Two-loop electroweak corrections to the Higgs boson rare decay process $H\to Z\gamma$

TL;DR

This paper calculates next-to-leading order electroweak corrections to the rare Higgs decay $H\to Z\gamma$, improving theoretical predictions and indicating potential new physics beyond the Standard Model due to persistent experimental discrepancies.

Contribution

It provides the first detailed NLO electroweak correction calculation for $H\to Z\gamma$, enhancing the accuracy of SM predictions for this rare decay process.

Findings

NLO EW corrections significantly improve prediction reliability.

The SM cannot fully explain the observed excess in $H\to Z\gamma$ decay.

Higher order corrections increase the discrepancy with experimental data.

Abstract

Recently, the ATLAS and CMS collaborations jointly announced the first evidence of the rare Higgs boson decay channel $H\to Z\gamma$, with a ratio of $2.2\pm 0.7$ times the leading order standard model (SM) prediction. In order to face this challenge, it is urgent to produce an even more accurate calculation within the SM. To this end, we calculate in this paper the next-to-leading order (NLO) electroweak (EW) corrections to the $H\to Z\gamma$ process, in which the NLO quantum chromodynamics (QCD) corrections were found tiny. Our calculation finds that the inclusion of NLO EW corrections greatly enhances the prediction reliability. To tame the theoretical uncertainty, we adopt five different renormalization schemes. Combining our result with previous NLO QCD corrections and the signal-background interference, we conclude that the excess in $H\to Z\gamma$ cannot be explained within the SM. In fact, the incompatibility between the SM prediction and the LHC measurement of the concerned process is exacerbated upon considering the higher order EW corrections, which implies that something beyond the SM could be involved.