9,950 research outputs found
Masses of light tetraquarks and scalar mesons in the relativistic quark model
Masses of the ground state light tetraquarks are dynamically calculated in
the framework of the relativistic diquark-antidiquark picture. The internal
structure of the diquark is taken into account by calculating the form factor
of the diquark-gluon interaction in terms of the overlap integral of the
diquark wave functions. It is found that scalar mesons with masses below 1 GeV:
f_0(600) (\sigma), K^*_0(800) (\kappa), f_0(980) and a_0(980) agree well with
the light tetraquark interpretation.Comment: 9 pages, Report-no adde
Charm mass corrections to the bottomonium mass spectrum
The one-loop corrections to the bottomonium mass spectrum due to the finite
charm mass are evaluated in the framework of the relativistic quark model. The
obtained corrections are compared with the results of perturbative QCD.Comment: 6 pages, references added, version to be published in Phys. Rev.
Excited heavy tetraquarks with hidden charm
The masses of the excited heavy tetraquarks with hidden charm are calculated
within the relativistic diquark-antidiquark picture. The dynamics of the light
quark in a heavy-light diquark is treated completely relativistically. The
diquark structure is taken into account by calculating the diquark-gluon form
factor. New experimental data on charmonium-like states above open charm
threshold are discussed. The obtained results indicate that X(3872), Y(4260),
Y(4360), Z(4248), Z(4433) and Y(4660) could be tetraquark states with hidden
charm.Comment: 11 page
Relativistic description of the charmonium mass spectrum
The charmonium mass spectrum is considered in the framework of the
constituent quark model with the relativistic treatment of the c quark. The
obtained masses are in good agreement with the existing experimental data
including the mass of eta_c(2S).Comment: 5 page
Bosonization in Particle Physics
Path integral techniques in collective fields are shown to be a useful
analytical tool to reformulate a field theory defined in terms of microscopic
quark (gluon) degrees of freedom as an effective theory of collective boson
(meson) fields. For illustrations, the path integral bosonization approach is
applied to derive a (non)linear sigma model from a Nambu-Jona-Lasinio (NJL)
quark model. The method can be extended to include higher order derivative
terms in meson fields or heavy-quark symmetries. It is also approximately
applicable to QCD.Comment: 12 pages, LaTeX, uses lamuphys.sty, 5 LaTeX figures, talk given at
the Workshop "Field Theoretical Tools in Polymer and Particle Physics",
University Wuppertal, June 17-19, 199
Gravitational catalysis of chiral and color symmetry breaking of quark matter in hyperbolic space
We study the dynamical breaking of chiral and color symmetries of dense quark
matter in the ultrastatic hyperbolic spacetime in the framework
of an extended Nambu--Jona-Lasinio model. On the basis of analytical
expressions for chiral and color condensates as functions of curvature and
temperature, the phenomenon of dimensional reduction and gravitational
catalysis of symmetry breaking in strong gravitational field is demonstrated in
the regime of weak coupling constants. In the case of strong couplings it is
shown that curvature leads to small corrections to the flat-space values of
condensate and thus enhances the symmetry breaking effects. Finally, using
numerical calculations phase transitions under the influence of chemical
potential and negative curvature are considered and the phase portrait of the
system is constructed.Comment: 14 pages, 5 figure
Benefits of host genetic diversity for resistance to infection depend on parasite diversity
Host populations with high genetic diversity are predicted to have lower levels of infection prevalence. This theory assumes that host genetic diversity results in variation in susceptibility and that parasites exhibit variation in infectivity. Empirical studies on the effects of host heterogeneity typically neglect the role of parasite diversity. We conducted three laboratory experiments designed to test if genetic variation in Daphnia magna populations and genetic variation in its parasites together influence the course of parasite spread after introduction. We found that a natural D. magna population exhibited variation in susceptibility to infection by three parasite species and had strong host clone–parasite species interactions. There was no effect of host heterogeneity in experimental host populations (polycultures and monocultures) separately exposed to single strains of three parasite species. When we manipulated the genetic diversity of a single parasite species and exposed them to host monocultures and polycultures, we found that parasite prevalence increased with the number of parasite strains. Host monocultures exposed to several parasite strains had higher mean parasite prevalence and higher variance than polycultures. These results indicate that effect of host genetic diversity on the spread of infection depends on the level of genetic diversity in the parasite population
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