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## (25) Production(s) de FRIGERIO M.

Holographic models of composite Higgs in the Veneziano limit. Part I. Bosonic sector Auteur(s): Elander D., Frigerio M., Knecht Marc, Kneur J.-L.
Ref HAL: hal-03022749_v1 Ref Arxiv: 2011.03003 Ref INSPIRE: 1828484 DOI: 10.1007/JHEP03(2021)182 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote Résumé: We study strongly-coupled, approximately scale-invariant gauge theories, which develop a mass gap in the infrared. We argue that a large number of fermion flavours is most suitable to provide an ultraviolet completion for the composite Higgs scenario. The holographic approach allows to describe the qualitative features of the non-perturbative dynamics in the Veneziano limit. We introduce new bottom-up holographic models, which incorporate the backreaction of flavour on the geometry, and show that this can correlate the mass gap to the scale of flavour-symmetry breaking. We compute the mass spectrum for the various composite bosonic states, and study its dependence on the scaling dimension of the symmetry-breaking operators, as well as on the number of flavours. The different regions with a light dilaton are critically surveyed. We carefully assess the domain of validity of the holographic approach, and compare it with lattice simulations and the Nambu-Jona-Lasinio model. |

On the spectrum of composite resonances Auteur(s): Frigerio M.
Conference: Strong dynamics for physics within and beyond the Standard Model at LHC and Future Colliders (Trento, IT, 2019-09-09) Ref HAL: hal-02550157_v1 Ref INSPIRE: 1789740 Exporter : BibTex | endNote Résumé: I discuss the infrared mass spectrum of strongly-coupled gauge theories, thatinduce the Higgs as a composite pseudo-Nambu-Goldstone boson. The set ofcomposite states accompanying the Higgs is determined by the symmetries of thetheory. Here we estimate their mass spectrum by non-perturbative techniquesinspired by QCD, as well as by exploiting gauge-gravity duality. 1 CompositeHiggs: motivations and relevant energy scales As the Large Hadron Collider (LHC)did not find new states significantly coupled to the Standard Model (SM) belowthe TeV scale, any SM extension by such heavy states suffers from a littlehierarchy problem, as the mass of the scalar Higgs boson lies close to the 100GeV scale. Still, some SM extensions have the potential to address the bighierarchy between the TeV scale and the Planck scale. One possibility is toavoid elementary scalar fields, and assume the observed Higgs is a compositeobject, with a compositeness scale f 1 TeV. This scenario requires a strongly-coupled sector, whose spectrum generically includes several additional compositestates besides the Higgs. The mass of the lowest-lying states cannot exceed ∼4πf , and some could be significantly lighter and within the LHC reach. Definitepredictions for the mass spectrum require to specify the strongly-coupled theoryin the ultraviolet (UV). Here we will assume it is a gauge theory of fermions,that confines in the infrared. We will estimate its mass spectrum in some well-defined approximations, by employing non-perturbative techniques inspired by QCD1) , as well as gauge-gravity duality techniques 2). In models where the Higgsis a pseudo-Nambu-Goldstone boson (pNGB) the electroweak scale, v 246 GeV, isinduced in two steps. The theory has a global (flavour) symmtry G F , that isspontaneously broken to a subgroup H F at the scale f. The electroweak symmetrySU (2) L × U (1) Y is embedded in 91 |

New physics in $b\to s\ell\ell$ transitions at one loop Auteur(s): Coy R., Frigerio M., Mescia Federico, Sumensari Olcyr
Ref HAL: hal-02340141_v1 Ref Arxiv: 1909.08567 Ref INSPIRE: 1754713 DOI: 10.1140/epjc/s10052-019-7581-y WoS: WOS:000523449400003 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 7 Citations Résumé: We investigate new-physics contributions to $b\rightarrow s \ell \ell $ transitions in the context of an effective field theory extension of the Standard Model, including operator mixing at one loop. We identify the few scenarios where a single Wilson coefficient, $C/\Lambda ^2 \sim 1/\mathrm{TeV}^2$, induces a substantial shift in the lepton flavour universality ratios $R_K$ and $R_{K^*}$ at one loop, while evading Z-pole precision tests, collider bounds, and other flavour constraints. Novel fits to the present data are achieved by a left-handed current operator with quark-flavour indices (2, 2) or (3, 3). Interestingly, the running of the Standard Model Yukawa matrices gives the dominant effect for these scenarios. We match the favoured effective-theory scenarios to minimal, single-mediator models, which are subject to additional stringent constraints. Notably, we recognise three viable instances of a leptoquark with one coupling to fermions only. If the anomalies were confirmed, it appears that one-loop explanations have good prospects of being directly tested at the LHC. |

Effective approach to lepton observables: The seesaw case Auteur(s): Coy R., Frigerio M.
Ref HAL: hal-01949587_v1 Ref Arxiv: 1812.03165 DOI: 10.1103/PhysRevD.99.095040 WoS: WOS:000470859800009 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 8 Citations Résumé: In the absence of direct evidence of new physics, any ultraviolet theory can be reduced to its specific set of low-energy effective operators. As a case study, we derive the effective field theory for the seesaw extension of the Standard Model, with sterile neutrinos of mass $M>m_W$. We systematically compute all Wilson coefficients generated at one loop. Hence, it becomes straightforward to (i) identify the seesaw parameters compatible with the smallness of neutrino masses; (ii) compute precision lepton observables, which may be sensitive to scales as large as $M\sim 10^3$ TeV; and (iii) establish sharp correlations among those observables. We find that the flavour-conserving Wilson coefficients set an upper bound on the flavour-violating ones. The low-energy limits on $\mu\to e$ and $\tau\to e,\mu$ transitions suppress flavour violation in $Z$ and Higgs decays, as well as electric dipole moments, far beyond the experimental reach. The bounds from the universality of $G_F$ and the invisible $Z$ width are more stringent than present and future limits on $\tau\to e,\mu$ transitions. We also present a general spurion analysis, to compare the seesaw with different models, thus assessing the discriminating potential of the effective approach. |

