,
and
.Once the tracks have been reconstructed in
the silicon telescope, the strange
particles are identified via the kinematical analysis of their decay
modes. Figures 1
and 2 show a diagram of the decay modes of
interest for
,
and
.
|
Figure 1: Scheme of the decay of a
|
Figure 2: Scheme of the decay of a
|
A set of geometrical cuts are applied in order to reject the
background. The
candidates are required to be kinematically unambiguous with the
,
and the
candidates to be unambiguous with the
decays [1,2,3].
The quality of the data can be judged from the plots in figure 3
and 4.
|
Figure 3: Invariant mass distribution for a sample of
|
Figure 4:
|
The charged particle multiplicity
measured by the MSD in Pb+Pb
collisions at 158 A GeV/c has been analysed in the framework
of the Wounded Nucleon Model (WNM). The WNM assumes that the average
multiplicity in a collision is proportional to the number of wounded
nucleons (
):
where q is the proportionality constant. The WNM provides a good description of the WA97 and NA57 multiplicity distributions both with respect to the shape and of the absolute normalization of the spectra.
For results and more information see:
Cern preprint CERN-EP-2000-002 (Postscript
format)
The WA97 experiment has measured the transverse mass
spectra for negative hadrons
and strange particles produced at mid-rapidity in Pb-Pb collisions.
The double differential
distributions for each particle and for each multiplicity
class were fitted using the expression
where
is the transverse mass. We assume the rapidity distribution to be
flat in our acceptance
region, and leave the inverse slope parameter T as a free
parameter of the fit.
For results and more informations see:
Cern preprint CERN-EP-2000-001 (Postscript
format)
Particle yields per event (Y) have been measured for p+Be, p+Pb and Pb+Pb events as a function of the number of wounded nucleons.
For results and more informations see:
F. Antinori et al., Nucl. Phys. A661
(1999) 130c-139c (Postscript format)
The numerical values of the yields can be found here.
Back to the WA97/NA57 home page.
versus
invariant mass for Pb+Pb events. Both
