Gerasimov-Drell-Hearn Sum Rule and the Discrepancy between the New CLAS and SAPHIR Data
Abstract
Contribution of the K+ channel to the Gerasimov-Drell-Hearn (GDH) sum rule has been calculated by using the models that fit the recent SAPHIR or CLAS differential cross section data. It is shown that the two data sets yield quite different contributions. Contribution of this channel to the forward spin polarizability of the proton has been also calculated. It is also shown that the inclusion of the recent CLAS Cx and Cz data in the fitting data base does not significantly change the result of the present calculation. Results of the fit, however, reveal the role of the S11(1650), P11(1710), P13(1720), and P13(1900) resonances for the description of the Cx and Cz data. A brief discussion on the importance of these resonances is given. Measurements of the polarized total cross section σTT' by the CLAS, LEPS, and MAMI collaborations are expected to verify this finding.