27 research outputs found
Vacuum replicas in two-dimensional QCD
Two-dimensional QCD is studied from the point of view of existence of
multiple chirally noninvariant solutions to the mass-gap equation. The
ground-state solution is reproduced and an infinite set of replica solutions is
discovered for this equation using the WKB quantisation procedure.Comment: LaTeX2e, 9 pages, 1 Postscript figure, uses epsfig.sty, to appear in
Phys.Lett.
1+1 string with quarks at the ends revisited
The canonical description is presented for the string with pointlike masses
at the ends in 1+1 dimensions in two different gauges: in the proper time gauge
and in the light cone one. The classical canonical transformation is written
out explicitly, which relates physical variables in both gauges, and
equivalence of two classical theories is demonstrated in such a way. Both
theories are quantized, and it is shown that quantum theories are not unitary
equivalent. It happens due to the fact that the canonical transformation
depends on interaction. The quantum Poincare algebra proves to be closed in
both cases, so that the requirement of Poincare covariance is not able to
distinguish between two versions of the theory.Comment: 9 pages, LaTeX 2.0
Comment on Possibility of Deeply Bound Hadronic Molecules from Single Pion Exchange
We demonstrate that in calculation, where unitarity constraints are properly imposed, the deeply bound hadronic molecules recently proposed by Close and Downum do not exist
Heavy-light mesons spectrum from the nonperturbative QCD in the einbein field formalism
The spectrum of B and D mesons (including the low lying orbitally and
radially excited states) is calculated using the quark-antiquark Hamiltonian
derived from QCD in the einbein field formalism. Spin-spin and spin-orbit terms
due to the confinement and OGE interactions are taken into account as
perturbations. Results for the masses and splittings are confronted to the
experimental and recent lattice data and are demonstrated to be in a reasonable
agreement with both. We find that the orbital excitations with l=2 and l=3 for
D meson lie approximately in the same region as its first radial excitation
that might solve the mystery of the extremely narrow D(2637) state recently
claimed by DELPHI Collaboration.Comment: 9 pages, LaTeX2e, no figures, 3 tables, typos in formulae and one
reference correcte
Potential regime for heavy quarks dynamics and Lorentz nature of confinement
Propagation of the heavy quark in the field of a static antiquark source is
studied in the framework of effective Dirac equation. The model of QCD vacuum
is described by bilocal gluonic correlators. In the heavy quark limit the
effective interaction is reduced to the potential one with 5/6 Lorentz scalar
and 1/6 Lorentz vector linear confinement, while spin-orbit term is in
agreement with Eichten-Feinberg-Gromes results. New spin-independent
corrections to the leading confining regime are identified, which arise due to
the nonlocality of the interaction in time direction and quark Zitterbewegung.Comment: 10 pages, LaTeX2e, no figure
Orbitally excited D and B mesons in the approach of the QCD string with quarks at the ends
In this letter we discuss the masses and the splittings of 1(2S+1)P_J states
in the spectrum of D and B mesons, as they appear in the approach of the QCD
string with quarks at the ends. We find good agreement of our predictions with
those of other QCD-motivated models as well as with the lattice and
experimental data, including recent experimental results. We discuss the
ordering pattern for P levels in D- and B-mesonic spectrum.Comment: 7 pages, LaTeX2e, 2 EPS figures, added comments, to appear in
Phys.Lett.
Fermion family recurrences in the Dyson-Schwinger formalism
We study the multiple solutions of the truncated propagator Dyson-Schwinger
equation for a simple fermion theory with Yukawa coupling to a scalar field.
Upon increasing the coupling constant , other parameters being fixed, more
than one non-perturbative solution breaking chiral symmetry becomes possible
and we find these numerically. These ``recurrences'' appear as a mechanism to
generate different fermion generations as quanta of the same fundamental field
in an interacting field theory, without assuming any composite structure. The
number of recurrences or flavors is reduced to a question about the value of
the Yukawa coupling, and has no special profound significance in the Standard
Model. The resulting mass function can have one or more nodes and the
measurement that potentially detects them can be thought of as a collider-based
test of the virtual dispersion relation for the charged
lepton member of each family. This requires three independent measurements of
the charged lepton's energy, three-momentum and off-shellness. We illustrate
how this can be achieved for the (more difficult) case of the tau lepton
Analytical approach to chiral symmetry breaking in Minkowsky space
The mass gap equation for spontaneous chiral symmetry breaking is studied
directly in Minkowsky space. In hadronic physics, spontaneous chiral symmetry
breaking is crucial to generate a constituent mass for the quarks, and to
produce the Partially Conserved Axial Current theorems, including a small mass
for the pion. Here a class of finite kernels is used, expanded in Yukawa
interactions. The Schwinger-Dyson equation is solved with an analytical
approach. This improves the state of the art of solving the mass gap equation,
which is usually solved with the equal-time approximation or with the Euclidean
approximation. The mapping from the Euclidean space to the Minkowsky space is
also illustrated.Comment: 7 pages, 3 figure
Glueballs, gluon condensate, and pure glue QCD below T_c
A quasiparticle description of pure glue QCD thermodynamics at T<T_c is
proposed and compared to recent lattice data. Given that a gas of glueballs
with constant mass cannot quantitatively reproduce the early stages of the
deconfinement phase transition, the problem is to identify a relevant mechanism
leading to the observed sudden increase of the pressure, trace anomaly, etc. It
is shown that the strong decrease of the gluon condensate near T_c combined
with the increasing thermal width of the lightest glueballs might be the
trigger of the phase transition.Comment: 5 pages, 5 figures; analysis refined in v2, explanations added; v3 to
appear in EPJ