93 research outputs found
Covariant oscillator quark model for glueballs and baryons
An analytic resolution of the covariant oscillator quark model for a
three-body system is presented. Our harmonic potential is a general quadratic
potential which can simulate both a -shape configuration or a
simplified Y-configuration where the junction is located at the center of mass.
The mass formulas obtained are used to compute glueball and baryon spectra. We
show that the agreement with lattice and experimental data is correct if the
Casimir scaling hypothesis is assumed. It is also argued that our model is
compatible with pomeron and odderon approaches.Comment: 2 figures; content changed and enlarge
Auxiliary fields and the flux tube model
It is possible to eliminate exactly all the auxiliary fields (einbein fields)
appearing in the rotating string Hamiltonian to obtain the classical equations
of motion of the relativistic flux tube model. A clear interpretation can then
be done for the characteristic variables of the rotating string model.Comment: No table, No figur
Lagrange mesh, relativistic flux tube, and rotating string
The Lagrange mesh method is a very accurate and simple procedure to compute
eigenvalues and eigenfunctions of nonrelativistic and semirelativistic
Hamiltonians. We show here that it can be used successfully to solve the
equations of both the relativistic flux tube model and the rotating string
model, in the symmetric case. Verifications of the convergence of the method
are given.Comment: 2 figure
On bound states of Dirac particles in gravitational fields
We investigate the quantum motion of a neutral Dirac particle bouncing on a
mirror in curved spacetime. We consider different geometries: Rindler,
Kasner-Taub and Schwarzschild, and show how to solve the Dirac equation by
using geometrical methods. We discuss, in a first-quantized framework, the
implementation of appropriate boundary conditions. This leads us to consider a
Robin boundary condition that gives the quantization of the energy, the
existence of bound states and of critical heights at which the Dirac particle
bounces, extending the well-known results established from the Schrodinger
equation. We also allow for a nonminimal coupling to a weak magnetic field. The
problem is solved in an analytical way on the Rindler spacetime. In the other
cases, we compute the energy spectrum up to the first relativistic corrections,
exhibiting the contributions brought by both the geometry and the spin. These
calculations are done in two different ways. On the one hand, using a
relativistic expansion and, on the other hand, with Foldy-Wouthuysen
transformations. Contrary to what is sometimes claimed in the literature, both
methods are in agreement, as expected. Finally, we make contact with the GRANIT
experiment. Relativistic effects and effects that go beyond the equivalence
principle escape the sensitivity of such an experiment. However, we show that
the influence of a weak magnetic field could lead to observable phenomena.Comment: ReVTeX, 24 pages, 2 figure
Existence of mesons after deconfinement
We investigate the possibility for a quark-antiquark pair to form a bound
state at temperatures higher than the critical one (), thus after
deconfinement. Our main goal is to find analytical criteria constraining the
existence of such mesons. Our formalism relies on a Schr\"{o}dinger equation
for which we study the physical consequences of both using the free energy and
the internal energy as potential term, assuming a widely accepted
temperature-dependent Yukawa form for the free energy and a recently proposed
nonperturbative form for the screening mass. We show that using the free energy
only allows for the 1S bottomonium to be bound above , with a dissociation
temperature around . The situation is very different with the
internal energy, where we show that no bound states at all can exist in the
deconfined phase. But, in this last case, quasi-bound states could be present
at higher temperatures because of a positive barrier appearing in the
potential.Comment: 14 pages, 3 figures; only the case T>T_c is discussed in v
Charm and bottom baryon masses in the combined and expansion versus quark model
A good agreement between a flux tube-based quark model of light baryons
(strange and nonstrange) and the expansion mass formula has been found
in previous studies. In the present work a larger connection is established
between the quark model and the and expansion method by
extending the previous procedure to baryons made of one heavy and two light
quarks. The compatibility between both approaches is shown to hold in this
sector too
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