494 research outputs found
Exclusive production in proton-proton collisions in the resonance model
The exclusive meson production in proton-proton reactions is
calculated within the resonance model. The considered model was already
successfully applied to the description of , , , ,
production in proton-proton collisions. The only new parameter
entering into the model is the mixing angle which
is taken equal to .Comment: 7 pages, 1 figure, to appear in the brief report section of PR
A relativistic quark model for the Omega- electromagnetic form factors
We compute the Omega- electromagnetic form factors and the decuplet baryon
magnetic moments using a quark model application of the Covariant Spectator
Theory. Our predictions for the Omega- electromagnetic form factors can be
tested in the future by lattice QCD simulations at the physical strange quark
mass.Comment: 13 pages, 5 figure
Lateral distribution of high energy hadrons and gamma ray in air shower cores observed with emulsion chambers
A high energy event of a bundle of electrons, gamma rays and hadronic gamma rays in an air shower core were observed. The bundles were detected with an emulsion chamber with thickness of 15 cm lead. This air shower is estimated to be initiated with a proton with energy around 10 to the 17th power to 10 to the 18th power eV at an altitude of around 100 gmc/2. Lateral distributions of the electromagnetic component with energy above 2 TeV and also the hadronic component of energy above 6 TeV of this air shower core were determined. Particles in the bundle are produced with process of the development of the nuclear cascade, the primary energy of each interaction in the cascade which produces these particles is unknown. To know the primary energy dependence of transverse momentum, the average products of energy and distance for various average energies of secondary particles are studied
Deep inelastic scattering on asymmetric nuclei
We study deep inelastic scattering on isospin asymmetric nuclei. In particular, the difference of the nuclear structure functions and the Gottfried sum rule for the lightest mirror nuclei, 3He and 3H, are investigated. It is found that such systems can provide significant information on charge symmetry breaking and flavor asymmetry in the nuclear medium. Furthermore, we propose a new method to extract the neutron structure function from radioactive isotopes far from the line of stability. We also discuss the flavor asymmetry in the Drell-Yan process with isospin asymmetric nuclei
The role of in and reactions
The near threshold meson production in proton-proton and
collisions is studied with the assumption that the production mechanism is due
to the sub--threshold resonance. The , and
-meson exchanges for proton-proton collisions are considered. It is
shown that the contribution to the reaction from the t-channel
meson exchange is dominant. With a significant
coupling ( = 0.13), both and
data are very well reproduced. The significant coupling of
the resonance to is compatible with previous indications
of a large component in the quark wave function of the
resonance and may be the real origin of the significant enhancement of the
production over the naive OZI-rule predictions.Comment: 15 pages, 6 figure
The effect of different baryons impurities
We demonstrate the different effect of different baryons impurities on the
static properties of nuclei within the framework of the relativistic mean-field
model. Systematic calculations show that and has the
same attracting role as hyperon does in lighter hypernuclei.
and hyperon has the attracting role only for the protons
distribution, and has a repulsive role for the neutrons distribution. On the
contrary, and hyperon attracts surrounding neutrons and
reveals a repulsive force to the protons. We find that the different effect of
different baryons impurities on the nuclear core is due to the different third
component of their isospin.Comment: 9 page
Does the effective Lagrangian for low-energy QCD scale?
QCD is not an approximately scale invariant theory. Hence a dilaton field is
not expected to provide a good description of the low-energy dynamics
associated with the gluon condensate. Even if such a field is introduced, it
remains almost unchanged in hadronic matter at normal densities. This is
because the large glueball mass together with the size of the phenomenological
gluon condensate ensure that changes to that condensate are very small at such
densities. Any changes in hadronic masses and decay constants in matter
generated by that condensate will be much smaller that those produced directly
by changes in the quark condensate. Hence masses and decay constants are not
expected to display a universal scaling.Comment: 7 pages (RevTeX), MC/TH 94/0
K^+ production in baryon-baryon and heavy-ion collisions
Kaon production cross sections in nucleon-nucleon, nucleon-delta and
delta-delta interactions are studied in a boson exchange model. For the latter
two interactions, the exchanged pion can be on-mass shell, only contributions
due to a virtual pion are included via the Peierls method by taking into
account the finite delta width. With these cross sections and also those for
pion-baryon interactions, subthreshold kaon production from heavy ion
collisions is studied in the relativistic transport model.Comment: to appear in Phys. Rev.
Variations of nuclear binding with quark masses
We investigate the variation with light quark mass of the mass of the nucleon as well as the masses of the mesons commonly used in a one-boson-exchange model of the nucleon-nucleon force. Care is taken to evaluate the meson mass shifts at the kinematic point relevant to that problem. Using these results, we evaluate the corresponding changes in the energy of the 1S0 antibound state and the binding energies of the deuteron, triton, and selected finite nuclei by using a one-boson exchange model. The results are discussed in the context of possible corrections to the standard scenario for Big Bang nucleosynthesis in the case where, as suggested by recent observations of quasar absorption spectra, the quark masses may have changed over the age of the Universe.M.E. Carrillo-Serrano, I.C. Cloët, K. Tsushima, A.W.Thomas and I.R. Afna
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