Total cross-sections of π+π− and π−π0 photoproduction on neutron in deuterium bubble chamber up to 900 MeV

Photoabsorption on a nucleon in theD13resonance energy region

“…The peak position of the γp → π + π − p cross section can be reproduced with this choice as shown in Fig.4-(i). We find that the curve with f s π∆N * > 0, f d π∆N * < 0, and f ρN N * < 0 agrees well with the γp → π + π − p data [13,14,17,18]. The range parameter Q ∆ (N → π∆) is taken to be 420 MeV/c.…”

“…Our calculation with this parameter-set is also in good agreement with the γn → π + π − n data [17,18]. This is different from the result by Tejedor et al [15].…”

“…Their studies show that their models can reproduce the γp → π + π − p reaction cross sections fairly well, but fail to explain the γp → π + π 0 n cross section. Tejedor et al, furthermore, calculated the cross sections for the neutron target, but the results are not in good agreement with the data [17,18]. In order to investigate the total nuclear photoabsorption cross section, their models should be improved.…”

πNNcoupling and two-pion photoproduction on the nucleon

“…We think that this inconsistency comes mainly from the way of the calculation of the diagram (e) in Refs. [1](triangle down), [2](open square), [4](black diamond), [5](star), [6](open circle), [7](triangle up and black square), [8](open diamond) and [9](black circle) . The data (black circle) of γn → π − π 0 p correspond to the cross section over the DAPHNE acceptance.…”

“…Many experiments [1][2][3][4][5][6][7][8][9]of two-pion photoproductions on the nucleon have been performed in the past over the second nucleon-resonance energy where the N * (1520) resonance plays an important role. Two charged pion photoproduction, i.e., γp → π + π − p, is well understood by theoretical models.…”