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Federica Bazzocchi

Publications and source records attributed to Federica Bazzocchi.

15 recordsLinked to original sources
arXiv2012

Constraining Flavour Symmetries At The EW Scale I: The A4 Higgs Potential

We consider an extension of the Standard Model in which the symmetry is enlarged by a global flavour factor A4 and the scalar sector accounts for three copies of the Standard Model Higgs, transforming as a triplet of A4. In this context, we study the most general scalar potential and its minima, performing for each of them a model independent analysis on the related phenomenology. We study the scalar spectrum, the new contributions to the oblique corrections, the decays of the Z and W, the new sources of flavour violation, which all are affected by the introduction of multiple Higgses transforming under A4. We find that this model independent approach discriminates the different minima allowed by the scalar potential.

hep-ph↗
arXiv2012

Constraining Flavour Symmetries At The EW Scale II: The Fermion Processes

We study the set of models in which the Standard Model symmetry is extended with the flavour group A4 and there are three copies of the Standard Model Higgs that transform as a triplet under this group. In this setup, new channels for flavour violating processes can be studied once the A4 representations of the fermions in the theory are given. We show that it is of great importance to take these constraints into account as they can put severe constraints on the viability of flavour models.

hep-ph↗
arXiv2012

Neutrino Mixings and the S4 Discrete Flavour Symmetry

Discrete non-Abelian Symmetries have been extensively used to reproduce the lepton mixings. In particular, the S4 group turned out to be suitable to describe predictive mixing patterns, such as the well-known Tri-Bimaximal and the Bimaximal schemes, which all represent possible first approximations of the experimental lepton mixing matrix. We review the main application of the S4 discrete group as a flavour symmetry, first dealing with the formalism and later with the phenomenological implications. In particular, we summarize the main features of flavour models based on S4, commenting on their ability in reproducing a reactor angle in agreement with the recent data and on their predictions for lepton flavour violating transitions.

hep-ph↗
arXiv2012

Leptogenesis in the presence of exact flavor symmetries

In models with flavor symmetries in the leptonic sector leptogenesis can take place in a very different way compared to the standard leptogenesis scenario. We study the generation of a $B-L$ asymmetry in these kind of models in the flavor symmetric phase pointing out that successful leptogenesis requires (i) the right-handed neutrinos to lie in different representations of the flavor group; (ii) the flavons to be lighter at least that one of the right-handed neutrino representations. When these conditions are satisfied leptogenesis proceeds due to new contributions to the CP violating asymmetry and -depending on the specific model- in several stages. We demonstrate the validity of these arguments by studying in detail the generation of the $B-L$ asymmetry in a scenario of a concrete $A_4$ flavor model realization.

hep-ph↗
arXiv2011

Quark mixing in the discrete dark matter model

We consider a model in which dark matter is stable as it is charged under a Z2 symmetry that is residual after an A4 flavour symmetry is broken. We consider the possibility to generate the quark masses by charging the quarks appropriately under A4. We find that it is possible to generate the CKM mixing matrix by an interplay of renormalisable and dimension-six operators. In this set-up, we predict the third neutrino mixing angle to be large and the dark matter relic density to be in the correct range. However, low energy observables - in particular meson-antimeson oscillations - strongly limit the available parameter space.

hep-ph↗
arXiv2011

Minimal Yukawa-Gauge Mediation

We consider a scenario in which Supersymmetry breaking is communicated to the MSSM fields through the interplay of yukawa and gauge interactions. The MSSM spectrum resembles that of split SUSY scenarios, but on top of that it develops some peculiar features like heavy higgsinos and an inverted hierarchy of sfermion masses. The predictions obtained are consistent with the most recent LHC SUSY and Higgs boson searches.

hep-ph↗
arXiv2010

The Interplay Between GUT and Flavour Symmetries in a Pati-Salam x S4 Model

Both Grand Unified symmetries and discrete flavour symmetries are appealing ways to describe apparent structures in the gauge and flavour sectors of the Standard Model. Both symmetries put constraints on the high energy behaviour of the theory. This can give rise to unexpected interplay when building models that possess both symmetries. We investigate on the possibility to combine a Pati-Salam model with the discrete flavour symmetry $S_4$ that gives rise to quark-lepton complementarity. Under appropriate assumptions at the GUT scale, the model reproduces fermion masses and mixings both in the quark and in the lepton sectors. We show that in particular the Higgs sector and the running Yukawa couplings are strongly affected by the combined constraints of the Grand Unified and family symmetries. This in turn reduces the phenomenologically viable parameter space, with high energy mass scales confined to a small region and some parameters in the neutrino sector slightly unnatural. In the allowed regions, we can reproduce the quark masses and the CKM matrix. In the lepton sector, we reproduce the charged lepton masses, including bottom-tau unification and the Georgi-Jarlskog relation as well as the two known angles of the PMNS matrix. The neutrino mass spectrum can present a normal or an inverse hierarchy, and only allowing the neutrino parameters to spread into a range of values between $λ^{-2}$ and $λ^2$, with $λ\simeq0.2$. Finally, our model suggests that the reactor mixing angle is close to its current experimental bound.

