Related papers: Extra quark-lepton generations and precision measu…
We discuss a model in which the third generation fermions undergo a different $SU(2)$ weak interaction from the first two generation fermions. In general, a flavor changing neutral current interaction is expected. Constrained by the…
The most important hint of physics beyond the Standard Model (SM) from the 1995 precision electroweak data is that the most precisely measured quantities, the total, leptonic and hadronic decay widths of the $Z$ and the effective weak…
Explicit expressions are derived for the oblique parameters $S$ and $T$ in certain extensions of the standard model. In particular, we consider leptoquarks and bileptons, and find phenomenological constraints on their allowed masses.…
We discuss gauge coupling unification in models with additional 1 to 4 complete vector-like families, and derive simple rules for masses of vector-like fermions required for exact gauge coupling unification. These mass rules and the…
SU(2)xU(1) electroweak gauge model without Higgs sector is extended by a new vector field C interacting with leptons and quarks of both chiralities. This interaction is treated under a dynamical assumption in a self-consistent…
We consider the extension of the standard model with an arbitrary number of U(1) gauge fields coupled to baryon-minus-lepton number and/or hypercharge. Under the assumption that A^b_FB from the LEP1 experiment is an unlucky fluctuation, we…
Enhanced radiative corrections generated in SUSY extensions of the Standard Model make the fit of the precision data ($Z$-boson decay parameters and $W$-boson mass) worse. This negative effect is washed out for heavy enough squarks due to…
We propose a new strategy to probe heavy neutrinos with non-universal fermion couplings at the Large Hadron Collider (LHC) using a novel production mechanism and machine-learning algorithms. Focusing on proton--proton collisions at…
A search for physics beyond the standard model in the final state with two same-flavour leptons (electrons or muons) and two quarks produced in proton-proton collisions at sqrt(s) = 13 TeV is presented. The data were recorded by the CMS…
A search for unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed at center-of-mass energies $\sqrt{s}$ = 183 and 189 GeV with the L3 detector at LEP. No evidence for their existence is found.…
An observation of any lepton number violating process will undoubtedly point towards the existence of new physics and indirectly to the clear Majorana nature of the exchanged fermion. In this work, we explore the potential of a minimal…
Searches for direct electroweak production of charginos and neutralinos in signatures with two light leptons of the same charge and with three or more leptons including up to two hadronically decaying {\tau} leptons are presented . The full…
We study the possibility of the existence of extra fermion families and an extra Higgs doublet. We find that requiring the extra Higgs doublet to be inert leaves space for three extra families, allowing for mirror fermion families and a…
We summarise the analyses that search for fourth generation quarks at the Central Muon Solenoid (CMS) experiment. Such particles provide a natural extension to the Standard Model (SM) and are still consistent with precision electroweak…
How light can a fermion be if it has unit electric charge? We revisit the lore that LEP robustly excludes charged fermions lighter than about 100 GeV. We review LEP chargino searches, and find them to exclude charged fermions lighter than…
We extend the commonly used mSUGRA framework to allow complex soft terms. We show how these phases can induce large changes of the SUSY threshold corrections to the b quark mass and affect the neutralino relic density predictions of the…
The Standard Model (SM) with a light Higgs boson provides a very good description of the precision electroweak observable data coming from the LEP, SLD and Tevatron experiments. Most of the observables, with the notable exception of the…
We study the impact of additional beyond-the-Standard Model (BSM) fermions, charged under the Standard Model (SM) $SU(2)_L \otimes U(1)_Y$ gauge group, on the electroweak phase transition (EWPT) in a 2-Higgs-Doublet-Model (2HDM) of type II.…
As experimental constraints on the parameter space of the MSSM and close variations thereof become stronger, the motivation to explore supersymmetric models that challenge some of the standard assumptions of the MSSM also become stronger.…
The minimal SU(5) theory augmented by the fermionic adjoint representation restores the coupling constant unification and gives realistic neutrino masses and mixing through the hybrid Type I and Type III seesaw. The crucial prediction of…