Neutral-PionPhotoproduction off Protons in the Energy Range0.3  GeV<Eγ<3  

Abstract

Single pi(0) photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of approximately 98% of 4pi. Differential cross sections dsigma/dOmega have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gammap-->N(*)(Delta(*))-->ppi(0). A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15.

Updated SAID analysis of pion photoproduction data

“…CLAS data (solid circles) are from [5]. CB-ELSA data (open circles [15] and solid triangles [27]). Notation of the solutions is the same as in Fig.…”

Partial wave analysis

“…Before 2006, data on photoproduction added information on the helicity couplings of resonances listed in the RPP, but the resonances were introduced into the respective analyses with fixed masses and widths. Early results of the BnGa group using data on photoproduction from the CB-ELSA experiment [65][66][67][68] were not yet included in the RPP [44,69] or not yet used to define particle properties [30,70] The BnGa group was the first one which combined pion and photoproduced reactions in a coupled channel fit, fitted masses and widths freely and searched systematically for new resonances [46][47][48][49]. In this way, the baryon resonances dismissed in the Arndt et al analysis [15] could be re-established [46].…”

Spectroscopy of baryon resonances

“…Differential cross sections for the reactions γp → π 0 p [70,71] and γp → ηp [73,74] have been measured at the beginning of the SFB, followed by additional measurements of γp → π 0 p [72] and γp → ηp and γp → η p [77] covering the full solid angle also in forward direction. Recently, differential cross sections and spin density matrix elements were determined for single ω meson photoproduction off the proton [88].…”