Related papers: Possible Resonances in $\mu^+e^- \to \mu^- e^+$ Co…
With $\mu\to e\gamma$ decay forbidden by multiplicative lepton number conservation, we study muonium--antimuonium transitions induced by neutral scalar bosons. Pseudoscalars do not induce conversion for triplet muonium, while for singlet…
Theoretical backgound for bileptonic gauge bosons is reviewed, both the SU(15) GUT model and the 3-3-1 model. Mass limits on bileptons are discussed coming from $e^+e^-$ scattering, polarized muon decay and muonium-antimuonium conversion.…
We study the sensitivity to doubly charged Higgs bosons, $\Delta^{--}$, in the process $e^-\gamma\to e^+ \mu^-\mu^-$ for centre of mass energies appropriate to future high energy $e^+e^-$ collider proposals. For $M_\Delta <…
If extra gauge bosons are observed at the LHC or at a linear e+e- collider, the reaction e+e- --> nu nubar gamma can give information on the couplings (W' nu l) and (Z' nu nubar). The total cross section and polarization asymmetries are the…
The observed interactions between particles are not fully explained in the successful theoretical description of the standard model to date. Due to the close confinement of the bound state muonium ($M = \mu^+ e^-$) can be used as an ideal…
Muon colliders offer special opportunities to discover and study new physics. With the high intensity source of muons at the front end, orders of magnitude improvements would be realized in searches for rare muon processes, in deep…
It is well known that at linear e^+e^-(e^-e^-) colliders using laser backscattering one can obtain colliding gamma-gamma, gamma-electron beams with energy and luminosity comparable to those in e^+e^- collisions. In this paper, it is…
This working group report focuses on the physics potential of $\mu^+\mu^-$ colliders beyond what can be accomplished at linear $e^+e^-$ colliders and the LHC. Particularly interesting possibilities include (i)~$s$-channel resonance…
A positive muon ($\mu^+$) and an electron ($e^-$) form the the hydrogen-like muonium atom ($M$=$\mu^+ e^-$). Since it consists of two leptonic particles which are according to present knowledge point-like, accurate calculations of its level…
We study the discovery potential for doubly charged Higgs bosons, Delta^--, in the process e- gamma -> e+ mu- mu- for centre of mass energies appropriate to high energy e^+e^- linear colliders and the CLIC proposal. For M_Delta < sqrt{s}_{e…
The ability of high energy $e^+e^-$ colliders to indirectly probe the existence of heavy new charged gauge bosons via their exchange in the reaction $e^+e^-\to \nu\bar\nu\gamma$ is investigated. It is shown that examination of the resulting…
We report on studies of the sensitivity to extra gauge bosons of the reactions e^+ e^- -> nu nubar gamma and e gamma -> nu q + X to extract discovery limits for W' 's. The discovery potential for a W' is, for some models, comparable to that…
We discuss the possibility of observing doubly charged Higgs bosons in $\gamma \gamma$ collisions. We find that one can increase the range of observability close to the kinematic limit by a judicious choice of the polarisations of the…
Any theory that have a global spontaneously broken symmetry will imply the existence of very light neutral bosons or massless bosons (sometimes called Majorons). For most of these models we have neutrino-Majoron couplings, that appear as…
We discuss a low energy $e^+e^-$ collider for production of the not yet observed ($\mu^+\mu^-$) bound system (dimuonium). Collider with large crossing angle for $e^+e^-$ beams intersection produces dimuonium with non-zero momentum,…
The phenomenological constraints on extra neutral gauge bosons at present and at future colliders are reviewed. Special attention is paid to the influence of radiative corrections, systematic errors, and kinematic cuts on the Z'…
We study and compare the discovery potential for heavy neutral gauge bosons (Z') at the various $e^+e^-$ and $\mu^+\mu^-$ colliders that have been proposed. Typical search limits for the e^+e^- colliders are 2-10 times sqrt{s} with the…
Possible influence of the weak interaction on the $\mu^+ + \mu^- \to \mu^+ + \mu^- $ scattering and the $\mu^+ + \mu^- \to e^+ + e^- $ reaction, both through the neutral lepton currents and the charged ones (in the second order on weak…
Theoretical backgound for bileptonic gauge bosons is reviewed, both the SU(15) GUT model and the 3-3-1 model. Then the mass limits for bileptons are discussed coming from $e^+e^-$ scattering, polarized muon decay and muonium-antimuonium…
We perform a complete simulation of the process $ e^+ e^- \to \tau^+ \tau^- \nu \bar{\nu}$, where $\nu$ can be an electron, muon or tau neutrino, in the context of a general Higgs coupling to $\tau$ leptons. We analyse various kinematical…