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We study the effects of non-commutative QED (NCQED) in fermion pair production, gamma + gamma -> f + bar{f} and Compton scattering, e + gamma -> e + gamma. Non-commutative geometries appear naturally in the context of string/M-theory and…
The exotic neutral gauge boson is a powerful candidate for the new physics beyond the standard model. As a promising model, the left-right symmetric model has been proposed to explain the neutrino mass, dark matter, and matter-antimatter…
High statistics Standard Model processes like fermion- and photon-pair production in e+e- collisions are studied at centre-of-mass energies up to 209 GeV. No significant deviation from the Standard Model is observed, leading to strong…
Fermion compositeness, and other types of new physics that can be described by the exchange of very massive particles, can manifest themselves as the result of an effective four-fermion contact interaction. In the case of the processes…
If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in…
We analyze the production in $e^+e^-$ collisions of new heavy fermions stemming from extensions of the Standard Model. We write down the most general expression for the production of two heavy fermions and their subsequent decays, allowing…
In the present letter we suggest a new model of preons-dyons making composite quark-leptons and bosons, described by the supersymmetric string-inspired flipped E_6\times \tilde E_6 gauge group of symmetry. This investigation predicts the…
We study theoretical and experimental constraints on electroweak theories including a new color-singlet and electrically-neutral gauge boson. We first note that the electric charges of the observed fermions imply that any such Z' boson may…
Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between gravitons and Standard Model particles is then predicted. Effects…
A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 237.4 pb-1 at e+e- centre-of-mass energies of 183 GeV and 189 GeV. The observed numbers of events - 78 at 183 GeV…
In this study, we explore the non-standard $\nu\bar{\nu}\gamma \gamma$ couplings parametrized by dimension-seven operators via $e^{+}e^{-} \to \nu\bar{\nu}\gamma$ process at the FCC-ee/CEPC and $\mu^{+}\mu^{-}\to\nu\bar{\nu}\gamma$ process…
By considering left-right (L-R) asymmetries we study the capabilities of lepton colliders in searching for new exotic vector bosons. Specifically we study the effect of a doubly charged bilepton boson and an extra neutral vector boson…
We study the process $e^- + e^+ \to e^+ + e^+ + e^- + e^-$ for ILC and CLIC energy regimes, in the minimal 3-3-1 model framework. The main contributions, for the production of two bileptons each one decaying into two same-sign leptons, come…
Cross-sections and angular distributions for hadronic and lepton pair final states in e+e- collisions at a centre-of-mass energy near 189 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the…
We merge two leading Beyond Standard Model scenarios, namely compositeness and left-right symmetry, and probe the resulting collider signatures in the leptonic case. The constraints on composite models for fermions leave open the…
We study the sensitivity of top pair production with six-fermion decay at the LHC to the presence and nature of an underlying Z' boson, accounting for full tree-level Standard Model ttbar interference, with all intermediate particles…
Production of events with hadronic and leptonic final states has been measured in e^+e^- collisions at centre-of-mass energies of 130-172 GeV, using the OPAL detector at LEP. Cross-sections and leptonic forward-backward asymmetries are…
$U(1)^\prime$ extensions of the standard model with generation-dependent couplings to quarks and leptons are investigated as an explanation of anomalies in rare $B$-decays, with an emphasis on stability and predictivity up to the Planck…
We propose a left-right symmetric framework with universal seesaw mechanism for the generation of masses of the Standard Model quarks and leptons. Heavy vector-like singlet quarks and leptons are required for generation of Standard…
The main possibilities of investigation of leptons and bosons production in interaction of polarized photons are considered. The usage of $\gamma\gamma\to f\bar{f}[+\gamma]$ reactions for the luminosity measurement on linear photon collider…