Speaker
Description
The study of the charged particle production as a function of the multiplicity in small colliding systems, as pp, 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 know in AA collisions, has been found experimentally even in small systems.
Recent results of the transverse momentum ($p_{\rm{T}}$) distributions of charged hadrons at central pseudo-rapidity as a function of multiplicity for pp ($\sqrt{s} = 5.02$ and $\sqrt{s} = 13$ TeV) are going to be presented.
In order to study the hard component of particle spectra, for 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 the minimum bias yield 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 multiplicity selection in different pseudo-rapidity windows.
A comparison with Monte Carlo event generators and models, like EPOS-LHC and PYTHIA 8 and 6, is also included.
