Investigating charm quark energy loss in medium with the nuclear modification factor of D$^0$-tagged jets

TL;DR

This study measures the nuclear modification factor of charm-tagged jets in Pb-Pb collisions, revealing hints of reduced suppression compared to inclusive jets, and emphasizes the importance of quark mass effects in energy loss models.

Contribution

First measurement of D$^0$-tagged jet nuclear modification factor in heavy-ion collisions, providing insights into charm quark energy loss mechanisms.

Findings

Hints of reduced suppression for charm jets compared to inclusive jets.

Data favor models including quark mass effects, especially LIDO.

Results suggest energy loss depends on quark mass and color charge.

Abstract

The nuclear modification factor $R_\mathrm{AA}$ of charm jets, identified by the presence of a D$^0$ meson among the jet constituents, has been measured for the first time in Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector at the LHC. The D$^0$ mesons and their charge conjugates are reconstructed from the hadronic decay D$^0\to \mathrm K^{-}\pi^{+}$. Jets are reconstructed from D$^0$-meson candidates and charged particles using the anti-$k_\mathrm{T}$ algorithm with jet resolution parameter $R=0.3$, in the jet transverse momentum ($p_\mathrm{T}$) range $5< p_\mathrm{T}^\mathrm{ch~jet}<50$ GeV/$c$ and pseudorapidity $|\eta^\mathrm{ch~jet}| < 0.6$. A hint of reduced suppression in the charm-jet $R_\mathrm{AA}$ is observed in comparison to inclusive jets in central Pb-Pb collisions with a significance of about 2$\sigma$ in $20< p_\mathrm{T}^\mathrm{ch~jet}<50$ GeV/$c$, suggesting the in-medium energy loss to depend on both the difference between quark and gluon coupling strength (Casimir colour-charge effect) and quark mass (dead-cone effect). The data are compared with model calculations that include mass effects in the in-medium energy loss. Among these, LIDO provides the best description of the data, highlighting the role of mass effects in interpreting the results.