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star physics results: HBT and interferometry

Note: Click on a figure for a larger version.

Figure. The energy dependence of HBT parameters for central Au+Au (Pb+Pb) collisions at midrapidity and pT = 0.17 GeV/c. The strong similarity between the HBT radii across a wide range of collision energies has been called the "HBT Puzzle."

The HBT puzzle

Hanbury-Brown Twiss (HBT) interferometry of two-pion correlations allows one to study the source size at thermal freeze-out, the point at which particles no longer interact. Predictions of long-lived systems, associated with quark-gluon plasma formation, led to predictions of much larger system sizes at RHIC. However, first HBT studies by STAR showed that the extracted source sizes are comparable to measurements at lower energies. Hydrodynamic models have been able to reproduce dynamic quantities such as elliptic flow and transverse momentum spectra, but their failure to reproduce HBT radii has been dubbed the "HBT puzzle."

Related STAR papers
Pion Interferometry of sqrt(snn) = 130 GeV Au+Au collisions at RHIC
Phys. Rev. Lett. 87 (2001) 082301
e-Print Archives (nucl-ex/0107008): Abstract | PS | PDF
Journal article: Phys. Rev. Lett. server

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