The flavor universality of some mass splittings in hadrons

TL;DR

The paper provides experimental evidence that certain mass splittings in mesons and baryons are approximately flavor-independent, suggesting a universal aspect of hadron mass differences related to chiral symmetry breaking.

Contribution

It demonstrates flavor universality of mass splittings in mesons and some baryons, enabling predictions of new hadron masses and quantum numbers.

Findings

Mass splittings in mesons are flavor-independent across tested cases.

Partial flavor independence observed in spin 1/2 baryons with non-$u/d$ quarks.

Predictions made for 10 new hadrons based on this universality.

Abstract

The approximate chiral invariance of the two-flavor QCD is known to be spontaneously broken. This effect explains the relatively small pion mass and, as is widely believed, the mass splittings of would-be chiral partners --- the hadrons of equal spin but opposite parity lying in one multiplet of the chiral symmetry. We present experimental evidences that in reality such mass splittings in the meson sector seem to be approximately flavor-independent in all cases where they can be tested experimentally --- the spin 0 and 1. In addition, a partial flavor independence holds for spin $1/2$ baryons (namely among states in which at least one of quarks is not $u$ or $d$ one). This property allows to predict masses and quantum numbers for 10 new hadrons. Some interesting consequences are discussed.