563 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
Glueballs, gluerings and gluestars in the d=2+1 SU(N) gauge theory
The 3d gluodynamics which governs the large T quark gluon plasma is studied
in the framework of the field correlator method. Field correlators and spacial
string tension are derived through the gluelump Green's functions. The glueball
spectrum is calculated both in C=-1 as well as in C=+1 sectors, and multigluon
bound states in the form of "gluon rings" and "gluon stars" are computed
explicitly. Good overall agreement with available lattice data is observed.Comment: 19 page
Dynamics of quark-gluon plasma from Field correlators
It is argued that strong dynamics in the quark-gluon plasma and bound states
of quarks and gluons is mostly due to nonperturbative effects described by
field correlators. The emphasis in the paper is made on two explicit
calculations of these effects from the first principles: one analytic using
gluelump Green's functions and another using independent lattice data on
correlators. The resulting hadron spectra are investigated in the range T_c < T
< 2T_c. The spectra of charmonia, bottomonia, light s-sbar mesons, glueballs
and quark-gluon states calculated numerically are in general agreement with
lattice MEM data. The possible role of these bound states in the thermodynamics
of quark-gluon plasma is discussed.Comment: Revised version with new comments and references and corrected tables
VII-IX; 34 pages + 6 figure
Coupled-channel model for charmonium levels and an option for X(3872)
The effects of charmed meson loops on the spectrum of charmonium are
considered, with special attention paid to the levels above open-charm
threshold. It is found that the coupling to charmed mesons generates a
structure at the D \bar{D}* threshold in the 1++ partial wave. The implications
for the nature of the X(3872) state are discussed.Comment: 27 pages, 7 EPS figure
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
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
Glueball spectrum and the Pomeron in the Wilson loop approach
Using a nonperturbative method based on asymptotic behaviour of Wilson loops
we calculate masses of glueballs and corresponding Regge-trajectories. The only
input is string tension fixed by meson Regge slope, while perturbative
contributions to spin splittings are defined by standard alpha_s values. The
masses of lowest glueball states are in a perfect agreement with lattice
results. The leading glueball trajectory which is associated with Pomeron is
discussed in details and its mixing with f and f' trajectories is taken into
account.Comment: LaTeX2e, 49 pages, 2 figure
Critical Behavior of Non Order-Parameter Fields
We show that all of the relevant features of a phase transition can be
determined using a non order parameter field which is a physical state of the
theory. This fact allows us to understand the deconfining transition of the
pure Yang-Mills theory via the physical excitations rather than using the
Polyakov loop.Comment: RevTeX, 4-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
- …