We study the evolution of jetty and underlying parts of the transverse momentum spectra as a function of multiplicity in pp 13 TeV collisions at midrapidity (|eta|<0.8) using pythia8 event generator. We observe that beyond a multiplicity of dN/deta ~ 40 the maximum reachable leading transverse momentum gets smaller and at the same time the slope of the spectra both in the jetty and underlying parts show a continuous rise. At high multiplicity (>70) a rise in pT spectra at very low momenta (~ 1GeV/c) is also observed. We interpret this as a possible loss of the momentum at a certain particle/energy density in pp collisions.
The similarity in the behavior of transverse momentum spectra in Pb-Pb and pp collisions (shown in arXiv:1805.04572v2) indicate that the same mechanism could be responsible for the parton energy loss in heavy ions collisions. Although the behaviour of the spectra at low momenta are usually explained by hydro flow mechanisms, we demonstrate that with the present mechanism the low momentum features are perfectly explained by the overall hardening of the spectra. The saturation of the sum of the transverse momenta with multiplicity gives strong base to our observations.
We will present the results obtained with Pythia8 using different multiplicity estimators (central multiplicity estimator and the one based on the multiplicity in the transverse side) for different pseudorapidity ranges.