Exploring a new SU(4) symmetry of meson interpolators

Abstract

In recent lattice calculations it has been discovered that mesons upon truncation of the quasi-zero modes of the Dirac operator obey a symmetry larger than the $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_A$ symmetry of the QCD Lagrangian. This symmetry has been suggested to be $SU(4)\supset SU(2{)}_L\times SU(2{)}_R\times U(1{)}_A$ that mixes not only the u- and d-quarks of a given chirality, but also the left- and right-handed components. Here it is demonstrated that bilinear $\overline{q}q$ interpolating fields of a given spin $J\ge 1$ transform into each other according to irreducible representations of $SU(4)$ or, in general, $SU(2N_F)$. This fact together with the coincidence of the correlation functions establishes $SU(4)$ as a symmetry of the $J\ge 1$ mesons upon quasi-zero mode reduction. It is shown that this symmetry is a symmetry of the confining instantaneous charge-charge interaction in QCD. Different subgroups of $SU(4)$ as well as the $SU(4)$ algebra are explored.

Comments: Implication chapter added, figure added; Version accepted for publication in Phys. Rev. D