Spectral functions in the sigma-channel near the critical end point

Abstract

Spectral functions in the $\sigma$-channel are investigated near the chiral critical end point (CEP), that is, the point where the chiral phase transition ceases to be first-ordered in the $(\mu ,T)$-plane of the QCD phase diagram. At that point the $\sigma$ meson becomes massless in spite of explicit breaking of the chiral symmetry. It is expected that experimental signatures peculiar to CEP can be observed through spectral changes in the presence of abnormally light $\sigma$ mesons. As a candidate, the invariant-mass spectrum for diphoton emission is estimated with the chiral quark model incorporated. The results show the characteristic shape with a peak in the low energy region, which may serve as a signal for CEP. However, we find that the diphoton multiplicity is highly suppressed by infrared behaviors of the $\sigma$ meson. Experimentally, in such a low energy region below the threshold of two pions, photons from ${\pi }^0\to 2\gamma$ are major sources of the background for the signal.

12 pages, 8 figures, 1 figure replaced, minor modifications

Cited by in corpus (14)

• Chiral effective model with the Polyakov loop
• QCD phase diagram and the critical point
• Hydrodynamical evolution near the QCD critical end point
• The finite temperature transition for 2-flavour lattice QCD at finite isospin density
• Isospin Chemical Potential and the QCD Phase Diagram at Nonzero Temperature and Baryon Chemical Potential
• Scalar density fluctuation at critical end point in NJL model
• Relation between the Polyakov loop and the chiral order parameter at strong coupling
• Model study of the sign problem in the mean-field approximation
• Wess-Zumino-Witten action and photons from the Chiral Magnetic Effect
• Fluctuations and phases in baryonic matter
• Susceptibilities and critical exponents within the Nambu--Jona-Lasinio model
• Dynamic aspect of the chiral phase transition in the mode coupling theory
• Isentropic thermodynamics and scalar-mesons properties near the QCD critical end point
• Dynamic nature at the QCD Critical End Point