Measurements of HD(gamma,pi) and Implications for the Convergence of the Gerasimov-Drell-Hern Integral

Hoblit, S.; Glückler, H.; Lehmann, A.; Di Salvo, R.; Ardashev, K.; Fantini, A.; D'Angelo, D.; Mahon, J.; Seyfarth, H.; Wang, K.; Whisnant, C.S.; Caracappa, A.; Khandaker, M.; Sandorfi, A.M.; Ströher, H.; Pap, M.; Wei, X.; Lowry, M.; Norum, B.; Lucas, M.; Honig, A.; Bade, C.; Hicks, K.; Kageya, T.; Gibson, C.; Moricciani, D.; Miceli, L.; Schaerf, C.; Blecher, M.; Kistner, O.C.; Bartalini, O.; Kizilgul, S.; Thorn, C.E.; Preedom, B.

doi:10.1103/PhysRevLett.102.172002

Journal Article

Measurements of HD(gamma,pi) and Implications for the Convergence of the Gerasimov-Drell-Hern Integral

Hoblit, S. ; Sandorfi, A. M. ; Ardashev, K. ; Bade, C. ; Bartalini, O. ; Blecher, M. ; Caracappa, A. ; D'Angelo, D. ; Di Salvo, R. ; Fantini, A. ; Gibson, C. ; Glückler, H.FZJ* ; Hicks, K. ; Honig, A. ; Kageya, T. ; Khandaker, M. ; Kistner, O. C. ; Kizilgul, S. ; Lehmann, A. ; Lowry, M. ; Lucas, M. ; Mahon, J. ; Miceli, L. ; Moricciani, D. ; Norum, B. ; Pap, M.FZJ* ; Preedom, B. ; Seyfarth, H.FZJ* ; Schaerf, C. ; Ströher, H.FZJ* ; Thorn, C. E. ; Whisnant, C. S. ; Wang, K. ; Wei, X.

2009
APS College Park, Md.

Physical review letters 102, 172002 (2009) [10.1103/PhysRevLett.102.172002]

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Please use a persistent id in citations: http://hdl.handle.net/2128/7225 doi:10.1103/PhysRevLett.102.172002

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.

Keyword(s): photon nucleon: inelastic scattering ; pi: photoproduction ; photon: polarized beam ; polarized target ; hydrogen: deuterium ; sum rule: Drell-Hearn-Gerasimov ; angular distribution ; Delta(1232) ; cross section: polarization ; spin: asymmetry ; energy dependence ; experimental results ; Brookhaven Lab ; 0.19-0.42 GeV

Classification:

Physics, Multidisciplinary

Note: This work was supported by the U. S. Department of Energy under Contract No. DE-AC02-98-CH10886, by the Istituto Nazionale di Fisica Nucleare, Italy, and by the U. S. National Science Foundation. We are indebted to Mr. F. Lincoln for his technical assistance. We thank Doctors C. Commeaux, J.-P. Didelez, and G. Rouille for their collaboration during the early stages of HD target development. One of us (A. M. S.) would like to thank Doctors A. Fix and H. Arenhovel for supplying their deuteron calculations.

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