Exotic decays of the 125 GeV Higgs boson at future e ⁺ e ⁻ colliders

Abstract

The discovery of unexpected properties of the Higgs boson would offer an intriguing opportunity to shed light on some of the most profound puzzles in particle physics. Beyond Standard Model (BSM) decays of the Higgs boson could reveal new physics in a direct manner. Future electron-positron lepton colliders operating as Higgs factories, including CEPC, FCC-ee and ILC, with the advantages of a clean collider environment and large statistics, could greatly enhance sensitivity in searching for these BSM decays. In this work, we perform a general study of Higgs exotic decays at future e + e − lepton colliders, focusing on the Higgs decays with hadronic final states and/or missing energy, which are very challenging for the High-Luminosity program of the Large Hadron Collider (HL-LHC). We show that with simple selection cuts, O(10 −3 −10 −5 ) limits on the Higgs exotic decay branching fractions can be achieved using the leptonic decaying spectator Z boson in the associated production mode e + e − → ZH. We further discuss the interplay between detector performance and Higgs exotic decays, and other possibilities of exotic decays. Our work is a first step in a comprehensive study of Higgs exotic decays at future lepton colliders, which is a key area of Higgs physics that deserves further investigation.

Light hidden mesons through the Z portal

“…Refs. [30,31]) and also at future Higgs factories [32,33], the sensitivity of Z decays to hidden sectors has been much less explored.…”

Probing flavor nonuniversal theories through Higgs physics at the LHC and future colliders

“…The Higgs physics exotic decays [50] are also modified by these operators. The operator O Hu contributes directly to h → Zuū decay through two additional diagrams.…”

Measuring the ratio of HW W and HZZ couplings through W +W −H production

“…(3.7) as in refs. [31,32]. 4 The asymmetric cut on the invariant mass of bb is required to take into account the effects of photons from initial-state radiation (ISR) [34] or unmeasured neutrinos from semi-leptonic b-decays [35].…”