# **Nuclear Physics Colloquium **

Location: ITP,
Science Campus Riedberg, Max-von-Laue-Str. 1, room 02.116 Time:
Thursday, April 11, 2013, 4:30-5:30 pm (plus 10min for
discussion)

Contact: hees@fias.uni-frankfurt.de

# The
relativistic distribution function for particles with spin at
local thermodynamical equilibrium

## Francesco Becattini
(Università di Firenze, Florence)

We present an
extension of relativistic single-particle distribution function
for weakly interacting particles at local thermodynamical
equilibrium including spin degrees of freedom, for massive
spin-1/2 particles. We infer, on the basis of the global
equilibrium case, that at local thermodynamical equilibrium
particles acquire a net polarization proportional to the vorticity
of the inverse temperature four-vector field. The obtained formula
for polarization also implies that a steady gradient of
temperature entails a polarization orthogonal to particle
momentum. The single-particle distribution function in momentum
space extends the so-called Cooper-Frye formula to particles with
spin 1/2 and allows to predict their polarization in relativistic
heavy ion collisions at the freeze-out.

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