Excitation Functions of Related Temperatures of η and η⁰ Emission Sources from Squared Momentum Transfer Spectra in High-Energy Collisions

The squared momentum transfer spectra of η and η0, produced in high-energy photon–proton (γp) →η(η0)+p processes in electron–proton (ep) collisions performed at CEBAF, NINA, CEA, SLAC, DESY, and WLS are analyzed. The Monte Carlo calculations are used in the analysis of the squared momentum transfer spectra, where the transfer undergoes from the incident γ to emitted η(η0) or equivalently from the target proton to emitted proton. In the calculations, the Erlang distribution and Tsallis–Levy function are used to describe the transverse momentum (pT) spectra of emitted particles. Our results show that the average transverse momentum (⟨pT⟩), the initial-state temperature (Ti), and the final-state temperature (T0) roughly decrease from the lower center-of-mass energy (W) to the higher one in the concerned energy range of a few GeV, which is different from the excitation function from heavy-ion collisions in the similar energy range.