ALICE studies the quark-gluon plasma expansion with charm quarks


ALICE studies the quark-gluon plasma expansion with charm quarks


Charm quarks serve as probes of the quark-gluon plasma (QGP) formed when lead nuclei collide in the LHC. When lead nuclei do not collide head on, the QGP system is elongated and the expansion leads to a dominant elliptical modulation - elliptic flow v2 - in the momentum distribution of hadrons.

The ALICE Collaboration recently measured, using the large lead-lead sample collected in 2018, the elliptic flow of hadrons containing charm quarks, either bound to a light quark (D meson) or in charm-anticharm pairs (J/ψ). The results are shown in the figure as a function of transverse momentum pT. At low momentum, the elliptic flow of D mesons is not as large as that of  pions (that contain only light quarks), while the elliptic flow of J/ψ is lower than both, but distinctly observed. This pattern indicates that the heavy charm quarks are dragged with the QGP expansion, but likely to a lesser extent than light quarks, and that both D mesons and J/ψ at low momentum are in part formed by the binding (recombination) of flowing quarks.

The INFN groups played a central role for achievement of these results.

CERN Media Update:

Further reading:

D meson anisotropy in Pb-Pb collisions:

J/ψ meson anisotropy in Pb-Pb collisions:

CSN3 Grants and job openings

The position of head of the nuclear science and instrumentation laboratory of the IAEA Laboratories in Seibersdorf (Austria) is open. More details at this link



Login Form

csn2 csn3 csn4 csn5 infn uffcom amministrazione-trasparente