相关论文: Possible Chandra-Mechanism for Generation Bound

We investigate the possibility of a fourth sequential generation in the lepton sector. Assuming neutrinos to be Majorana particles and starting from a recent - albeit weak - evidence for a non-zero admixture of a fourth generation neutrino…

A definition of `dynamical generation', a hotly debated topic at present, is proposed and its implications are discussed. This definition, in turn, leads to a method allowing to distinguish in principle tetraquark and molecular states. The…

A new mechanism is proposed to explain the appearance of the three known fermion generations in a natural way. The underlying idea is based on the discreteness of the spectrum of solutions of the gap equation appearing in models of…

We consider a simple model of a structural glass, represented by a lattice gas with kinetic constraints in contact with a particle reservoir. Quench below the glass transition is represented by the jump of the chemical potential above a…

We perform an exploratory study of the allowed parameter range for the CKM-like mixing of hypothetical quarks of a fourth generation. As experimental constraints we use the tree-level determinations of the 3 $\times$ 3 CKM elements and FCNC…

We study the upper bound on the scale of fermion mass generation in a two-Higgs-doublet model. If the model is weakly-coupled, the scale of fermion mass generation is much less than the Appelquist-Chanowitz unitarity bound. However, if we…

The masses of quarks and leptons suggest a strong hierarchical structure. We argue that their patterns can be reproduced through the introduction of a new Abelian symmetry. The data suggest that this symmetry is anomalous. We suggest that…

A new mechanism is presented for the generation of quark and lepton masses, based on a heavy fourth family and a new sector of massless fermions. The massless fermions have only discrete chiral symmetries and they are confined by the…

We suggest a mechanism whereby the three generations of quarks and leptons correspond to surface modes in a five-dimensional theory. These modes arise from a nonlinear fermion dispersion relation in the extra dimension, much in the same…

A summary is given on the experimental bounds for the couplings and masses of scalar and vector leptoquarks associated to the first fermion generation. We investigate to which extent an interpretation of the recently reported excess of…

We reconsider a generation of up-type quark mass hierarchy in the standard model and clarify how a mechanism works to realize the hierarchy without severe fine tuning.

While a chiral fourth generation of quarks is almost ruled out from the data on Higgs boson production and decay at the Large Hadron Collider, vector-like quarks are still a feasible option to extend the fermionic sector of the Standard…

We investigate the production of fourth family up-type quarks using effective lagrangian approach at future lepton-hadron colliders and study the kinematical characteristics of the signal with an optimal set of cuts. We obtain the upper…

In preon models based on chiral gauge theories, we show that light composite fermions can ensue as a result of gauging a subset of preons in a vector-like manner. After demonstrating how this mechanism works in a toy example, we construct a…

We show that the observed quark/lepton mass hierarchy can be realized dynamically on an interval extra dimension with point interactions. In our model, the positions of the point interactions play a crucial role to control the quark/lepton…

The mechanism of elementary particle mass generation is a fundamental issue of physics. While cardinal progress has recently been achieved in the case of leptons and current quarks through the Brout-Engler-Higgs mechanism, this issue is at…

The possible extension of generation structure is investigated on the basis of a composite model, in which leptons and quarks are composed of rishons $T$ with charge 1/3 and purely neutral $V$. In this sub-system, we regard $V$ as the…

Assuming that the leptons and quarks other than top are massless at tree level, we show that their masses may be induced by loops involving the top quark. As a result, the generic features of the fermion mass spectrum arise from…

We discuss the possibility of measuring the generation mixing for the leptons in $e^+e^-$ collision experiments within the framework of the supersymmetric standard model.

We consider implications of a fourth generation of leptons, allowing for the most general mass patterns for the fourth generation neutrino. We determine the constraints due to the precision electroweak measurements and outline the…