Charges In Heavy Ion Collisions Research Articles

New proxies for second-order cumulants of conserved charges in heavy-ion collisions within the EPOS4 framework

New proxies for second-order cumulants of conserved charges in heavy-ion collisions within the EPOS4 framework

Fluctuations of conserved charges in hydrodynamics and molecular dynamics

We present an overview of recent theoretical results on fluctuations of conserved charges in heavy-ion collisions obtained in relativistic hydrodynamics and molecular dynamics frameworks. In particular, we discuss the constraints on the location of the QCD critical point based on comparisons of experimental data on proton number cumulants with precision calculations of noncritical contributions. We also cover recent developments on critical fluctuations in molecular dynamics simulations.

Studies of Quark and Gluon Contributions to Jets using Jet Charge Measurements in pp and PbPb Collisions

Jet charge, defined as the momentum-weighted sum of the electric charges of particles inside a jet is sensitive to the electric charge of the initiating parton and can be used to study the color charge dependence of the parton energy loss in the QGP. In this paper, the first measurements of jet charge in heavy-ion collisions are presented using lead-lead (PbPb) collision data and compared to results from proton-proton (pp) data at the same collision energy. The measurements are unfolded for detector and background effects and are studied differentially in pT and additionally as a function of collision centrality in PbPb collisions. We also present a template fitting technique for estimating the fractions of quark- and gluon-initiated jets in pp and PbPb collisions based on Monte Carlo templates. This analysis uses pp and PbPb collision data collected by the CMS experiment at sNN=5.02TeV.

Jet charge in heavy-ion collisions

Jet quenching effects have been widely used to study the properties of strongly-interacting matter, quark-gluon plasma, in heavy-ion collisions. Flavor tagging in heavy-ion collisions plays an important role to reveal the medium parton showers for quark and gluon evolution. Combining with kinematic information, the average jet charge can be used to separate the contribution of different jet flavors, which is defined as the momentum- weighted sum of the charges of hadrons inside a given jet. Using soft-collinear effective theory with medium interactions, we investigate the factorization of the jet charge in QCD medium. We provide predictions for jet charge distributions and their modifications compared to the ones in proton-proton collisions.

Chemical freeze-out conditions and fluctuations of conserved charges in heavy-ion collisions within a quantum van der Waals model

The chemical freeze-out parameters in central nucleus-nucleus collisions are extracted consistently from hadron yield data within the quantum van der Waals (QvdW) hadron resonance gas model. The beam energy dependences for skewness and kurtosis of net baryon, net electric, and net strangeness charges are predicted. The QvdW interactions in asymmetric matter, $Q/B \neq 0.5$, between (anti)baryons yield a non-congruent liquid-gas phase transition, together with a nuclear critical point (CP) with critical temperature of $T_c=19.5$ MeV. The nuclear CP yields the collision energy dependence of the skewness and the kurtosis to both deviate significantly from the ideal hadron resonance gas baseline predictions even far away, in $(T,\mu_B)$-plane, from the CP. These predictions can readily be tested by STAR and NA61/SHINE Collaborations at the RHIC BNL and the SPS CERN, respectively, and by HADES at GSI. The results presented here offer a broad opportunity for the search for signals of phase transition in dense hadronic matter at the future NICA and FAIR high intensity facilities.

Medium modification of averaged jet charge in heavy-ion collisions

Jet charge characterizes the electric charge distribution inside a jet. In this talk we make the first theoretical study of jet charge in high-energy nuclear collisions and calculate numerically the medium alternations of jet charge due to parton energy loss in the quark-gluon plasma. The parton multiple scattering in hot/dense QCD medium is simulated by a modified version of PYQUEN Monte Carlo model with 3+1D ideal hydrodynamical evolution of the fireball. Our preliminary results show that the averaged jet charge is significant modified in A+A collisions relative to that in p+p. The different features of quark jet charge and gluon jet charge in heavy-ion collisions, and the sensitivity of jet charge modifications to flavour dependence of energy loss are observed, which could then be used to discriminate quark and gluon jet as well as their energy loss patterns in heavy-ion collisions.

Production of charge in heavy ion collisions

By analyzing preliminary experimental measurements of charge-balance functions from the STAR Collaboration at the Relativistic-Heavy-Ion Collider (RHIC), it is found that pictures where balancing charges are produced in a single surge, and therefore separated by a single length scale, are inconsistent with data. In contrast, a model that assumes two surges, one associated with the formation of a thermalized quark-gluon plasma and a second associated with hadronization, provides a far superior reproduction of the data. A statistical analysis of the model comparison finds that the two-surge model best reproduces the data if the charge production from the first surge is similar to expectations for equilibrated matter taken from lattice gauge theory. The charges created in the first surge appear to separate by approximately one unit of spatial rapidity before emission, while charges from the second wave appear to have separated by approximately a half unit or less.

Higher order fluctuations of conserved charges in heavy ion collisions

We investigate the effect of the global charge conservation on the cumulants of conserved charges in relativistic heavy ion collisions in a finite rapidity window by studying the time evolution of cumulants in the hadronic medium. It is argued that the global charge conservation does not affect the experimental result of the net-electric charge fluctuation observed by ALICE, because of the finite diffusion distance of charged particles in the hadronic stage.

Production and Detection of Fractional Charge in Heavy-Ion Collisions

The glow model of broken QCD allows for free, low-mass, fractionally charged, glow-singlet, color 6 diquarks $Q$. Apparently the $Q'\mathrm{s}$ are nearly confined at present ${e}^{+}{e}^{\ensuremath{-}}$ and hadronic energies. The situation can be quite different in heavy-ion collisons. In contrast to other models, the glow model allows for parameters which could lead to fractional charge production at Bevalac energies. A search at the Bevalac is proposed that is sensitive to the production of \ensuremath{\sim} ${10}^{\ensuremath{-}11}$ diquark/collision.