Graciela B. Gelmini

Cosmic abundances of stable particles: Improved analysis

Abstract An exact relativistic single-integral formula for the thermal average of the annihilation cross section times velocity, the key quantity in the determination of the cosmic relic abundance of a species, is obtained. Since it does not require expansion of the cross section at low relative velocity, it can also be used when the cross section varies rapidly with energy, e.g. near the formation of a resonance or the opening of a new annihilation channel. We discuss approximate formulas in these cases, and we find that dips in the relic density near resonances are significantly broader and shallower than previously thought and that spurious reductions near thresholds disappear.

Compatibility of DAMA/LIBRA dark matter detection with other searches

The DAMA/NaI and DAMA/LIBRA annual modulation data, which may be interpreted as a signal for the existence of weakly interacting dark matter (WIMPs) in our galactic halo, are examined in light of null results from other experiments: CDMS, XENON10, CRESST I, CoGeNT, TEXONO, and Super-Kamiokande (SuperK). We use the energy spectrum of the combined DAMA modulation data given in 36 bins, and include the effect of channeling. Several statistical tools are implemented in our study: likelihood ratio with a global fit and with raster scans in the WIMP mass and goodness-of-fit (g.o.f.). These approaches allow us to differentiate between the preferred (global best fit) and allowed (g.o.f.) parameter regions. It is hard to find WIMP masses and couplings consistent with all existing data sets; the surviving regions of parameter space are found here. For spin-independent (SI) interactions, the best fit DAMA regions are ruled out to the 3σ C.L., even with channeling taken into account. However, for WIMP masses of ~ 8 GeV some parameters outside these regions still yield a moderately reasonable fit to the DAMA data and are compatible with all 90% C.L. upper limits from negative searches, when channeling is included. For spin-dependent (SD) interactions with proton-only couplings, a range of masses below 10 GeV is compatible with DAMA and other experiments, with and without channeling, when SuperK indirect detection constraints are included; without the SuperK constraints, masses as high as ~ 20 GeV are compatible. For SD neutron-only couplings we find no parameters compatible with all the experiments. Mixed SD couplings are examined: e.g. ~ 8 GeV mass WIMPs with an = ±ap are found to be consistent with all experiments. In short, there are surviving regions at low mass for both SI and SD interactions; if indirect detection limits are relaxed, some SD proton-only couplings at high masses also survive.

Astrophysical constraints on massive unstable neutral relic particles

Abstract There has recently been renewed interest in massive neutral dark-matter particle candidates with masses greater than ∼ 1 TeV which may be unstable. We re-evaluate the constraints on such particles from the possible effects of their decays on the spectrum of the microwave background-radiation and the primordially synthesised abundances of the light elements, from observations of the diffuse gamma-ray background radiation, and from searches for muons and neutrinos in nucleon-decay and cosmic-ray detectors. We find that such unstable neutral relics may well have the cosmological critical density if their lifetime exceeds ∼ 1016 yr. We illustrate our arguments by applying them to technicolour baryons and to “cryptons” in superstring-inspired models.

Neutralino with the right cold dark matter abundance in (almost) any supersymmetric model

We consider nonstandard cosmological models in which the late decay of a scalar field

XENON10/100 dark matter constraints in comparison with CoGeNT and DAMA: examining the Leff dependence

\ensuremath{\phi}

Neutralino dark matter searches

reheats the Universe to a low reheating temperature, between 5 MeV and the standard freeze-out temperature of neutralinos of mass

Effect of a late decaying scalar on the neutralino relic density

{m}_{\ensuremath{\chi}}

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

. We point out that in these models all neutralinos with standard density

Cosmic neutrinos from unstable relic particles

{\ensuremath{\Omega}}_{\mathrm{std}}\ensuremath{\gtrsim}{10}^{\ensuremath{-}5}(100\text{ }\text{ }\mathrm{GeV}/{m}_{\ensuremath{\chi}})

Generalized halo independent comparison of direct dark matter detection data

can have the density of cold dark matter, provided the right combination of the following two parameters can be achieved in the high-energy theory: the reheating temperature, and the ratio of the number of neutralinos produced per