Speaker
Description
Various recent measurements of high-multiplicity pp and p-A collisions at the LHC center-of-mass energies have revealed, surprisingly, that these small collision systems exhibit some of the quark-gluon plasma features, e.g. collective behaviour and strangeness enhancement, formerly thought to be achievable only in heavy-ion collisions. A promising method to narrow down the origin of this behaviour is to study the effect of Multi-Parton Interactions (MPIs). The underlying event (UE), which is the collection of particles not originating from the primary hard parton-parton scattering or the related fragmentation, is thought to be highly sensitive to the MPIs. To access the mean number of MPIs experimentally, it has been proposed to use the self-normalised charged particle density in the region transverse to a jet, $R_\mathrm{T} = N_\mathrm{ch}^\mathrm{trans} / \langle N_\mathrm{ch}^\mathrm{trans} \rangle$, as it effectively disentangles the soft processes of interest from the hard component.
In this contribution, we report on the $\pi$, $p$, $K$, $\phi$, $\Lambda$, and $\Xi$ transverse momentum spectra—covering both mesons and baryons, as well as non-strange and strange hadrons—as a function of $R_\mathrm{T}$ in pp collisions at $\sqrt{s}=13$TeV measured with the ALICE detector at the LHC. Thus, we probe collective behaviour and strangeness enhancement in both the low-UE and the high-UE extremes and provide results with a good discriminatory potential for theoretical models.
