Experimental studies of QCD using flavour tagged jets with DELPHI

TL;DR

This paper uses DELPHI data to measure the ratio of charged particle multiplicities in gluon versus quark jets, revealing differences in radiation patterns and providing insights into b-quark mass effects.

Contribution

It presents the first detailed measurement of the multiplicity ratio between gluon and quark jets as a function of energy using flavour-tagged jets from DELPHI.

Findings

Gluon jets have higher charged particle multiplicity than quark jets.

The multiplicity ratio varies with jet energy, consistent across detectors.

b quarks radiate less than light quarks, supporting mass-dependent radiation effects.

Abstract

Identified $b\overline{b}g$ and $q\overline{q}\gamma$ events from DELPHI are used to measure the ratio of the mean charged particle multiplicity distribution between gluon and quark jets. The dependence of this ratio with the jet energy is established using about three million Z$^0$ decays. Results from all other detectors are discussed and compared. A nice agreement is found among all them. The ratio between the normalized total three-jet cross sections of $b\overline{b}g$ and $q\overline{q}g, q \equiv u,d,s$ events is also determined. The preliminary value obtained indicates that $b$ quarks are experimentaly seen to radiate less than light quarks due to their higher mass. The suggested experimental error is $\sim$300 MeV for the $b$ mass determination at the M$_Z$ scale.