Pentaquarks: Review on Models and Solitonic Calculations of Antidecuplet Magnetic Moments

Abstract

After a quick look at the present status of experiments we shortly review in a first step the ongoing discussions on some of the basic theoretical approaches to pentaquarks: Chiral solitons, Large-$N_c$ considerations, quark models, and lattice gauge approaches. In a second step we apply the chiral quark-soliton approach including linear $m_s$-corrections to the calculation of magnetic moments of the baryons of the anti-decuplet. In this approach the parameters are fixed solely by experimental data for the magnetic moments of the baryon octet and for the masses of the octet, decuplet and of ${\Theta }^{+}$. The magnetic moment of ${\Theta }^{+}$ depends rather strongly on the pion-nucleon sigma term and reads $-1.19n.m.$ to $-0.33n.m.$ for ${\Sigma }_{\pi N}=45$ and 75 MeV respectively. As a byproduct the strange magnetic moment of the nucleon is obtained with a value of ${\mu }_N^{(s)}=+0.39$ n.m.

Comments: 24 pages, 2 figures, To be published in Prog.Part. Nucl. Phys