Metaspin and dirishonic dark matter

The antisymmetry requirement of rishon bound state wave functions suggests a new rishon quantum number called M spin. From M spin conservation and the Nussinov-Weingarten-Witten theorem we predict the existence of a stable pseudoscalar dirishonic meson, called zeta, that is lighter than the lightest neutrino. Its mass is estimated as m(zeta) = 10^{-9} eV. This particle could make up the major part of cold dark matter in the Universe.Comment: 8 pages, 1 figur

Exchange currents in octet hyperon charge radii

Octet hyperon charge radii are calculated in a chiral constituent quark model including electromagnetic exchange currents between quarks. In the impulse approximation one observes a decrease of the hyperon charge radii with increasing strangeness. This effect is reduced by exchange currents. Due to exchange currents, the charge radius of the negatively charged hyperons is close to the proton charge radius.Georg Wagner, A. J. Buchmann, and Amand Faessle

Baryon Charge Radii and Quadrupole Moments in the 1/N_c Expansion: The 3-Flavor Case

We develop a straightforward method to compute charge radii and quadrupole moments for baryons both with and without strangeness, when the number of QCD color charges is N_c. The minimal assumption of the single-photon exchange ansatz implies that only two operators are required to describe these baryon observables. Our results are presented so that SU(3) flavor and isospin symmetry breaking can be introduced according to any desired specification, although we also present results obtained from two patterns suggested by the quark model with gluon exchange interactions. The method also permits to extract a number of model-independent relations; a sample is r^2_Lambda / r_n^2 = 3/(N_c+3), independent of SU(3) symmetry breaking.Comment: 30 pages, no figures, REVTeX

Large N_c, Constituent Quarks, and N, Delta Charge Radii

We show how one may define baryon constituent quarks in a rigorous manner, given physical assumptions that hold in the large-N_c limit of QCD. This constituent picture gives rise to an operator expansion that has been used to study large-N_c baryon observables; here we apply it to the case of charge radii of the N and Delta states, using minimal dynamical assumptions. For example, one finds the relation r_p^2 - r_{Delta^+}^2 = r_n^2 - r_{Delta^0}^2 to be broken only by three-body, O(1/N_c^2) effects for any N_c.Comment: 15 pages, 1 eps figure. Version to appear in Phys. Rev.

On the Flavor Structure of the Constituent Quark

We discuss the dressing of constituent quarks with a pseudoscalar meson cloud within the effective chiral quark model. SU(3) flavor symmetry breaking effects are included explicitly. Our results are compared with those of the traditional meson cloud approach in which pions are coupled to the nucleon. The pionic dressing of the constituent quarks explains the experimentally observed violation of the Gottfried Sum Rule and leads to an enhanced nonperturbative sea of quark-antiquark pairs in the constituent quark and consequently in the nucleon. We find 2.5 times more pions and 10-15 times more kaons in the nucleon than in the traditional picture.Comment: 7 pages, LaTeX, 4 Postscript figures, to appear in J. Phys.