General Charge Balance Functions, A Tool for Studying the Chemical Evolution of the Quark-Gluon Plasma

Abstract

In the canonical picture of the evolution of the quark-gluon plasma during a high-energy heavy-ion collision, quarks are produced in two waves. The first is during the first fm/c of the collision, when gluons thermalize into the QGP. After a roughly isentropic expansion that roughly conserves the number of quarks, a second wave ensues at hadronization, 5-10 fm/c into the collision. Since each hadron contains at least two quarks, the majority of quark production occurs at this later time. For each quark produced in a heavy-ion collision, an anti-quark of the same flavor is created at the same point in space-time. Charge balance functions identify, on a statistical basis, the location of balancing charges for a given hadron, and given the picture above one expects the distribution in relative rapidity of balancing charges to be characterized by two scales. After first demonstrating how charge balance functions can be created using any pair of hadronic states, it will be shown how one can identify and study both processes of quark production. By considering balance functions of several hadronic species, and by performing illustrative calculations, this class of measurement appears to hold the prospect of providing the field's most stringent insight into the chemical evolution of the QGP.

11 pages, 1 figure (explanations and steps added to derivations, typos fixed, minor error in calculation fixed and some signs fixed)

References in corpus (2)

• Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR
• Charge conservation in RHIC and contributiuons to local parity violation observables

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• Quark charge balance function and hadronization effects in relativistic heavy ion collisions
• Multiplicity and transverse momentum dependence of charge-balance functions in pPb and PbPb collisions at LHC energies
• Differential Correlation Measurements with the Identity Method
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• Charm balance function in relativistic heavy-ion collisions
• Thermal fluctuations on the freeze-out surface of heavy-ion collisions and their impact on particle correlations
• A test of strangeness quantum number conservation in proton-proton collisions
• System size and event shape dependence of particle-identified balance functions in proton-proton collisions at $\sqrt{s}=13$ TeV using PYTHIA 8 and EPOS models
• Two-particle number and transverse momentum balance function with event topology in pp collisions at $\sqrt{s}=13$ TeV
• Balance functions of charged hadron pairs $(\pi ,K,p)\otimes (\pi ,K,p)$ in Pb--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$2.76 TeV