Radiative Width of theηMeson

Nuclear incoherent photoproduction ofπ0andηfrom 4 to 12 GeV

“…For the case of Cornell experiment [23], on the other hand, the cross sections of η photoproduction from complex nuclei were not published and the only information available are the meson yields, which are the number of two γ events within the invariant mass of the η meson at a given angular bin. Therefore, in order to compare theory and experiment, a separate Monte Carlo algorithm was developed to account for the η → γ γ decay.…”

“…Such amplitude is not known precisely at our energies of interest and we adopted the same parametrization of Ref. [23] for the case of η photoproduction (L = 4k). The NI cross section is obtained from the cascade calculations such that:…”

“…At extreme forward angles, the total cross section for pseudoscalar meson photoproduction from complex nuclei is assumed to be in the form [2,3,23,57,58]:…”

“…The η → γ γ decay width has been measured in collider experiments [17][18][19][20][21][22] and also using the Primakoff method at Cornell [23]. There is also another Primakoff-type experiment [24], but the uncertainty from the separation of the Coulomb and nuclear contributions was probably underestimated.…”

“…The calculations for incoherent π 0 photoproduction are successfully applied for the interpretation of the magnitude and energy dependence of the measured ratio σ γ A /σ γ N taken for several nuclei (Be, C, Al, Cu, Ag, and Pb) at Cornell [29]. In this section we also present a detailed explanation for the incoherent background of η mesons in another Cornell experiment [23], extracting the η → γ γ decay width via the Primakoff method. The conclusions and final remarks are presented in Sec.…”