Estimation of electric conductivity of the quark gluon plasma via asymmetric heavy-ion collisions

20 May 2014, 16:30
spectrum (darmstadtium)



Board: H-11
Poster Collective Dynamics Poster session


Yuji Hirono (The University of Tokyo)


The quark gluon plasma (QGP), which consists of deconfined quarks and gluons, is expected to have filled the early Universe, and is also produced experimentally through the relativistic heavy-ion collisions at Relativistic Heavy Ion Collider (RHIC) in BNL and Large Hadron Collider (LHC) in CERN. There has been much effort to extract detailed properties of the QGP by constraining transport coefficients such as shear viscosity, bulk viscosity, and charge diffusion constants. We here propose a new way of estimating the electric conductivity of the QGP via asymmetric nucleus-nucleus collisions at ultrarelativistic energies [1]. Theoretically, lattice QCD simulations and perturbative QCD calculations have been utilized to estimate electric conductivity of the QGP. So far, the estimated values of have differed significantly from each other and experimental information is very much awaited. Very recently, asymmetric collisions between copper and gold nuclei have been performed at RHIC. We point out that Cu+Au collisions can be useful for extracting the electric conductivity of the QGP. We show that, in off-central Cu+Au collisions, a substantial magnitude of electric field directed from a colliding Au nucleus to Cu nucleus is generated in the overlapping region, by performing event-by-event calculations of produced electromagnetic fields. This happens only when colliding two nuclei carry the different number of electric charge. The electric field would induce a current in the matter created after the collision, resulting in a dipole deformation of the charge distribution in the medium. We show that the charge-dependent directed flow parameters $v_1^{\pm}$ of the observed hadrons are sensitive to the electric conductivity of the QGP. References: [1] Yuji Hirono, Masaru Hongo, Tetsufumi Hirano, arXiv:1211.1114.

Primary author

Yuji Hirono (The University of Tokyo)


Masaru Hongo (The University of Tokyo) Tetsufumi Hirano (Sophia Univ)

Presentation Materials