Does the Z boson have a lighter cousin?

TL;DR

This paper constructs gauge-invariant states in lattice electroweak theory to study the spectrum of vector bosons, finding evidence for additional bosons beyond the photon and Z, with potential lighter states around 3-4 GeV.

Contribution

It introduces a method to identify physical vector boson states on the lattice using eigenstates of the covariant Laplacian, revealing possible lighter bosons in the spectrum.

Findings

Identifies a massless photon and a massive Z boson as expected.

Provides evidence for additional vector bosons with masses around 3-4 GeV.

Suggests the existence of a lighter cousin of the Z boson.

Abstract

In the quenched electroweak theory on the lattice I construct a set of physical states which overlap the physical photon and Z boson states. This is done by employing eigenstates of the covariant lattice Laplacian, in addition to the Higgs and lattice link variables, to construct gauge invariant vector boson creation operators. Diagonalizing the transfer matrix in the subspace of Hilbert space spanned by this set yields a massless photon and massive Z particle, as expected. But in the numerical data there is evidence for more vector bosons in the spectrum, albeit with considerable uncertainty in their masses, with the lowest finite mass particle in the range of 3-4 GeV.