Marco Cirelli

Minimal Dark Matter

Abstract A few multiplets that can be added to the SM contain a lightest neutral component which is automatically stable and provides allowed DM candidates with a non-standard phenomenology. Thanks to coannihilations, a successful thermal abundance is obtained for well defined DM masses. The best candidate seems to be a SU ( 2 ) L fermion quintuplet with mass 4.4 TeV, accompanied by a charged partner 166 MeV heavier with life-time 1.8 cm , that manifests at colliders as charged tracks disappearing in π ± with 97.7% branching ratio. The cross section for usual NC direct DM detection is σ SI = f 2 1.0 × 10 −43 cm 2 where f ∼ 1 is a nucleon matrix element. We study prospects for CC direct detection and for indirect detection.

Model-independent implications of the e±, p¯ cosmic ray spectra on properties of Dark Matter

Abstract Taking into account spins, we classify all two-body non-relativistic Dark Matter annihilation channels to the allowed polarization states of Standard Model particles, computing the energy spectra of the stable final-state particles relevant for indirect DM detection. We study the DM masses, annihilation channels and cross sections that can reproduce the PAMELA indications of an e + excess consistently with the PAMELA p ¯ data and the ATIC/PPB-BETS e + + e − data. From the PAMELA data alone, two solutions emerge: (i) either the DM particles that annihilate into W , Z , h must be heavier than about 10 TeV or (ii) the DM must annihilate only into leptons. Thus in both cases a DM particle compatible with the PAMELA excess seems to have quite unexpected properties. The solution (ii) implies a peak in the e + + e − energy spectrum, which, indeed, seems to appear in the ATIC/PPB-BETS data around 700 GeV. If upcoming data from ATIC-4 and GLAST confirm this feature, this would point to a O ( 1 ) TeV DM annihilating only into leptons. Otherwise the solution (i) would be favored. We comment on the implications of these results for DM models, direct DM detection and colliders as well as on the possibility of an astrophysical origin of the excess.

Cosmology and Astrophysics of Minimal Dark Matter

Abstract We consider DM that only couples to SM gauge bosons and fills one gauge multiplet, e.g., a fermion 5-plet (which is automatically stable), or a wino-like 3-plet. We revisit the computation of the cosmological relic abundance including non-perturbative corrections. The predicted mass of, e.g., the 5-plet increases from 4.4 to 10 TeV, and indirect detection rates are enhanced by 2 orders of magnitude. Next, we show that due to the quasi-degeneracy among neutral and charged components of the DM multiplet, a significant fraction of DM with energy E ≳ 10 17 eV (possibly present among ultra-high energy cosmic rays) can cross the Earth exiting in the charged state and may in principle be detected in neutrino telescopes.

Gamma-ray and radio tests of the e± excess from DM annihilations

PAMELA and ATIC recently reported an excess in e± cosmic rays. We show that if it is due to Dark Matter annihilations, the associated gamma-ray flux and the synchrotron emission produced by e± in the galactic magnetic field violate HESS and radio observations of the galactic center and HESS observations of dwarf spheroidals, unless the DM density profile is significantly less steep than the benchmark NFW and Einasto profiles.

Minimal Dark Matter predictions for galactic positrons, anti-protons, photons

Abstract We present the energy spectra of the fluxes of positrons, anti-protons and photons generated by Dark Matter annihilations in our galaxy, as univocally predicted by the model of Minimal Dark Matter. Due to multi-TeV masses and to the Sommerfeld enhancement of the annihilation cross section, distinctive signals can be generated above the background, even with a modest astrophysical boost factor, in the range of energies soon to be explored by cosmic ray experiments.

Minimal dark matter: model and results

We recap the main features of minimal dark matter (MDM) and assess its status in the light of recent experimental data. The theory selects an electroweak 5-plet with hypercharge Y=0 as a fully successful DM candidate, automatically stable against decay and with no free parameters: DM is a fermion with a 9.6?TeV mass. The direct detection cross-section, predicted to be 10?44?cm2, is within reach of next-generation experiments. DM is accompanied by a charged fermion 166?MeV heavier: we discuss how it might manifest. Thanks to an electroweak Sommerfeld enhancement of more than 2 orders of magnitude, DM annihilations into W+W? give, in the presence of a modest astrophysical boost factor, an e+ flux compatible with the PAMELA excess (but not with the ATIC hint for a peak: MDM instead predicts a quasi-power-law spectrum), a flux concentrated at energies above 100?GeV, and photon fluxes comparable with present limits, depending on the DM density profile.

Tools for model-independent bounds in direct dark matter searches

We discuss a framework (based on non-relativistic operators) and a self-contained set of numerical tools to derive the bounds from some current direct detection experiments on virtually any arbitrary model of Dark Matter elastically scattering on nuclei.

Inverse Compton constraints on the Dark Matter e+e- excesses

Abstract Recent results from experiments like PAMELA have pointed to excesses of e ± in cosmic rays. If interpreted in terms of Dark Matter annihilations, they imply the existence of an abundant population of e ± in the galactic halo at large. We consider the high energy gamma ray fluxes produced by Inverse Compton Scattering of interstellar photons on such e ± , and compare them with the available data from EGRET and some preliminary data from FERMI. We consider different observation regions of the sky and a range of DM masses, annihilation channels and DM profiles. We find that large portions of the parameter space are excluded, in particular for DM masses larger than 1 TeV, for leptonic annihilation channels and for benchmark Einasto or NFW profiles.

Probing oscillations into sterile neutrinos with cosmology, astrophysics and experiments

Abstract We perform 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. We consider the following probes: solar, atmospheric, reactor and beam neutrinos, big-bang nucleosynthesis (helium-4, deuterium), cosmic microwave background, large scale structure, supernovae, neutrinos from other astrophysical sources. We find no evidence for a sterile neutrino in present data, identify the still allowed regions, and study which future experiments can best probe them: sub-MeV solar experiments, more precise studies of CMB or BBN, future supernova explosions, etc. We discuss how the LSND hint is strongly disfavoured by the constraints of (standard) cosmology.

Antiproton constraints on the GeV gamma-ray excess: a comprehensive analysis

A GeV gamma-ray excess has possibly been individuated in Fermi-LAT data from the Galactic Center and interpreted in terms of Dark Matter (DM) annihilations, either in hadronic (essentially