The SM expected branching ratio for $h \to γγ$ and an excess for $h \to Z γ$
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| Format: | Preprint |
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2024
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| _version_ | 1866909355357503488 |
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| author | He, Xiao-Gang Huang, Zhong-Lv Li, Ming-Wei Liu, Chia-Wei |
| author_facet | He, Xiao-Gang Huang, Zhong-Lv Li, Ming-Wei Liu, Chia-Wei |
| contents | The recent measurements of $h \to Z γ$ from ATLAS and CMS show an excess of the signal strength $μ_Z = (σ\cdot{\cal B})_{\mathrm{obs}}/(σ\cdot{\cal B})_{\mathrm{SM}}=2.2\pm 0.7$, normalized as 1 in the standard model~(SM). If confirmed, it would be a signal of new physics (NP) beyond the SM. We study NP explanation for this excess. In general, for a given model, it also affects the process $h \to γγ$. Since the measured branching ratio for this process agrees well with the SM prediction, the model is severely constrained. We find that a minimally fermion singlets and doublet extended NP model can explain simultaneously the current data for $h \to Z γ$ and $h\to γγ$. There are two solutions. Although both solutions enhance the amplitude of $h \to Z γ$ to the observed one, in one of the solutions the amplitude of $h \to γγ$ flips sign to give the observ ed branching ratio. This seems to be a contrived solution although cannot be ruled out simply using branching ratio measurements alone. However, we find another solution that naturally enhances $h \to Z γ$ to the measured value, but keeps the amplitude of $h \to γγ$ close to its SM prediction. We also comment on the phenomenology associated with these new fermions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2402_08190 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The SM expected branching ratio for $h \to γγ$ and an excess for $h \to Z γ$ He, Xiao-Gang Huang, Zhong-Lv Li, Ming-Wei Liu, Chia-Wei High Energy Physics - Phenomenology High Energy Physics - Experiment The recent measurements of $h \to Z γ$ from ATLAS and CMS show an excess of the signal strength $μ_Z = (σ\cdot{\cal B})_{\mathrm{obs}}/(σ\cdot{\cal B})_{\mathrm{SM}}=2.2\pm 0.7$, normalized as 1 in the standard model~(SM). If confirmed, it would be a signal of new physics (NP) beyond the SM. We study NP explanation for this excess. In general, for a given model, it also affects the process $h \to γγ$. Since the measured branching ratio for this process agrees well with the SM prediction, the model is severely constrained. We find that a minimally fermion singlets and doublet extended NP model can explain simultaneously the current data for $h \to Z γ$ and $h\to γγ$. There are two solutions. Although both solutions enhance the amplitude of $h \to Z γ$ to the observed one, in one of the solutions the amplitude of $h \to γγ$ flips sign to give the observ ed branching ratio. This seems to be a contrived solution although cannot be ruled out simply using branching ratio measurements alone. However, we find another solution that naturally enhances $h \to Z γ$ to the measured value, but keeps the amplitude of $h \to γγ$ close to its SM prediction. We also comment on the phenomenology associated with these new fermions. |
| title | The SM expected branching ratio for $h \to γγ$ and an excess for $h \to Z γ$ |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2402.08190 |