Emergence and Violation of Geometrical Scaling in pp Collisions§

Michal Praszalowicz*
M. Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow, Poland

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© Michal Praszalowicz; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow, Poland; Tel: +48 12 663 56 77; Fax: +48 12 633 40 79; E-mail:
§ Presented at the Low x Workshop, May 30 - June 4 2013, Rehovot and Eilat, Israel.


We argue that geometrical scaling (GS) proposed originally in the context of Deep Inelastic Scattering (DIS) at HERA works also in pp collisions at the LHC energies and in NA61/SHINE experiment. We show that in DIS GS is working up to relatively large Bjorken x ~ 0.1 . As a consequence negative pion multiplicity pT distributions at NA61/SHINE energies exhibit GS in mid rapidity region. For y ≠ 0 clear sign of scaling violations can be seen when one of the colliding partons has Bjorken x ≥ 0.1 . Finally, we argue that in the case of identified particles GS scaling is still present but the scaling variable is a function of transverse mass rather than pT.

PACS number(s): 13.85.Ni,12.38.Lg.

Keywords:: Gluon saturation, low x physics, geometrical scaling.