Enhancements in the low momentum part of invariant cross section spectra
were discovered in heavy ion reactions at CERN and AGS. Although several
explanations were suggested by theorists,
the phenomena related to pion 
spectra under 200 MeV/c is not fully
understood
[[12], [13], [14], [15]].
First results from the AGS
for low 
kaons also reveal
a very steep component at very low 
(below 50 MeV/c) which might be
linked to a QGP phenomenon [[16]].
If these enhancements persist at the higher incident RHIC energies and in
the baryon free rapidity region studied with STAR, explanations based on
resonance models [[17]] could be excluded in favor of more exotic models based
on some form of phase transition [[15]].
The high position resolution and low 
acceptance of the SVT for
pions, kaons and protons is mandatory for such studies at RHIC.
Several collective effects have been hypothesized which predict changes
(enhancements) in the low 
particle spectra as well as correlations
among the low 
particles.
`Van Hove bubbles' [[17]], localized plasma
formation, might lead to spatially correlated hadronization of low
particles and
can be verified by measuring fluctuations of the yield in rapidity.
Chiral condensate models [[15]] predict enhancements in the low
particle spectra; disoriented chiral condensate models
[[18]] in addition predict anomalous ratios of charged to neutral
pions on an event-by-event basis. Hints of this behavior may have been
observed in cosmic ray collisions [[19]].
Information on the yield of low 
charged pions on an event-by-event
basis, as well as their correlation behavior as a function of centrality may
provide information about the hadronization of a chiral condensate
[[20]].
Bose-Einstein condensation [[21]] of pions is predicted to occur
if a critical pion density can be reached at RHIC energies. If so, the
majority of the pions will be emitted with very low momenta.
In the case of coherent emission
the mean momentum depends only on the source radius.
SVT capabilities for detecting Bose-Einstein condensation effects in the
RHIC environment are detailed in [[22]]. Fig. 3a shows the
magnitude of the effect.
Figure: a.)The effect of Bose Einstein condensation and n-body
symmetrization on the 
spectrum.
b.) momentum resolution for 
reconstructed in the SVT
alone
Fig. 3b shows the
pion momentum resolution for reconstructed tracks between 60 MeV/c and
250 MeV/c. The open dots represent the improvement achievable by
including de/dx information from the SVT in the calculation. Although
moderate, the resolution in fig. 3b is sufficient to permit momentum
reconstruction, which preserves the shape of the spectrum at low p
.
The presence of a low p
enhancement will not only be determined
for a large ensemble of events but, given the charged pion multiplicities
expected at RHIC, it is statistically feasible to
measure a shift in the mean of the momentum spectrum,
event-by-event, which could be used as an exotic third level trigger
(see section 2.4).