Gerasimov-Drell-Hearn Sum Rule and the Discrepancy between the New CLAS and SAPHIR Data

TL;DR

This paper investigates the impact of recent experimental data on the Gerasimov-Drell-Hearn sum rule, highlighting discrepancies between datasets and analyzing the role of specific resonances in proton spin polarizability.

Contribution

It compares the effects of SAPHIR and CLAS data on the GDH sum rule and identifies key resonances influencing the polarized cross sections.

Findings

Different data sets lead to significantly different contributions to the sum rule.

Inclusion of CLAS C_x and C_z data does not alter the main results.

Certain resonances are crucial for describing the polarization data.

Abstract

Contribution of the K^+\Lambda 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 C_x and C_z 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 S_{11}(1650), P_{11}(1710), P_{13}(1720), and P_{13}(1900) resonances for the description of the C_x and C_z data. A brief discussion on the importance of these resonances is given. Measurements of the polarized total cross section \sigma_{TT'} by the CLAS, LEPS, and MAMI collaborations are expected to verify this finding.