π0photoproduction on the proton for photon energies from 0.675 to 2.875 GeV

Abstract

Differential cross sections for the reaction γ p → p π 0 have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged photon beam with energies from 0.675 to 2.875 GeV. The results reported here possess greater accuracy in the absolute normalization than previous measurements. They disagree with recent CB-ELSA measurements for the process at forward scattering angles. Agreement with the SAID and MAID fits is found below 1 GeV. The present set of cross sections has been incorporated into the SAID database, and exploratory fits have been extended to 3 GeV. Resonance couplings have been extracted and compared to previous determinations.

Updated SAID analysis of pion photoproduction data

“…Our last full analysis [3] has been revised twice [4,5] to include CLAS differential cross sections for neutral and charged pion production off proton targets. Some recent neutron target data were poorly predicted by these and the MAID [6] solutions, requiring changes in the neutron multipoles and resonance couplings.…”

Recent progress in baryon spectroscopy at BESIII

“…Charmonium decays offer a complementary source of information to existing data, which derives primarily from photon and meson beam experiments [5,6,7]. This is particularly true if one expects the coupling of excited baryon states to three gluons to be enhanced relative to their coupling to single pions.…”

Measurement of the π0 differential cross-section with CLAS and outlook into 12 GeV Hall C

“…There has been multiple measurements of the π 0 cross-section in single pion photoproduction that can be compared to g12 measurements [14,15,16,17,18,19]. However, no experiment has produced the cross-section continuously at beam energies greater than 3 GeV.…”

“…• , as a function of s (center of mass energy squared). Experimental data are from the current measurement (red filled circles), CLAS [14,22] (blue circles), MAMI [28] (magenta circles), old measurements [29] (black open circle plus). The dash dotted line is a result of the fit performed at θ = 90…”

“…Black solid lines give the BG2011-02 BnGa [20]) predictions. Experimental data are from the current measurement (red filled circles), CLAS [14] (black filled circles), GRAAL [17] (magenta open circles), LEPS [18] (blue plus), CB-ELSA [15] [16] (green crosses). Plotted uncertainties are statistical.…”