696 research outputs found
Zero mode effect in the four quark states
We calculate the masses of the four quark states which decay
dominantly into and respectively by QCD sum rules approach.
We include the zero mode contribution and find it plays an important role in
the sum rules. We predict that the masses of the states and
both are 1.4-1.5 GeV. This is close to the experimental candidates
and .Comment: 5 pages, 4 Postscript figure
Spontaneous symmetry breaking for long-wave gravitons in the early Universe
It is shown that nonlinear terms in equations of gravitons on the background
of curved space-time of the expanding Universe can solve the problem of the
negative square of the effective mass formally arising in linear approximation
for gravitons. Similar to well known spontaneous breaking of symmetry in
Goldstone model one must take another vacuum so that nonzero vacuum expectation
value of the quantized graviton field leads to change of spectrum for
gravitons. There appears two graviton fields, one with the positive mass,
another with the zero mass. Energy density and the density of particles created
by gravitation of the expanding Universe are calculated for some special cases
of the scale factor. Numerical results are obtained for the dust universe case.Comment: 13 page
Conductivity in Two-Dimensional Disordered Model with Anisotropic Long-Range Hopping
We consider two-dimensional system of particles localized on randomly
distributed sites of squared lattice with anisotropic transfer matrix elements
between localized sites. By summing of "diffusion ladder" and "cooperon ladder"
type vertices we calculated the conductivity for various sites and particles
densities.Comment: Latex, 10 page
Radiative Effects in the Standard Model Extension
The possibility of radiative effects induced by the Lorentz and CPT
non-invariant interaction term for fermions in the Standard Model Extension is
investigated. In particular, electron-positron photo-production and photon
emission by electrons and positrons are studied. The rates of these processes
are calculated in the Furry picture. It is demonstrated that the rates obtained
in the framework of the model adopted strongly depend on the polarization
states of the particles involved. As a result, ultra-relativistic particles
produced should occupy states with a preferred spin orientation, i.e., photons
have the sign of polarization opposite to the sign of the effective potential,
while charged particle are preferably in the state with the helicity coinciding
with the sign of the effective potential. This leads to evident spatial
asymmetries which may have certain consequences observable at high energy
accelerators, and in astrophysical and cosmological studies.Comment: 10 pages, 2 figures, Revtex4, to appear in Phys.Rev.D, misprints are
correcte
Spin-down of neutron stars by neutrino emission
We study the spin-down of a neutron star during its early stages due to the
neutrino emission. The mechanism we consider is the subsequent collisions of
the produced neutrinos with the outer shells of the star. We find that this
mechanism can indeed slow down the star rotation but only in the first tens of
seconds of the core formation, which is when the appropriate conditions of flux
and collision rate are met. We find that this mechanism can extract less than 1
% of the star angular momentum, a result which is much less than previously
estimated by other authors.Comment: 9 pages, 2 eps figures, RevTeX 4-1. The paper was significantly
modified. Now it addresses only the issues of a neutron star spin-down.
Version to be published in Phys. Rev.
A search for J^{PC}=1^{-+} exotic mesons in the pi- pi- pi+ and pi- pi0 pi0 systems
A partial wave analysis (PWA) of the pi-pi-pi+ and pi-pi0pi0 systems produced
in the reaction pi- p -> (3pi)-p at 18 GeV/c was carried out using an isobar
model assumption. This analysis is based on 3.0M pi-pi0pi0 events and 2.6M
pi-pi-pi+ events and shows production of the a2(1320), pi2(1670) and \pi(1800)
mesons. An earlier analysis of 250K pi-pi-pi+ events from the same experiment
showed possible evidence for a J^{PC}=1^{-+}$ exotic meson with a mass of 1.6
GeV/c^2 decaying into rho pi. In this analysis of a higher statistics sample of
the (3pi)- system in two charged modes we find no evidence of an exotic meson.Comment: 4 pages, 5 figures, added comment about the negative reflectivity
exotic wave
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