Leptoquark Interactions Research Articles

Neutrino masses and mixing angles from leptoquark interactions

In this paper we show that the mixing between leptoquarks (LQ's) from different $SU(2)_l$ multiplets can generate a non-trivial Majorana mass matrix for neutrinos through one loop self energy diagrams. Such mixing can arise from gauge invariant and renormalizable LQ-Higgs interaction terms after EW symmetry breaking. We use the experimental indication on neutrino oscillation to find constraints on specific combinations of LQ couplings to quark-lepton pairs and to the SM higgs boson. These constraints are compared with the ones from $\pi\to e\bar {\nu}_e$.

Physics implications of flat directions in free fermionic superstring models. I. Mass spectrum and couplings

From the "top-down" approach we investigate physics implications of the class of D- and F- flat directions formed from non-Abelian singlets which are proven flat to all orders in the nonrenormalizable superpotential, for a prototype quasi-realistic free fermionic string model with the standard model gauge group and three families (CHL5). These flat directions have at least an additional U(1)' unbroken at the string scale. For each flat direction, the complete set of effective mass terms and effective trilinear superpotential terms in the observable sector are computed to all orders in the VEV's of the fields in the flat direction. The "string selection-rules" disallow a large number of couplings allowed by gauge invariance, resulting in a massless spectrum with a large number of exotics, in most cases excluded by experiment, thus signifying a generic flaw of these models. Nevertheless, the resulting trilinear couplings of the massless spectrum possess a number of interesting features which we analyse for two representative flat directions: for the fermion texture; baryon- and lepton-number violating couplings; R-parity breaking; non-canonical mu terms; and the possibility of electroweak and intermediate scale symmetry breaking scenarios for U(1)'. The gauge coupling predictions are obtained in the electroweak scale case. Fermion masses possess t-b and tau-mu universality, with the string scale Yukawa couplings g and $g/\sqrt{2}$, respectively. Fermion textures are present for certain flat directions, but only in the down-quark sector. Baryon- and lepton- number violating couplings can trigger proton-decay, $N-{\bar N}$ oscillations, leptoquark interactions and R-parity violation, leading to the absence of a stable LSP.

Signal and backgrounds for leptoquarks at the CERN LHC

We study the potentiality of the CERN Large Hadron Collider (LHC) to unravel the existence of first generation scalar leptoquarks. Working with the most general $SU(2)_L \otimes U(1)_Y$ invariant leptoquark interactions, we analyze in detail the signals and backgrounds that lead to a final state containing a pair $e^+e^-$ and jets. Our results indicate that a machine like the LHC will be able to discover leptoquarks with masses up to 2--3 TeV depending on their couplings.

Rajpoot–Samuel four-preon model of elementary particles

A study of the four-preon model of quarks, leptons, and gauge bosons recently developed by Rajpoot and Samuel has been presented in this paper with reference to a number of electromagnetic, weak, and lepto-quark interactions. It is pointed out that neutrino oscillations and neutrinoless double β-decay are not likely to occur according to this model, but the process μ → e−γ may. Further, in the context of new heavy leptons and a new scalar particle recently discussed in the literature, an attempt at identification of these particles is also made here.