Locating the QCD critical end point through the peaked baryon number susceptibilities along the freeze-out line

Understand

We investigate the baryon number susceptibilities up to fourth order along different freeze-out lines in a holographic QCD model with the critical end point (CEP), and we propose that the peaked baryon number susceptibilities along the freeze-out line can be used as a clean signature to locate the CEP in the QCD phase diagram.

• On the temperature and baryon chemical potential plane, the ratio of the baryon number susceptibilities (up to fourth order) forms a ridge along the phase boundary, and develops a sword shape mountain standing upright around the CEP in a narrow and oblate region.
• This feature is model independent and universal if the CEP exists.
• The measurement of the baryon number susceptibilities from heavy-ion collision experiment is along the freeze-out line.