Paolo Gondolo

Neutralino relic density including coannihilations

We evaluate the relic density of the lightest neutralino, the lightest supersymmetric particle, in the minimal supersymmetric extension of the standard model. For the first time, we include all coannihilation processes between neutralinos and charginos for any neutralino mass and composition. We use the most sophisticated routines for integrating the cross sections and the Boltzmann equation. We properly treat (sub)threshold and resonant annihilations. We also include one-loop corrections to neutralino masses. We find that coannihilation processes are important not only for light Higgsino-like neutralinos, as pointed out before, but also for heavy Higgsinos and for mixed and gauginolike neutralinos. Indeed, coannihilations should be included whenever {vert_bar}{mu}{vert_bar}{approx_lt}2{vert_bar}M{sub 1}{vert_bar}, independently of the neutralino composition. When {vert_bar}{mu}{vert_bar}{approximately}{vert_bar}M{sub 1}{vert_bar}, coannihilations can increase or decrease the relic density in and out of the cosmologically interesting region. We find that there is still a window of light Higgsino-like neutralinos that are viable dark matter candidates and that coannihilations shift the cosmological upper bound on the neutralino mass from 3 to 7 TeV. {copyright} {ital 1997} {ital The American Physical Society}

DARK MATTER ANNIHILATION AT THE GALACTIC CENTER

Cold dark matter near the galactic center is accreted by the central black hole into a dense spike. Particle dark matter annihilation makes the spike a compact source of photons, electrons, positrons, protons, antiprotons, and neutrinos. The spike luminosity depends on the halo density profile: halos with finite cores have unnoticeable spikes; halos with inner cusps may have spikes so bright that the absence of a neutrino signal from the galactic center already places upper limits on the density slope of the inner halo. Future neutrino telescopes observing the galactic center could probe the inner structure of the dark halo or indirectly find the nature of dark matter.

Accurate relic densities with neutralino, chargino and sfermion coannihilations in mSUGRA

Neutralinos arise as natural dark matter candidates in many supersymmetric extensions of the Standard Model. We present a novel calculation of the neutralino relic abundance in which we include all so-called coannihilation processes between neutralinos, charginos and sfermions, and, at the same time, we apply the state of the art technique to trace the freeze-out of a species in the early Universe. As a first application, we discuss here results valid in the mSUGRA framework; we describe general trends as well as performing a detailed study of the neutralino relic densities in the mSUGRA parameter space. The emerging picture is fair agreement with previous analyses in the same framework, however we have the power to discuss it in much more detail than previously done. For example, we find that the cosmological bound on the neutralino mass is pushed up to ~565 GeV in the stau coannihilation region and to ~1500 GeV in the chargino coannihilation region.

Clumpy neutralino dark matter

We investigate the possibility to detect neutralino dark matter in a scenario in which the galactic dark halo is clumpy. We find that under customary assumptions on various astrophysical parameters, the antiproton and continuum

Neutralino annihilation into two photons

\ensuremath{\gamma}

A New model independent method for extracting spin dependent (cross-section) limits from dark matter searches

-ray signals from neutralino annihilation in the halo put the strongest limits on the clumpiness of a neutralino halo. We argue that indirect detection through neutrinos from the Earth and the Sun should not be affected much by clumpiness. We identify situations in parameter space where the

Indirect detection of dark matter in km size neutrino telescopes

\ensuremath{\gamma}

WIMP annual modulation with opposite phase in Late-Infall halo models

-ray line, positron and diffuse neutrino signals from annihilations in the halo may provide interesting signals in upcoming detectors.

Future Type Ia Supernova Data as Tests of Dark Energy from Modified Friedmann Equations

Abstract We compute the annihilation cross-section of two neutralinos at rest into two photons, which is of importance for the indirect detection of neutralino dark matter in the galactic halo through a quasi-monochromatic gamma-ray line. We include all diagrams to one-loop level in the minimal supersymmetric extension of the standard model. We use the helicity formalism, the background-field gauge, and an efficient loop-integral reduction method. We confirm the result recently obtained by Bergstrom and Ullio in a different gauge, which disagrees with other published calculations.

Fluid interpretation of Cardassian expansion

Abstract A new method is proposed for extracting limits on spin-dependent WIMP-nucleon interaction cross sections from direct detection dark matter experiments. The new method has the advantage that the limits on individual WIMP-proton and WIMP-neutron cross sections for a given WIMP mass can be combined in a simple way to give a model-independent limit on the properties of WIMPs scattering from both protons and neutrons in the target nucleus. Extension of the technique to the case of a target material consisting of several different species of nuclei is discussed.