Jul 16 – 22, 2009
Kraków, Poland
Europe/Warsaw timezone

Correction of the Cooper-Frye prescription

Not scheduled
Auditorium Maximum (Kraków, Poland)

Auditorium Maximum

Kraków, Poland

The Auditorium Maximum of the Jagiellonian University 33 Krupnicza Street 31-123 Kraków
Heavy Ions


Mr Iurii Timrov (National Taras Shevchenko University of Kyiv)


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)


Mr Dmitry Anchishkin (Bogolyubov Institute for Theoretical Physics of the National Academy of Sciences of Ukraine)

Presentation materials

There are no materials yet.