Violation of Geometrical Scaling in pp Collisions at NA61/SHINE

Abstract

We analyze geometrical scaling (GS) of negative pion multiplicity p_T distributions at NA61/SHINE energies. We show that even though NA61/SHINE energies are low, one may expect to find GS in the particle spectra. We argue that qualitative behavior of ratios of multiplicities at different energies is in agreement with a simple picture of GS which is violated for p_T smaller than some nonperturbative scale Lambda and when larger Bjorken x of one of the scattering patrons crosses x_max above which gluonic cloud becomes dilute and quark degrees of freedom become important.

Comments: 5 pages, 3 figures, in v3 minor typos corrected, references added. Version accepted in Phys. Rev. D