Heavy-flavour correlations in pp, p–Pb and Pb–Pb collisions

Heavy quarks (charm and beauty) are produced in initial hard scattering processes in heavy-ion collisions, before the formation of a strongly interacting medium, the Quark Gluon Plasma. Insight into the effects of the medium on charm and beauty production can be obtained by measuring the angular correlations between open heavy-flavour hadrons and charged particles. In Pb–Pb collisions, the azimuthal correlation can provide information on the way heavy quarks lose energy in the QGP and is sensitive to possible modifications of the charm parton shower and hadronisation in the presence of the medium. The observed double-ridge long-range correlations in p–Pb collisions for light-flavour hadrons could originate from a collective expansion of the system, as well as from gluon saturation in the initial state (colour glass condensate). The same effect can be studied for heavier quarks via the correlation between heavy-flavour hadrons (or their decay electrons) and charged particles.