STAR focus: ΛΛ Correlation Function in Au+Au collisions at √sNN = 200 GeV

The STAR Collaboration published in Physical Review Letters, Phys. Rev. Lett. 114, 022301 (2015), the first high statistics measurement of ΛΛ correlation function in Au+Au collisions at √sNN = 200 GeV and it is also highlighted as PRL editors' suggestion. This research pioneered the venue of using RHIC as a hyperon factory to investigate hyperon-hyperon interactions. The STAR measurement can provide precious data for the understanding of hyperon-hyperon interaction which is an important input to various baryon-baryon interaction potential model as well as for the study of equation of state for neutron stars. The ΛΛ interaction is also closely related to the existence of the H dibaryon, one of the most searched for exotic hadrons in nuclear collisions.

Left Fig. The combined ΛΛ and anti-Λ anti-Λ correlation function for 0-80% centrality Au+Au collisions at √sNN = 200 GeV. Curves correspond to fits using the Lednicky and Lyuboshitz analytical model with and without a residual correlation term. The dotted line corresponds to Fermi statistics with a source size of 3.13 fm. The shaded band corresponds to the systematic error.

The Lednicky and Lyuboshitz analytical model is used to fit the experimental correlation function and the resulting parameters suggest that the strength of the ΛΛ interaction is weak. The measured ΛΛ correlation shows deviation from unity as well as the free correlation expected from Fermi statistics. The correlation measurement also allowed extraction of an upper limit for possible production of the H dibaryon in Au+Au collisions at 200 GeV which is significantly lower than theoretical predictions based on coalescence calculations.

Posted Jan. 28, 2015

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December 18, 2014
Congratulations to Qiye Shou from Shanghai Institute of Applied Physics, CAS/China for the successful defense of his PhD thesis, titled "A Study of Charge Separation Effect and Chiral Magnetic Wave in Strong Magnetic Fields at RHIC".

December 18, 2014
Congratulations to David Tlusty from the Czech Technical University in Prague for the successful defense of his PhD thesis, titled "A Study of Open Charm Production in p+p Collisions at STAR".

December 8, 2014
Congratulations to Li Yi from Purdue University for the successful defense of her PhD thesis, titled "Study Quark Gluon Plasma by Particle Correlations in Heavy Ion Collisions".

November 14, 2014
Howard H. Wieman wins 2015 APS Bonner Prize "For developing foundational experimental and theoretical tools to enable and guide generations of experiments in relativistic heavy ion physics. The combination of experiment and theory led to the initial discoveries at RHIC, ongoing precision studies of the properties of hot nuclear matter, and to exploration of the nuclear matter phase diagram."

November 3, 2014
L. Chanaka De Silva (Creighton) and Chi Yang (USTC) joined Joey Butterworth (Rice) as junior council representatives.

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