Improved supernova bounds on CP-even scalars: cooling and decay constraints

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Main Authors: Joseph, Melissa, Liebersbach, Samuel, Madathil, Anirudhan A., Marques-Tavares, Gustavo
Format: Preprint
Published: 2026
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author Joseph, Melissa
Liebersbach, Samuel
Madathil, Anirudhan A.
Marques-Tavares, Gustavo
author_facet Joseph, Melissa
Liebersbach, Samuel
Madathil, Anirudhan A.
Marques-Tavares, Gustavo
contents Supernovae provide among the most powerful probes of weakly-coupled new particles in the MeV mass range, where laboratory experiments lose sensitivity. In this work, we derive improved supernova constraints on CP-even scalars mixing with the Higgs boson, combining an updated production rate calculation, which improves the cooling bound by more than an order of magnitude, with new decay-based constraints from the galactic 511~keV positron flux and energy deposition in low-energy Type~II-P supernovae. Together, these constraints probe mixing angles as small as $\sinθ\sim 10^{-9}$, more than five orders of magnitude below existing collider bounds. We also extend our analysis to a hadrophilic scalar model, constraining Yukawa couplings down to $y_N \sim 10^{-10}$. Our results demonstrate that the combination of astrophysical and collider probes covers over nine orders of magnitude in coupling for these classes of models, probing a large region of parameter space motivated by dark matter considerations.
format Preprint
id arxiv_https___arxiv_org_abs_2603_04513
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Improved supernova bounds on CP-even scalars: cooling and decay constraints
Joseph, Melissa
Liebersbach, Samuel
Madathil, Anirudhan A.
Marques-Tavares, Gustavo
High Energy Physics - Phenomenology
Supernovae provide among the most powerful probes of weakly-coupled new particles in the MeV mass range, where laboratory experiments lose sensitivity. In this work, we derive improved supernova constraints on CP-even scalars mixing with the Higgs boson, combining an updated production rate calculation, which improves the cooling bound by more than an order of magnitude, with new decay-based constraints from the galactic 511~keV positron flux and energy deposition in low-energy Type~II-P supernovae. Together, these constraints probe mixing angles as small as $\sinθ\sim 10^{-9}$, more than five orders of magnitude below existing collider bounds. We also extend our analysis to a hadrophilic scalar model, constraining Yukawa couplings down to $y_N \sim 10^{-10}$. Our results demonstrate that the combination of astrophysical and collider probes covers over nine orders of magnitude in coupling for these classes of models, probing a large region of parameter space motivated by dark matter considerations.
title Improved supernova bounds on CP-even scalars: cooling and decay constraints
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2603.04513