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[en] A search for pair-produced leptoquarks has been performed using a sample of e+e- collision events collected by the OPAL detector at LEP at e+e- centre-of-mass energies of about 183 GeV. The data sample corresponds to an integrated luminosity of 55.9 pb-1. The leptoquarks were assumed to be produced via couplings to the photon and the Z0 and then to decay within a single fermion generation. No evidence for contributions from leptoquark pair production processes was observed. Lower limits on scalar and vector leptoquark masses are obtained. The existing limits are improved in the region of large decay branching ratio to quark-neutrino. (orig.)
Journal
European Physical Journal. C; ISSN 1434-6044; 
; v. 13(1); p. 15-27
; v. 13(1); p. 15-27
[en] Several new physics scenarios that address anomalies in B-physics predict an enhancement of b → sττ with respect to its Standard Model prediction. Such scenarios necessarily imply modifications of the lifetime ratio τ/τ and the lifetime difference ΔΓ. In this work, we explore indirect bounds provided by these observables over new physics scenarios. We also estimate future projections, showing that future experimental and theoretical improvements on both τ/τ and ΔΓ have the potential to provide bounds competitive with those directly extracted from b → sττ transitions. After performing a model-independent analysis, we apply our results to the particular case of leptoquark mediators proposed to address the R anomalies.
Journal
European Physical Journal. C, Particles and Fields (Online); ISSN 1434-6052; ; CODEN EPCFFB; v. 83(9); vp
; CODEN EPCFFB; v. 83(9); vp
[en] B-Physics anomalies have recently raised renewed interest in leptoquarks, predicted in several theoretical frameworks. Under simplifying but conservative assumptions, we show that the current limits from LHC searches together with the requirement to explain the observed value for R constrain the R leptoquark mass to be in the range of 800 1000 GeV. We study the search for R at the LHeC via its resonance in the b final state by performing a cut-and-count analysis of the signal and the dominant Standard Model backgrounds. We find that the LHeC has an excellent discovery potential for the R leptoquark even for couplings to the first generation as small as O(10).
Journal
European Physical Journal. C, Particles and Fields (Online); ISSN 1434-6052; ; CODEN EPCFFB; v. 81(12); vp
; CODEN EPCFFB; v. 81(12); vp
[en] In this study, we investigate muon , , and anomalies in a specific model with one doublet, one triplet, and one singlet scalar leptoquark (LQ). When the strict limits from the , , , and processes are considered, it is difficult to use one scalar LQ to explain all of the anomalies due to the strong correlations among the constraints and observables. After ignoring the constraints and small couplings, the muon can be explained by the doublet LQ alone due to the enhancement, whereas the measured and unexpected smaller requires the combined effects of the doublet and triplet LQs, and the and excesses depend on the singlet LQ through scalar- and tensor-type interactions.
Journal
[en] We discuss the modes in the context of non-standard neutrino interactions that add incoherently to the SM rates. We consider two scenarios: an additional light neutrino; and neutrino lepton flavour violation. We find that an additional light neutrino that interacts with SM fields via a non-universal can increase by up to a factor of two without conflicting with mixing. This model then predicts rates for up to six times larger than the SM. In the context of neutrino lepton flavour violation mediated by leptoquarks we find that the current experimental upper bounds on are already more constraining than direct bounds from and modes for .
Journal
[en] We present the importance of the pseudo-Riemannian structure in the spectral triple formalism that is used to describe the Standard Model of Particle Physics. The filnite case is briefly described and its role in the context of leptoquarks is presented. The proposal for the reverse engineering program for the Standard Model is also described, together with recent results.
Journal
EPJ. Web of Conferences; ISSN 2100-014X; ; v. 201; vp
; v. 201; vp
[en] Leptoquarks have been proposed as a possible explanation of anomalies in decays, the apparent anomalies in experiments and a violation of lepton universality. Motivated by this, we examine other motivations of leptoquarks: radiatively induced neutrino masses in the presence of a discrete symmetry that prevents a tree level see-saw mechanism, gauge coupling unification, and vacuum stability at least up to the unification scale. We present a new model for radiatively generating a neutrino mass which can significantly improve gauge coupling unification at one loop. We discuss this, and other models in the light of recent work on flavour anomalies.
Journal
[en] We construct a model where the Yukawa couplings of the Standard Model (SM) fermions arise from the breaking of a Z2 symmetry and through mixing with a fourth family of vector-like fermions. By adding a scalar leptoquark, which is an electroweak triplet and odd under the Z2 symmetry, we obtain an explanation for that is linked to the origin of the Yukawa couplings. The coupling of SM fermions to the leptoquark is mediated by the fourth family fermions, and is predicted to be related to CKM entries and mass ratios of SM fermions.
Journal
Journal of High Energy Physics (Online); ISSN 1029-8479; ; v. 2018(11); p. 1-17
; v. 2018(11); p. 1-17
[en] In the Standard Model, there are many striking similarities between the quark and the lepton sector, like the number of families and the mass hierarchy between them. Leptoquarks are hypothetical particles that occur in various models for physics beyond the Standard Model and provide a connection between the two sectors. They are commonly assumed to couple to quarks and leptons of the same fermion generation but this need not be the case. This contribution gives an overview of the motivation for and presents important aspects of the search for scalar leptoquarks performed by the ATLAS collaboration using proton-proton collision data collected at a centre-of-mass energy of √(s) = 13 TeV.
Journal
Verhandlungen der Deutschen Physikalischen Gesellschaft; ISSN 0420-0195; ; CODEN VDPEAZ; (Muenster 2017 issue); [1 p.]
; CODEN VDPEAZ; (Muenster 2017 issue); [1 p.]
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