2,373 research outputs found
Gerasimov-Drell-Hearn Sum Rule and the Discrepancy between the New CLAS and SAPHIR Data
Contribution of the K^+\Lambda channel to the Gerasimov-Drell-Hearn (GDH) sum
rule has been calculated by using the models that fit the recent SAPHIR or CLAS
differential cross section data. It is shown that the two data sets yield quite
different contributions. Contribution of this channel to the forward spin
polarizability of the proton has been also calculated. It is also shown that
the inclusion of the recent CLAS C_x and C_z data in the fitting data base does
not significantly change the result of the present calculation. Results of the
fit, however, reveal the role of the S_{11}(1650), P_{11}(1710), P_{13}(1720),
and P_{13}(1900) resonances for the description of the C_x and C_z data. A
brief discussion on the importance of these resonances is given. Measurements
of the polarized total cross section \sigma_{TT'} by the CLAS, LEPS, and MAMI
collaborations are expected to verify this finding.Comment: 15 pages, 8 figure
Dynamical coupled-channel approach to hadronic and electromagnetic production of kaon-hyperon on the proton
A dynamical coupled-channel formalism for processes and
is presented which provides a comprehensive investigation of
recent data on the reaction. The non-resonant
interactions within the subspace are derived from effective
Lagrangians, using a unitary transformation method. The calculations of
photoproduction amplitudes are simplified by casting the coupled-channel
equations into a form such that the empirical amplitudes
are input and only the parameters associated with the channel are
determined by performing -fits to all of the available data for and . Good
agreement between our models and those data are obtained. In the fits to channels, most of the parameters are constrained within of
the values given by the Particle Data Group and/or quark model predictions,
while for parameters, ranges compatible with broken
symmetry are imposed. The main reaction mechanisms in photoproduction are singled out and issues related to newly suggested
resonances , , and are studied. Results illustrating
the importance of using a coupled-channel treatment are reported. Meson cloud
effects on the transitions are also discussed.Comment: Accepted Physical Review
Isovector Channel Role of Relativistic Mean Field Models in the Neutrino Mean Free Path
An improvement in the treatment of the isovector channel of relativistic mean
field (RMF) models based on effective field theory (E-RMF) is suggested, by
adding an isovector scalar (delta) meson and using a similar procedure to the
one used by Horowitz and Piekarewicz to adjust the isovector-vector channel in
order to achieve a softer density dependent symmetry energy of the nuclear
matter at high density. Their effects on the equation of state (EOS) at high
density and on the neutrino mean free path (NMFP) in neutron stars are
discussed.Comment: 20 pages, 8 figure
Strange Particle Production Via The Weak Interaction
The differential cross sections for the neutrino-induced weak charged current
production of strange particles in the threshold energy region are presented.
The general representation of the weak hadronic current is newly developed in
terms of eighteen unknown invariant amplitudes to parametrize the hadron
vertex. The Born term approximation is used for the numerical calculations in
the framework of the Cabibbo theory and SU(3) symmetry. For unpolarized octet
baryons four processes are investigated, whereas in the case of polarized
baryons only one process is chosen to study the sensitivity of the differential
cross section to the various polarizations of the initial state nucleon and the
final state hyperon.Comment: This paper was originally submitted to Physical Review C and
published on 30 August, 201
Photodefinition of channel waveguide in electro-optic polymer
Polymers with optically active nonlinear chromophores have been shown to have a promising future in low cost and high speed electro–optic device applications. However, a main question of concern is the photochemical stability of the chromophores for long term application. The chromophore TCVDPA with a benzene bridge between a tricyanovinyl acceptor and an amino donor has been reported to have high photochemical stability combined with high electro-optic activity. In the current work direct waveguide definition of the host polymer SU-8, a negative photoresist, containing this chromophore by masked UV exposure followed by development, has been demonstrated. This was possible by utilizing the chromophore low absorption window in the UV region that allows crosslinking of the host polymer by exposing to UV light followed by thermal curing
Neutrino Electromagnetic Form Factors Effect on the Neutrino Cross Section in Dense Matter
The sensitivity of the differential cross section of the interaction between
neutrino-electron with dense matter to the possibly nonzero neutrino
electromagnetic properties has been investigated. Here, the relativistic mean
field model inspired by effective field theory has been used to describe non
strange dense matter, both with and without the neutrino trapping. We have
found that the cross section becomes more sensitive to the constituent
distribution of the matter, once electromagnetic properties of the neutrino are
taken into account. The effects of electromagnetic properties of neutrino on
the cross section become more significant for the neutrino magnetic moment
mu_nu > 10^{-10} mu_B and for the neutrino charge radius R > 10^{-5} MeV^{-1}.Comment: 24 pages, 10 figures, submitted to Physical Review
Gauge-invariant tree-level photoproduction amplitudes with form factors
We show how the gauge-invariance formulation given by Haberzettl is
implemented in practice for photoproduction amplitudes at the tree level with
form factors describing composite nucleons. We demonstrate that, in contrast to
Ohta's gauge-invariance prescription, this formalism allows electric current
contributions to be multiplied by a form factor, i.e., it does not require that
they be treated like bare currents. While different in detail, this
nevertheless lends support to previous ad hoc approaches which multiply the
Born amplitudes by an overall form factor. Numerical results for kaon
photoproduction off the nucleon are given. They show that the gauge procedure
by Haberzettl leads to much improved values as compared to Ohta's
prescription.Comment: 5 pages, RevTeX, two eps figure
Lazy AC-Pattern Matching for Rewriting
We define a lazy pattern-matching mechanism modulo associativity and
commutativity. The solutions of a pattern-matching problem are stored in a lazy
list composed of a first substitution at the head and a non-evaluated object
that encodes the remaining computations. We integrate the lazy AC-matching in a
strategy language: rewriting rule and strategy application produce a lazy list
of terms.Comment: In Proceedings WRS 2011, arXiv:1204.531
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