Search for Higgs boson decays into two neutral scalars with unequal masses in final states with b quarks and tau leptons in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for Higgs boson (H) decays into a pair of neutral scalars ${\phi }_1$ and ${\phi }_2$, with ${\phi }_2$ heavier than ${\phi }_1$, is performed in final states with b quarks and tau leptons. Depending on the masses of the neutral scalars, ${\phi }_2$ can undergo a cascade decay into ${\phi }_1{\phi }_1$. For both the cascade and non-cascade scenarios, one ${\phi }_1$ is required to decay to a pair of tau leptons. Proton-proton collision data corresponding to an integrated luminosity of 138 fb${}^{-1}$ collected with the CMS detector at the LHC at $\sqrt{s}$ = 13 TeV are analyzed. No statistically significant excess over the standard model expectation is observed. Upper limits are set on the products $\sigma \mathcal{B}$(H $\to$ ${\phi }_1{\phi }_2$ $\to$ 3${\phi }_1$ $\to$ 2$\tau$4b) and $\sigma \mathcal{B}$(H $\to$ ${\phi }_1{\phi }_2$) $\mathcal{B}$(${\phi }_1$ $\to$ 2$\tau$) $\mathcal{B}$(${\phi }_2$ $\to$ 2b) where $\sigma$ is the Higgs boson production cross section. The observed upper limits range between 0.9 and 36.8 pb at 95% confidence level, depending on the mass hypothesis and decay scenario.