Measurement of the average transverse momentum of forward prompt charged particles in $pp$ and $p\mathrm{P}\mathrm{b}$ collisions at $\sqrt{s_{NN}}=5.02\mathrm{T}\mathrm{e}\mathrm{V}$

This letter presents the first measurements of the average transverse momentum of prompt charged particles in $pp$ and $p\mathrm{P}\mathrm{b}$ collisions as a function of collision multiplicity and pseudorapidity. The data were recorded at nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}=5.02\mathrm{T}\mathrm{e}\mathrm{V}$ with the LHCb experiment. The pseudorapidity dependence of the multiplicity distribution is also measured. The average transverse momentum results show a decreasing trend with pseudorapidity, more pronounced in high-multiplicity events, consistent with the collective behaviour of the produced matter. The measurements are reproduced by state-of-the-art (3+1D) hydrodynamic calculations, while saturation models are not compatible with the data.