I believe this to be one of the most interesting fields at the present time, for a number of reasons. On one side, the recent harvest of data (from the particle accelerators, from the neutrino experiments and the cosmological observations) seems to beautifully confirm our ``standard models'': the SM of Particle Physics with the precision electro-weak tests, the consistent picture of neutrino oscillations, the hot inflationary cosmology. On the other side, it also unveiled hints of New Physics and posed basic questions: the SM cannot be the whole story, given the well known arbitrariness built in it and the incomplete description of the fundamental interactions; the mass of neutrinos needs to be measured and explained; the dark matter and the dark acceleration of the Universe are puzzling.
However, the near future reserves a new harvest of data (from the LHC, the new generation of neutrino experiments and the many cosmological efforts) which promises to test a number of ``Beyond the SM constructions'' (SuSy, TC, GUT, xD, LH...) and to shed light on darkness. This is what most attracts my interest. In all this, I believe I have a taste for sound computations and testable predictions, as opposed to sometimes speculative model building. Though I keep a very open attitude towards any new idea.

In this broad context, my main current interests lie in Neutrino Cosmology and in exploring the phenomenology of Dark Matter models, with a special attention to our recent proposal of Minimal Dark Matter.


In the following, I briefly review my past research activity in some detail, and give an outlook of the open projects and directions.

I began my work in Particle Theory Beyond the SM by computing some relevant observables in the framework of the theory proposed by R. Barbieri, L. Hall and Y. Nomura (Phys.Rev.D63:105007,2001), an extension of the Standard Model to five dimensions endowed with a supersymmetric structure.
The theory is successful in providing a description of the mechanism of electroweak symmetry breaking thanks to the extra dimension, while ensuring calculability for several quantities, a property that is not so common among extra dimensional models.
In collaboration with G. Cacciapaglia and G. Cristadoro, in [1] I found that the production rate of the Higgs boson via gluon fusion (which is the main channel at a hadron collider) is significantly suppressed, due to cancellations among the additional (Kaluza-Klein) states of the theory.
In [2] we showed that the theory is compatible with the precision measurements of muon anomalous magnetic moment, by explicitly computing all the relevant additional contributions to such a quantity and finding them small.

In [4], in collaboration with A. Romanino, Y. Lin and G. Cacciapaglia, I shifted to a more general class of models, characterized by large flat extra dimension accessible to a sterile neutrino.
We analysed the effects in the context of supernova physics, where resonant oscillations between the Standard Model electron neutrino and the additional sterile states provide an unconventional escape channel.
We showed (via numerical and analytical work) how previous bounds can be largely overcome, thanks to a feedback mechanism that self-limits the energy loss, and we discussed positive effects towards supernova explosion.

In [5] we completed the previous analysis including the effects of muon and tau neutrinos escape, showing how a feedback prevents an unacceptable energy loss also in this case.  For all the different scenarios, we discussed the signatures in the neutrino signal on Earth.

In [7] we performed a thorough analysis of oscillation signals generated by one extra sterile neutrino, extending previous analyses done in simple limiting cases and including the effects of established oscillations among active neutrinos. Many New Physics candidates act effectively as sterile neutrinos, so that we include them all.
We consider as probes the solar, atmospheric, reactor and beam neutrinos, Big-Bang Nucleosynthesis (He4, D), the Cosmic Microwave Background,
Large Scale Structure, supernovae and neutrinos from other astrophysical sources. We found no evidence for a sterile neutrino in present data, we identified the still allowed regions, and studied which future experiments can best probe them: sub-MeV solar experiments, more precise studies of CMB or BBN, future supernova explosions... I particularly was involved in the SN and cosmological studies.

In [9], we addressed the implications on solar neutrino oscillations of the recent proposal that the mass of the neutrinos and the field responsible for dark energy may be connected, leading to the effect of mass varying neutrinos depending on environment. We stressed the model independent consequences, finding in particular that a connection between the effective Delta m^2 in the Sun and the absolute neutrino mass scale is established in these scenarios. This leads to the possibility of explicitly testing the model and to other interesting consequences both for the neutrinos and for the mechanism of dark energy.

In [10] we presented results on neutrino fluxes from the annihilation of Dark Matter particles accumulated in the center of the Earth and the Sun. They will be hopefully detected in the Neutrino Telescopes (Antares, IceCube, a large Cerenkov detector...). The neutrino fluxes carry precious information on the main properties of DM (its abundance, its mass and its annihilation branching ratios), opening unique windows on its nature and on the theory that encompasses it.
We computed precisely the expected neutrino yield and, especially, the neutrino spectra, which are more free from astrophysical uncertainties. We develop the appropriate formalism to follow the neutrino production, the evolution of the fluxes in the matter of the Earth and the Sun (determined by flavor oscillations, absorptions/scatterings and tau regeneration) and in the vacuum and finally the detection signatures.

In [11] we explored a new approach to the Dark Matter problem: while Beyond-the-SM theories often provide DM candidates with an obscure phenomenology and an ad-hoc method for stabilization (such as R-parity in SuSy), we looked for a viable candidate just adding to the SM a multiplet in some representation of SU_L(2) x U_Y(1).
We find that a quintuplet with zero hypercharge provides a new minimal candidate for Dark Matter that is fully successful: weakly interacting, electrically neutral and (most importantly) automatically stable on cosmological time scales. We computed its distinctive phenomenology at colliders (the LHC) and in experiments of direct and indirect DM detection, finding that the particle can be detected in the next generation of experiments.

