Quantum tomography of $H \to ZZ, WW$ beyond leading order

TL;DR

This paper examines quantum tomography of Higgs decays to ZZ and WW, emphasizing the need for correction subtraction to ensure physical spin density operators, and highlights potential to observe parity violation in H to WW decays.

Contribution

It demonstrates that higher-order corrections must be subtracted for consistent quantum tomography of Higgs decays, revealing new insights into parity violation effects.

Findings

Higher-order corrections are necessary for physical spin density operators.

Subtractions are small compared to current experimental uncertainties.

Potential to observe parity violation in H to WW decays.

Abstract

We revisit quantum tomography of $H \to ZZ$ and $H \to WW$ in the presence of higher-order corrections. We verify that neither the use of an effective spin analysing power (only for $ZZ$) or a photon veto are sufficient to render the naively-constructed spin density operators physical. A subtraction of higher-order corrections is thus necessary to perform consistent quantum tomography. Such corrections are small when compared to expected experimental uncertainties with current data. As a by-product, we point out the striking possibility to observe parity-violating effects in $H \to WW$.