The Bearable Compositeness of Leptons Auteur(s): Frigerio M., Nardecchia Marco, Serra Javi, Vecchi Luca
Ref HAL: hal-01851263_v1 Ref Arxiv: 1807.04279 Ref INSPIRE: 1681965 DOI: 10.1007/JHEP10(2018)017 WoS: 000446567500001 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 7 Citations Résumé: Partial compositeness as a theory of flavor in the lepton sector is assessed. We begin presenting the first systematic analysis of neutrino mass generation in this context, and identifying the distinctive mass textures. We then update the bounds from charged lepton flavor and CP violating observables. We put forward a U(1)$^{3}$ × CP symmetry of the composite sector, in order to allow the new physics to be not far above the TeV scale. This hypothesis effectively suppresses the new contributions to the electron EDM and μ → eγ, by far the most constraining observables, and results in a novel pattern of flavor violation and neutrino masses. The CP violation in the elementary-composite mixing is shown to induce a CKM phase of the correct size, as well as order-one phases in the PMNS matrix. We compare with the alternative possibility of introducing multiple scales of compositeness for leptons, that also allow to evade flavor and CP constraints. Finally, we examine violations of lepton flavor universality in B-meson semi-leptonic decays. The neutral-current anomalies can be accommodated, predicting strong correlations among different lepton flavors, with a few channels close to the experimental sensitivity. |

Dynamical Clockwork Axions Auteur(s): Coy R., Frigerio M., Ibe Masahiro
Ref HAL: hal-02172478_v1 Ref Arxiv: 1706.04529 Ref INSPIRE: 1605142 DOI: 10.1007/JHEP10(2017)002 WoS: 000412101600002 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 21 Citations Résumé: The clockwork mechanism is a novel method for generating a large separation between the dynamical scale and interaction scale of a theory. We demonstrate how the mechanism can arise from a sequence of strongly-coupled sectors. This framework avoids elementary scalar fields as well as ad hoc continuous global symmetries, both of which are subject to serious stability issues. The clockwork factor, q, is determined by the consistency of the strong dynamics. The preserved global U(1) of the clockwork appears as an accidental symmetry, resulting from discrete or U(1) gauge symmetries, and it is spontaneously broken by the chiral condensates. We apply such a dynamical clockwork to construct models with an effectively invisible QCD axion from TeV-scale strong dynamics. The axion couplings are determined by the localisation of the Standard Model interactions along the clockwork sequence. The TeV spectrum includes either coloured hadrons or vector-like quarks. Dark matter can be accounted for by the axion or the lightest neutral baryons, which are accidentally stable. |

Non-perturbative analysis of the spectrum of meson resonances in an ultraviolet-complete composite-Higgs model Auteur(s): Bizot N., Frigerio M., Knecht Marc, Kneur J.-L.
Ref HAL: hal-01775256_v1 Ref Arxiv: 1610.09293 DOI: 10.1103/PhysRevD.95.075006 WoS: 000399390900010 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 11 Citations Résumé: We consider a vector-like gauge theory of fermions that confines at the multi-TeV scale, and that realizes the Higgs particle as a composite Goldstone boson. The weak interactions are embedded in the unbroken subgroup Sp(4) of a spontaneously broken SU (4) flavour group. The meson resonances appear as poles in the two-point correlators of fermion bilinears, and include the Goldstone bosons plus a massive pseudoscalar η , as well as scalars, vectors and axial vectors. We compute the mass spectrum of these mesons, as well as their decay constants, in the chiral limit, in the approximation where the hypercolour Sp(2N) dynamics is described by four-fermion operators, ` a la Nambu-Jona Lasinio. By resumming the leading diagrams in the 1/N expansion, we find that the spin-one states lie beyond the LHC reach, while spin-zero electroweak-singlet states may be as light as the Goldstone-boson decay constant, f ∼ 1 TeV. We also confront our results with a set of available spectral sum rules. In order to supply composite top-quark partners, the theory contains additional fermions carrying both hypercolour and ordinary colour, with an associated flavour symmetry-breaking pattern SU (6)/SO(6). We identify and analyse several non-trivial features of the complete two-sector gauge theory: the 't Hooft anomaly matching conditions; the higher-dimension operator which incorporates the effects of the hypercolour axial-singlet anomaly; the coupled mass-gap equations; the mixing between the singlet mesons of the two sectors, resulting in an extra Goldstone boson η0, and novel spectral sum rules. Assuming that the strength of the four-fermion interaction is the same in the two sectors, we find that the coloured vector and scalar mesons have masses 4f , while the masses of coloured pseudo-Goldstone bosons, induced by gluon loops, are 1.5f. We discuss the scaling of the meson masses with the values of N , of the four-fermion couplings, and of a possible fermion mass. Commentaires: 65 pages, 25 figures |