The SM expected branching ratio for h → γγ and an excess for h → Zγ
Abstract The recent measurements of h → Zγ from ATLAS and CMS show an excess of the signal strength μ Z = σ · B obs / σ · B SM $$ {\left(\sigma \cdotp \mathcal{B}\right)}_{\textrm{obs}}/{\left(\sigma \cdotp \mathcal{B}\right)}_{\textrm{SM}} $$ = 2.2 ± 0.7, normalized as 1 in the standard model (SM)....
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2024-10-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/JHEP10(2024)135 |
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| Summary: | Abstract The recent measurements of h → Zγ from ATLAS and CMS show an excess of the signal strength μ Z = σ · B obs / σ · B SM $$ {\left(\sigma \cdotp \mathcal{B}\right)}_{\textrm{obs}}/{\left(\sigma \cdotp \mathcal{B}\right)}_{\textrm{SM}} $$ = 2.2 ± 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 → 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 → Zγ and h → γγ. There are two solutions. Although both solutions enhance the amplitude of h → Zγ to the observed one, in one of the solutions the amplitude of h → γγ flips sign to give the observed 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 → Zγ to the measured value, but keeps the amplitude of h → γγ close to its SM prediction. We also comment on the phenomenology associated with these new fermions. |
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| ISSN: | 1029-8479 |