Search

The exotic neutral gauge boson is a powerful candidate for the new physics beyond the standard model. As a promising model, the left-right symmetric model has been proposed to explain the neutrino mass, dark matter, and matter-antimatter asymmetry, etc., in which exotic gauge bosons $Z^\prime, W^{\prime \pm}$ have been put forward as well as other new right-handed particles. We investigate the $\mu^+ \mu^- \to q\bar{q} $ and $ \mu^+ \mu^- \to l^+ l^- $ processes involving the $Z^\prime$ boson as an intermediate particle. The coupling strength, decay width and mass are the key parameters on the production and decay processes of the $Z^\prime$ boson. The results indicate that the angular distributions of final particles are sensitive to the couplings of $Z^\prime$ to the other fermions. Asymmetries defined from the angular distributions are ideal quantities to demonstrate the discrepancy between the standard model process and the processes with $Z^\prime$ participated and they are also appropriate observables to discriminate the couplings of $Z^\prime$ to other particles. Compared with the current results at the Large Hadron Collider (LHC), the future muon collider has a great potential to explore the new parameter space with $Z^\prime$ boson., Comment: 22 pages, 10 figures

Heavy neutral gauge boson $Z^\prime$ is proposed in many new physics models. It has rich phenomena at the future muon collider. We study the properties of $Z^\prime$ boson with the process of $\mu^+ \mu^- \rightarrow q \bar{q}$, $\mu^+ \mu^- \rightarrow l^+ l^-$, $\mu^+ \mu^- \rightarrow Z H$ and $\mu^+ \mu^- \rightarrow W^+ W^-$. The discrepancy of $Z^\prime$ coupling to different types of particles can be shown in the cross section distributions around the resonance peak of various decay modes. Angular distributions of the final quark or lepton in $\mu^+ \mu^- \rightarrow q \bar{q}/l^+ l^- $ process are sensitive to the parameters such as mass of $Z^\prime$ and the $Z-Z^\prime$ mixing angle. The interaction of new gauge boson coupling to the standard model gauge particles and Higgs boson are also studied through $\mu^+ \mu^- \rightarrow Z H \rightarrow l^+l^- b \bar{b}$ and $\mu^+ \mu^- \rightarrow W^+W^- \rightarrow l^+l^- \nu_l \bar{\nu}_l$. The cross section and the final particles' angular distributions with the contribution of $Z^\prime$ boson differ from those processes with only standard model particles. A forward-backward asymmetry defined by the angular distribution is provided to show the potential of searching for new physics at the muon collider. Especially, the beam polarization with certain value can effectively enlarge the forward-backward asymmetry., Comment: 41 pages, 25 figures

The neutrinophilic two Higgs doublet model is one of the simplest models to explain the origin of tiny Dirac neutrino masses. This model introduces a new Higgs doublet with eV scale VEV to naturally generate the tiny neutrino masses. Depending on the same Yukawa coupling, the neutrino oscillation patterns can be probed with the dilepton signature from the decay of charged scalar $H^\pm$. For example, the normal hierarchy predicts BR$(H^+\to e^+\nu)\ll$ BR$(H^+\to \mu^+\nu)\approx$ BR$(H^+\to \tau^+\nu)\simeq0.5$ when the lightest neutrino mass is below 0.01 eV, while the inverted hierarchy predicts BR$(H^+\to e^+\nu)/2\simeq$ BR$(H^+\to \mu^+\nu)\simeq$ BR$(H^+\to \tau^+\nu)\simeq0.25$. By precise measurement of BR$(H^+\to \ell^+\nu)$, we are hopefully to probe the lightest neutrino mass and the atmospheric mixing angle $\theta_{23}$. Through the detailed simulation of the dilepton signature and corresponding backgrounds, we find that the 3 TeV CLIC could discover $M_{H^+}\lesssim1220$ GeV for NH and $M_{H^+}\lesssim1280$ GeV for IH. Meanwhile, the future 100 TeV FCC-hh collider could probe $M_{H^+}\lesssim1810$ GeV for NH and $M_{H^+}\lesssim2060$ GeV for IH., Comment: 18 pages, 9 figures

$Z^\prime$ boson as a new gauge boson has been proposed in many new physics models. The interactions of $Z^\prime$ coupling to fermions are detailed studied at the large hadron collider. A $Z^\prime$ with the mass of a few TeV has been excluded in some special models. The future lepton colliders will focus on the studies of Higgs physics which provide the advantage to investigate the interactions of Higgs boson with the new gauge bosons. We investigate the $Z^\prime ZH$ interaction via the process of $e^+e^- \to Z^\prime/Z \to ZH \to l^+l^- b \bar{b}$. The angular distribution of the final leptons decaying from the $Z$-boson is related to the mixing of $Z^\prime$-$Z$ and the mass of $Z^\prime$. The forward-backward asymmetry has been proposed as an observable to investigate the $Z^\prime$-$Z$ mixing. The angular distributions change significantly with some special beam polarization comparing to the unpolarized condition., Comment: 15 pages, 7 figures