Abstract
This paper presents the measurements of pi ^{pm }, mathrm {K}^{pm }, text {p} and overline{mathrm{p}} transverse momentum (p_{text {T}}) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at sqrt{s} = 13 text {TeV} with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a p_{text {T}} range from 0.1 to 20 text {GeV}/c and are done in the rapidity interval |y|<0.5. The p_{text {T}}-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at sqrt{s} = 7 text {TeV}, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the p_{text {T}}-integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems.
Highlights
The unprecedented energies available at the Large Hadron Collider (LHC) provide unique opportunities to investigate the properties of strongly-interacting matter
We observe that the measured pT spectra become harder with increasing d Nch/dη, and the effect is more pronounced for protons
We have studied π, K, and p√production as a function of multiplicity in pp collisions at s = 13 TeV
Summary
The unprecedented energies available at the Large Hadron Collider (LHC) provide unique opportunities to investigate the properties of strongly-interacting matter. Recent reports on the enhancement of (multi)strange hadrons [6], double-ridge structure [7,8], non-zero v2 coefficients [9], mass ordering in hadron pT spectra, and characteristic modifications of baryon-to-meson ratios [10] suggest that collective phenomena are present at the LHC energies in p–Pb collisions. This is furth√er smaller systems, such as pp collisions at s extended to even = 7 TeV, where similar observations have been reported in high multiplicity events, indicating that the collective effects are not characteristic of heavy-ion collisions only.
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