811 research outputs found
The matrix Hamiltonian for hadrons and the role of negative-energy components
The world-line (Fock-Feynman-Schwinger) representation is used for quarks in
arbitrary (vacuum and valence gluon) field to construct the relativistic
Hamiltonian. After averaging the Green's function of the white system
over gluon fields one obtains the relativistic Hamiltonian, which is matrix in
spin indices and contains both positive and negative quark energies. The role
of the latter is studied in the example of the heavy-light meson and the
standard einbein technic is extended to the case of the matrix Hamiltonian.
Comparison with the Dirac equation shows a good agreement of the results. For
arbitrary system the nondiagonal matrix Hamiltonian components are
calculated through hyperfine interaction terms. A general discussion of the
role of negative energy components is given in conclusion.Comment: 29 pages, no figure
Diquark and triquark correlations in the deconfined phase of QCD
We use the non-perturbative Q\bar Q potential at finite temperatures derived
in the Field Correlator Method to obtain binding energies for the lowest
eigenstates in the Q\bar Q and QQQ systems (Q=c,b). The three--quark problem is
solved by the hyperspherical method. The solution provides an estimate of the
melting temperature and the radii for the different diquark and triquark bound
states. In particular we find that J/\psi and ground states survive up to
T \sim 1.3 T_c, where T_c is the critical temperature, while the corresponding
bottomonium states survive even up to higher temperature, T \sim 2.2 T_c.Comment: 11 pages, 1 figure; published versio
QCD string and the Lorentz nature of confinement
We address the question of the Lorentz nature of the effective long-range
interquark interaction generated by the QCD string with quarks at the ends.
Studying the Dyson-Schwinger equation for a heavy-light quark-antiquark system,
we demonstrate explicitly how a Lorentz-scalar interaction appears in the
Diraclike equation for the light quark, as a consequence of chiral symmetry
breaking. We argue that the effective interquark interaction in the Hamiltonian
of the QCD string with quarks at the ends stems from this effective scalar
interaction.Comment: LaTeX2e, 5 pages, uses jetpl.cls (included), to appear in JETP Let
QCD string in light-light and heavy-light mesons
The spectra of light-light and heavy-light mesons are calculated within the
framework of the QCD string model, which is derived from QCD in the Wilson loop
approach. Special attention is payed to the proper string dynamics that allows
us to reproduce the straight-line Regge trajectories with the inverse slope
being 2\pi\sigma for light-light and twice as small for heavy-light mesons. We
use the model of the rotating QCD string with quarks at the ends to calculate
the masses of several light-light mesons lying on the lowest Regge trajectories
and compare them with the experimental data as well as with the predictions of
other models. The masses of several low-lying orbitally and radially excited
heavy--light states in the D, D_s, B, and B_s meson spectra are calculated in
the einbein (auxiliary) field approach, which has proven to be rather accurate
in various calculations for relativistic systems. The results for the spectra
are compared with the experimental and recent lattice data. It is demonstrated
that an account of the proper string dynamics encoded in the so-called string
correction to the interquark interaction leads to an extra negative
contribution to the masses of orbitally excited states that resolves the
problem of the identification of the D(2637) state recently claimed by the
DELPHI Collaboration. For the heavy-light system we extract the constants
\bar\Lambda, \lambda_1, and \lambda_2 used in Heavy Quark Effective Theory
(HQET) and find good agreement with the results of other approaches.Comment: RevTeX, 42 pages, 7 tables, 7 EPS figures, uses epsfig.sty, typos
corrected, to appear in Phys.Rev.
Spectroscopy of Baryons Containing Two Heavy Quarks in Nonperturbative Quark Dynamics
We have studied the three quark systems in an Effective Hamiltonian approach
in QCD. With only two parameters: the string tension sigma and the strong
coupling constant alpha_s we obtain a good description of the ground state
light and heavy baryons. The prediction of masses of the doubly heavy baryons
not discovered yet are also given. In particular, a mass of 3620 MeV for the
lightest (ccu) baryon is found by employing the hyperspherical formalism to the
three quark confining potential with the string junction.Comment: 8 pages, LaTe
Effects of perturbative exchanges in a QCD-string model
The QCD-string model for baryons derived by Simonov and used for the
calculation of baryon magnetic moments in a previous paper is extended to
include also perturbative gluon and meson exchanges. The mass spectrum of the
baryon multiplet is studied. For the meson interaction either the pseudoscalar
or pseudovector coupling is used. Predictions are compared with the
experimental data. Besides these exchanges the influence of excited quark
orbitals on the baryon ground state are considered by performing a multichannel
calculation. The nucleon-Delta splitting increases due to the mixing of higher
quark states while the baryon magnetic momenta decrease. The multichannel
calculation with perturbative exchanges is shown to yield reasonable magnetic
moments while the mass spectrum is close to experiment.Comment: 37 pages Revtex with 2 figures, to be published in Phys. Atom. Nucl.
dedicated to the 70th Birthday of Yu. A. Simono
Casimir scaling as a test of QCD vacuum
Recent accurate measurements of static potentials between sources in various
representations of the gauge group SU(3) performed by G.Bali provide a crucial
test of the QCD vacuum models and different approaches to confinement. The
Casimir scaling of the potential observed for all measured distances implies
strong suppression of higher cumulant contributions. The consequences for the
instanton vacuum model and the spectrum of the QCD string are also discussed.Comment: LaTeX, 15 pages, 1 figur
Vibrating the QCD string
The large distance behaviour of the adiabatic hybrid potentials is studied in
the framework of the QCD string model. The calculated spectra are shown to be
the result of interplay between potential-type longitudinal and string-type
transverse vibrations.Comment: LaTeX2e, 9 pages, 2 Postscript figures, final version to appear in
Yad.Fi
Di-Pion Decays of Heavy Quarkonium in the Field Correlator Method
Mechanism of di-pion transitions in
bottomonium and charmonium is studied with the use of the chiral
string-breaking Lagrangian allowing for the emission of any number of
and not containing fitting parameters. The transition amplitude
contains two terms, , where first term (a) refers to subsequent one-pion
emission: and second term
(b) refers to two-pion emission: . The one-parameter formula for the di-pion mass
distribution is derived, (phase space) , where
. The
parameter dependent on the process is calculated, using SHO wave
functions and imposing PCAC restrictions (Adler zero) on amplitudes a,b. The
resulting di-pion mass distributions are in agreement with experimental data.Comment: 62 pages,8 tables,7 figure
Static potential in baryon in the method of field correlators
The static three-quark potential in arbitrary configuration of quarks is
calculated analytically. It is shown to be in a full agreement with the precise
numerical simulations in lattice QCD. The results of the work have important
application in nuclear physics, as they allow to perform accurate analytic
calculations of spectra of the baryons.Comment: 12 pages, 4 eps figures, latex2e, to appear in Yad.Fi
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