Related papers: $Z$ Boson Decay into Light and Darkness
Spontaneous violation of R parity can induce rare single photon decays of the $Z^0$ involving the emission of (nearly) massless pseudoscalar Goldstone bosons, majorons, as well as massive CP even or CP odd spin zero bosons that arise in the…
We study models that produce a Higgs boson plus photon ($h^0 \gamma$) resonance at the LHC. When the resonance is a $Z'$ boson, decays to $h^0 \gamma$ occur at one loop. If the $Z'$ boson couples at tree-level to quarks, then the $h^0…
We have performed a complete one-loop calculation of $\gamma \gamma \rightarrow ZZ$ in the Standard Model, including both gauge bosons and fermions in the loop. We confirm the large irreducible continuum background from the $W$-boson loop…
We demonstrate that rare decays of the Standard Model $Z$ boson can be used to discover and characterize the nature of new hidden-sector particles. We propose new searches for these particles in soft, high-multiplicity leptonic final states…
In order to investigate various decay channels of the Higgs boson $h$ or the hypothetical dilaton, we consider a neutral particle $X$ with zero spin and arbitrary $CP$ parity. This particle can decay into two off-mass-shell $Z$ bosons…
We examine the decay of $Z_1$ in electrons with recent data from LEP. The partial width $\Gamma(Z_1\to e^-e^+)$ is studied in the framework of a left-right symmetric model with standard electroweak corrections. Processes measured near the…
If the standard electroweak gauge model is extended to include two or more Higgs doublets, there may be a neutral Higgs boson $h$ which is light (with a mass of say 10 GeV) but the $hZZ$ coupling is suppressed so that it has so far escaped…
Results are presented from a search for a narrow, spin-2 resonance decaying into a pair of Z bosons, with one Z-boson decaying into leptons (e+e- or mu+mu-) and the other into jets. An example of such a resonance is the Kaluza--Klein…
We compute the decay rates for the processes $Z\to V+\gamma$, where $Z$ is the $Z$ boson, $\gamma$ is the photon, and $V$ is one of the vector quarkonia $J/\psi$ or $\Upsilon(nS)$, with $n=1$, $2$, or $3$. Our computations include…
A multi-Higgs model with an extra neutral gauge boson ($Z'$) is introduced. One scalar Higgs boson ($H_2$) in this model decays dominantly into a photon pair. The $Z'$ decay to $\mu^+\mu^-$ gets a much larger branching ratio than the $Z$…
We improve the theoretical predictions for rare $Z$-boson decays, $Z\to V\ell^+\ell^-$ ($\ell=e$ or $\mu$), where $V$ denotes a heavy vector quarkonium including $J/\Psi$, $\Psi (2S)$, and $\Upsilon (nS)$ with $n=1,2,3$. These processes are…
The simplest little Higgs model predicts a light pseudoscalar boson $\eta$ and opens up some new decay modes for $Z$-boson, such as $Z \to \bar{f} f \eta$, $Z\to \eta\eta\eta$, $Z\to \eta\gamma$ and $Z\to \eta gg$. We examine these decay…
The $Z\to \gamma \gamma$ and $Z\to gg$ decays are studied in the context of the renormalizable version of the Standard Model Extension. The $CPT$-odd $\bar{\psi}\gamma_5 \gamma^\mu b_\mu\psi$ bilinear interaction, which involves the…
Motivated by dark-photon $\bar{\gamma}$ scenarios extensively considered in the literature, we explore experimentally allowed models where the Higgs boson coupling to photon and dark photon $H\gamma\bar{\gamma}$ can be enhanced.…
In this article, we study the rare decay process in which a Higgs boson decays into a $Z$ boson and a photon. In the first part of the paper, we analyze the Standard Model (SM) contributions to the corresponding decay width, including the…
The precision data on Z boson decays from LEP-I and SLC colliders are compared with the predictions based on the Minimal Standard Theory. The Born approximation of the theory is based on three most accurately known observables: G_mu -- the…
We computed the kinematics of Z-boson decay into a heavy-light neutrino pair when the Z-boson is produced at rest in electron-positron collisions, including the subsequent decay of the heavy neutrino into a visible final state containing a…
We introduce an $SU(2)_X^{}$ dark sector without any fermions and then realize a non-abelian kinetic mixing between the dark $SU(2)_X^{}$ gauge fields and the standard model $SU(2)_L^{}\times U(1)_Y^{}$ gauge fields. While one of the dark…
In extensions of the standard model, light scalar particles are often possible because of symmetry considerations. We study the decay of the Z boson into such particles. In particular, we consider for illustration the scalar sector of a…
The first observation of the Z boson decaying to four leptons in proton-proton collisions is presented. The analyzed data set corresponds to an integrated luminosity of 5.02 inverse femtobarns at sqrt(s) = 7 TeV collected by the CMS…