Speaker
Mr
Iurii Timrov
(National Taras Shevchenko University of Kyiv)
Description
We consider a single-particle spectrum of secondary hadrons created in
relativistic nucleus-nucleus collisions. The particles are radiated from the
system (fireball) which exhibits a sharp kinetic freeze-out: space-like and
time-like hypersurfaces separate the exited (interacting) system of particles
from its noninteracting stage of the evolution process. The standard and
widely used method to get the spectra is the so-called Cooper-Frye pre-
scription (CFp), that treat the system at the decay stage of evolution as a
locally equilibrated ideal gas at a space-like hypersurface. Meanwhile, this
prescription presents some serious problems, because, usually, the freeze-out
hypersurface contains nonspace-like sectors. We propose a certain correction
of the CFp which allows to drop out the problem. We prove that the cor-
rected prescription is valid for both pieces of the freeze-out hypersurface, for
the space-like and for the time-like as well. It is important to note, that
the problem of negative contribution to the spectra, caused by integration
over a time-like piece of the hypersurface, emerges for a "model" distribution
function (MDF), for instance when one takes a distribution function defined
for local thermodynamic equilibrium. Meanwhile, there is no such a problem
for a "true" distribution function, which can be obtained, for instance, from
the transport Boltzmann equation. We show also, that even for MDF the
corrected CFp gives a right result. Indeed, in this case the integration over
the time-like piece of the hypersurface gives negative contribution which is
compensated by the positive contribution obtained as a result of integration
over a proper piece of the space-like hypersurface.
Primary author
Mr
Iurii Timrov
(National Taras Shevchenko University of Kyiv)
Co-author
Mr
Dmitry Anchishkin
(Bogolyubov Institute for Theoretical Physics of the National Academy of Sciences of Ukraine)
