The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a...The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a fundamental property of quantum chromodynamics (QCD) and, therefore, an observation of the CME would have far-reaching impact on our understanding of QCD and Nature. The measurements of the CME-sensitive azimuthal correlator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow anisotropy. Several novel approaches have been carried out, including a dedicated isobar collision program, to address this flow-induced background. Further background effects, arising from nonflow correlations, have been studied. While the isobar data are consistent with zero CME signal with an upper limit of 10% of the measured Δγ, the Au+Au midcentral data suggest a positive CME signal on the order of 10% of the measured Δγ with a significance of ~2 standard deviations. Future increased statistics and improved detector capability should yield a firm conclusion on the existence (or the lack) of the CME in relativistic heavy-ion collisions.展开更多
The time evolution of both proton and anti-proton v2 flows from Au＋Au collisions at √SNN=7.7 GeV are examined by using both pure cascade and mean-field potential versions of the UrQMD model. Due to a stronger repuls...The time evolution of both proton and anti-proton v2 flows from Au＋Au collisions at √SNN=7.7 GeV are examined by using both pure cascade and mean-field potential versions of the UrQMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller v2 values. Therefore, the experimental data of anti-proton v2 as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD.展开更多
文摘The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a fundamental property of quantum chromodynamics (QCD) and, therefore, an observation of the CME would have far-reaching impact on our understanding of QCD and Nature. The measurements of the CME-sensitive azimuthal correlator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow anisotropy. Several novel approaches have been carried out, including a dedicated isobar collision program, to address this flow-induced background. Further background effects, arising from nonflow correlations, have been studied. While the isobar data are consistent with zero CME signal with an upper limit of 10% of the measured Δγ, the Au+Au midcentral data suggest a positive CME signal on the order of 10% of the measured Δγ with a significance of ~2 standard deviations. Future increased statistics and improved detector capability should yield a firm conclusion on the existence (or the lack) of the CME in relativistic heavy-ion collisions.
基金the National Natural Science Foundation of China(Grant Nos.1137506211547312,and 11275068)the project sponsored by SRF for ROCS,SEM,and the Doctoral Scientific Research Foundation(Grant No.11447109)
文摘The time evolution of both proton and anti-proton v2 flows from Au＋Au collisions at √SNN=7.7 GeV are examined by using both pure cascade and mean-field potential versions of the UrQMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller v2 values. Therefore, the experimental data of anti-proton v2 as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD.
