Multiplicity dependence of $$\pi $$, K, and p production in pp collisions at $$\sqrt{s} = 13$$ TeV

Abstract

This paper presents the measurements of $$\pi ^{\pm }$$π±, $$\mathrm {K}^{\pm }$$K±, $$\text {p}$$p and $$\overline{\mathrm{p}} $$p¯ transverse momentum ($$p_{\text {T}}$$pT) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at $$\sqrt{s}\ =\ 13\ \text {TeV}$$s=13TeV 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 $$p_{\text {T}}$$pT range from 0.1 to 20 $$\text {GeV}/c$$GeV/c and are done in the rapidity interval $$|y|<0.5$$|y|<0.5. The $$p_{\text {T}}$$pT-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at $$\sqrt{s}\ =\ 7\ \text {TeV}$$s=7TeV, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the $$p_{\text {T}}$$pT-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.

Multiparton interactions in pp collisions from machine learning-based regression

“…The bump at intermediate p T resembles the Cronin effect [38] observed in p-Pb collisions [39]. Albeit the effect is rather large (≈40%), it is worth mentioning that, given the limitations of the multiplicity estimators used in the experiments [23], the bump has not been observed in pp data [21].…”

“…Results within the string percolation framework have also been reported [19]. Moreover, HERWIG7.1 [20], which recently updated its CR model, has significantly improved the description of hadron-to-pion ratios as a function of charged-particle multiplicity [21]. From the above discussion, it is clear that the unified description of the observed phenomena across different collision systems is still an open problem [22].…”

The multiple-charm hierarchy in the statistical hadronization model

“…The thermal particle spectra are obtained from a simple freeze-out surface with a given freeze-out temperature and with parametrized radial velocity profile. This thermal blast-wave model has been used extensively in the past to fit and characterize the experimentally measured identified particle spectra [59][60][61][62].…”

Possible early universe signals in proton collisions at the Large Hadron Collider

“…Fits of the low part of p T -spectra (up to 2-3 GeV/c) of identified charged particles using the Blast-wave model yield the temperature at the kinetic freeze-out (T kin ) and the average collective radial flow velocity (< β T >) of the system. Figure 4 shows the results of Blast-wave fits in terms of T kin and < β T > for proton-proton, proton-Pb, and Pb-Pb collisions [17,18]. Going from left to right along the x-axis, one moves from collisions yielding low to high particle multiplicity.…”