Luca Di Luzio

Gauge leptoquark as the origin of B-physics anomalies.

The vector leptoquark representation, Uμ ¼ ð3; 1; 2=3Þ, was recently identified as an exceptional single mediator model to address experimental hints on lepton flavor universality violation in semileptonic B-meson decays, both in neutral (b → sμμ) and charged (b → cτν) current processes. Nonetheless, it is well known that massive vectors crave an ultraviolet (UV) completion. We present the first full-fledged UV complete and calculable gauge model which incorporates this scenario while remaining in agreement with all other indirect flavor and electroweak precision measurements, as well as, direct searches at high-pT . The model is based on a new non-Abelian gauge group spontaneously broken at the TeV scale, and a specific flavor structure suppressing flavour violation in ΔF ¼ 2 processes while inducing sizeable semileptonic transitions

Accidental matter at the LHC

A bstractWe classify weak-scale extensions of the Standard Model which automatically preserve its accidental and approximate symmetry structure at the renormalizable level and which are hence invisible to low-energy indirect probes. By requiring the consistency of the effective field theory up to scales of Λeff ≈ 1015 GeV and after applying cosmological constraints, we arrive at a finite set of possibilities that we analyze in detail. One of the most striking signatures of this framework is the presence of new charged and/or colored states which can be efficiently produced in high-energy particle colliders and which are stable on the scale of detectors.

The vacuum of the minimal nonsupersymmetric SO(10) unification

We study a class of nonsupersymmetric SO(10) grand-unified scenarios where the first stage of the symmetry breaking is driven by the vacuum expectation values of the 45- dimensional adjoint representation. Three- decade- old results claim that such a Higgs setting may lead exclusively to the flipped SU(5) circle times U(1) intermediate stage. We show that this conclusion is actually an artifact of the tree- level potential. The study of the accidental global symmetries emerging in various limits of the scalar potential offers a simple understanding of the tree- level result and a rationale for the drastic impact of quantum corrections. We scrutinize in detail the simplest and paradigmatic case of the 45(H) circle plus 16(H) Higgs sector triggering the breaking of SO(10) to the standard electroweak model. We show that the minimization of the one- loop effective potential allows for intermediate SU(4)(C) circle times SU(2)(L) circle times U(1)(R) and SU(3)(c) circle times SU(2)(L) circle times SU(2)(R) circle times U(1)(B-L) symmetric stages as well. These are the options favored by gauge unification. Our results, that apply whenever the SO(10) breaking is triggered by , open the path for hunting the simplest realistic scenario of nonsupersymmetric SO(10) grand unification.

Seesaw Scale in the Minimal Renormalizable SO(10) Grand Unification

Simple SO(10) Higgs models with the adjoint representation triggering the grand-unified symmetry breaking, discarded a long ago due to inherent tree-level tachyonic instabilities in the physically interesting scenarios, have been recently brought back to life by quantum effects. In this work we focus on the variant with 45_H+126_H in the Higgs sector and show that there are several regions in the parameter space of this model that can support stable unifying configurations with the B-L breaking scale as high as 10^14 GeV, well above the previous generic estimates based on the minimal survival hypothesis. This admits for a renormalizable implementation of the canonical seesaw and makes the simplest potentially realistic scenario of this kind a good candidate for a minimal SO(10) grand unification. Last, but not least, this setting is likely to be extensively testable at future large-volume facilities such as Hyper-Kamiokande.

Light color octet scalars in the minimal SO(10) grand unification

We analyze the relation between the present (and foreseen) bounds on matter stability and the presence of TeV-scale color octet scalar states in nonsupersymmetric SO(10) grand unification with one adjoint Higgs representation triggering the symmetry breaking. This scenario, discarded long ago due to tree-level tachyonic instabilities appearing in all phenomenologically viable breaking patterns, has been recently revived at the quantum level. By including the relevant two-loop corrections we find a tight correlation between the octet mass and the unification scale which either requires a light color octet scalar within the reach of the LHC or, alternatively, a proton lifetime accessible to the forthcoming megaton-scale facilities.

What is the scale of new physics behind the B-flavour anomalies?

Motivated by the recent hints of lepton flavour non-universality in B-meson semi-leptonic decays, we study the constraints of perturbative unitarity on the new physics interpretation of the anomalies in

g-2

b \rightarrow c \ell \bar{\nu }

Window for preferred axion models

b→cℓν¯ and