Kinematical Constraints on QCD Factorization in the Drell-Yan Process

We study factorization schemes for parton shower models in hadron-hadron collisions. As an example, we calculate lepton pair production mediated by a virtual photon in quark--anti-quark annihilation, and we compare factorized cross sections obtained in the conventional $\bar{\rm MS}$ scheme with those obtained in a factorization scheme in which a kinematical constraint due to parton radiation is taken into account. We discuss some properties of factorized cross sections.Comment: 10 pages, PTPTeX.sty, 1 Postscript figur

Two-loop Renormalization Factors of Dimension-six Proton Decay Operators in the Supersymmetric Standard Models

The renormalization factors of the dimension-six effective operators for proton decay are evaluated at two-loop level in the supersymmetric grand unified theories. For this purpose, we use the previous results in which the quantum corrections to the effective Kahler potential are evaluated at two-loop level. Numerical values for the factors are presented in the case of the minimal supersymmetric SU(5) grand unified model. We also derive a simple formula for the one-loop renormalization factors for any higher-dimensional operators in the Kahler potential, assuming that they are induced by the gauge interactions.Comment: 11 pages. Version accepted for publication in Phys. Lett.

A characterization of the alpha-connections on the statistical manifold of multivariate normal distributions

We study a statistical manifold $(\mathcal{N}, g^F, \nabla^{A}, \nabla^{A*})$ of multivariate normal distributions, where $g^F$ is the Fisher metric and $\nabla^{A}$ is the Amari-Chentsov connection and $\nabla^{A*}$ is its conjugate connection. We will show that it admits a solvable Lie group structure and moreover the Amari-Chentsov connection $\nabla^{A}$ on $(\mathcal{N}, g^F)$ will be characterized by the conjugate symmetry, i.e., a curvatures identity $R=R^*$ of a connection $\nabla$ and its conjugate connection $\nabla^*$

Bulk scalar emission from a rotating black hole pierced by a tense brane

We study the emission of scalar fields into the bulk from a six-dimensional rotating black hole pierced by a 3-brane. We determine the angular eigenvalues in the presence of finite brane tension by using the continued fraction method. The radial equation is integrated numerically, giving the absorption probability (graybody factor) in a wider frequency range than in the preexisting literature. We then compute the power and angular momentum emission spectra for different values of the rotation parameter and brane tension, and compare their relative behavior in detail. As is expected from the earlier result for a nonrotating black hole, the finite brane tension suppresses the emission rates. As the rotation parameter increases, the power spectra are reduced at low frequencies due to the smaller Hawking temperature and are enhanced at high frequencies due to superradiance. The angular momentum spectra are enhanced over the whole frequency range as the rotation parameter increases. The spectra and the amounts of energy and angular momentum radiated away into the bulk are thus determined by the interplay of these effects.Comment: 10 pages, 7 figures; v2: references added; v3: Figs. 4, 5, 6 corrected. Numerical results changed; v4: references added, minor clarification, accepted for publication in Physical Review

Spin-polarized scanning tunneling microscopy of half-metallic ferromagnets: Non-quasiparticle contributions

The role of the many-body (spin-polaronic) effects in the scanning tunneling spectroscopy of half-metallic ferromagnets (HMF) is considered. It is shown that the non-quasiparticle (NQP) states exist in the majority or minority spin gap in the presence of arbitrary external potential and, in particular, at the surfaces and interfaces. Energy dependence of the NQP density of states is obtained in various models of HMF, an important role of the hybridization nature of the energy gap being demonstrated. The corresponding temperature dependence of spin polarization is calculated. It is shown that the NQP states result in a sharp bias dependence of the tunneling conductance near zero bias. Asymmetry of the NQP states with respect to the Fermi energy provides an opportunity to separate phonon and magnon peaks in the inelastic spectroscopy by STM.Comment: 13 pages, 6 figure