Single photoproduction of neutral π-mesons on hydrogen in the forward direction at 4 GeV

Regge phenomenology in π0 and η photoproduction

“…In the fits we have used the experimental data for the differential cross sections dσ/dt from DESY at E γ = 4 GeV [4] and E γ = 4, 5, and 5.8 GeV [5], and SLAC [6] at E γ = 6, 9, 12, and 15 GeV; the polarized-beam asymmetry Σ from SLAC [6] at E γ = 4, 6, and 10 GeV and GlueX [7] at E γ = 8.7 GeV; the target asymmetry T from Daresbury [32] and DESY [33], both at E γ = 4 GeV; the recoil polarization observable P from CEA [34] at E γ = 4.1 − 6.3 GeV; the differential cross section ratio of neutrons and protons, R np for π 0 photoproduction at E γ = 4 GeV [35,36] and E γ = 4.7 and 8.2 GeV [37].…”

“…Therefore, we conclude, that a strong energy dependence of the beam asymmetry between 6 and 10 GeV, as suggested by the GlueX data, cannot be described within our model without adding additional dynamics. There is also some disagreement be- [5] DESY [4] SLAC [6] GlueX [7] Dares [32] DESY [33] CEA [34] DESY [35] CEA [36] tween the data and the Solution I for the differential cross sections at E γ = 4 GeV, see Figs. 5 and 7.…”

“…Differential cross sections for γp → π 0 p. The solid red, dashed black, dash-dotted blue (coincide mostly with red curves), and dotted green lines are our solutions I, II, III, and IV, respectively. Data are from SLAC [6] (black circles) and from DESY: [5] (red triangles) and [4] (blue squares).…”

“…Above this resonance region, at W 3 GeV, the reaction dynamics changes and can be described most effectively by particle (reggeon) exchanges in the crossed t-channel [2]. Experimental data on π and η photoproduction in this high-energy region were mainly measured in the 1970s at DESY [3][4][5] and SLAC [6], but only a limited amount of target and recoil polarization data is available. Only recently, the new GlueX experiment in Hall-D at JLab started data taking and first results on differential cross sections with a linearly polarized photon beam at E γ = 8.7 GeV were already obtained [7].…”

Neutral pion photoproduction in a Regge model

“…The exact region of validity of Regge theory will be deduced by analyzing the data. In the region E γ ≥ 2 GeV and |t| < 3 GeV 2 there are data on differential cross sections [18][19][20][21][22] shown in Fig. 1, the beam asymmetry [18], shown in Fig.…”