Effect of color reconnection on forward-backward multiplicity and mean transverse momentum correlation

Abstract

Color reconnection (CR) mechanism in PYTHIA model has been reported to be essential to describe the flow-like collective effect observed in high multiplicity $p$+$p$ and $p$+Pb collisions. In this work, we test this mechanism towards explaining the Forward-Backward multiplicity correlation (b$_{\mathrm {cor}}$) measurements in $p$+$p$ collisions at the LHC energies. Out of the three different CR schemes implemented in PYTHIA, (a) MPI based CR (default mechanism), (b) QCD based CR and (c) Gluon moved CR, we found that the QCD based CR scheme describes relatively better the ALICE measurements of b$_{\mathrm {cor}}$ in $p$+$p$ collisions at $\sqrt{\mathrm s}$ = 0.9 and 7 TeV. In addition, we have tuned the parameters of the default CR mechanism in PYTHIA to describe simultaneously the measured charged particle multiplicity pseudo-rapidity ($\eta$) distribution and b$_{\mathrm {cor}}$. We found that an average number of multipartonic interactions ($\langle N_{\mathrm {MPI}} \rangle$) between 2.5 to 3 and CR range between 0.9 to 2.5 best describes the experimental data. Finally, we have presented a study using PYTHIA events for $p$+$p$ collisions at $\sqrt{\mathrm s}$ = 7 TeV which shows that the strength of Forward-Backward mean transverse momentum correlation (b$^{\langle p_{\mathrm{T}}\rangle \langle p_{\mathrm{T}} \rangle}_{\rm {cor}}$) is found to increase with CR in contrast to decrease of b$_{\rm {cor}}$ values with CR effect. Hence, simultaneously studying the b$^{\langle p_{\mathrm{T}}\rangle \langle p_{\mathrm{T}} \rangle}_{\rm {cor}}$ and b$_{\mathrm {\rm {cor}}}$ in the experiments will help in establishing the arguments either in favour or in disfavour of CR effect in the measurements.