A New Light Particle in B Decays?

We investigate the possibility whether the tensions with SM expectations observed in several b -> sll transitions, including hints for lepton flavour non-universality, could be due to the decay of B into a new light resonance. We find that qualitative agreement with the data can be obtained with a light vector resonance dominantly decaying invisibly. This scenario predicts a shift in the muon anomalous magnetic moment that could explain the long-standing discrepancy. The most stringent constraint comes from searches for B decays with missing energy. A striking prediction is a strong q^2 dependence of the lepton flavour universality ratios R_K and R_K* that should allow to clearly confirm or rule out this possibility experimentally. We also comment on the possible connection of the invisible decay product with Dark Matter.Comment: 5 pages, 2 figures. v2: typos corrected, references and clarifications adde

Radiative Corrections to Dark Matter Indirect Signals

The computation of the energy spectra of Standard Model particles originated from the annihilation/decay of Dark Matter is of primary importance in indirect searches for Dark Matter. We compute such spectra for a large set of DM masses and annihilation/decay channels. In doing so, we employ the Monte Carlo simulation program HERWIG, and compare our results with the same analyses done with PYTHIA, obtaining in this way an estimation of the MC errors in the fluxes. MC parton shower programs do not include electroweak radiation effects, that are relevant when the DM mass is of the order of a TeV or higher, like experiments seem to suggest. Thus we consider a model-independent inclusion of electroweak corrections in the computation of the spectra by means of a new general partonic technique, and we check it by comparing the results of its application with a full computation we perform in the specific Minimal Dark Matter model, finding a very good agreement. In this model the two natural candidates for DM are a fermionic quintuplet and a scalar eptaplet, their only annihilation channel is into gauge bosons. For the both of them we consider the three body processes DM DM -> W W gamma and DM DM -> W W Z and perform the full computation of the gamma, W and Z energy spectra dN/dE. Incidentally we also find that at O(M_W/M), with M DM mass, the results are the same for both scalar and fermionic DM

Homeopathic Dark Matter, or how diluted heavy substances produce high energy cosmic rays

We point out that current and planned telescopes have the potential of probing annihilating Dark Matter (DM) with a mass of O(100) TeV and beyond. As a target for such searches, we propose models where DM annihilates into lighter mediators, themselves decaying into Standard Model (SM) particles. These models allow to reliably compute the energy spectra of the SM final states, and to naturally evade the unitarity bound on the DM mass. Indeed, long-lived mediators may cause an early matter-dominated phase in the evolution of the Universe and, upon decaying, dilute the density of preexisting relics thus allowing for very large DM masses. We compute this dilution in detail and provide results in a ready-to-use form. Considering for concreteness a model of dark U(1) DM, we then study both dilution and the signals at various high energy telescopes observing gamma rays, neutrinos and charged cosmic rays. This study enriches the physics case of these experiments, and opens a new observational window on heavy new physics sectors.Comment: 39 pages, 11 figures. v2: reference added, fixed technical issue causing 2 figures not to show properly. v3: BBN constraints amended, conclusions unchanged. Matches published versio

New LHC bound on low-mass diphoton resonances

We derive a new bound on diphoton resonances using inclusive diphoton cross section measurements at the LHC, in the so-far poorly constrained mass range between the Upsilon and the SM Higgs. This bound sets the current best limit on axion-like particles that couple to gluons and photons, for masses between 10 and 65 GeV. We also estimate indicative sensitivities of a dedicated diphoton LHC search in the same mass region, at 7, 8 and 14 TeV. As a byproduct of our analysis, we comment on the axion-like particle interpretation of the CMS excesses in low-mass dijet and diphoton searches.Comment: 7 pages + appendices, 5 figures, 2 tables. v2: discussion improved, new bound derived also from Tevatron, conclusions unchanged. v3: matches PLB versio

Gamma ray tests of Minimal Dark Matter

We reconsider the model of Minimal Dark Matter (a fermionic, hypercharge-less quintuplet of the EW interactions) and compute its gamma ray signatures. We compare them with a number of gamma ray probes: the galactic halo diffuse measurements, the galactic center line searches and recent dwarf galaxies observations. We find that the original minimal model, whose mass is fixed at 9.4 TeV by the relic abundance requirement, is constrained by the line searches from the Galactic Center: it is ruled out if the Milky Way possesses a cuspy profile such as NFW but it is still allowed if it has a cored one. Observations of dwarf spheroidal galaxies are also relevant (in particular searches for lines), and ongoing astrophysical progresses on these systems have the potential to eventually rule out the model. We also explore a wider mass range, which applies to the case in which the relic abundance requirement is relaxed. Most of our results can be safely extended to the larger class of multi-TeV WIMP DM annihilating into massive gauge bosons.Comment: 25 pages, 8 figures. v2: a few comments and references added, matches version published on JCA

One or more Higgs bosons?

Now that one has been found, the search for signs of more scalars is a primary task of current and future experiments. In the motivated hypothesis that the extra Higgs bosons of the next-to-minimal supersymmetric Standard Model (NMSSM) be the lightest new particles around, we outline a possible overall strategy to search for signs of the CP-even states. This work complements Ref. arXiv:1304.3670.Comment: 14 pages, 7 figures. v2: references added, published in PR