In [12] we investigate the cosmology of ordinary neutrinos and of possible extra light particles. We make use of the most recent data from Cosmic Microwave Background, Supernovae type Ia, Large Scale Structure, Lyman-alpha forest, Baryon Acoustic Oscillation peaks etc. We obtain stringent constraints on the neutrino mass, the effective neutrino density and the properties of proposed new interacting light particles that diminish the neutrino free-streaming. It should be noted that we performed all the analysis making use of numerical codes and tools written and developed by ourselves instead of the commonly used CMBfast-derived tools.

With [13] we investigated how unconventional cosmologies can relax the stringent bounds on sterile neutrinos. We open the way to a possible primordial leptonic asymmetry, that has the effect of suppressing the production of sterile neutrinos in the Early Universe, therefore modifying the constraints from BBN and from LSS. We identify the portions of the parameter space that can be reopened by introducing a given asymmetry. In the case of the LSND sterile neutrino, we find that a primordial asymmetry of the order of 10e-4 is needed in order to lift the conflicts with cosmology.

With [14] we revisited the computation of the cosmological relic abundance in the Minimal Dark Matter proposal introduced in [11], including non-perturbative 'Sommerfeld' corrections. These were found to have a very relevant effect in enhancing the DM annihilations. We also study the peculiar behavior of the DM particles while crossing the Earth at Ultra High Energies, in order to assess the possible detectability in future cosmic ray and neutrino telescopes (e.g. Icecube, Auger, Antares).

In [15] we precisely calculated the indirect detection signatures of the Minimal Dark Matter model of [11]. We computed the fluxes of positrons, antiprotons and gamma rays from the annihilations of DM particles in the galactic halo and their propagation in the galaxy (designing our own computational tools). We found distinctive and univocal predictions (the model has no free parameters). The enhancement in the annihilation cross section discussed in [14] put the foreseen fluxes within the reach of those that were upcoming experiments, PAMELA in particular.

When the PAMELA satellite announced preliminary data on the positron flux, showing confirmation for an excess over the expected background that previous experiments had already exposed, we compared in [16] the fluxes from Minimal DM annihilations predicted in [15] with such data. We found a remarkably good agreement, and we were able to determine the set of astrophysical parameters that gives the best fit. Later, we summarized in [19] the status of the model.

In a subsequent paper [17], we performed a model independent analysis of the PAMELA preliminary data on positrons and anti-protons, together with less known but relevant data from cosmic ray balloon experiments (ATIC and PPB-BETS). We looked for which DM models can explain the signals that appear in the data while remaining compatible with the searches in all other channels. We find that the PAMELA results alone, if due to DM annihilations, individuate a quite unusual DM particle: either very heavy (above 10 TeV) or lighter but annihilating mainly into leptonic channels such as DM DM --> e+ e-. Adding the balloon datasets, only the second possibility is favored.

In [18] we pursued the model independent analysis of multi-messenger indirect signatures extending to gamma rays and synchrotron radiation from the galactic center and dwarf satellite galaxies. We found that these observations impose stringent constraints: a tension is present with the explanation of the PAMELA and ATIC data in terms of DM annihilations, unless the DM halo profile is significantly more smooth than expected from numerical simulations.

In [20] we considered another interesting possible signal of DM indirect detection: fluxes of anti-deuterium synthetized in galactic annihilations. We focussed on the `very heavy Dark Matter' scenarios individuated by the recent data, and we found promising perspectives especially for primary annihilation channels into quarks.

Another relevant test of the Dark Matter invoked to explain the positron excess in PAMELA is the flux of gamma rays produced by inverse Compton scattering of such energetic positrons on low energy ambient photons in the galactic halo. This signal has the advantage of being less sensitive to astrophysical details than the gamma rays from the Galactic Center discussed above. We computed this flux for several cases and for a range of DM models in [21], finding again stringent constraints.

In [22] we looked once again at the implications of Dark Matter annihilations, this time on the cosmological evolution of the universe. Indeed, the annihilations of Dark Matter during the epoch of galaxy formation inject charged particles and energy, producing reionization and heating of the primordial gas. Comparing with the observed optical depth (from CMB) and the measured temperature of the intergalactic gas we found relevant constraints on DM properties, in the particular for the PAMELA-motivated models. We also found general constraints for more `ordinary' Dark Matter.


In the upcoming future, I plan to further explore the indirect detection signatures of Dark Matter and to investigate the effect of non-standard neutrino interactions in the core of Supernovae. On this latter topic, preliminary results obtained in collaboration with Renata Zukanovich-Funchal (Sao Paulo) show that even a tiny amount of non-standard neutrino interactions that convert an electron neutrino into a muon or tau neutrino (as predicted by many extensions of the SM) drastically modify the transport of energy outside of the core of the collapsing star, since electron and muon/tau neutrinos have very different transport properties. So we expect that SN physics will impose stringent bounds on such interactions, currently poorly constrained by experiments.
Concerning Dark Matter, the concrete goal is to develop the tools to assess which DM models can explain possible signals that might appear in the data (e.g. the current PAMELA excess in positron fluxes, or future possible results from the Fermi telescope in gamma rays...) while remaining compatible with the searches in other channels, or producing predictions for other channels. This multi-messenger approach will be further enriched and complemented by the information on Dark Matter (and on new particle physics in general) to be gathered at the LHC. Hopefully, the next few years will see us gaining a precise insight on the properties of Dark Matter and the theory encompassing it, finally getting to identify its nature.


During my laurea thesis work I also dealt with the physics of Strong Interactions and Quantum Chromodynamics, under the supervision of P. Nason and G. Marchesini. We derived a formula for a particular regime in Drell-Yan processes (the production of a lepton--antilepton pair in proton--antiproton collisions). Namely, the intersection of threshold production and small transverse momentum regimes. I had the opportunity of studying in a certain detail the resummation of soft gluon emissions.