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We derive the low-energy electroweak effective lagrangian for the case of additional heavy, unmixed, sequential fermions. Present LEP1 data still allow for the presence of a new quark and/or lepton doublet with masses greater than $M_Z/2$,…
New physics is being explored with the Large Hadron Collider at CERN and with Intensity Frontier programs at Fermilab and KEK. The energy scale for new physics is known to be in the multi-TeV range, signaling the need for a future collider…
The discovery of Standard-Model like Higgs at 125 GeV may raise more questions than the answers it provides. In particular, the hierarchy problem remains unsolved, and the Standard Model Higgs quartic self-coupling becomes negative below…
Preliminary results of measurements of fermion-pair production at LEP2 are used to derive limits on new physics phenomena. Combinations of the cross sections and asymmetrie of the 4 LEP collaborations are interpreted in terms four-fermion…
In models with TeV-scale gravity it is expected that mini black holes will be produced in near-future accelerators. On the other hand, TeV-scale gravity is plagued with many problems like fast proton decay, unacceptably large…
The dynamics of {\it light} fermions propagating in a spatial direction at high temperatures can be described effectively by a two--dimensional Schr\"odinger equation with {\it heavy} effective mass $m_{\rm eff} = \pi T$. Starting from QED,…
We derive the low-energy electroweak effective lagrangian for the case of additional heavy, unmixed, sequential fermions. Present data still allow for the presence of a new quark and/or lepton doublet with masses greater than $M_Z/2$,…
We propose a new mechanism for explanation of the fermion hierarchy without introducing any family symmetries. Instead, we postulate that different generations live on different branes embedded in a relatively large extra dimension, where…
The problem of the origin of the mu parameter in the Minimal Supersymmetric Standard Model can be solved by introducing singlet supermultiplets with non-renormalizable couplings to the ordinary Higgs supermultiplets. The Peccei-Quinn…
We define the three-body scattering hypervolume $D_F$ for identical spin-polarized fermions in two dimensions, by considering the wave function of three such fermions colliding at zero energy and zero orbital angular momentum. We derive the…
Atomic spectroscopy can be used to search for new bosons that carry exotic forces between elementary fermions. A comparison of a recent precise measurement [Bullis \textit{et al.}, Phys. Rev. Lett. \textbf{130}, 203001 (2023)] of the…
We analyze the potentiality of the new generation of $e^+e^-$ linear colliders to search for large extra dimensions via the production of fermion pairs in association with Kaluza-Klein gravitons (G), i.e. $e^+e^- \leftarrow f\bar{f}G$. This…
Top quark pair production close to threshold at a next linear collider is discussed, with special focus on the influence of rescattering corrections. Numerical results are shown for the differential cross-section, i.e. the momentum…
A search for fermionic top quark partners T of charge 2/3 is presented. The search is carried out in proton-proton collisions corresponding to an integrated luminosity of 19.7 inverse femtobarns collected at a center-of-mass energy of…
Folded supersymmetry is a natural theory of the electroweak scale in which the scalar top partner responsible for canceling the ultraviolet sensitivity of the Higgs mass at one loop carries no color. As a result, bounds on naturalness on…
We study two flavors of massless staggered fermions interacting via an on-site four-fermion inter- action and argue that the model contains an exotic quantum critical point separating the perturba- tive massless phase from a massive fermion…
At future e+- e- linear colliders, the event rates and clean signals of scalar fermion production - in particular for the scalar leptons - allow very precise measurements of their masses and couplings and the determination of their quantum…
We investigate the effect of one loop quantum corrections on the elastic scattering of dark matter off the nucleon in a fermionic dark matter model. The model introduces two new singlet fermions and a singlet scalar. The fermions…
The Standard Model of particle physics has been remarkably successful in describing present experimental results. However, it is assumed to be only a low-energy effective theory which will break down at higher energy scales, theoretically…
Discovery of the Higgs boson and lack of discovery of superpartners in the first run at LHC are both predictions of split supersymmetry with thermal dark matter. We discuss what it would take to find gluinos at hadron supercolliders,…