8,431 research outputs found

### Parity Nonconservation in the Photodisintegration of the Deuteron at Low Energy

The parity-nonconserving asymmetry in the deuteron photodisintegration,
$\vec{\gamma}+d\to n+p$, is considered with the photon energy ranged up to 10
MeV above the threshold. The aim is to improve upon a schematic estimate
assuming the absence of tensor as well as spin-orbit forces in the
nucleon-nucleon interaction. The major contributions are due to the
vector-meson exchanges, and the strong suppression of the pion-exchange
contribution is confirmed. A simple argument, going beyond the observation of
an algebraic cancellation, is presented. Contributions of meson-exchange
currents are also considered, but found to be less significant.Comment: 12 pages, 6 figures, typeset by REVTeX (two-column format) and BIBTe

### Parity violation in $pp$ scattering and vector-meson weak-coupling constants

We calculate the parity-nonconserving longitudinal asymmetry in the elastic
$\vec{p} p$ scattering at the energies where experimental data are available.
In addition to the standard one-meson exchange weak potential, the variation of
the strong-coupling constants and the non-standard effects such as form factors
and $2 \pi$-exchange description of the $\rho$-exchange potential are taken
into account. With the extra effects, we investigate the compatibility of the
experimental data and the presently-known range of the vector-meson
weak-coupling constants.Comment: Contribution to the proceedings of the 3rd Asia-Pacific conference on
few-body problems in physics, Suranaree Univ. of Technology, Nakhon
Ratchasima, Thailand, July 26 - 30, 200

### Deuteron Anapole Moment with Heavy Mesons

Parity-nonconserving two-body currents due to vector meson exchange are
considered with the aim to determine the related contributions to the anapole
moment. A particular attention is given to the requirement of current
conservation which is essential for a reliable estimate of this quantity. An
application is made for the deuteron case.Comment: 23 pages, 5 EPS figures, uses REVTeX 4, v2: fixes layout problem

### Neutron Stars with Bose-Einstein Condensation of Antikaons as MIT Bags

We investigate the properties of an antikaon in medium, regarding itas a MIT
bag. We first construct the MIT bag model for a kaon with$\sigma^*$ and $\phi$
in order to describe the interaction of$s$-quarks in hyperonic matter in the
framework of the modifiedquark-meson coupling model. The coupling constant
$g'^{B_K}_\sigma$in the density-dependent bag constant $B(\sigma)$ is treated
as afree parameter to reproduce the optical potential of a kaon in asymmetric
matter and all other couplings are determined by usingSU(6) symmetry and the
quark counting rule. With various values ofthe kaon potential, we calculate the
effective mass of a kaon inmedium to compare it with that of a point-like kaon.
We thencalculate the population of octet baryons, leptons and $K^-$ and
theequation of state for neutron star matter. The results show thatkaon
condensation in hyperonic matter is sensitive to the $s$-quarkinteraction and
also to the way of treating the kaon. The mass andthe radius of a neutron star
are obtained by solving theTolmann-Oppenheimer-Volkoff equation.Comment: 14 figure

### Optical conductivity of one-dimensional narrow-gap semiconductors

The optical conductivities of two one-dimensional narrow-gap semiconductors,
anticrossing quantum Hall edge states and carbon nanotubes, are studied using
bosonization method. A lowest order renormalization group analysis indicates
that the bare band gap can be treated perturbatively at high
frequency/temperature. At very low energy scale the optical conductivity is
dominated by the excitonic contribution, while at temperature higher than a
crossover temperature the excitonic features are eliminated by thermal
fluctuations. In case of carbon nanotubes the crossover temperature scale is
estimated to be 300 K.Comment: RevTeX4 file, 6 pages, no figur

### Two-pion-exchange parity-violating potential and $\vec{n} p \to d \gamma$

We calculate the parity-violating nucleon-nucleon potential in heavy-baryon
chiral perturbation theory up to the next-to-next-to-leading order. The
one-pion exchange comes in the leading order and the next-to-next-to-leading
order consists of two-pion-exchange and the two-nucleon contact terms. In order
to investigate the effect of the higher order contributions, we calculate the
parity-violating asymmetry in $\vec{n} p \to d \gamma$ at the threshold. The
one-pion dominates the physical observable and the two-pion contribution is
about or less than 10% of the one-pion contribution.Comment: 3 pages, contribution to the workshop PAVI06 held in Milos island,
Greece, May 16-20, 200

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