Forward-backward multiplicity correlations in pp collisions at sqrt(s)=0.9, 2.76 and 7 TeV

Submission Date: 
01/02/2015
Article Information
Submission Form
System: 
p-p
Energy: 
900 GeV
Energy: 
2.76 TeV
Energy: 
7 TeV
Abstract Plain Text: 
The strength of forward-backward (FB) multiplicity correlations was measured by the~ALICE detector in proton-proton (pp) collisions at $\sqrt{s}$=0.9, 2.76 and 7~TeV.
The measurement is performed in the central pseudorapidity region ($|\eta| < 0.8$) for the transverse momentum range pT>0.3 GeV/c.
Two separate pseudorapidity windows with widths ($\delta \eta$) ranging from 0.2  to 0.8 are chosen  symmetrically around $\eta$ = 0.
The multiplicity correlation strength ($\bcor$) is studied as a function of the pseudorapidity gap ($\eta_{gap}$) between the two windows as well as the width of these windows.
The correlation is found to decrease with increasing $\eta_{gap}$ and the dependence of $\bcor$ on $\delta \eta$ is non linear.
A sizeable increase of the correlation strength with the collision energy, which can not be explained  exclusively by the increase of the mean multiplicity inside the windows, is observed.
The correlation coefficient is also measured for multiplicities 
in different configurations of two azimuthal sectors selected within the symmetric FB $\eta$-windows.
Two distinct contributions, the short-range (SR) and the long-range (LR),  are observed.
The energy dependence of $\bcor$ is found to be weak for the SR component while  it is strong for the LR component.
Moreover, the correlation coefficient is studied for particles belonging to various transverse momentum intervals containing the same mean multiplicity.
Both SR and LR contributions to $\bcor$ are found to increase with pT.
Results are compared to PYTHIA and PHOJET event generators and to a string-based phenomenological model.