Subjet Multiplicity in Quark and Gluon Jets at Dzero

TL;DR

This paper measures the subjet multiplicity in quark and gluon jets at different energies, compares experimental data with Monte Carlo predictions, and extracts the ratio of subjet multiplicities between gluon and quark jets.

Contribution

It provides the first measurement of subjet multiplicities in quark and gluon jets at Tevatron energies and compares these with Monte Carlo simulations.

Findings

Gluon jets have higher subjet multiplicity than quark jets.

The measured ratio R=1.84 indicates more complex structure in gluon jets.

Monte Carlo predictions are consistent with the measured multiplicities.

Abstract

We measure the subjet multiplicity M in jets reconstructed with a successive combination type of jet algorithm (kT). We select jets with 55<pT<100 GeV and |eta|<0.5. We compare similar samples of jets at sqrt(s)=1800 and 630 GeV. The HERWIG Monte Carlo simulation predicts that 59% of the jets are gluon jets at sqrt(s)=1800 GeV, and 33% at sqrt(s)=630 GeV. Using this information, we extract the subjet multiplicity in quark (Mq) and gluon (Mg) jets. We also measure the ratio R= (<Mg> -1)/(<Mq>-1)= 1.84 +- 0.15(stat) +0.22-0.18(sys).