We report new measurements of inclusive pi production from frozen-spin HD for polarized photon beams covering the Delta(1232) resonance. These provide data simultaneously on both H and D with nearly complete angular distributions of the spin-difference cross sections entering the Gerasimov-Drell-Hearn (GDH) sum rule. Recent results from Mainz and Bonn exceed the GDH prediction for the proton by 22 mu b, suggesting as yet unmeasured high-energy components. Our pi(0) data reveal a different angular dependence than assumed in Mainz analyses and integrate to a value that is 18 mu b lower, suggesting a more rapid convergence. Our results for deuterium are somewhat lower than published data, considerably more precise, and generally lower than available calculations.
Hoblit, S., Sandorfi, A., Ardashev, K., Bade, C., Bartalini, O., Blecher, M., et al. (2009). Measurements of HD(gamma,pi) and Implications for the Convergence of the Gerasimov-Drell-Hern Integral. PHYSICAL REVIEW LETTERS, 102, 172002-172002--1--172002--5 [10.1103/PhysRevLett.102.172002].
Measurements of HD(gamma,pi) and Implications for the Convergence of the Gerasimov-Drell-Hern Integral
BARTALINI, ORIETTA;D'ANGELO, ANNALISA;FANTINI, ALESSIA;SCHAERF, CARLO;
2009-01-01
Abstract
We report new measurements of inclusive pi production from frozen-spin HD for polarized photon beams covering the Delta(1232) resonance. These provide data simultaneously on both H and D with nearly complete angular distributions of the spin-difference cross sections entering the Gerasimov-Drell-Hearn (GDH) sum rule. Recent results from Mainz and Bonn exceed the GDH prediction for the proton by 22 mu b, suggesting as yet unmeasured high-energy components. Our pi(0) data reveal a different angular dependence than assumed in Mainz analyses and integrate to a value that is 18 mu b lower, suggesting a more rapid convergence. Our results for deuterium are somewhat lower than published data, considerably more precise, and generally lower than available calculations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.