Multistage Monte Carlo simulation of jet modification in a static medium

The modification of hard jets in an extended static medium held at a fixed temperature is studied using three different Monte Carlo event generators: linear Boltzmann transport (LBT), modular all twist transverse-scattering elastic-drag and radiation (MATTER), and modular algorithm for relativistic treatment of heavy-ion interactions (MARTINI). Each event generator contains a different set of assumptions regarding the energy and virtuality of the partons within a jet versus the energy scale of the medium and, hence, applies to a different epoch in the space-time history of the jet evolution. Here modeling is developed where a jet may sequentially transition from one generator to the next, on a parton-by-parton level, providing a detailed simulation of the space-time evolution of medium modified jets over a much broader dynamic range than has been attempted previously in a single calculation. Comparisons are carried out for different observables sensitive to jet quenching, including the parton fragmentation function and the azimuthal distribution of jet energy around the jet axis. The effect of varying the boundary between different generators is studied and a theoretically motivated criterion for the location of this boundary is proposed. The importance of such an approach with coupled generators to the modeling of jet quenching is discussed.

Figure 1

Separation time $t_0$ between MATTER and MARTINI/LBT as functions of parton energy for different initial parton energy $E_{\mathrm{init}}$, brick size $L$, and separation virtuality scale $Q_0$. The main figures show results in a brick with length of 4 fm, and the inset subfigures show the ratio between 4 and 8 fm.

Figure 2

Energy distribution of final partons with a $L=4$ fm brick: (a) for $E_{\mathrm{init}}=50\mathrm{GeV}$ and (b) for 200 GeV for the initial quark.

Figure 3

The length dependence of the energy spectra: (a) for $E_{\mathrm{init}}=50\mathrm{GeV}$ and (b) for 200 GeV for the initial quark.

Figure 4

Energy distribution with respect to the jet cone angle (for $E_{\mathrm{init}}=50$ GeV and $L=4$ fm).