Experimental Results on Chiral Magnetic and Vortical Effects

Wang, Gang; Wen, Liwen

doi:10.1155/2017/9240170

Cited by 8 publications

(6 citation statements)

References 123 publications

(181 reference statements)

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“…In fact, the magnitude of the possible resonance decay backgrounds was estimated before, but unfortunately with wrong values, and was thus incorrectly thought to be negligible [113,136,137]. This has led to the premature claim that the CME must be invoked to explain the experimental data [36,157].…”

Section: Nature Of Charge-dependent Backgroundsmentioning

confidence: 99%

Experimental searches for the chiral magnetic effect in heavy-ion collisions

Zhao

Wang

2019

Progress in Particle and Nuclear Physics

108

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The chiral magnetic effect (CME) in quantum chromodynamics (QCD) refers to a charge separation (an electric current) of chirality imbalanced quarks generated along an external strong magnetic field. The chirality imbalance results from interactions of quarks, under the approximate chiral symmetry restoration, with metastable local domains of gluon fields of non-zero topological charges out of QCD vacuum fluctuations. Those local domains violate the P and CP invariance, potentially offering a solution to the strong CP problem in explaining the magnitude of the matterantimatter asymmetry in today's universe. Relativistic heavy-ion collisions, with the likely creation of the high energy density quark-gluon plasma and restoration of the approximate chiral symmetry, and the possibly long-lived strong magnetic field, provide a unique opportunity to detect the CME. Early measurements of the CME-induced charge separation in heavy-ion collisions are dominated by physics backgrounds. Major efforts have been devoted to eliminate or reduce those backgrounds. We review those efforts, with a somewhat historical perspective, and focus on the recent innovative experimental undertakings in the search for the CME in heavy-ion collisions.Keywords: heavy-ion collisions, chiral magnetic effect, three-point correlator, elliptic flow background, invariant mass, harmonic plane Our universe started from the Big Bang singularity [1] with equal amounts of matter and antimatter, but is today dominated by only matter. No significant concentration of antimatter has ever been found in the observable universe [2]. This matter-antimatter asymmetry is caused by CP (chargeconjugation parity) violation, a slight difference in the physics governing matter and antimatter [3,4], as in e.g. electroweak baryogenesis [5,6]. CP is violated in the weak interaction but the magnitude of the CKM quark-sector CP violation [7,8] is too small to explain the present universe matter-antimatter asymmetry [9]. It is unclear whether the lepton-sector CP violation through leptogenesis [3,10] is large enough to account for the matter-antimatter asymmetry. CP violation in the strong interaction in the early universe may be needed. CP violation is not prohibited in the strong interaction [11] but none has been experimentally observed [12,13]. This is called the strong CP problem [11,14]. To solve the strong CP problem, Peccei and Quinn [14,15] proposed to extend the QCD (quantum chromodynamics) Lagrangian by a CP-violating θ term, first introduced by 't Hooft [16,17] in resolving the axial U (1) problem [18]. It predicts the existence of a new particle called the axion. If axions exist, they would not only offer a solution to the strong CP problem, but could also be a dark matter candidate [19]. On the other hand, the Peccei-Quinn mechanism would remove the large, flavour diagonal CP violation, precluding a solution to the strong CP problem to arise from QCD. However, axions have not been detected after four decades of search since its conception [20,21].Here, we concent...

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Section: Nature Of Charge-dependent Backgroundsmentioning

confidence: 99%

Experimental searches for the chiral magnetic effect in heavy-ion collisions

Zhao

Wang

2019

Progress in Particle and Nuclear Physics

108

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“…Such interferences are predicted to lead to interesting effects, some of which were observed but the interpretation of the observations is ambiguous because alternative explanations are possible-Refs. [4][5][6][7] are recent reviews on this. An adversity here is that the fields are created early in the collision and weaken fast as the system expands [3,8].…”

Section: Introductionmentioning

confidence: 99%

Anisotropic electrical conductivity of magnetized hot quark matter

Ghosh,

Bandyopadhyay,

Farias

et al. 2019

Preprint

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We studied the effect of a strong magnetic field (B) on the electrical conductivity of hot quark matter. The electrical conductivity is a key transport coefficient determining the time dependence and strength of magnetic fields generated in a relativistic heavy-ion collision. A magnetic field induces Hall anisotropic conduction, phase-space Landau-level quantization and, if sufficiently strong, interferes with prominent QCD phenomena such as dynamical quark mass generation, likely affecting the quark matter electrical conductivity, which depends strongly on the quark masses. To address these issues, we used a quasi-particle description of quark matter in which the electric charge carriers are constituent quarks with temperature-and magnetic-field-dependent masses predicted by a Nambu-Jona-Lasinio model. The model accurately describes recent lattice QCD results showing magnetic catalysis at low temperatures and inverse magnetic catalysis at temperatures close to the pseudocritical temperature (T pc ) of the QCD phase transition. We found that the magnetic field increases the conductivity component parallel to it and decreases the transverse component, in qualitative agreement with recent lattice QCD results. In addition, we found that: (1) for a fixed value of B, increasing temperature causes enhancement in all the components of the conductivity, (2) the anisotropy increases with B, (3) longitudinal conductivity is increased due to the quantum effects leading to phase-space Landau-level quantization, (4) lowest Landau level approximation behaves poorly for temperatures close to T pc , and (5) inverse magnetic catalysis leaves a distinctive signal in all components of the conductivity, a kink at T pc . Our study adds to the existing body of work on the hot quark matter electrical conductivity by incorporating nontrivial temperature and magnetic field effects on dynamical mass generation. Our results are useful both for studies employing magnetohydrodynamics simulations of heavy-ion collisions and for getting insight on lattice QCD results.

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“…Secondly, QCD which describes the behavior of the QGP allows topological charge changing transition that can induce chirality imbalance [5]. The magnetic field is the driving force and the electric charge separation is the manifestation of the CME [15]. Therefore, the CME is very likely to exist in relativistic heavy -ion collisions.…”

Section: Introductionmentioning

confidence: 99%

Chiral magnetic currents with QGP medium response in heavy-ion collisions at RHIC and LHC energies

et al. 2018

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We calculate the electromagnetic current with a more realistic approach in the RHIC and LHC energy regions in the article. We take the partons formation time as the initial time of the magnetic field response of QGP medium. The maximum electromagnetic current and the time-integrated current are two important characteristics of the chiral magnetic effect (CME), which can characterize the intensity and duration of fluctuations of CME. We consider the finite frequency response of CME to a time-varying magnetic field, find a significant impact from QGP medium feedback, and estimate the generated electromagnetic current as a function of time, beam energy and impact parameter.

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Experimental Results on Chiral Magnetic and Vortical Effects

Cited by 8 publications

References 123 publications

Experimental searches for the chiral magnetic effect in heavy-ion collisions

Experimental searches for the chiral magnetic effect in heavy-ion collisions

Anisotropic electrical conductivity of magnetized hot quark matter

Chiral magnetic currents with QGP medium response in heavy-ion collisions at RHIC and LHC energies

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