Measurements of groomed heavy-flavour jet substructure with ALICE

Abstract

We report the first measurements of the groomed heavy-flavour jet substructure variables \( z_{\text{g}} \), \( R_{\text{g}} \), and \( n_{\text{SD}} \) using the Soft Drop algorithm for charged-particle jets tagged by fully reconstructed \({\text{D}^{\text{0}}}\) mesons in pp collisions at \(\sqrt{s} = 13\,\mathrm{TeV}\). Iterative declustering techniques access the jet splitting tree of track-based jets, with grooming techniques isolating the perturbative branches. \({\text{D}^{\text{0}}}\)-tagged jets give access to an enriched quark-initiated sample of jets down to low jet transverse momenta ($p^{\text{jet ch}}_{\text{T}}$). This provides a new opportunity to explore the differences between quark and gluon fragmentations in vacuum in the region of phase space where the inclusive-jet sample is dominated by gluon-initiated jets and where the mass effects of heavy-flavour quarks are also expected to be the strongest. The shared momentum fraction of the first splitting accepted by the grooming procedure, $z_{\text{g}}$, and the aperture angle between the prongs of that splitting, $R_{\text{g}}$, fully corrected to particle level, are presented. The grooming is performed using the iterative Soft Drop technique with parameters $z_{\text{cut}} = 0.1$ and $\beta = 0$. In addition, the number of splittings per jet satisfying the grooming condition, $n_{\text{SD}}$, is also reported. The results are presented in the $15 \leq p^{\text{jet ch}}_{\text{T}} < 30\,\mathrm{GeV}/c$ range and are compared to complementary measurements of inclusive jets as well as to theoretical models. These results also provide a reference for future \({\text{D}^{\text{0}}}\)-tagged jet substructure measurements in heavy-ion collisions, to explore the different energy loss of gluon, light-quark, and heavy-quark jets in the presence of a deconfined QCD medium.