Maximum azimuthal anisotropy of neutrons from Nb-Nb collisions at 400A MeV and the nuclear equation of state.

We measured the first azimuthal distributions of triple–differential cross sections of neutrons emitted in heavy-ion collisions, and compared their maximum azimuthal anisotropy ratios with Boltzmann–Uehling–Uhlenbeck (BUU) calculations with a momentum-dependent interaction. The BUU calculations agree with the tripleand double-differential cross sections for positive rapidity neutrons emitted at polar angles from 7 to 27 degrees; however, the maximum azimuthal anisotropy ratio for these free neutrons is insensitive to the size of the nuclear incompressibility modulus K characterizing the nuclear matter equation of state.