Search for Higgs boson decays into Z and J/$\psi$ and for Higgs and Z boson decays into J/$\psi$ or $\Upsilon$ pairs in pp collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This study searches for rare Higgs and Z boson decays into quarkonium states using CMS data, setting upper limits on their branching fractions due to no observed evidence, thus testing the standard model's predictions.

Contribution

First search for Higgs and Z boson decays into quarkonium pairs in pp collisions at 13 TeV with CMS, establishing upper limits on branching fractions.

Findings

No evidence for the targeted decays was observed.

Upper limits on branching fractions are set at 1.9×10⁻³ for H→J/ψ.

Upper limits on branching fractions are set at 6.6×10⁻³ for H→Zψ(2S).

Abstract

Decays of the Higgs boson into a Z boson and a J/$\psi$ or $\psi$(2S) meson are searched for in four-lepton final states with the CMS detector at the LHC. A data set of proton-proton collisions corresponding to an integrated luminosity of 138 fb$^{-1}$ is used. Using the same data set, decays of the Higgs and Z boson into quarkonium pairs are also searched for. An observation of such decays with this sample would indicate the presence of physics beyond the standard model. No evidence for these decays has been observed and upper limits at the 95% confidence level are placed on the corresponding branching fractions ($\mathcal{B}$). Assuming longitudinal polarization of the Higgs boson decay products, 95% confidence level observed upper limits for $\mathcal{B}$(H $\to$ J/$\psi$) and $\mathcal{B}$(H $\to$ Z$\psi$(2S)) are 1.9$\times$10$^{-3}$ and 6.6$\times$10$^{-3}$, respectively.