Limits on scalar leptoquark interactions and consequences for GUTs

We demonstrate the viability of the one-loop neutrino mass mechanism within the framework of grand unification when the loop particles comprise scalar leptoquarks (LQs) and quarks of the matching electric charge. This mechanism can be implemented in both supersymmetric and nonsupersymmetric models and requires the presence of at least one LQ pair. The appropriate pairs for the neutrino mass generation via the up-type and down-type quark loops are S 3 -R 2 and S 1, 3 -R 2 , respectively. We consider two distinct regimes for the LQ masses in our analysis. The first regime calls for very heavy LQs in the loop. It can be naturally realized with the S 1, 3 -R 2 scenarios when the LQ masses are roughly between 10 12 and 5 × 10 13 GeV. These lower and upper bounds originate from experimental limits on partial proton decay lifetimes and perturbativity constraints, respectively. Second regime corresponds to the collider accessible LQs in the neutrino mass loop. That option is viable for the S 3 -R 2 scenario in the models of unification that we discuss. If one furthermore assumes the presence of the type II seesaw mechanism there is an additional contribution from the S 3 -R 2 scenario that needs to be taken into account beside the type II see-saw contribution itself. We provide a complete list of renormalizable operators that yield necessary mixing of all aforementioned LQ pairs using the language of SU (5). We furthermore discuss several possible embeddings of this mechanism in SU (5) and SO(10) gauge groups. a

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“…The VEV normalization yields v 2 5 /2 + 12v 2 45 = v 2 , where v(= 246 GeV) is the electroweak VEV [34]. The SU (5) symmetry thus dictates that…”

Section: Grand Unification Vs One-loop Neutrino Massmentioning

confidence: 99%

Leptoquark mechanism of neutrino masses within the grand unification framework

2017

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“…We take α GUT = 0.033 [32] and m GUT = 4×10 15 GeV for definiteness in our numerical analysis of partial proton decay widths. Recall, m GUT can be identified with the mass of proton decay mediating gauge bosons in SU (5).…”

Section: Predictionsmentioning

confidence: 99%

“…One possibility is to add extra scalar multiplet(s) within SU (5) [27]. The main drawback of this approach is the loss of predictive power due to the fact that these extra scalar multiplets have large dimensions [28][29][30][31][32][33]. Another possibility is the introduction of higher-dimensional operators in the Yukawa sector of the theory.…”

Section: Introductionmentioning

confidence: 99%

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Light vectorlike fermions in a minimalSU(5)setup

2014

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The Standard Model fermion sector is enlarged by either one light singlet vector-like downtype quark or one light vector-like lepton doublet, which might be accommodated within a fivedimensional representation of SU (5). At low energies the inclusion of these states affects precisely measured observables in flavor physics, as well as electroweak precision measurements. These experimental results strongly constrain couplings of vector-like states to the Standard Model particles. Having these bounds, we investigate the impact of vector-like fermions on the mass matrices for down-type quarks and charged leptons in an SU (5) setting. We find that unitary transformations relating an arbitrary flavor basis to the mass eigenstate basis depend only on three free parameters. Then we discuss the parameter space constrained by low-energy data assuming vector-like quark and vector-like lepton masses to be 800 GeV and 400 GeV, respectively. We demonstrate that these two scenarios generate unique patterns for relevant proton decay widths. A further improvement of experimental bounds on proton decay modes would thus differentiate the allowed parameter space. We finally present two full-fledged SU (5) models that allow for gauge coupling unification with light vector-like fermions under consideration and discuss their viability. * Electronic address:ilja.dorsner@ijs.si † Electronic address:svjetlana.fajfer@ijs.si ‡ Electronic address:ivana.mustac@ijs.si

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“…In scenarios with a charged Higgs interfering with the SM, useful bounds on tan β vs. the mass of the charged Higgs can be obtained, as presented in [4,5]. The presence of weak triplet, doublet or singlet leptoquarks in charm meson leptonic decays was investigated in [6]. The triplet leptoquarks with electric charge −1/3 can contribute to D q → ν but also to τ → η µ, τ → π µ, K → µν µ , K + → π + νν, K L → µ + µ − and to the ratio BR(τ → πν)/BR(π → µν).…”

Section: Leptonic Charm Decaysmentioning

confidence: 99%

Theory Overview of Charm Physics

Fajfer¹

2011

Proceedings of the 13th International Conference on B-Physics at Hadron Machines — PoS(BEAUTY 2011)

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Recent developments in charm physics within the standard model and beyond are reviewed. The precision study of leptonic charm meson decays accompanied with the constraints coming from K, B and τ physics enables to determine constraints on models of new physics. The standard model contributions in the D 0 −D 0 system are still under investigation including operators of higher dimensions. New physics models such as the Littlest Higgs model or warped extra-dimensional models might modify the amount of CP violation, although CP violating asymmetries are still predicted to be at most of the order 1%. The forward-backward asymmetry in the top anti-top pair production at the Tevatron is opening a new window in the study of new physics in the charm sector. A few of the models considered to explain the observed asymmetry might modify flavor changing neutral current mediated charm processes. New physics searches in rare charm decays are discussed. It is pointed out that in most models new physics effects in rare charm decays are insignificant.

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Limits on scalar leptoquark interactions and consequences for GUTs

Cited by 70 publications

References 86 publications

Leptoquark mechanism of neutrino masses within the grand unification framework

Leptoquark mechanism of neutrino masses within the grand unification framework

Light vectorlike fermions in a minimalSU(5)setup

Theory Overview of Charm Physics

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