Speaker
Grigori Feofilov
(St. Petersburg State University)
Description
Long-Range (Forward-Backward) Pt and Multiplicity Correlations
in pp Collisions at 0.9 and 7 TeV
The ALICE Collaboration
(Submitted by Grigory Feofilov)
Long-range rapidity and azimuthal correlations (LRC) of charged particles are a sensitive
tool to study the initial conditions for the Quark Gluon Plasma (QGP) formation [1],[2],[3].
Measured in separated pseudorapidity intervals, these correlations, if they exist, mainly Pt-
Nch and Pt-Pt, could be the indication in case of pp collisions of processes like color string
fusion[2] or glasma flux tubes formation[3]. The event-by-event analysis of the long-range
Forward-Backward (FB) Nch-Nch, Pt-Nch and Pt-Pt correlations has been performed on
data of the ALICE experiment obtained in the pp runs at 0.9 and 7 TeV pp collision energies.
The following observables were defined: Pt (the average transverse momentum in the event)
and Nch (the event multiplicity of charged particles). Two pseudorapidity intervals (the
"forward" and the "backward" windows) of the variable width from 0.2 to 0.8 rapidity units
were chosen. Correlations were studied as a function of the width of these windows and
on the gap between them, as well as for the different configurations of four pi/2 azimuthal
sectors relevant to these windows. Methods for separating the short-range correlations and to
measure the long-range correlations strength in the limited acceptance of the ALICE central
barrel (-0.8, 0.8) are discussed. Analysis results show a behaviour compatible with LRC
phenomena for these pp collisions. They are compared to PYTHIA and to the model with
independent emitters (strings) [4].
References
[1] Abramovskii V. A., Gedalin E. V., Gurvich E. G., Kancheli O. V. , JETP Lett., vol.47,
337-339 , 1988.
[2] M.A.Braun, C.Pajares, Phys.Lett. B287 (1992) 154; Nucl.Phys. B390 (1993) 542;
Eur.Phys.J. C16 (2000) 349; N.S.Amelin, N.Armesto, M.A.Braun, E.G.Ferreiro,
C.Pajares, Phys.Rev.Lett. 73 (1994) 2813; M.A.Braun, C.Pajares, V.V.Vechernin,
Phys.Lett. B493 (2000) 54; Internal Note/FMD, ALICE-INT-2001-16, CERN, Geneva
(2001) 13p.; M.A.Braun, R.S.Kolevatov, C.Pajares, V.V.Vechernin, Eur.Phys.J. C32
(2004) 535; V.V.Vechernin, R.S.Kolevatov, Phys. of Atom.Nucl. 70 (2007) 1797; 1809.
[3] L.McLerran, "The Color Glass Condensate and the Glasma", Proceedings of the Inter-
national School of Subnuclear Physics, Subnuclear Series, Vol. 45, 2010.
[4] V.V. Vechernin, arXiv:1012.0214, 2010.
Primary author
Grigori Feofilov
(St. Petersburg State University)
Co-author
2 1
(3)
