Dead-cone searches in heavy-ion collisions using the jet tree

Abstract

We explore the possibility of using the dead cone of heavy quarks as a region of the Lund plane where medium-induced gluon radiation can be isolated and characterised. The filling of the dead cone by medium-induced gluons is expected to be the result of the interplay between the minimum angle of such radiation due to transverse momentum broadening and the dead-cone angle. Since the measurement of a fully corrected Lund plane in heavy-ion collisions is currently challenging, we propose to use jet grooming techniques to identify a particular splitting in the jet tree that is both perturbative and sensitive to the dead-cone effect. To that end, we propose a new jet substructure groomer, dubbed Late-$k_t$, that selects the most collinear splitting in a QCD jet above a certain transverse momentum cutoff $k_{t,\mathrm{cut}}$. The role of $k_{t,\mathrm{cut}}$ is to guarantee perturbative splittings, while selecting the most collinear splitting enhances the sensitivity to mass effects. As a proof of concept, we study the angular distribution of the splitting tagged by Late-$k_t$ both analytically and with Monte Carlo simulations. First, we derive the logarithmic resummation structure in vacuum and demonstrate its capability to distinguish between inclusive and heavy-flavoured jets. Next, we extend the calculation for in-medium jets and show that medium-induced emissions lead to an enhancement of collinear emissions below the dead cone angle. Numerically, we demonstrate an excellent resilience of Late-$k_t$ against uncorrelated thermal background, thus confirming this observable as a potential candidate to unveil medium dynamics around the dead cone regime.

v2: fixed typo in vacuum splitting function. Conclusions remain unchanged

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Cited by in corpus (7)

• The ALICE experiment: a journey through QCD
• On heavy-flavour jets with Soft Drop
• Isolating perturbative QCD splittings in heavy-ion collisions
• Measurement of groomed event shape observables in deep-inelastic electron-proton scattering at HERA
• Heavy Flavour Jet Substructure
• Mass suppression effect in QCD radiation and hadron angular distribution in jet
• Jet substructure of light and heavy flavor jets at RHIC