7,312 research outputs found
Nonleptonic two-body B-decays including axial-vector mesons in the final state
We present a systematic study of exclusive charmless nonleptonic two-body B
decays including axial-vector mesons in the final state. We calculate branching
ratios of B\to PA, VA and AA decays, where A, V and P denote an axial-vector, a
vector and a pseudoscalar meson, respectively. We assume naive factorization
hypothesis and use the improved version of the nonrelativistic ISGW quark model
for form factors in B\to A transitions. We include contributions that arise
from the effective \Delta B=1 weak Hamiltonian H_{eff}. The respective
factorized amplitude of these decays are explicitly showed and their penguin
contributions are classified. We find that decays B^-to a_1^0\pi^-,\barB^0\to
a_1^{\pm}\pi^{\mp}, B^-\to a_1^-\bar K^0, \bar B^0\to a_1^+K^-, \bar B^0\to
f_1\bar K^0, B^-\to f_1K^-, B^-\to K_1^-(1400)\etap, B^-\to b_1^-\bar K^{0},
and \bar B^0\to b_1^+\pi^-(K^-) have branching ratios of the order of 10^{-5}.
We also study the dependence of branching ratios for B \to K_1P(V,A) decays
(K_1=K_1(1270),K_1(1400)) with respect to the mixing angle between K_A and K_B.Comment: 28 pages, 2 tables and one reference added, notation changed in
appendices, some numerical results and abstract correcte
Gluon Regge trajectory at two loops from Lipatov's high energy effective action
We present the derivation of the two-loop gluon Regge trajectory using
Lipatov's high energy effective action and a direct evaluation of Feynman
diagrams. Using a gauge invariant regularization of high energy divergences by
deforming the light-cone vectors of the effective action, we determine the
two-loop self-energy of the reggeized gluon, after computing the master
integrals involved using the Mellin-Barnes representations technique. The
self-energy is further matched to QCD through a recently proposed subtraction
prescription. The Regge trajectory of the gluon is then defined through
renormalization of the reggeized gluon propagator with respect to high energy
divergences. Our result is in agreement with previous computations in the
literature, providing a non-trivial test of the effective action and the
proposed subtraction and renormalization framework.Comment: 22 page
Dijet Production at Large Rapidity Separation in N=4 SYM
Ratios of azimuthal angle correlations between two jets produced at large
rapidity separation are studied in the N=4 super Yang-Mills theory (MSYM). It
is shown that these observables, which directly prove the SL(2,C) symmetry
present in gauge theories in the Regge limit, exhibit an excellent perturbative
convergence. They are compared to those calculated in QCD for different
renormalization schemes concluding that the momentum-substraction (MOM) scheme
with the Brodsky-Lepage-Mackenzie (BLM) scale-fixing procedure captures the
bulk of the MSYM results.Comment: 13 pages, 7 figure
Dissipative inertial transport patterns near coherent Lagrangian eddies in the ocean
Recent developments in dynamical systems theory have revealed long-lived and
coherent Lagrangian (i.e., material) eddies in incompressible,
satellite-derived surface ocean velocity fields. Paradoxically, observed
drifting buoys and floating matter tend to create dissipative-looking patterns
near oceanic eddies, which appear to be inconsistent with the conservative
fluid particle patterns created by coherent Lagrangian eddies. Here we show
that inclusion of inertial effects (i.e., those produced by the buoyancy and
size finiteness of an object) in a rotating two-dimensional incompressible flow
context resolves this paradox. Specifically, we obtain that anticyclonic
coherent Lagrangian eddies attract (repel) negatively (positively) buoyant
finite-size particles, while cyclonic coherent Lagrangian eddies attract
(repel) positively (negatively) buoyant finite-size particles. We show how
these results explain dissipative-looking satellite-tracked surface drifter and
subsurface float trajectories, as well as satellite-derived \emph{Sargassum}
distributions.Comment: Submitted to \emph{Chaos} Focus Issue on Objective detection of
Lagrangian Coherent Structures. Revised 23-Feb-1
Travel time stability in weakly range-dependent sound channels
Travel time stability is investigated in environments consisting of a
range-independent background sound-speed profile on which a highly structured
range-dependent perturbation is superimposed. The stability of both
unconstrained and constrained (eigenray) travel times are considered. Both
general theoretical arguments and analytical estimates of time spreads suggest
that travel time stability is largely controlled by a property of the background sound speed profile. Here, is
the range of a ray double loop and is the ray action variable. Numerical
results for both volume scattering by internal waves in deep ocean environments
and rough surface scattering in upward refracting environments are shown to
confirm the expectation that travel time stability is largely controlled by
.Comment: Submitted to J. Acoust. Soc. Am., 30 June 200
Ray stability in weakly range-dependent sound channels
Ray stability is investigated in environments consisting of a
range-independent background sound-speed profile on which a range-dependent
perturbation, such as that produced by internal waves in deep ocean
environments, is superimposed. Numerical results show that ray stability is
strongly influenced by the background sound speed profile. Ray instability is
shown to increase with increasing magnitude of alpha := I omega^{prime} /
omega, where 2 pi / omega(I) is the range of a ray double loop and I is the ray
action variable. The mechanism, shear-induced instability enhancement, by which
alpha controls ray instability is described.Comment: To appear in JAS
- …