Related papers: Z decays into light gluinos: a calculation based o…
Single-minus tree-level $n$-gluon scattering amplitudes are reconsidered. Often presumed to vanish, they are shown here to be nonvanishing for certain "half-collinear" configurations existing in Klein space or for complexified momenta. We…
The scattering amplitude for the longitudinal weak bosons is investigated in the SU(3) gauge-Higgs unification as a function of the scattering energy, the Wilson line phase \theta_H and the warp factor. The \theta_H-dependence of the…
Models of particle physics based on manifolds of $G_2$ holonomy are in most respects much more complicated than other string-derived models, but as we show here they do have one simplification: threshold corrections to grand unification are…
In this paper, we propose a method to construct the decay amplitudes in the orbital ($L$) and spin ($S$) coupling scheme for particles with arbitrary spins. For the $1\to 2$ decay with only massive particles involved, the angular dependence…
We present the two-loop amplitudes for a self-dual Higgs boson with up to four positive helicity gluons in the heavy top-quark limit. Because the tree amplitudes in the all-plus sector vanish, we can construct simple representations of the…
We studied the decays of Heavy baryon into a pseudoscalar meson and a dark baryon in the recently developed $B$-Mesogenesis scenario, where the two types of effective Lagrangians proposed by the scenario are both considered. The decay…
An investigation of the processes Z to gluon-gluon and Z to photon-photon in a background magnetic field is presented. For homogeneous fields corrections to the charged fermion propagator can be calculated in leading orders of the magnetic…
We give a status report on the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment from the Dyson-Schwinger approach. We discuss novel, model-independent properties of the light-by-light amplitude: we…
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 CMS Collaboration at the LHC recently reported an accumulation of data around 28 GeV in the invariant-mass distribution of muon pairs in association with a b quark jet and at least a second jet. This is analysed here in the light of the…
This paper describes the search for a high-mass narrow-width scalar particle decaying into a Z boson and a photon. The analysis is performed using proton-proton collision data recorded with the CMS detector at the LHC at center-of-mass…
We search for the decay Y(1S) -> gamma A0, A0 -> gg or ss-bar, where A0 is the pseudoscalar light Higgs boson predicted by the next-to-minimal supersymmetric standard model. We use a sample of (17.6 +- 0.3)x 10^6 Y(1S) mesons produced in…
The phenomenological model of an extra U(1) neutral gauge Z' boson coupled to heavy quarks is presented. In particular, we discuss the probability for a light $Z_{2}$ mass eigenstate decay into a bound state composed of heavy quarks via…
Any loop QCD amplitude at full colour is constructed from kinematic and gauge-group building blocks. In a unitarity-based on-shell framework, both objects can be reconstructed from their respective counterparts in tree-level amplitudes.…
We discuss recently reported experimental hints for a bottom squark with mass around 3.5 GeV decaying as sbottom -> charm + lepton + anti-sneutrino. We correlate the sbottom lifetime with the decay rates for bottom -> sbottom + neutrino +…
We study rare four-body decays of the Z-boson involving at least one neutrino and one charged lepton. Large destructive interferences make these decays very sensitive to the Z couplings to neutrinos. As the identified charged leptons can…
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…
This note reports on an independent implementation of calculating one-loop amplitudes semi-numerically using generalized unitarity techniques. The algorithm implemented in form of a C++ code closely follows the method by Ellis, Giele,…
Phenomenologically relevant electroweak precision pseudo-observables related to Z-boson physics are discussed in the context of the strong experimental demands of future $e^+e^-$ colliders. The recent completion of two-loop Z-boson results…
We derive the kinematical constraints which characterize the decay of any massless particle in flat spacetime. We show that in perturbation theory the decay probabilities of photons and Yang-Mills bosons vanish to all orders; the decay…