https://doi.org/10.1140/epjc/s10052-025-14184-z
Regular Article - Theoretical Physics
Leading two-loop corrections to the Higgs di-photon decay in the inert doublet model
1
National Institute of Technology, Miyakonojo College, 885-8567, Miyakonojo, Miyakonojo, Japan
2
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607, Hamburg, Germany
3
Department of Physics, The University of Osaka, 560-0043, Toyonaka, Osaka, Japan
Received:
25
October
2024
Accepted:
14
April
2025
Published online:
5
May
2025
Leading two-loop contributions to the di-photon decay of the Higgs boson are evaluated for the first time in the inert doublet model (IDM). We employ for this calculation the Higgs low-energy theorem, meaning that we obtain corrections to the Higgs decay process by taking Higgs-field derivatives of the leading two-loop contributions to the photon self-energy. Specifically, we have included corrections involving inert BSM Higgs bosons and gauge bosons, as well as external-leg contributions involving inert scalars, gauge bosons and fermions. Our calculation has been performed with a full on-shell renormalization, and in the gauge-less limit. Moreover, we performed two independent calculations, using the background-field method and the pinch technique, in order to apply the Higgs low-energy theorem consistently, and found full agreement between the two calculations. We investigate our results numerically in two scenarios of the IDM: one with a light dark matter (DM) candidate (Higgs resonance scenario), and another with all additional scalars heavy (heavy Higgs scenario). In both cases, we find that the inclusion of two-loop corrections qualitatively modifies the behavior of the decay width, compared with the one-loop (i.e. leading) order, and that they increase the deviation from the Standard Model. Furthermore, we demonstrate that the inclusion of the newly-computed two-loop corrections is essential to reliably interpret the observation or non-observation of a deviation in the Higgs di-photon decay width at current and future colliders.
© The Author(s) 2025
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