Effects of the higher partial waves and relativistic terms on the accuracy of the calculation of the hypertriton electroproduction

We have investigated the accuracies of calculations made by omitting the higher partial waves of nuclear wave functions and the elementary relativistic terms in the hypertriton electroproduction. We found that an accurate calculation would still be obtained if we used at least three lowest partial waves with isospin T = 0. Furthermore, we found that the omission of the relativistic terms in the elementary process amplitude could lead to a large deviation from the full calculation. We also present the cpu-times required to calculate the cross sections. For future consideration the use of these lowest partial waves is suggested, since the calculated cross section deviates only about 0.17 nb/sr (approximately 4%), at most, from the full calculation, whereas the cpu-time is reduced by a factor of 60. Comparison of our result with the available experimental data supports these findings.Comment: 12 pages, 4 figures, submitted to Nucl. Phys.

Kaon photoproduction and electroproduction near threshold

We analyze the electromagnetic production of K^+Lambda and K^0Lambda near their production thresholds by using isobar models. In the K^+Lambda channel we show that the model can nicely describe the available experimental data. In the K^0Lambda channel we demonstrate that the K^0 charge form factor has sizable effects on the longitudinal cross section. By extending the model up to W = 1730 MeV, we are able to observe the existence of the narrow P_{11} (J^p = 1/2^+) resonance in the kaon photoproduction process. It is found that the most convincing mass (width) of this resonance is 1650 MeV (5 MeV).Comment: 11 pages, 5 figures, Talk given at Baryons'10: International Conference on the Structure of Baryons, December 7-11, 2010, Osaka, Japa

Photoproduction of Pentaquark in Feynman and Regge Theories

Photoproduction of the Theta+ pentaquark on the proton is analyzed by using an isobar and a Regge models. The difference in the calculated total cross section is found to be more than two orders of magnitude for a hadronic form factor cut-off Lambda > 1 GeV. Comparable results would be obtained for 0.6 < Lambda < 0.8 GeV. We also calculate contribution of the Theta+ photoproduction to the GDH integral. By comparing with the current phenomenological calculation, it is found that the GDH sum rule favors the result obtained from Regge approach and isobar model with small Lambda.Comment: 5 pages, 5 figures, submitted to Phys.Rev.C as a Rapid Communicatio

Evidence for the J^p=1/2^+ narrow state at 1650 MeV in the photoproduction of KLambda

We have investigated the existence of the J^p=1/2^+ narrow resonance predicted by the chiral soliton model by utilizing the kaon photoproduction process gamma + p --> K^+ + Lambda. For this purpose we have constructed two phenomenological models based on our previous effective Lagrangian model, which are able to describe kaon photoproduction from threshold up to W = 1730 MeV. By varying the mass (width) of an inserted P_{11} resonance from 1620 to 1730 MeV (0.1 to 1 MeV and 1 to 10 MeV) a number of fits has been performed in order to search for the resonance mass. Our result indicates that the most promising candidate mass (width) of this resonance is 1650 MeV (5 MeV). Although our calculation does not exclude the possibility of narrow resonances with masses of 1680, 1700 and 1720 MeV, the mass of 1650 MeV is obtained for all phenomenological models used in this investigation. Variations of the resonance width and $K\Lambda$ branching ratio are found to have a mild effect on the chi^2. The possibility that the obtained result originates from other resonance states is also discussed.Comment: 27 pages, 19 figures, submitted to Phys. Rev.