6,547 research outputs found
Color Transparency Effects in Electron Deuteron Interactions at Intermediate Q^2
High momentum transfer electrodisintegration of polarized and unpolarized
deuterium targets, is studied. We show that the importance of final
state interactions-FSI, occuring when a knocked out nucleon interacts with the
other nucleon, depends strongly on the momentum of the spectator nucleon. In
particular, these FSI occur when the essential contributions to the scattering
amplitude arise from internucleon distances . But the absorption
of the high momentum may produce a point like configuration, which
evolves with time. In this case, the final state interactions probe the point
like configuration at the early stage of its evolution. The result is that
significant color transparency effects, which can either enhance or suppress
computed cross sections, are predicted to occur for .Comment: 37 pages LaTex, 12 uuencoded PostScript Figures as separate file, to
be published in Z.Phys.
The alpha-effect and current helicity for fast sheared rotators
We explore the alpha-effect and the small-scale current helicity, for the
case of weakly compressible magnetically driven turbulence that is subjected to
the differential rotation. No restriction is applied to the amplitude of
angular velocity, i.e., the derivations presented are valid for an arbitrary
Coriolis number, though the differential rotation itself is assumed to be weak.
The expressions obtained are used to explore the possible distributions of
alpha-effect and current helicity in convection zones (CZ) of the solar-type
stars. The implications of the obtained results to the mean-field dynamo models
are discussed.Comment: 20 pages, 6 figure
Two-Body Cabibbo-Suppressed Charmed Meson Decays
Singly-Cabibbo-suppressed decays of charmed particles governed by the quark
subprocesses and are analyzed using a
flavor-topology approach, based on a previous analysis of the Cabibbo-favored
decays governed by . Decays to and , where is a
pseudoscalar meson and is a vector meson, are considered. We include
processes in which and are produced.Comment: 18 pages, latex, 2 figures, to be submitted to Phys. Rev.
Koszul binomial edge ideals
It is shown that if the binomial edge ideal of a graph defines a Koszul
algebra, then must be chordal and claw free. A converse of this statement
is proved for a class of chordal and claw free graphs
Investigation of the high momentum component of nuclear wave function using hard quasielastic A(p,2p)X reactions
We present theoretical analysis of the first data on the high energy and
momentum transfer (hard) quasielastic reactions. The cross section
of hard reaction is calculated within the light-cone impulse
approximation based on two-nucleon correlation model for the high-momentum
component of the nuclear wave function. The nuclear effects due to modification
of the bound nucleon structure, soft nucleon-nucleon reinteraction in the
initial and final states of the reaction with and without color coherence have
been considered. The calculations including these nuclear effects show that the
distribution of the bound proton light-cone momentum fraction shifts
towards small values (), effect which was previously derived only
within plane wave impulse approximation. This shift is very sensitive to the
strength of the short range correlations in nuclei. Also calculated is an
excess of the total longitudinal momentum of outgoing protons. The calculations
are compared with data on the reaction obtained from the EVA/AGS
experiment at Brookhaven National Laboratory. These data show -shift in
agreement with the calculations. The comparison allows also to single out the
contribution from short-range nucleon correlations. The obtained strength of
the correlations is in agreement with the values previously obtained from
electroproduction reactions on nuclei.Comment: 30 pages LaTex file and 19 eps figure
Effects of disorder on the wave front depinning transition in spatially discrete systems
Pinning and depinning of wave fronts are ubiquitous features of spatially
discrete systems describing a host of phenomena in physics, biology, etc. A
large class of discrete systems is described by overdamped chains of nonlinear
oscillators with nearest-neighbor coupling and subject to random external
forces. The presence of weak randomness shrinks the pinning interval and it
changes the critical exponent of the wave front depinning transition from 1/2
to 3/2. This effect is derived by means of a recent asymptotic theory of the
depinning transition, extended to discrete drift-diffusion models of transport
in semiconductor superlattices and confirmed by numerical calculations.Comment: 4 pages, 3 figures, to appear as a Rapid Commun. in Phys. Rev.
Final-State Phases in Charmed Meson Two-Body Nonleptonic Decays
Observed decay rates indicate large phase differences among the amplitudes
for the charge states in and but
relatively real amplitudes in the charge states for . This
feature is traced using an SU(3) flavor analysis to a sign flip in the
contribution of one of the amplitudes contributing to the latter processes in
comparison with its contribution to the other two sets. This amplitude may be
regarded as an effect of rescattering and is found to be of magnitude
comparable to others contributing to charmed particle two-body nonleptonic
decays.Comment: 19 pages, latex, 4 figures, to be submitted to Phys. Rev.
Evidence for Color Fluctuations in Hadrons from Coherent Nuclear Diffraction}
A QCD-based treatment of projectile size fluctuations is used to compute
inelastic diffractive cross sections for coherent
hadron-nuclear processes. We find that fluctuations near the average size give
the major contribution to the cross section with contribution
from small size configurations.
The computed values of are consistent with the limited
available data. The importance of coherent diffraction studies for a wide range
of projectiles for high energy Fermilab fixed target experiments is emphasized.
The implications of these significant color fluctuations for relativistic heavy
ion collisions are discussed.Comment: Report number DOE/ER 40427-13-N93 11 pages, 3 figures available from
author Mille
Finite sum of gluon ladders and high energy cross sections
A model for the Pomeron at is suggested. It is based on the idea of a
finite sum of ladder diagrams in QCD. Accordingly, the number of -channel
gluon rungs and correspondingly the powers of logarithms in the forward
scattering amplitude depends on the phase space (energy) available, i.e. as
energy increases, progressively new prongs with additional gluon rungs in the
-channel open. Explicit expressions for the total cross section involving
two and three rungs or, alternatively, three and four prongs (with
and as highest terms, respectively) are fitted to the proton-proton
and proton-antiproton total cross section data in the accelerator region. Both
QCD calculation and fits to the data indicate fast convergence of the series.
In the fit, two terms (a constant and a logarithmically rising one) almost
saturate the whole series, the term being small and the next one,
, negligible. Theoretical predictions for the photon-photon total
cross section are also given.Comment: 18 pages, LaTeX, 2 EPS figures, uses axodraw.st
Three flavors of extremal Betti tables
We discuss extremal Betti tables of resolutions in three different contexts.
We begin over the graded polynomial ring, where extremal Betti tables
correspond to pure resolutions. We then contrast this behavior with that of
extremal Betti tables over regular local rings and over a bigraded ring.Comment: 20 page
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