π~0 MESON PRODUCTION IN Ta+Au COLLISIONS AT 40A MeV

摘要

Angular and transverse momentum distributions have been measured for the Ta+Au collisions at 40A MeV using the TAPS photon spectrometer installed at GANIL, Caen. The data sample of 528 π~0 mesons is superior compared to the previous measurement at the beam energy being only 14% of the free nucleon-nucleon threshold. The angular distribution has been found to be almost symmetric and can be described well within a parametri-sation using a second-order Legendre polynomial. The correction of data by the simple reabsorption model based on static geometrical considerations indicates, that the angular distribution of primordial neutral mesons might be almost isotropic, in contrast to many of the results obtained from the reanalysis of published data. The transverse momentum spectrum cannot be reasonably described within the thermal model, even when the spectrum is corrected for the reabsorption effects.