Energy and system-size dependence of the Chiral Magnetic Effect

Abstract

Abstract. The energy dependence of the local P and CP violation in Au+Au and Cu+Cu collisions in a large energy range is estimated within a simple phenomenological model. It is expected that at LHC the chiral magnetic effect will be about 20 times weaker than at RHIC. At lower energy range, covered by the low-energy scan at RHIC and future NICA/FAIR facilities, the created magnetic field strength and energy density of deconfined matter are rather high providing necessary conditions for the chiral magnetic effect. However, the particular model for the chiral magnetic effect predicts that this effect should vanish sharply at energy somewhere above the top SPS one. To elucidate CME background effects the Hadron-String-Dynamics (HSD) transport model including electromagnetic fields is put forward. Importance of new planning experiments at LHC and for the low-energy RHIC scan program is emphasized.

Study of charge-dependent azimuthal correlations using reaction-plane-dependent balance functions

“…Another topic of interest is the beam energy dependence of the CME. Recent calculations show that it only exists in the deconfined, chirally symmetric phase [4] and decreases with increasing beam energy [11]. The right panel of figure 2 shows the same parity observable calculated from balance functions at √ s NN = 200, 62.4, 39, 11.5 and 7.7 GeV.…”

“…We can see that, for all four centralities shown here, the data show a smooth decrease with decreasing collision energy. This smooth decrease is different from the CME expectation which predicts an increasing signal with decreasing beam energy and sharply disappearance of signal near the top energy of SPS [11], but is consistent with the fact that v 2 decreases smoothly with beam energy in the same energy range.…”

Study of Particle Ratio Fluctuations and Charge Balance Functions at RHIC

“…This smooth decrease differs from the CME calculation, which predicts an increasing signal with decreasing beam energy and sharply disappearance of signal near the top energy of SPS [77]. However, these results are consistent with the fact that v 2 decreases smoothly with decreasing beam energy in the same energy range.…”

“…Another topic of interest is the beam energy dependence of the CME. Recent calculations show it only exists in the deconfined, chirally symmetric phase [72] and decreases with increasing beam energy [77]. In addition, the CME effect should disappear at energies below √ s NN = 10 GeV.…”