Constraints on the time-scale of nuclear breakup from thermal hard-photon emission

Abstract

Measured hard photon multiplicities from second-chance nucleon-nucleon collisions are used in combination with a kinetic thermal model, to estimate the break-up times of excited nuclear systems produced in nucleus-nucleus reactions at intermediate energies. The obtained nuclear break-up time for the ${}^{129}${Xe} + ${}^{nat}${Sn} reaction at 50{\it A} MeV is $\hat{I}”$$\ddot{I}„$ $\approx$ 100 -- 300 fm/$c$ for all reaction centralities. The lifetime of the radiating sources produced in seven other different heavy-ion reactions studied by the TAPS experiment are consistent with $\hat{I}”$$\ddot{I}„$ $\approx$ 100 fm/$c$, such relatively long thermal photon emission times do not support the interpretation of nuclear breakup as due to a fast spinodal process for the heavy nuclear systems studied.

11 pages, 9 figures, submitted to EPJA