Search for exotic decays of the Higgs boson to a pair of pseudoscalars in the $\upmu \upmu \text{ b } \text{ b } $ and $\uptau \uptau \text{ b } \text{ b } $ final states
(2024) European Physical Journal C — Vol. 84 (2024)
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- A search for exotic decays of the Higgs boson ($\text {H}$) with a mass of 125$\,\text {Ge}\hspace{-.08em}\text {V}$ to a pair of light pseudoscalars $\text {a}_{1} $ is performed in final states where one pseudoscalar decays to two ${\textrm{b}}$ quarks and the other to a pair of muons or $\tau $ leptons. A data sample of proton–proton collisions at $\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $ corresponding to an integrated luminosity of 138$\,\text {fb}^{-1}$ marc:recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level ($\text {CL}$) on the Higgs boson branching fraction to $\upmu \upmu \text{ b } \text{ b } $ and to $\uptau \uptau \text{ b } \text{ b },$ via a pair of $\text {a}_{1} $s. The limits depend on the pseudoscalar mass $m_{\text {a}_{1}}$ and are observed to be in the range (0.17–3.3) $\times 10^{-4}$ and (1.7–7.7) $\times 10^{-2}$ in the $\upmu \upmu \text{ b } \text{ b } $ and $\uptau \uptau \text{ b } \text{ b } $ final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction ${\mathcal {B}}(\text {H} \rightarrow \text {a}_{1} \text {a}_{1} \rightarrow \ell \ell \text{ b } \text{ b})$ at 95% $\text {CL}$, with $\ell $ being a muon or a $\uptau $ lepton. For different types of 2HDM+S, upper bounds on the branching fraction ${\mathcal {B}}(\text {H} \rightarrow \text {a}_{1} \text {a}_{1} )$ are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, ${\mathcal {B}}(\text {H} \rightarrow \text {a}_{1} \text {a}_{1} )$ values above 0.23 are excluded at 95% $\text {CL}$ for $m_{\text {a}_{1}}$ values between 15 and 60$\,\text {Ge}\hspace{-.08em}\text {V}$.
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Benecke, A., Bruno, G., Caputo, C., Delaere, C., Donertas, I. S., Giammanco, A., Jaffel, K., Jain, S., Jain, S., Lemaitre, V., Lidrych, J., Mastrapasqua, P., Mondal, K., Tran, T. T., Wertz, S., CMS, Bethani, A., & et al. (2024). Search for exotic decays of the Higgs boson to a pair of pseudoscalars in the $\upmu \upmu \text{ b } \text{ b } $ and $\uptau \uptau \text{ b } \text{ b } $ final states. European Physical Journal C, 84. https://doi.org/10.1140/epjc/s10052-024-12727-4 (Original work published 2024)