Order and anarchy hand in hand in 5D SO(10)

We update a five-dimensional SO(10) grand unified model of fermion masses and mixing angles originally proposed by Kitano and Li. In our setup Yukawa couplings are anarchical and quark and lepton sectors are diversified by the profiles of the fermion zero modes in the extra dimension. The breaking of SO(10) down to SU(5)×U(1) X provides the key parameter that distinguishes the profiles of the different SU(5) components inside the same 16 representation. With respect to the original version of the model, we extend the Higgs sector to explicitly solve the doublet-triplet splitting problem through the missing partner mechanism and we perform a fit to an idealized set of data. By scanning the Yukawa couplings of the model we find that, for large tan β , both normal and inverted ordered neutrino spectrum can be accommodated. However, while the case of inverted order requires a severe fine tuning of the Yukawa parameters, the normal ordering is compatible with an anarchical distribution of Yukawa couplings. Thus, in a natural portion of the parameter space, the model predicts a normal ordered neutrino spectrum, the lightest neutrino mass below 5 meV, and | m ββ | in the range 0.1-5 meV. No particular preference is found for the Dirac CP phase in the lepton sector while the right-handed neutrino masses are too small to explain the baryon asymmetry of the universe through thermal leptogenesis

On sgoldstino-less supergravity models of inflation

We go a step further in the search for a consistent and realistic supergravity model of large-field inflation by building a class of models with the following features: during slow-roll, all the scalar fields other than the inflaton are frozen by large inflatondependent masses or removed from the spectrum; at the end of inflation, supersymmetry is spontaneously broken with naturally vanishing classical vacuum energy. We achieve this by combining some geometrical properties of the Kähler potential with the consistent use of a single nilpotent chiral superfield, in one-to-one correspondence with the supersymmetrybreaking direction in field space at the vacuum

Beyond the minimal top partner decay

Light top partners are the prime sign of naturalness in composite Higgs models. We explore here the possibility of non-standard top partner phenomenology. We show that even in the simplest extension of the minimal composite Higgs model, featuring an extra singlet pseudo Nambu-Goldstone boson, the branching ratios of the top partners into standard channels can be significantly altered, with no substantial change in the generated Higgs potential. Together with the variety of possible final states from the decay of the pseudo-scalar singlet, this motivates more extensive analyses in the search for the top partners

An Equivalent Gauge and the Equivalence Theorem

I describe a novel covariant formulation of massive gauge theories in which the longitudinal polarization vectors do not grow with the energy. Therefore in the present formalism, differently from the ordinary one, the energy and coupling power-counting is completely transparent at the level of individual Feynman diagrams, with obvious advantages both at the conceptual and practical level

A realistic pattern of fermion masses from a five-dimensional SO(10) model

We provide a unified description of fermion masses and mixing angles in the framework of a supersymmetric grand unified SO(10) model with anarchic Yukawa couplings of order unity. The space-time is five dimensional and the extra flat spatial dimension is compactified on the orbifold S 1 /( Z 2  ×  Z 2 ' ), leading to Pati-Salam gauge symmetry on the boundary where Yukawa interactions are localised. The gauge symmetry breaking is completed by means of a rather economic scalar sector, avoiding the doublet-triplet split-ting problem. The matter fields live in the bulk and their massless modes get exponential profiles, which naturally explain the mass hierarchy of the different fermion generations. Quarks and leptons properties are naturally reproduced by a mechanism, first proposed by Kitano and Li, that lifts the SO(10) degeneracy of bulk masses in terms of a single parameter. The model provides a realistic pattern of fermion masses and mixing angles for large values of tan β . It favours normally ordered neutrino mass spectrum with the lightest neutrino mass below 0 . 01 eV and no preference for leptonic CP violating phases. The right handed neutrino mass spectrum is very hierarchical and does not allow for thermal leptogenesis. We analyse several variants of the basic framework and find that the results concerning the fermion spectrum are remarkably stable

Topological duality twist and brane instantons in F-theory

A variant of the topological twist, involving SL(2, ℤ) dualities and hence named topological duality twist, is introduced and explicitly applied to describe a U(1) N = 4 super Yang-Mills theory on a Kähler space with holomorphically space-dependent coupling. Three-dimensional duality walls and two-dimensional chiral theories naturally enter the formulation of the duality twisted theory. Appropriately generalized, this theory is relevant for the study of Euclidean D3-brane instantons in F-theory compactifications. Some of its properties and implications are discussed

Fusion of 40 Ca + 96 Zr revisited: Transfer couplings and hindrance far below the barrier

The sub-barrier fusion excitation function of 40 Ca + 96 Zr has been measured down to cross sections ≃2.4 μb, i.e. two orders of magnitude smaller than obtained in a previous experiment, where the sub-barrier fusion of this system was found to be greatly enhanced with respect to 40 Ca + 90 Zr, and the need of coupling to transfer channels was suggested relying on coupled-channels calculations. The purpose of this work has been to investigate the behavior of 40 Ca + 96 Zr fusion far below the barrier, thereby disentangling the elusive interplay of effects due to inelastic couplings, transfer couplings and, possibly, the appearance of the fusion hindrance. The smooth trend of the excitation function has been found to continue, and the logarithmic slope increases very slowly. No indication of hindrance shows up, and a comparison with 48 Ca + 96 Zr is illuminating in this respect. A new CC analysis of the complete excitation function has been performed, including explicitly one- and two-nucleon <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>Q</mi><mo>&gt;</mo><mn>0</mn></math> transfer channels. Such transfer couplings bring significant cross section enhancements, even at the level of a few μb. Locating the hindrance threshold, if any, in 40 Ca + 96 Zr would require challenging measurements of cross sections in the sub-μb range

Oscillations above the barrier in the fusion of 28 Si + 28 Si

Fusion cross sections of 28 Si + 28 Si have been measured in a range above the barrier with a very small energy step ( ΔElab=0.5 MeV ). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y + repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simple relation between a peak in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier

Symmetries, sum rules and constraints on effective field theories

Using unitarity, analyticity and crossing symmetry, we derive universal sum rules for scattering amplitudes in theories invariant under an arbitrary symmetry group. The sum rules relate the coefficients of the energy expansion of the scattering amplitudes in the IR to total cross sections integrated all the way up to the UV. Exploiting the group structure of the symmetry, we systematically determine all the independent sum rules and positivity conditions on the expansion coefficients. For effective field theories the amplitudes in the IR are calculable and hence the sum rules set constraints on the parameters of the effective Lagrangian. We clarify the impact of gauging on the sum rules for Goldstone bosons in spontaneously broken gauge theories. We discuss explicit examples that are relevant for WW -scattering, composite Higgs models, and chiral perturbation theory. Certain sum rules based on custodial symmetry and its extensions provide constraints on the Higgs boson coupling to the electroweak gauge bosons

Future tests of Higgs compositeness: direct vs indirect

We estimate the reach of the 14 TeV LHC and future hadronic and leptonic colliders in the parameter space of the minimal composite Higgs model, outlining the complementarity of direct resonance searches and indirect information from the measurements of the Higgs boson couplings. The reach on electroweak charged spin-one resonances, taken here as representative direct signatures, is obtained from the current 8 TeV LHC limits by an extrapolation procedure which we outline and validate. The impact of electroweak precision tests, and their possible improvement at future colliders, is also quantified