3,087 research outputs found
Spin structure and longitudinal polarization of hyperon in e+e- annihilation at high energies
Longitudinal polarizations of different kinds of hyperons produced in e+e-
annihilation at LEP I and LEP II energies in different event samples are
calculated using two different pictures for the spin structure of hyperon: that
drawn from polarized deep inelastic lepton-nucleon scattering data or that
using SU(6) symmetric wave functions. The result shows that measurements of
such polarizations should provide useful information to the question of which
picture is more suitable in describing the spin effects in the fragmentation
processes.Comment: 26 pages with 10 figures. Submitted to Phys. Rev.
Contact symmetry of time-dependent Schr\"odinger equation for a two-particle system: symmetry classification of two-body central potentials
Symmetry classification of two-body central potentials in a two-particle
Schr\"{o}dinger equation in terms of contact transformations of the equation
has been investigated. Explicit calculation has shown that they are of the same
four different classes as for the point transformations. Thus in this problem
contact transformations are not essentially different from point
transformations. We have also obtained the detailed algebraic structures of the
corresponding Lie algebras and the functional bases of invariants for the
transformation groups in all the four classes
Hyperon polarization in semi-inclusive deeply inelastic lepton-nucleon scattering at high energy
We calculate the polarizations for different octet hyperons produced in the
current fragmentation regions of the deeply inelastic lepton-nucleon
scatterings and at high energy
using different models for spin transfer in fragmentation processes. The
results show that measurements of those hyperon polarizations should provide
useful information to distinguish between different models in particular the
SU(6) and the DIS pictures used frequently in the literature. We found, in
particular, that measuring the polarization of produced in these
processes can give a better test to the validity of the different spin transfer
models.Comment: 30 pages, 13 figure
Three-dimensional Aeroelastic and Aerothermoelastic Behavior in Hypersonic Flow
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76667/1/AIAA-2005-2175-915.pd
Perturbative QCD and factorization of coherent pion photoproduction on the deuteron
We analyze the predictions of perturbative QCD for pion photoproduction on
the deuteron, gamma D -> pi^0 D, at large momentum transfer using the reduced
amplitude formalism. The cluster decomposition of the deuteron wave function at
small binding only allows the nuclear coherent process to proceed if each
nucleon absorbs an equal fraction of the overall momentum transfer.
Furthermore, each nucleon must scatter while remaining close to its mass shell.
Thus the nuclear photoproduction amplitude, M_{gamma D -> pi^0 D}(u,t),
factorizes as a product of three factors: (1) the nucleon photoproduction
amplitude, M_{gamma N_1 -> pi^0 N_1}(u/4,t/4), at half of the overall momentum
transfer, (2) a nucleon form factor, F_{N_2}(t/4), at half the overall momentum
transfer, and (3) the reduced deuteron form factor, f_d(t), which according to
perturbative QCD, has the same monopole falloff as a meson form factor. A
comparison with the recent JLAB data for gamma D -> pi^0 D of Meekins et al.
[Phys. Rev. C 60, 052201 (1999)] and the available gamma p -> pi^0 p data shows
good agreement between the perturbative QCD prediction and experiment over a
large range of momentum transfers and center of mass angles. The reduced
amplitude prediction is consistent with the constituent counting rule, p^11_T
M_{gamma D -> pi^0 D} -> F(theta_cm), at large momentum transfer. This is found
to be consistent with measurements for photon lab energies E_gamma > 3 GeV at
theta_cm=90 degrees and \elab > 10 GeV at 136 degrees.Comment: RevTeX 3.1, 17 pages, 6 figures; v2: incorporates minor changes as
version accepted by Phys Rev
An explicit height bound for the classical modular polynomial
For a prime m, let Phi_m be the classical modular polynomial, and let
h(Phi_m) denote its logarithmic height. By specializing a theorem of Cohen, we
prove that h(Phi_m) <= 6 m log m + 16 m + 14 sqrt m log m. As a corollary, we
find that h(Phi_m) <= 6 m log m + 18 m also holds. A table of h(Phi_m) values
is provided for m <= 3607.Comment: Minor correction to the constants in Theorem 1 and Corollary 9. To
appear in the Ramanujan Journal. 17 pages
Superconductors with Magnetic Impurities: Instantons and Sub-gap States
When subject to a weak magnetic impurity potential, the order parameter and
quasi-particle energy gap of a bulk singlet superconductor are suppressed.
According to the conventional mean-field theory of Abrikosov and Gor'kov, the
integrity of the energy gap is maintained up to a critical concentration of
magnetic impurities. In this paper, a field theoretic approach is developed to
critically analyze the validity of the mean field theory. Using the
supersymmetry technique we find a spatially homogeneous saddle-point that
reproduces the Abrikosov-Gor'kov theory, and identify instanton contributions
to the density of states that render the quasi-particle energy gap soft at any
non-zero magnetic impurity concentration. The sub-gap states are associated
with supersymmetry broken field configurations of the action. An analysis of
fluctuations around these configurations shows how the underlying supersymmetry
of the action is restored by zero modes. An estimate of the density of states
is given for all dimensionalities. To illustrate the universality of the
present scheme we apply the same method to study `gap fluctuations' in a normal
quantum dot coupled to a superconducting terminal. Using the same instanton
approach, we recover the universal result recently proposed by Vavilov et al.
Finally, we emphasize the universality of the present scheme for the
description of gap fluctuations in d-dimensional superconducting/normal
structures.Comment: 18 pages, 9 eps figure
A Possible Crypto-Superconducting Structure in a Superconducting Ferromagnet
We have measured the dc and ac electrical and magnetic properties in various
magnetic fields of the recently reported superconducting ferromagnet
RuSr2GdCu2O8. Our reversible magnetization measurements demonstrate the absence
of a bulk Meissner state in the compound below the superconducting transition
temperature. Several scenarios that might account for the absence of a bulk
Meissner state, including the possible presence of a sponge-like non-uniform
superconducting or a crypto-superconducting structure in the chemically uniform
Ru-1212, have been proposed and discussed.Comment: 8 pages, 5 PNG figures, submitted to Proceedings of the 9th Japan-US
Workshop on High-Tc Superconductors, Yamanashi, Japan, October 13-15, 1999;
accepted for publication in Physica C (December 24, 1999
Heavy Fermion Stabilization of Solitons in 1+1 Dimensions
We find static solitons stabilized by quantum corrections in a
(1+1)-dimensional model with a scalar field chirally coupled to fermions. This
model does not support classical solitons. We compute the renormalized energy
functional including one-loop quantum corrections. We carry out a variational
search for a configuration that minimizes the energy functional. We find a
nontrivial configuration with fermion number whose energy is lower than the
same number of free fermions quantized about the translationally invariant
vacuum. In order to compute the quantum corrections for a given background
field we use a phase-shift parameterization of the Casimir energy. We identify
orders of the Born series for the phase shift with perturbative Feynman
diagrams in order to renormalize the Casimir energy using perturbatively
determined counterterms. Generalizing dimensional regularization, we
demonstrate that this procedure yields a finite and unambiguous energy
functional.Comment: 27 papes Latex, equation labels corrected, version to be published in
Nucl. Phys.
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