hep-ph↗
arXiv2009

Fermion Masses and Mixings in a S4 Based Model

It has been recently claimed that the symmetry group S4 yields to the Tri-bimaximal neutrino mixing in a "natural" way from the group theory point of view. Approving of this feature as an indication, we build a supersymmetric model of lepton and quark masses based on this family symmetry group. In the lepton sector, a correct mass hierarchy among the charged leptons is achieved together to a neutrino mass matrix which can be diagonalized by the Tri-bimaximal pattern. Our model results to be phenomenologically unequivalent with respect to other proposals based on different flavour groups but still predicting the Tri-bimaximal mixing. In the quark sector a realistic pattern for masses and mixing angles is obtained. The flavour structures of the mass matrices in both the sectors come from the spontaneously symmetry breaking of S4, due to several scalar fields, which get non-zero vacuum expectation values. A specific vacuum alignment is required and it is shown to be a natural results of the minimization of the scalar potential and, moreover, to be stable under the corrections from the higher order terms.

hep-ph↗
arXiv2008

S4 as a natural flavor symmetry for lepton mixing

Group theoretical arguments seem to indicate the discrete symmetry S4 as the minimal flavour symmetry compatible with tribimaximal neutrino mixing. We prove in a model independent way that indeed S4 can realize exact tribimaximal mixing through different symmetry breaking patterns. We present two models in which lepton tribimaximal mixing is realized in different ways and for each one we discuss the superpotential that leads to the correct breaking of the flavor symmetry.

hep-ph↗
arXiv2008

Fermion masses and mixing in models with SO(10) x A_4 symmetry

We study the flavour sector in models where the three families of matter are unified in a $(16,3)$ representation of the $SO(10)\times A_4$ group. The necessary ingredients to realize tri-bi-maximal mixing in the lepton sector are identified systematically. The non-renormalizable operators contributing to the fermion mass matrices play an important role. We also present a mechanism to explain the inter-family mass hierarchy of quarks and charged leptons, which relies on a `universal seesaw' mechanism and is compatible with tri-bi-maximal mixing.

hep-ph↗
arXiv2008

X-ray photons from late-decaying majoron dark matter

An attractive way to generate neutrino masses as required to account for current neutrino oscillation data involves the spontaneous breaking of lepton number. The resulting majoron may pick up a mass due to gravity. If its mass lies in the kilovolt scale, the majoron can play the role of late-decaying Dark Matter (LDDM), decaying mainly to neutrinos. In general the majoron has also a sub-dominant decay to two photons leading to a mono-energetic emission line which can be used as a test of the LDDM scenario. We compare expected photon emission rates with observations in order to obtain model independent restrictions on the relevant parameters. We also illustrate the resulting sensitivities within an explicit seesaw realisation, where the majoron couples to photons due to the presence of a Higgs triplet.

astro-ph↗
arXiv2007

Embedding A4 into left-right flavor symmetry: Tribimaximal neutrino mixing and fermion hierarchy

We address two fundamental aspects of flavor physics: the mass hierarchy and the large lepton mixing angles. On one side, left-right flavor symmetry realizes the democratic mass matrix patterns and explains why one family is much heavier than the others. On the other side, discrete flavor symmetry such as A4 leads to the observed tribimaximal mixing for the leptons. We show that, by explicitly breaking the left-right flavor symmetry into the diagonal A4, it is possible to explain both the observed charged fermion mass hierarchies and quark and lepton mixing angles. In particular we predict a heavy 3rd family, the tribimaximal mixing for the leptons, and we suggest a possible origin of the Cabibbo and other mixing angles for the quarks.

hep-ph↗
arXiv2004

A heavy Higgs boson from flavor and electroweak symmetry breaking unification

We present a unified picture of flavor and electroweak symmetry breaking based on a nonlinear sigma model spontaneously broken at the TeV scale. Flavor and Higgs bosons arise as pseudo-Goldstone modes. Explicit collective symmetry breaking yields stable vacuum expectation values and masses protected at one loop by the little-Higgs mechanism. The coupling to the fermions generates well-definite mass textures--according to a U(1) global flavor symmetry--that correctly reproduce the mass hierarchies and mixings of quarks and leptons. The model is more constrained than usual little-Higgs models because of bounds on weak and flavor physics. The main experimental signatures testable at the LHC are a rather large mass m_{h^0} = 317\pm 80 GeV for the (lightest) Higgs boson and a characteristic spectrum of new bosons and fermions at the TeV scale.

hep-ph↗
arXiv2004

Phenomenology of the little flavon model

The phenomenology of the little-flavon model is discussed. Flavor changing neutral current and lepto-quark compositeness set the most stringent bounds to the lowest possible value for the scale at which the flavons arise as pseudo-Goldstone bosons.

hep-ph↗