Related papers: $Z$ Boson Decay into Light and Darkness
We consider the phenomenology of the decay of a Z boson into a photon and a Kaluza-Klein excitation of the graviton in the ADD model. Using LEP data, we obtain an upper bound on the branching ratio corresponding to this process of ~10^-11.…
A model of a light $Z'$ boson based on gauged $L_\mu - L_\tau$ $U(1)$ symmetry is constructed. The $Z'$ boson mass is constrained to be in the range of 0.8 to 1 GeV from Z and $Z'$ mass relation, g-2 of muon, and tau decays. The two body…
Yang's theorem states that an initial J=1 state cannot decay into two photons. Because of this result some reactions relating to elementary particles or atomic transitions can be ruled out. The theorem is not valid in the presence of…
We first confirm that Nishijima's method of the $\pi^0 \rightarrow \gamma +\gamma $ calculation can precisely reproduce the observed life time of $\pi^0$ decay. Then, we calculate, for the first time, the T-matrix of the $Z^0 \rightarrow…
If there is an additional U(1) symmetry under which Standard Model particles are singlets, then there can be mixing between the additional gauge boson and the hypercharge gauge boson. This can lead to a very light, but weakly coupled "dark"…
We study the decay process of the Z boson to a photon and a graviton. The most general form of the on-shell amplitude, subject to the constraints due to the conservation of the electromagnetic and the energy-momentum tensor, is determined.…
We study the $ZH$ associated production followed by the Higgs $H\to \gamma \bar{\gamma}$ decay into a photon plus an invisible and massless dark photon, at future high-energy $e^+e^-$ facilities. Large $H\to \gamma \bar{\gamma}$ decay rates…
A search for the decay of the Higgs boson to a $Z$ boson and a light, pseudoscalar particle, $a$, decaying respectively to two leptons and to two photons is reported. The search uses the full LHC Run 2 proton-proton collision data at…
In the standard model production of on-shell Z boson at a photon collider (or Z decays into $\gamma\gamma$) is strictly forbidden by angular momentum conservation and Bose statistics (the Yang's Theorem). In the standard model with…
We study the radiative decay of the $Z$ boson, $Z \to \mu^+\mu^-\gamma$, at the LHC, providing both Standard Model (SM) precision analysis and new physics projections. With detailed analysis of Run-2 and future HL-LHC performances, we…
A Higgs particle produced in association with a Z boson and decaying into two photons is searched for in the data collected by the L3 experiment at LEP. All possible decay modes of the Z boson are investigated. No signal is observed in…
We discuss some rare Z decay signatures associated with extensions of the Standard Model with spontaneous lepton number violation at the electroweak scale. We show that single-photon Z decays such as $Z \to \gamma H$ and $Z \to \gamma J J$…
The Z boson can decay to a pair of light gluinos through loop-mediated processes. Based on unitarity of the S-matrix, the imaginary part of the decay amplitude is computed in the presence of a light bottom squark. This imaginary part can…
In the large extra dimensional ADD scenario, Z bosons undergo a one-loop decay into a photon and Kaluza-Klein towers of gravitons/gravi-scalars. We calculate such a decay width, extending previous arguments about the general form of the…
We propose novel collider searches which can significantly improve the LHC reach to new gauge bosons $Z'$ with mixed anomalies with the electroweak (EW) gauge group. Such a $Z'$ necessarily acquires a Chern-Simons coupling to the EW gauge…
The double-radiative process e+e- -> Z gamma gamma -> q q~ gamma gamma, where the two hard photons escape detection at low polar angles into opposite directions, is studied in 0.62/fb of data collected with the L3 detector at LEP at…
Results on the search for particles decaying into Zgamma to llgamma are presented. Using roughly 1 fb-1 of data, dilepton-plus-photon invariant mass distributions have been examined for an excess over the theoretical predictions. Having…
We search for the rare decay of the $D^{0}$ meson to two photons, $D^0 \rightarrow \gamma \gamma$, and present a measurement of the branching fraction for a $D^0$ meson decaying to two neutral pions, ${B}(D^0 \rightarrow \pi^0 \pi^0)$. The…
Landau Yang theorem is well known for the past several decades. It prohibits the decay of a massive spin 1 particle to two photons. This emerges simply from the representation theory of the Poincare group and Bose Statistics. It does not…
A complete study of the one-loop induced decay Z -> neutrino antineutrino photon is presented within the framework of the Standard Model. The advantages of using a nonlinear gauge are stressed. We have found that the main contributions come…