Chiral symmetry breaking and scalar string confinement

Abstract

We address the old difficulty in accommodating the scalar quark-antiquark confining potential together with chiral symmetry breaking. We develop a quark confining potential inspired in the QCD scalar flux tube. The coupling to quarks consists in a double vector vertex. We study the Dirac and spin structure of this potential. In the limit of massless quarks, the quark vertex is vector. Nevertheless, symmetry breaking generates a new scalar quark vertex. In the heavy quark limit, the coupling is mostly scalar. We solve the mass gap equation and find that this potential produces spontaneous chiral symmetry breaking for light quarks. The quantitative results of this model are encouraging.

Pentaquark baryon in anisotropic lattice QCD

“…Positive parity is supported by various model calculations, i.e., soliton models [2,5,10,11,12,41], chiral bag model [13], the Jaffe-Wilczek's diquark model [14], the Karliner-Lipkin's diquark-triquark model [15], some quark model calculations [16,17,18,19,20], and other model calculations [21,22]. Negative parity is supported by some other quark model calculations [3,4,23,24,25], and QCD sum rules [28].…”

“…Hence, it would be natural that mass of Λ(1405) cannot be properly reproduced in quenched lattice QCD with a standard three-quark interpolating field. Actually, Θ + (1540) itself is hypothesized to be a bound state of KπN , i.e., the hepta-quark [21,22,54]. If this is really the case, it would be natural that Θ + (1540) is difficult to be observed in quenched lattice QCD with "ordinary" penta-quark interpolating fields.…”

“…Numerous theoretical studies of penta-quark baryons have appeared since its discovery [5,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]. One of the important issues is the spin and parity of Θ + .…”

Adventures in Theoretical Physics

“…The original intention had been for a graduate student in either Princeton or Cambridge to work on solving the extended model, but in view of the Lorentz structure problem this was not done a covariant treatment of the gap equation model was later given by von Smekal, Amundsen, and Alkofer (1991) . For various proposals for addressing the Lorentz structure issue, see Lagaë (1992), Szczepaniak and Swanson (1997), and Bicudo and Marques (2004).…”

?Super-radiance? and the width of exotic baryons

“…In addition to quasimolecular states, one should consider many-quark bag dynamics in a system of five or even seven quarks [36] formed after the photon absorption by the original proton. Among the intrinsic states there are groups with the same quantum numbers, including "normal" quark states, quarkgluon states, paired states with singlet or triplet diquark(s), states with pions and so on.…”