Constraining $A\to ZH$ with $H\to t\bar t$ in the Low-Mass Region
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2025
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| author | Ashanujjaman, Saiyad Coloretti, Guglielmo Crivellin, Andreas Maharathy, Siddharth P. Mellado, Bruce |
| author_facet | Ashanujjaman, Saiyad Coloretti, Guglielmo Crivellin, Andreas Maharathy, Siddharth P. Mellado, Bruce |
| contents | The decay $A\to ZH$ is a characteristic signal of two-Higgs-doublet models (2HDMs), where $A$ and $H$ lie primarily within the same $SU(2)_L$ multiplet, leading to a coupling of order $g_2$ to the $Z$ boson. The subsequent decay $H\to tt^{(*)}$ is particularly promising, as it gives rise to distinct final states involving multiple leptons and $b$-jets. The required splitting between $m_A$ and $m_H$ can naturally occur near the electroweak scale while being consistent with perturbative unitarity. Whereas dedicated ATLAS and CMS searches focused on the region with both top-quarks on-shell, we cover lower masses where one top quark is off-shell by recasting Standard Model $t\bar{t}Z$ measurements of ATLAS and CMS. The obtained limits on $σ(A\to ZH)\times {\rm Br} (H\to t\bar t)$ are between $0.12$ pb and $0.62$ pb. Interestingly, we observe these stringent limits despite a preference (up to $2.5σ$) for a non-zero new physics signal, most pronounced around for $m_A \approx 450-460$ GeV and $m_H\approx 290$ GeV, with a best-fit value of $σ(A \to ZH) \times {\rm Br}(H \to t\bar t) \approx 0.3$ pb. This cross section can be accommodated within a top-philic 2HDM for a top-Yukawa coupling of the second Higgs doublet of $μ_t \gtrsim 0.16$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_23714 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Constraining $A\to ZH$ with $H\to t\bar t$ in the Low-Mass Region Ashanujjaman, Saiyad Coloretti, Guglielmo Crivellin, Andreas Maharathy, Siddharth P. Mellado, Bruce High Energy Physics - Phenomenology High Energy Physics - Experiment The decay $A\to ZH$ is a characteristic signal of two-Higgs-doublet models (2HDMs), where $A$ and $H$ lie primarily within the same $SU(2)_L$ multiplet, leading to a coupling of order $g_2$ to the $Z$ boson. The subsequent decay $H\to tt^{(*)}$ is particularly promising, as it gives rise to distinct final states involving multiple leptons and $b$-jets. The required splitting between $m_A$ and $m_H$ can naturally occur near the electroweak scale while being consistent with perturbative unitarity. Whereas dedicated ATLAS and CMS searches focused on the region with both top-quarks on-shell, we cover lower masses where one top quark is off-shell by recasting Standard Model $t\bar{t}Z$ measurements of ATLAS and CMS. The obtained limits on $σ(A\to ZH)\times {\rm Br} (H\to t\bar t)$ are between $0.12$ pb and $0.62$ pb. Interestingly, we observe these stringent limits despite a preference (up to $2.5σ$) for a non-zero new physics signal, most pronounced around for $m_A \approx 450-460$ GeV and $m_H\approx 290$ GeV, with a best-fit value of $σ(A \to ZH) \times {\rm Br}(H \to t\bar t) \approx 0.3$ pb. This cross section can be accommodated within a top-philic 2HDM for a top-Yukawa coupling of the second Higgs doublet of $μ_t \gtrsim 0.16$. |
| title | Constraining $A\to ZH$ with $H\to t\bar t$ in the Low-Mass Region |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2510.23714 |