Glueball Spin

TL;DR

This paper reexamines the spin of glueballs using the QCD field angular momentum operator, exploring theoretical restrictions and expectations to better understand their spin structure beyond constituent gluon models.

Contribution

It introduces a new analysis of glueball spin based on the QCD field angular momentum operator and its commutation relations, challenging traditional constituent gluon assumptions.

Findings

Restrictions on glueball structure from angular momentum operator

Comparison to electromagnetic charge/monopole quantization

Preliminary expectation values of the angular momentum operator

Abstract

The spin of a glueball is usually taken as coming from the spin (and possibly the orbital angular momentum) of its constituent gluons. In light of the difficulties in accounting for the spin of the proton from its constituent quarks, the spin of glueballs is reexamined. The starting point is the fundamental QCD field angular momentum operator written in terms of the chromoelectric and chromomagnetic fields. First, we look at the restrictions placed on the structure of glueballs from the requirement that the QCD field angular momentum operator should satisfy the standard commutation relationships. This can be compared to the electromagnetic charge/monopole system, where the quantization of the field angular momentum places restrictions (i.e. the Dirac condition) on the system. Second, we look at the expectation value of this operator under some simplifying assumptions.