Measurements of two particle Bose-Einstein correlations
can be interpreted in terms of the
space-time structure of the emitting source (HBT interferometry)
and may provide a
signature of QGP formation [[23], [24]].
Theoretical studies show that kaon interferometry offers significant
advantages over pions with respect to final state interactions and resonance
formation, which obscure the interpretation of the data
[[25], [26]].
Also, studies of interferometry based on hydrodynamic models
[[27]] reveal
that in order to best determine the structure
of the emitting system
the two-particle spectrum should include a wide range of the
total two particle
momenta including very low momenta.
We discuss two applications of HBT interferometry for STAR in which the SVT
makes a vital
contribution: (1) by extending the acceptance to low
and (2) by enabling neutral kaon (
) interferometry.
Increasing the 
acceptance improves the two pion
statistics and might
enable STAR to perform 
HBT on an event-by-event basis. Also,
the study of two-particle correlations over an extended range of
two-particle mean 
will provide better constraints on collision dynamics.
Neutral kaon interferometry
via SVT is unique to STAR.
Central Au+Au collisions produce on the order of 200 short
lived neutral kaons per event and of these approximately 10% are expected
to be reconstructed using SVT tracking of the decay pions.
The K
correlation function offers an obvious
advantage due to the absence of Coulomb effects. A comparison between
the results from
charged and neutral kaon HBT will quantitatively determine the Coulomb
effect. K
HBT is also not affected by two-track resolution, which is a
limiting factor in charged particle correlations. K
are identified
by their decay into charged pions. These
pions are emitted back-to-back along a line oriented randomly in the K
rest frame. Even for two K
at exactly zero relative momentum the decay
pions are well separated in configuration and momentum space and can be
measured with the same efficiency as if the relative momentum of the kaons
was large.
Moreover, because the K
is not a strangeness
eigenstate,
the K
-K
correlation includes a unique interference term that provides
additional space-time information [[28]] as well as insight
into possible strangeness distillation effects [[29]] in cases
where the source baryon density is appreciable.
We simulated the K
HBT performance of STAR with the SVT for central Au+Au
HIJING events including an imposed Bose-Einstein correlation enhancement as expected from a
10 fm radius spherical source. Considering that the kaons can be expected
to freeze out earlier than the pions, this radius is plausible. The event
reconstruction was simplified by assuming perfect matching
between SVT and TPC tracks. Tracking inefficiencies and detector resolution were
taken into account however. Details of the procedure can be found in
[[30]]. Fig. 4 shows the correlation functions C(Q
) and
C(Q
) [[23], [24]]. Q
, which
refers to the relative transverse momentum along the direction of the
average pair momentum is predicted to offer the best discrimination between
plasma and hadron gas scenarios [[24], [31]].
Our simulation suggests that with the SVT a measurement of Q
from
K
HBT is achievable. The SVT is essential for
K
interferometry, because of its tracking capability
which enables efficient secondary vertex reconstruction.
Figure: Measurements of correlation functions C(Q
) and
C(Q
) from K
pair reconstruction with SVT and TPC