Related papers: New Bounds on Leptoquark Couplings
We provide an explicit structure of the charged lepton mass matrix which is 2-3 symmetric except for a single breaking of this symmetry by the muon mass. We identify a flavor symmetric limit for the mass matrices where the first generation…
We have searched for the pair production of first generation scalar leptoquarks in the eejj channel using the full data set (123 pb-1) collected with the D0 detector at the Fermilab Tevatron during 1992--1996. We observe no candidates with…
CKM mixing between third family quarks and a possible fourth family is constrained by global fits to the precision electroweak data. The dominant constraint is from nondecoupling oblique corrections rather than the Zbb vertex correction…
Leptoquark (LQ) models are well motivated solutions to the $(g-2)_{\mu}$ anomaly. In the minimal LQ models, only specific representations can lead to the chiral enhancements. For the scalar LQs, the $R_2$ and $S_1$ can lead to the top quark…
The possibility to explain the CMB measurement of the baryon asymmetry with leptogenesis results in a stringent bound on the neutrino masses such that [(m_1)^2+(m_2)^2+(m_3)^2]^(1/2) < 0.30 eV. We discuss the implications of such a bound…
We apply LHC data to constrain a simplified extension of the Standard Model containing a new spin-1 mediator $R$, which does not couple to first generation quarks, and a spinor dark matter particle $\chi$. We recast ATLAS and CMS searches…
Motivated by the long-standing discrepancy in lepton flavor universality ratios $R_D$ and $R_{D^{\ast}}$ we assess the status of scalar leptoquark states $R_2$, $\widetilde R_2$ and $S_1$ which can in principle provide a desired enhancement…
We clarify open issues in relating low- and high-energy observables, at next-to-leading order accuracy, in models with a massive leptoquark embedded in a flavor non-universal $SU(4) \times SU(3) \times SU(2) \times U(1)$ gauge group.…
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 analyse the most recent experimental data regarding D^0 - \bar{D^0} mixing, allowing for CP violation. We focus on the dispersive part of the mixing amplitude, M^D_{12}, which is sensitive to new physics contributions. We obtain a…
We propose a model in which the Yukawa couplings of Higgs doublets are related to the couplings of the chiral fermions to a scalar leptoquark triplet. This is due to their common origin via mixing with a vector-like family distinguished by…
In the heavy quark limit, there are three independent strong axial coupling constants in chiral Lagrangians for ground-state heavy hadrons: g in the meson sector, and g_1, g_2 in the baryon sector. The coupling g_2 is extracted from recent…
We investigate the constraints on the leptoquark Yukawa couplings and Higgs-leptoquark quartic couplings for scalar doublet leptoquark $\tilde{R}_2$, scalar triplet leptoquark $\vec S_3$ and their combination with both three generations and…
We analyse $\Delta C=2$ transitions in the framework of a minimal extension of the Standard Model where either a $Q=2/3$ or a $Q=-1/3$ isosinglet quark is added to the standard quark spectrum. In the case of a $Q=2/3$ isosinglet quark, it…
This review addresses the question of the chirality of $b$ quark weak couplings from a theoretical and from a purely phenomenological point of view. Due to their small magnitude $b$ decay couplings are subject to possible large corrections…
Anomalous Wtb couplings modify the angular correlations of the top quark decay products and change the single top quark production cross section. We present limits on anomalous top quark couplings by combining information from W boson…
Physics from beyond the Standard Model, such as leptoquarks, can induce four fermion operators involving a quark, an anti-quark, a lepton and an anti-lepton. We update the (flavour dependent) constraints on the coefficients of such…
We study generic effects of new physics on the rare decay modes $K_L \to \pi^0 \nu \bar\nu$ and $K^+ \to \pi^+ \nu \bar\nu$. We discuss several cases: left-handed neutrino couplings; right handed neutrino couplings; neutrino lepton flavour…
The effective Hamiltonian for the R-parity violating couplings induced nonleptonic decay $B^-\to K^-K^0$ is calculated including leading log QCD corrections running from $m_{\tilde q}$, the mass of the up-type squark, to $m_b$. Experimental…
We perform a systematical and analytical study of lepton mixing which can be derived from the subgroups of $SU(3)$ under the assumption that neutrinos are Dirac particles. We find that type D groups can predict lepton mixing patterns…