Origin of collectivity and strangeness enhancement in p–Pb collisions

Determine the physical origin of the collective behavior and strangeness enhancement observed in proton–lead collisions at a centre-of-mass energy per nucleon–nucleon collision of 5.02 TeV, clarifying whether these effects arise from quark–gluon plasma formation or other mechanisms specific to small systems.

Background

The paper notes that proton–lead collisions at LHC energies exhibit features—collectivity and strangeness enhancement—traditionally associated with quark–gluon plasma formation in heavy-ion collisions. However, in small systems like p–Pb, the underlying mechanism responsible for these signals is unsettled.

This unresolved origin motivates comprehensive measurements of charged-particle multiplicity distributions over wide pseudorapidity ranges, providing quantitative inputs to constrain and improve theoretical models of particle production in p–Pb.

References

The origin of these phenomena is not yet fully understood, and it is crucial to investigate and understand the global properties of the system formed in \pPb collisions, which makes the measurement of multiplicity distributions important.

— Charged-particle multiplicity distributions over a wide pseudorapidity range in p-Pb collisions at $\mathbf{\sqrt{s}_{\rm NN} = 5.02}$ TeV  (2502.18081 - Collaboration, 25 Feb 2025) in Section 1 (Introduction), p. 2

Although the qualitative features of these correlations resemble those observed in heavy-ion collisions, their underlying physical mechanism is still being actively investigated in experiment and theory.

— Study of the multiplicity dependence of non-flow correlations in pp collisions at $\sqrt{s}=200$ GeV using PYTHIA  (2609.11526 - Stojanovic et al., 10 Sep 2026) in Section 1, Introduction