Speaker
Description
The study of the charged particle production as a function of the multiplicity in small colliding systems, as pp and p-Pb, is an attractive tool to understand the similarities and differences between small and large colliding systems. Evidence of similarities, like coherent and collective effects, well known in nucleous-nucleous (A-A) collisions, has been found experimentally in small systems.
New results on the primary charged-particle pseudo-rapidity density and transverse momentum ($p_{\rm{T}}$) distributions at central pseudo-rapidity in pp ($\sqrt{s} = 5.02$ and $\sqrt{s} = 13$ TeV) and p-Pb ($\sqrt{s} = 5.02$ and $8.16$ TeV) collisions as a function of multiplicity are going to be presented.
In order to study the hard component of particle spectra in pp collisions, a power law fit of the distributions for $p_{\rm{T}}> 4$ GeV/$c$ is performed and the evolution with multiplicity of the resulting fit parameters is discussed. To the same purpose, the ratio of multiplicity-dependent yields over minimum bias yields integrated over $4 < p_{\rm{T}} < 8$ GeV/$c$ is studied and compared to results for heavy-flavour particles. Results are presented using two multiplicity estimators, at mid pseudo-rapidity ($|\eta| < 0.8$) and forward-backward pseudo-rapidity ($- 3.7 < \eta < - 1.7$ and $2.8 < \eta < 5.1$) to study the differences caused by the multiplicity selection in different pseudo-rapidity windows.
A comparison with Monte Carlo event generators and models, like EPOS-LHC and PYTHIA 8, will be shown.
