Determining the jet transport coefficient <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mi>q</mml:mi><mml:mo></mml:mo></mml:mover></mml:math> from inclusive hadron suppression measurements using Bayesian parameter estimation

Abstract

We report a new determination of $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}$, the jet transport coefficient of the quark-gluon plasma. We use the JETSCAPE framework, which incorporates a novel multistage theoretical approach to in-medium jet evolution and Bayesian inference for parameter extraction. The calculations, based on the Matter and Lbt jet quenching models, are compared to experimental measurements of inclusive hadron suppression in $\mathrm{Au}+\mathrm{Au}$ collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN Large Hadron Collider (LHC). The correlation of experimental systematic uncertainties is accounted for in the parameter extraction. The functional dependence of $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}$ on jet energy or virtuality and medium temperature is based on a perturbative picture of in-medium scattering, with components reflecting the different regimes of applicability of Matter and Lbt. In the multistage approach, the switch between Matter and Lbt is governed by a virtuality scale ${Q}_{0}$. Comparison of the posterior model predictions to the RHIC and LHC hadron suppression data shows reasonable agreement, with moderate tension in limited regions of phase space. The distribution of $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}/{T}^{3}$ extracted from the posterior distributions exhibits weak dependence on jet momentum and medium temperature $T$, with 90% credible region (CR) depending on the specific choice of model configuration. The choice of Matter$+$Lbt, with switching at virtuality ${Q}_{0}$, has 90% CR of $2&lt;\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}/{T}^{3}&lt;4$ for ${p}_{T,\mathrm{jet}}&gt;40 \mathrm{GeV}/c$. The value of ${Q}_{0}$, determined here for the first time, is in the range 2.0--2.7 GeV.