Polarisation parameters in positive pion photoproduction

Beam asymmetryΣforπ+andπ0photoproduction on the proton for photon energies from 1.102 to 1.862 GeV

“…The CLAS beam asymmetries obtained here for γp → pπ 0 (700 data points represented as filled circles) are compared in Figs. 8−9 with previous data from Bonn [12,13] (open circles), Yerevan [14][15][16][17][18][19] (open triangle), GRAAL [20] (open squares), CEA [21] (filled squares), DNPL [22,23] (crosses), and LEPS [24] (asterisks). The results for the reaction γp → nπ + CLAS beam asymmetries (386 data points shown as filled circles) are compared in Fig.…”

“…The results for the reaction γp → nπ + CLAS beam asymmetries (386 data points shown as filled circles) are compared in Fig. 10 to previous data from GRAAL [25] (open squares), Yerevan [26] (open triangles), CEA [21] (filled squares), and DNPL [23] (crosses). Only those world data that are within ±3 MeV of the CLAS photon energies E γ are shown.…”

“…For the single Yerevan measurment of beam asymmetry [26], the agreement is good. Comparisons between CLAS and DNPL [23] are mixed. The DNPL results were taken with two different sets of beam energies.…”

“…Dashed (short-dashed) lines give the MAID07 [28] (BG2011-02 BnGa [29]) predictions. Experimental data are from the current (filled circles), Bonn [12,13] (open circles), Yerevan [14][15][16][17][18][19] (open triangle), GRAAL [20] (open square), CEA [21] (filled square), DNPL [22,23] (cross), and LEPS [24] (asterisk). Plotted uncertainties are statistical.…”

“…which for m = 0, reduces to the familiar form for a Poisson distributed random variable divided by a constant [29]) predictions. Experimental data are from the current (filled circles), GRAAL [25] (open square), Yerevan [26] (open triangle), CEA [21] (filled square), and DNPL [23] (cross). Plotted uncertainties are statistical.…”