The data recorded with Xe–Xe collisions by the ALICE experiment in 2017 gives the unprecedented opportunity to investigate the effect of different heavy-ion collision systems on the kinematic and chemical features of the particle production at the LHC energies.

For the first time, the production of pions, kaons, (anti-)protons and φ mesons at midrapidity has been measured  in Xe–Xe collisions at √sNN = 5.44 TeV.

The study of Xe–Xe and Pb–Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe–Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the φ -to-pion ratio with increasing final-state multiplicity.

Further reading

ALICE Collaboration 2021