Speaker
Description
We investigate the potential reach of a search for a long-lived dark vector boson, a dark $Z$ or $Z_D$, through exotic decays of the standard model (SM) Higgs boson $h$ into either $Z_DZ_D$ or $ZZ_D$. In addition, we study a decay of $h$ into two dark Higgs bosons $h_Dh_D$. We consider the production of the SM Higgs boson at the large hadron collider (LHC) via gluon-gluon fusion and use production cross sections for Run 3 of the LHC (i.e., 14 TeV) calculated to a combination of next-to-next-to-next-to-leading order with QCD corrections (N$^{3}$LO QCD) and next-to-leading order with electroweak corrections (NLO EW) from the literature. The $Z_D$ production through the Higgs portal is completed via one of two mechanisms, kinetic mixing of $Z_D$ with the SM $Z$ boson and the mixing of $h_D$ with $h$. The branching fractions are calculated to NLO and scanned over the relevant mixing parameters and particle masses in Monte Carlo (MC) simulation using the {\textsc{MadGraph5}}_aMC@NLO v2.7.0 framework. We focus on a final state of multiple dimuon pairs, displaced up to \mbox{7500 mm}, where the muons can be reconstructed without vertex constraint using data from the ATLAS and CMS detectors to be collected in Run~3 of the LHC. Integrated luminosities of 300 and 3000 fb$^{-1}$ for Run 3 and High Luminosity (HL), respectively, of the LHC are used for estimating the expected search sensitivity of the LHC to each decay mode. Finally, we investigate the decay lengths of $Z_D$ and $h_D$ in the detectors as well as kinematics of the displaced dimuons in the final state.
