Speaker
Description
Femtoscopy allows us to measure the space-time characteristics of the system
at the moment of particle emission using two-particle correlations. In comparison to the most abundant pions, kaons provide a cleaner probe as they are less affected by resonance decays. Since kaons contain strange
quarks and have smaller cross section with hadronic matter than pions, they
may be sensitive to different effects and earlier collision stages. In
particular,
these measurements are of interest with the data from RHIC Beam Energy
Scan (BES).
In this talk, we will present the STAR preliminary results on
femtoscopic correlations
of like-sign and unlike-sign kaons from high-statistics dataset of
Au+Au collisions
at $\sqrt{s_{\mathrm{NN}}}$=200 GeV and Au+Au collisions from BES. The kaon source radii
for 200 GeV are compared to those for pions and the Blast-Wave model
predictions.
The common $m_T$-scaling for pions and kaons would be an indication of the simultaneous
thermal freeze-out. The $m_T$-scaling
breaking is observed
for both 1D and 3D femtoscopic analyses. Such behavior can be
interpreted as earlier
decoupling of kaons compared with pions.
Moreover, the system of unlike-sign kaons contains $\phi$(1020)
resonance which exhibits
high sensitivity. Systematic measurements in the region of resonance
are able to provide
complementary information about the source-size and can serve as a
test of femtoscopic formalism which was developed for measurement at
low relative momenta. Experimental results indicate a breakdown of the
formalism in the region of the resonance in peripheral collisions.
The measured unlike-sign correlation functions are compared to the
Lednicky final state interaction model which includes the treatment of
the resonance decay.
Finally, the technique of decomposition of the experimental 3D
correlation function into the spherical harmonics are used to study
the possible difference between positive and negative kaon sources at
the BES collision energies.
| Preferred Track | Correlations and Fluctuations |
|---|---|
| Collaboration | STAR |
