|
|
BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Search for the rare decay B -> Kv(v)over-bar. Phys. Rev. D, 82(11), 112002–10pp.
Abstract: We present a search for the rare decays B+ -> K+ v (v) over bar and B-0 -> K-0 v (v) over bar using 459 x 10(6) B (B) over bar pairs collected with the BABAR detector at the SLAC National Accelerator Laboratory. Flavor-changing neutral-current decays such as these are forbidden at tree level but can occur through one-loop diagrams in the standard model (SM), with possible contributions from new physics at the same order. The presence of two neutrinos in the final state makes identification of signal events challenging, so reconstruction in the semileptonic decay channels B -> D-(*) lv of the B meson recoiling from the signal B is used to suppress backgrounds. We set an upper limit at the 90% confidence level (CL) of 1.3 x 10(-5) on the total branching fraction for B+ -> K+ v (v) over bar, and 5.6 x 10(-5) for B-0 -> K-0 v (v) over bar. We additionally report 90% CL upper limits on partial branching fractions in two ranges of dineutrino mass squared for B+ -> K+ v (v) over bar.
|
|
|
|
SciBooNE Collaboration(Kurimoto, Y. et al), Catala-Perez, J., Gomez-Cadenas, J. J., & Sorel, M. (2010). Measurement of inclusive neutral current pi(0) production on carbon in a few-GeV neutrino beam. Phys. Rev. D, 81(3), 033004–18pp.
Abstract: The SciBooNE Collaboration reports inclusive neutral current neutral pion production by a muon neutrino beam on a polystyrene target (C8H8). We obtain (7.7 +/- 0.5(stat) +/- 0.5(sys)) X 10(-2) as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein-Sehgal model implemented in our neutrino interaction simulation program with nuclear effects. The spectrum shape of the pi(0) momentum and angle agree with the model. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be (0.7 +/- 0.4) X 10(-2).
|
|
|
|
Aguilar, A. C., & Papavassiliou, J. (2010). Gluon mass generation without seagull divergences. Phys. Rev. D, 81(3), 034003–19pp.
Abstract: Dynamical gluon mass generation has been traditionally plagued with seagull divergences, and all regularization procedures proposed over the years yield finite but scheme-dependent gluon masses. In this work we show how such divergences can be eliminated completely by virtue of a characteristic identity, valid in dimensional regularization. The ability to trigger the aforementioned identity hinges crucially on the particular Ansatz employed for the three-gluon vertex entering into the Schwinger-Dyson equation governing the gluon propagator. The use of the appropriate three-gluon vertex brings about an additional advantage: one obtains two separate (but coupled) integral equations, one for the effective charge and one for the gluon mass. This system of integral equations has a unique solution, which unambiguously determines these two quantities. Most notably, the effective charge freezes in the infrared, and the gluon mass displays power-law running in the ultraviolet, in agreement with earlier considerations.
|
|
|
|
Mathieu, V., & Vento, V. (2010). Pseudoscalar glueball and eta-eta ' mixing. Phys. Rev. D, 81(3), 034004–12pp.
Abstract: We have performed a dynamical analysis of the mixing in the pseudoscalar channel with the goal of understanding the existence and behavior of the pseudoscalar glueball. Our philosophy has not been to predict precise values of the glueball mass but to exploit an adequate effective theory to the point of breaking and to analyze which kind of mechanisms restore compatibility with data. Our study has led to analytical solutions which allow a clear understanding of the phenomena. The outcome of our calculation leads to a large mass glueball M-Theta > 2000 MeV, to a large glue content of the eta ', and to mixing angles in agreement with previous numerical studies.
|
|
|
|
Kochelev, N. I., & Vento, V. (2010). Gluonic components of the pion and the transition form factor gamma*gamma* -> pi(0). Phys. Rev. D, 81(3), 034009–5pp.
Abstract: We propose an effective Lagrangian for the coupling of the neutral pion with gluons whose strength is determined by a low-energy theorem. We calculate the contribution of the gluonic components arising from this interaction to the pion transition form factor gamma*gamma* -> pi(0) using the instanton liquid model to describe the quantum chromodynamics vacuum. We find that this contribution is large and might explain the anomalous behavior of the form factor at large virtuality of one of the photons, a feature which was recently discovered by the BABAR Collaboration.
|
|
