Related papers: Constraints on two-lepton, two quark operators
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…
A fermion-boson-type composite model for quarks and leptons is proposed. Elementary fields are only one kind of spin-1/2 and spin-0 preon. Both are in the global supersymmetric pair with the common electric charge of e/6 and belong to the…
The Standard Model Effective Field Theory (SMEFT) provides a systematic framework to probe indirect effects of heavy new physics via precision measurements. While SMEFT constraints have been extensively studied using purely leptonic $Z$…
We consider lepton flavour violating decays of the top quark, mediated by four-fermion operators. We compile constraints on a complete set of SU(3)*U(1)-invariant operators, arising from their loop contributions to rare decays and from…
The charge asymmetry in top quark production at hadron colliders is sensitive to beyond-the-Standard-Model four-fermion interactions. In this study we compare the sensitivity of cross-section and charge asymmetry measurements to effective…
Leptoquarks provide some of the simplest explanations to the hints of lepton flavor non-universality in $B$ decays. In particular, a new confining gauge group can provide a natural and appealing origin for the leptoquarks. So far, direct…
Dipole interactions encode a rich variety of phenomena, such as radiative decays and electric dipole moments in both quark and lepton sectors, which probe physics beyond the Standard Model up to very high energy scales; due to…
We argue that simpler fermionic contents, responsible for the extension of the standard model with gauged lepton and baryon charges, can be constructed by assuming existence of so-called leptoquarks (j,k) with exotic electric charges…
In this paper we present updated constraints on the top-quark sector of the Standard Model Effective Field Theory using data available from Tevatron, LEP and the LHC. Bounds are obtained for the Wilson coefficients from a global fit…
A brief review of the current state of observed deviations of theoretical predictions from experimental data in semileptonic decays of $B$ and $B_c$ mesons is given. A theoretical analysis of these decays is carried out, taking into account…
We study lepton flavour violating two- and three-body decays of pseudoscalar mesons in Effective Field Theory (EFT). We give analytic formulae for the decay rates in the presence of a complete basis of QED and QCD-invariant operators. The…
Processes commonly studied at the Large Hadron Collider (LHC) are induced by quarks and gluons inside the protons of the LHC beams. In this letter we demonstrate that, since protons also contain leptons, it is possible to target…
The most severe constraints on quark-lepton four-fermion contact interactions come from the agreement of atomic parity violation measurements with the Standard Model. In this letter I note that for contact interactions which arise in…
We study renormalizable extensions of the standard model that contain vector-like fermions in a (single) complex representation of the standard model gauge group. There are 11 models where the vector-like fermions Yukawa couple to the…
The low-energy manifestations of a minimal extension of the electroweak standard model based on the quark-lepton symmetry $SU(4)_V \otimes SU(2)_L \otimes G_R$ of the Pati--Salam type are analyzed. Given this symmetry the third type of…
We study the properties of vectorlike fermions that have the same gauge charges as the Standard Model lepton doublets, but opposite lepton number. These antileptons undergo decays mediated by heavier scalar leptoquarks, while the symmetries…
Effects of four-Fermi-type new interactions are studied in top-quark pair production and their subsequent decays at future e^+e^- colliders. Secondary-lepton-energy distributions are calculated for arbitrary longitudinal beam polarizations.…
The standard model weak interactions can be described by four-fermion V-A operators at low energies. New physics at the TeV scale can, however, generate the other Lorentz structures. In this talk, we review the constraints on such…
We obtain constraints on four-lepton interactions in the effective field theory with dimension-6 operators. To this end, we combine the experimental input from Z boson measurements in LEP-1, W boson mass and decays, muon and tau decays,…
We consider the three CP-conserving dimension-6 operators that encode the leading new-physics effects in the triple gauge couplings. The contributions to the standard-model electromagnetic dipole and semi-leptonic vector and axial-vector…