405) contribution in slow K- absorption.
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Steinhardt, T., Eberth, J., Skoda, S., Thelen, O., Schwengner, R., Donau, F., et al. (2012). Stabilization of prolate deformation at high spin in Kr-75. Phys. Rev. C, 86(6), 064310–16pp.
Abstract: The neutron-deficient nucleus Kr-75 has been studied in two EUROBALL experiments. The analysis yielded a considerably extended level scheme including two newly observed excited high spin bands. The results are interpreted in the framework of the cranked Nilsson-Strutinsky approach. The calculations compare well to the experimentally established level scheme and predict the nucleus to be mainly prolate or triaxially deformed at high spin. Evidence for an oblate-prolate shape coexistence could not be found at high spin.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2012). Underlying event characteristics and their dependence on jet size of charged-particle jet events in pp collisions at root(s)=7 TeV with the ATLAS detector. Phys. Rev. D, 86(7), 072004–34pp.
Abstract: Distributions sensitive to the underlying event are studied in events containing one or more chargedparticle jets produced in pp collisions at root s = 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect 800 μb(-1) of data taken during 2010. Jets are reconstructed using the anti-k(t) algorithm with radius parameter R varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle p(T) are measured as functions of p(T)(jet) in regions transverse to and opposite the leading jet for 4 GeV < p(T)(jet) < 100 GeV. In addition, the R dependence of the mean values of these observables is studied. In the transverse region, both the multiplicity and the scalar sum of the transverse momentum at fixed p(T)(jet) vary significantly with R, while the average charged- particle transverse momentum has a minimal dependence on R. Predictions from several Monte Carlo tunes have been compared to the data; the predictions from Pythia 6, based on tunes that have been determined using LHC data, show reasonable agreement with the data, including the dependence on R. Comparisons with other generators indicate that additional tuning of soft-QCD parameters is necessary for these generators. The measurements presented here provide a testing ground for further development of the Monte Carlo models.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Measurement of the semileptonic branching fraction of the B(s) meson. Phys. Rev. D, 85(1), 011101–9pp.
Abstract: We report a measurement of the inclusive semileptonic branching fraction of the B(s) meson using data collected with the BABAR detector in the center-of-mass energy region above the Y(4S) resonance. We use the inclusive yield of phi mesons and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B(s) mesons relative to all B mesons as a function of center-of-mass energy. The inclusive semileptonic branching fraction of the B(s) meson is determined to be B(B(s) -> l nu X) = 9.5(-2.0)(+2.5)(stat)(-1.9)(+1.1)(syst)% where l indicates the average of e and mu.
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