Masses and other parameters of the light hadrons

On the effective string spectrum of the tridimensional Bbb Z2gauge model

“…The numerical method they used to extract the lowest energy in the various Γ sectors goes through evaluation of generalised Wilson loops, whose spatial edges were replaced by well-suited combinations of paths, transforming according to the quantum numbers of the considered Γ state. They focused their study on a regime of intermediate distances, and the results show rather good agreement with the predictions of the adiabatic approximation of the bag picture [50], which provides a phenomenological model expected to interpolate between the short and long length scales; at large distances, however, the energies associated with the internal "gluonic" excitations of the stretched bag will become irrelevant to the lowest spectrum states, and a convenient description for the flux-tube will be given in terms of an effective string model. They also observe fine-structure deviations with respect to the nπ r gaps expected from free-string model, that they compare with the Nambu-Goto spectrum (leaving room for the possibility that further physical effects can enter the effective string description in this regime).…”

Strange exotic states and compact stars

“…for the charmonium states, it is essential to include explicitly the colour-electric interaction terms. This modified bag model can describe reasonably well both, light nonstrange and strange hadrons as well as charmed hadrons with a slightly larger bag constant [15] compared to the standard MIT bag model [16]. A shell-model calculation of multiply charmed and strange quark states, however, does not give bound candidates.…”

Dynamical properties and flux tubes of the Friedberg-Lee model

“…(11) can also be obtained by minimizing t after eliminating E via (13). As a measure for the radius of the flux tube we define (16) In order to make a calculation we have to specify the functional forms of U and "'· As in previous references [1,2,3] we use a quartic polynomial for U: (17) For c > 0 and 0 < aM < av 12 this potential has a minimum at 0 and av and a maximum at aM. The ratio aM I av determines the shape of the potential, whereas c and av simply rescale it 2 • Most previous approaches made the ansatz that K( a) is a polynomial of the form 11-(a I av )n lm [1 ,2,3].…”

“…In a quantum mechanical calculation the situation is somewhat different. Following De Grand et al [17] one usually omits the magnetic self-interaction within all kind of bag models. Since the self-interaction is negative the total energy is increased and becomes positive for the ~-resonance.…”

“…In fact, it is even necessary that a( 0) =/= 0 since otherwise the differential equation ( 11) (1-alav)M/mu which contradicts the requirement dKidaluv = 0. ForK behaving like ( 1 -a I av )n near av (so that dn, Ida ---t 0) one gets M = nm 17 being the analogue of a type I superconductor. In the functional form we have introduced above K and thus D falls off faster than exponential for large p, which definitely corresponds to the behaviour of a type I superconductor.…”