Notes on exotic anti-decuplet of baryons

We emphasize the importance of identifying non-exotic SU(3) partners of the Theta^+ pentaquark, and indicate possible ways how to do it. We also use the soliton picture of baryons to relate Reggeon couplings of various baryons. These relations are used to estimate the Theta^+ production cross section in high energy processes. We show that the corresponding cross sections are significantly suppressed relative to the production cross sections of usual baryons. Finally, we present spin non-flip form factors of the anti-decuplet baryons in the framework of the chiral quark soliton model.Comment: Contribution to the Workshop On The Physics Of Excited Nucleons (NSTAR 2004) 24-27 Mar 2004, Grenoble, Franc

Mixing and decays of the antidecuplet in the context of approximate SU(3) symmetry

We consider mixing of the antidecuplet with three J^P=1/2^+ octets (the ground-state octet, the octet containing N(1440), \Lambda(1600), \Sigma(1660) and \Xi(1690) and the octet containing N(1710), \Lambda(1800), \Sigma(1880) and \Xi(1950)) in the framework of approximate flavor SU(3) symmetry. We give general expressions for the partial decay widths of all members of the antidecuplet as functions of the two mixing angles. Identifying N_{anti-10} with the N(1670) observed by the GRAAL experiment, we show that the considered mixing scenario can accommodate all present experimental and phenomenological information on the \Theta^+ and N_{anti-10} decays: \Theta^+ could be as narrow as 1 MeV; the N_{anti-10} -> N + \eta decay is sizable, while the N_{anti-10} ->N + \pi decay is suppressed and the N_{anti-10} ->\Lambda + K decay is possibly suppressed. Constraining the mixing angles by the N_{anti-10} decays, we make definite predictions for the \Sigma_{anti-10} decays. We point out that \Sigma_{anti-10} with mass near 1770 MeV could be searched for in the available data on K_S p invariant mass spectrum, which already revealed the \Theta^+ peak. It is important to experimentally verify the decay properties of \Sigma(1770) because its mass and J^P=1/2^+ make it an attractive candidate for \Sigma_{anti-10}.Comment: 57 pages, 31 figures, 4 table

DVCS on the nucleon to the twist-3 accuracy

The amplitude of the deeply virtual Compton scattering off nucleon is computed to the twist-3 accuracy in the Wandzura-Wilczek (WW) approximation. The result is presented in the form which can be easily used for the analysis of DVCS observables.Comment: 18 pages, no figures, typos are remove