Forward-backward correlation strength (b) as a function of pesudorapidity
intervals for experimental data from p+pˉ non-singly diffractive
collisions are compared to PYTHIA and PHOJET model calculations. The
correlations are discussed as a function of rapidity window (Δη)
symmetric about the central rapidity as well as rapidity window separated by a
gap (ηgap) between forward and backward regions. While the correlations
are observed to be independent of Δη, it is found to decrease with
increase in ηgap. This reflects the role of short range correlations
and justifies the use of ηgap to obtain the accurate information about
the physics of interest, the long range correlations. The experimental b
value shows a linear dependence on lns with the maximum value of
unity being reached at s = 16 TeV, beyond the top LHC energy. However
calculations from the PYTHIA and PHOJET models indicate a deviation from linear
dependence on lns and saturation in the b values being reached
beyond s = 1.8 TeV. Such a saturation in correlation values could have
interesting physical interpretations related to clan structures in particle
production. Strong forward-backward correlations are associated with cluster
production in the collisions. The average number of charged particles to which
the clusters fragments, called the cluster size, are found to also increase
linearly with lns for both data and the models studied. The rate of
increase in cluster size vs. lns from models studied are larger
compared to those from the data and higher for PHOJET compared to PYTHIA. Our
study indicates that the forward-backward measurements will provide a clear
distinguishing observable for the models studied at LHC energies.Comment: 15 pages, 14 Figures, accepted for publication in International
Journal of Modern Physics