LIP Lisboa

Direct observation of the dead-cone effect in QCD

by Nima Zardoshti (CERN)

Seminar Room (LIP)

Seminar Room


Av. Prof. Gama Pinto, n.2 Complexo Interdisciplinar (3is) 1649-003 Lisboa Portugal

The fragmentation properties of colour charges in QCD exhibit strong flavour dependence. For heavy-flavour quarks, a significant component of this flavour dependence is driven by their large masses. The mechanism responsible for generating these mass-dependent properties in QCD is the dead-cone effect, which sets a cone surrounding each emitter within which emissions are suppressed. The opening angle of this cone is proportional to the mass of the emitter and inversely proportional to its energy, meaning that the effect is largest for low energy heavy-flavour quarks. Here the first direct observation of the QCD dead cone is presented, by studying the gluon radiation pattern from charm quarks generated in proton-proton collisions at 13 TeV using the ALICE detector. Charm-initiated track-based jets are tagged via the presence of a fully reconstructed D0 meson amongst their constituents, with iterative decluttering techniques used to reconstruct the resulting parton shower. The techniques are further extended to enact a program to quantify properties of charm emissions, with measurements mapping the c->cg splitting function also presented.