10,677 research outputs found
Production of pair in electron-positron annihilation in the Nambu-Jona-Lasinio model
The process is described in the framework of the
expanded NJL model in the energy region from 0.9 GeV to 1.5 GeV. The
contribution of intermediate state with vector mesons , and , where is the first radial
excitation of - meson was taken into account. Results obtained are in
satisfactory agreement with experimental data.Comment: 5 pages, 1 figure, 1 tabl
Excited scalar mesons in a chiral quark model
First radial excitations of the isoscalar and isovector scalar mesons
f_0(400-1200), f_0(980) and a_0(980) are investigated in the framework of a
nonlocal version of a chiral quark model of the Nambu--Jona-Lasinio type. It is
shown that f_0(1370), f_J(1710) and a_0(1450) are the first radially excited
states of f_0(400-1200), f_0(980) and a_0(980) which are ground states of the
scalar meson nonet. The mesons' masses and strong decay widths are calculated.
The scalar resonance f_0(1500) is supposed to be a glueball. The status of
K_0^*(1430) is discussed.Comment: LaTeX, 1 figure, minor misprints eradicate
Relativistic particle dynamics in D=2+1
We propose a SUSY variant of the action for a massless spinning particles via
the inclusion of twistor variables. The action is constructed to be invariant
under SUSY transformations and -reparametrizations even when an
interaction field is including. The constraint analysis is achieved and the
equations of motion are derived. The commutation relations obtained for the
commuting spinor variables show that the particle states have
fractional statistics and spin. At once we introduce a possible massive term
for the non-interacting model.Comment: 11 page
Convergence in a multidimensional randomized Keynesian beauty contest
We study the asymptotics of a Markovian system of particles in
in which, at each step in discrete time, the particle farthest from
the current centre of mass is removed and replaced by an independent random particle. We show that the limiting configuration contains
coincident particles at a random location . A key tool
in the analysis is a Lyapunov function based on the squared radius of gyration
(sum of squared distances) of the points. For d=1 we give additional results on
the distribution of the limit , showing, among other things, that it
gives positive probability to any nonempty interval subset of , and
giving a reasonably explicit description in the smallest nontrivial case, N=3.Comment: 26 pages, 4 figure
Proximity-induced transport in hybrid mesoscopic normal-superconducting metal structures
Using an approach based on quasiclassical Green's functions we present a
theoretical study of transport in mesoscopic S/N structures in the diffusive
limit. The subgap conductance in S/N structures with barriers (zero bias and
finite bias anomalies) are discused. We also analyse the temperature dependence
of the conductance variation for a Andreev interferometer. We
show that besides the well know low temperature maximum a second maximum near
may appear. We present the results of studies on the Josephson effect in
4 terminal S/N/S contacts and on the possible sign reversal of the Josephson
critical current.Comment: 8 pages, 5 figures, with added refrence
rho(omega)-> pi^0 pi^0 gamma, rho(omega) -> eta pi^0 gamma decays in the local quark Nambu--Jona-Lasinio model
The branching ratios and photon spectra of the rare processes rho(omega)->
pi^0 pi^0 gamma, rho(omega) -> eta pi^0 gamma are calculated in the framework
of the standard local quark Nambu--Jona-Lasinio (NJL) model. Three types of
diagrams are considered: the quark box and the pole diagrams with scalar
(sigma,a_0(980)) and vector (rho,omega) mesons. The obtained estimations for
the widths of the processes rho(omega)-> pi^0 pi^0 gamma are in satisfactory
agreement with existing experimental data. Predictions are made for the widths
of the processes rho(omega) -> eta pi^0 gamma.Comment: 6 pages, 5 figure
Two-photon decays of vector mesons and dilepton decays of scalar mesons in dense matter
Two-photon decays of vector mesons and dilepton decays of scalar mesons which
are forbidden in vacuum and can occur in dense baryonic matter due to the
explicit violation of Lorentz symmetry are described within a quark model of
the Nambu--Jona-Lasinio type. The temperature and chemical potential dependence
of these processes is investigated. It is found that their contribution to the
production of photons and leptons in heavy-ion collisions is enhanced near the
conditions corresponding to the restoration of chiral symmetry. Moreover, in
the case of the a_0 meson and especially the \rho-meson, a resonant behaviour
(an additional amplification) is observed due to the degeneration of \rho and
a_0 masses when a hot hadron matter is approaching a chirally symmetric phase.Comment: 20 figures, IOP styl
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