Isabella Masina

The universal Higgs fit

A bstractWe perform a state-of-the-art global fit to all Higgs data. We synthesise them into a ‘universal’ form, which allows to easily test any desired model. We apply the proposed methodology to extract from data the Higgs branching ratios, production cross sections, couplings and to analyse composite Higgs models, models with extra Higgs doublets, supersymmetry, extra particles in the loops, anomalous top couplings, and invisible Higgs decays into Dark Matter. Best fit regions lie around the Standard Model predictions and are well approximated by our ‘universal’ fit. Latest data exclude the dilaton as an alternative to the Higgs, and disfavour fits with negative Yukawa couplings. We derive for the first time the SM Higgs boson mass from the measured rates, rather than from the peak positions, obtaining Mh = 124.4 ± 1.6 GeV.

Higgs boson and top quark masses as tests of electroweak vacuum stability

The measurements of the Higgs boson and top quark masses can be used to extrapolate the Standard Model Higgs potential at energies up to the Planck scale. Adopting a NNLO renormalization procedure, we: i) find that electroweak vacuum stability is at present allowed, discuss the associated theoretical and experimental errors and the prospects for its future tests; ii) determine the boundary conditions allowing for the existence of a shallow false minimum slightly below the Planck scale, which is a stable configuration that might have been relevant for primordial inflation; iii) derive a conservative upper bound on type I seesaw right-handed neutrino masses, following from the requirement of electroweak vacuum stability.

Can neutrino mixings arise from the charged lepton sector

The neutrino mixing matrix U is in general of the form U = U † eU�, where Ue arises from the diagonalization of charged leptons and Uis from the neutrino sector. We discuss the possibility that Uis nearly diagonal (in the lagrangian basis) and the observed mixing arises with good accuracy from Ue. We find that the fact that, in addition to the nearly maximal atmospheric mixing angle �23, the solar angle �12 is definitely also large while at the same time the third mixing angle �13 is small, makes the construction of a natural model of this sort considerably more complicated. We present an example of a natural model of this class. We also find that the case that Uis exactly of the bimixing type is severely constrained by the bound on �13 but not excluded. We show that planned experimental searches for �13 could have a strong impact on bimixing models.

Models of Neutrino Masses: Anarchy versus Hierarchy

We present a quantitative study of the ability of models with difierent levels of hierarchy to reproduce the solar neutrino solutions, in particular the LA solution. As a ∞exible testing ground we consider models based on SU(5)£ U(1)F. In this context, we have made statistical simulations of models with difierent patterns from anarchy to various types of hierachy: normal hierarchical models with and without automatic suppression of the 23 (sub)determinant and inverse hierarchy models. We flnd that, not only for the LOW or VO solutions, but even in the LA case, the hierarchical models have a signiflcantly better success rate than those based on anarchy. The normal hierachy and the inverse hierarchy models have comparable performances in models with see-saw dominance, while the inverse hierarchy models are particularly good in the no see-saw versions. As a possible distinction between these categories of models, the inverse hierarchy models favour a maximal solar mixing angle and their rate of success drops dramatically as the mixing angle decreases, while normal hierarchy models are far more stable in this respect.

Repressing anarchy in neutrino mass textures

A bstractThe recent results that θ13 is relatively large, of the order of the previous upper bound, and the indications of a sizable deviation of θ23 from the maximal value are in agreement with the predictions of Anarchy in the lepton sector. The quark and charged lepton hierarchies can then be reproduced in a SU(5) GUT context by attributing non-vanishing U(1)FN charges, different for each family, only to the SU(5) tenplet states. The fact that the observed mass hierarchies are stronger for up quarks than for down quarks and charged leptons supports this idea. As discussed in the past, in the flexible context of SU(5) ⊗ U(1)FN, different patterns of charges can be adopted going from Anarchy to various types of hierarchy. We revisit this approach by also considering new models and we compare all versions to the present data. As a result we confirm that, by relaxing the ansatz of equal U(1)FN charges for all SU(5) pentaplets and singlets, better agreement with the data than for Anarchy is obtained without increasing the model complexity. We also present the distributions obtained in the different models for the Dirac CP-violating phase. Finally we discuss the relative merits of these simple models.

Measuring our peculiar velocity on the CMB with high-multipole off-diagonal correlations

Our peculiar velocity with respect to the CMB rest frame is known to induce a large dipole in the CMB. However, the motion of an observer has also the effect of distorting the anisotropies at all scales, as shown by Challinor and Van Leeuwen (2002), due to aberration and Doppler effects. We propose to measure independently our local motion by using off-diagonal two-point correlation functions for high multipoles. We study the observability of the signal for temperature and polarization anisotropies. We point out that Planck can measure the velocity β with an error of about 30% and the direction with an error of about 20°. This method constitutes a cross-check, which can be useful to verify that our CMB dipole is due mainly to our velocity or to disentangle the velocity from other possible intrinsic sources. Although in this paper we focus on our peculiar velocity, a similar effect would result also from other intrinsic vectorial distortion of the CMB which would induce a dipolar lensing. Measuring the off-diagonal correlation terms is therefore a test for a preferred direction on the CMB sky.

Standard Model False Vacuum Inflation: Correlating the Tensor-to-Scalar Ratio to the Top Quark and Higgs Boson masses

For a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a false minimum at energies of about 10(16)  GeV, where primordial inflation could have started in a cold metastable state. A graceful exit to a radiation-dominated era is provided, e.g., by scalar-tensor gravity models. We pointed out that if inflation happened in this false minimum, the Higgs boson mass has to be in the range 126.0±3.5  GeV, where ATLAS and CMS subsequently reported excesses of events. Here we show that for these values of the Higgs boson mass, the inflationary gravitational wave background has be discovered with a tensor-to-scalar ratio at hand of future experiments. We suggest that combining cosmological observations with measurements of the top quark and Higgs boson masses represent a further test of the hypothesis that the standard model false minimum was the source of inflation in the universe.

On the Veltman Condition, the Hierarchy Problem and High-Scale Supersymmetry

In this paper we have considered the possibility that the Standard Model, and its minimal extension with the addition of singlets, merges with a high-scale supersymmetric theory at a scale satisfying the Veltman condition and therefore with no sensitivity to the cuto. The matching of the Standard Model is achieved at Planckian scales. In its complex singlet extension the matching scale depends on the strength of the coupling between the singlet and Higgs elds. For order one values of the coupling, still in the perturbative region, the matching scale can be located in the TeV ballpark. Even in the absence of quadratic divergences there remains a nite adjustment of the parameters in the high-energy theory which should guarantee that the Higgs and the singlets in the low-energy theory are kept light. This ne-tuning (unrelated to quadratic divergences) is the entire responsibility of the ultraviolet theory and remains as the missing ingredient to provide a full solution to the hierarchy problem.

Higgs mass range from standard model false vacuum inflation in scalar-tensor gravity

If the Standard Model is valid up to very high energies it is known that the Higgs potential can develop a local minimum at field values around

Fermion Generations, Masses and Mixing Angles from Extra Dimensions

10^{15}-10^{17}