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

Neutron contribution to nuclear DVCS asymmetries

Using a simple model for nuclear GPDs, we study the role of the neutron contribution to nuclear DVCS observables. As an example, we use the beam-spin asymmetry A_{LU}^A measured in coherent and incoherent DVCS on a wide range of nuclear targets in the HERMES and JLab kinematics. We find that at small values of the momentum transfer t, A_{LU}^A is dominated by the coherent-enriched contribution, which enhances A_{LU}^A compared to the free proton asymmetry A_{LU}^p, A_{LU}^A(\phi)/A_{LU}^p(\phi)=1.8-2.2. At large values of t, the nuclear asymmetry is dominated by the incoherent contribution and A_{LU}^A/(\phi)A_{LU}^p(\phi)=0.66-0.74. The deviation of A_{LU}^A(\phi)/A_{LU}^p(\phi) from unity at large t is a result of the neutron contribution, which gives a possibility to constain neutron GPDs in incoherent nuclear DVCS. A similar trend is expected for other DVCS asymmetries.Comment: 24 pages, 7 figure

The Electron-Ion Collider

The future Electron-Ion Collider (EIC) is a proposed new facility to collide high-energy electrons with beams of polarized protons/light nuclei and unpolarized nuclei. We overview the goals of the project and key measurements at the EIC. We also briefly comment on recent developments of the project.Comment: 4 pages, 1 figure. Presented at CIPANP 2009: 10th Conference on the Intersections of Particle and Nuclear Physics, La Jolla, California, May 26-31, 200