# Distinguishing between quark and gluon jets

How do experimentalists at the LHC differentiate between jets produced by quarks and those produced by gluons. I know that for b quarks there is a b-tagging method, but what do they do for the others in order to separate them from gluon induced jets?

## 1 Answer

I found a good paper here titled Distinguishing quark and gluon jets at the LHC from CERN's website that answers your question. The introduction states

"Partons emitted from hard scattering process at the LHC form, due to QCD confinement and hadronization process, hadronic jets, which can be revealed with tracking and calorimeter systems. As known from theoretical principles and from experimental measurements, reconstructed jets show different properties depending on flavor of original parton. In general, due to the large color factor of gluons, gluon-initiated jets have higher particle multiplicity, a softer fragmentation function, and are less collimated than quark-initiated jets. These differences can be exploited to tag jets, and such a capability plays a fundamental role in several physics analyses. It results in an increased ability to discriminate full-hadronic final searches - composed mainly by quark-originated jets, from QCD background - where the gluon component is predominant".

• In the heavy-ion sector, we've also been experimenting with using the jet's total charge to distinguish quark and gluon jets: arxiv.org/abs/2004.00602 – probably_someone Sep 29 at 22:08
• Thanks @probably_someone! – Dr jh Sep 29 at 22:32