Related papers: Lower Bounds on Bilepton Processes at e-e- and mu-…
We chart new-physics models that produce exotic, high-multiplicity muon decays featuring prompt or displaced $e^+e^-$ pairs and/or photons, with or without missing energy, such as $\mu \to 5e$, $\mu \to 7e$, etc. Starting from an…
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…
Complementing the preceding study of charged scalar leptons, the sector of the neutral scalar leptons, sneutrinos, is investigated in a high-precision analysis for future e+e- linear colliders. The theoretical predictions for the…
Events with a final state consisting of two or more photons and large missing transverse energy have been observed in e+e- collisions at centre-of-mass energies in the range 192 - 209 GeV using the OPAL detector at LEP. Cross-section…
Construction of future Muon Collider tangential to the Large Hadron Collider will give opportunity to realize mu-p collisions at multi-TeV center of mass energies. Using nominal parameters of high luminosity and high energy upgrades of the…
Rare flavour-changing neutral-current transitions $b \to s \mu^+ \mu^-$ probe higher energy scales than what is directly accessible at the LHC. Therefore, the presence of new physics in such transitions, as suggested by the present-day LHCb…
We review the pair-production and decay of selectrons in $e^-e^-$ collisions and show how the standard model backgrounds can be virtually eliminated with polarized beams. The exceedingly simple analysis involved and the large sample of…
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 <…
We demonstrate that mu/e slepton mixing is significantly more restricted than previously thought within the already remarkably flavor-safe R-symmetric supersymmetric standard model. We calculate bounds from mu to e gamma, mu to 3e and, most…
The inclusion of an additional $U(1)$ gauge symmetry is a common feature in many extensions of the Standard Model, revealing the intricate connections between particle physics and cosmology. The $L_{\mu} - L_{\tau}$ model stands as a…
We analyze the effects of a doubly charged vector bilepton as well as exotic quarks with charge 5/3 e and -4/3 e on light by light scattering. We consider mass values in the range 0.3--1 TeV, which would be reached at the planned future…
The possibility of single and pair excited neutrino production in high energy e+e-, gamma-e and gamma-gamma collisions on linear colliders is studied. The integrated cross sections of these subproceses are calculated. Special attention is…
Events containing a pair of charged leptons and significant missing transverse momentum are selected from a data sample corresponding to a total integrated luminosity of 20.6 pb^-1 at centre-of-mass energies of 161 GeV and 172 GeV. The…
The cross sections for the multiple production of the lightest neutral Higgs boson at high--energy $e^+ e^-$ colliders are presented in the framework of the Minimal Supersymmetric extension of the Standard Model (MSSM). We consider…
We study dilepton, proton-antiproton and diphoton production in ultraperipheral lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 and 5.5 TeV. The nuclear calculations are based on equivalent photon approximation in the impact…
We calculate the cross section for e+e- --> H+ e- nubar in the two-Higgs-doublet model from one-loop diagrams involving top and bottom quarks. This process offers the possibility of producing the charged Higgs boson at the e+e- collider…
In theories with gauge mediated supersymmetry breaking, the scalar tau, (${\tilde \tau_1}$) is the lightest superpartner for a large range of the parameter space. At the large electron positron collider (LEP 2) this scenario can give rise…
Model independent constraints on the mass of an extra neutral gauge boson and its couplings to charged leptons are given for the $e^-e^-$ option of a future linear collider. Analytic exclusion limits are derived in the Born approximation.…
The discovery potential for detecting new heavy Majorana and Dirac neutrinos at some recently proposed high energy $e^+e^-$ colliders is discussed. These new particles are suggested by grand unified theories and superstring-inspired models.…
We show that new physics explanations of the muon $g-2$ anomaly by the contributions of new leptons mediated by the standard model Higgs boson necessarily lead to large rates for $\mu^+ \mu^- \to hh$ and $\mu^+ \mu^- \to hhh$ irrespectively…