Medium modifications of heavy-flavor jet angularities in high-energy nuclear collisions

Abstract

We present the first theoretical study of heavy-flavor jet angularities ($\lambda^{\kappa}_{\alpha}$) in Pb+Pb collisions at $\sqrt{s_{\rm NN}}=$ 5.02 TeV. The initial production of heavy-flavor jets is carried out using the POWHEG+PYTHIA8 prescription, while the jet evolution in the quark-gluon plasma (QGP) is described by the SHELL transport model. In p+p collisions, we observe narrower angularity distributions for D$^0$-tagged jets compared to inclusive jets, consistent with the ALICE preliminary results. We then demonstrate that jet quenching in the QGP slightly widens the angularity distribution of D$^0$-tagged jets in Pb+Pb collisions relative to that in p+p collisions for jet transverse momentum of $10 < p_{\rm T,jet} < 20$ GeV/c, while the angularity distributions of inclusive and D$^0$-tagged jets become narrower in Pb+Pb collisions relative to p+p at $p_{\rm T,jet} > 20$ GeV/c due to the strong influence of the selection bias. Additionally, by comparing the average angularities $\langle \lambda^{\kappa}_{\alpha} \rangle$ of inclusive, D$^0$-tagged and B$^0$-tagged jets with varying $\alpha$ and $\kappa$, we show that the larger the quark mass is, the lower the jet's $\langle \lambda^{\kappa}_{\alpha} \rangle$ values are. As a result of the slenderer initial distribution, we predict that as compared to inclusive jets, the heavy-flavor jets, especially the B$^0$-tagged ones, will suffer stronger modifications of $\langle \lambda^{\kappa}_{\alpha} \rangle$ in Pb+Pb relative to p+p at $10 < p_{\rm T,jet} < 20$ GeV/c. For a larger jet radius, a more significant broadening of jet angularities is predicted because of the enhanced contributions of the wide-angle particles.