A. Bottino

Neutralino dark matter in supersymmetric models with non-universal scalar mass terms

Abstract Neutralino dark matter is studied in the context of a supergravity scheme where the soft scalar mass terms are not constrained by universality conditions at the grand unification scale. We analyse in detail the consequences of the relaxation of this universality assumption on the supersymmetric parameter space, on the neutralino relic abundance and on the event rate for the direct detection of relic neutralinos.

Probing the supersymmetric parameter space by weakly interacting massive particle direct detection

We discuss to which extent the present experiments of direct search for WIMPs, when interpreted in terms of relic neutralinos, probe interesting regions of the supersymmetric parameter space, which are also being progressively explored at accelerators. Our analysis is performed in a number of different supersymmetric schemes. We derive the relevant neutralino cosmological properties, locally and on the average in the universe. We prove that part of the susy configurations probed by current WIMP experiments entail relic neutralinos of cosmological interest. The main astrophysical and particle physics uncertainties, relevant for a proper comparison between theory and experimental data, are stressed and taken into account.

Implications for relic neutralinos of the theoretical uncertainties in the neutralino nucleon cross-section

Abstract We discuss the effect induced on the neutralino–nucleon cross section by the present uncertainties in the values of the quark masses and of the quark scalar densities in the nucleon. We examine the implications of this aspect on the determination of the neutralino cosmological properties, as derived from measurements of WIMP direct detection. We show that, within current theoretical uncertainties, the DAMA annual modulation data are compatible with a neutralino as a major dark matter component, to an extent which is even larger than the one previously derived. We also comment on implications of the mentioned uncertainties for experiments of indirect dark matter detection.

Observations of annual modulation in direct detection of relic particles and light neutralinos

The long-standing model-independent annual modulation effect measured by the DAMA Collaboration, which fulfills all the requirements of a dark matter annual modulation signature, and the new result by the CoGeNT experiment that shows a similar behavior are comparatively examined under the hypothesis of a dark matter candidate particle interacting with the detectors’ nuclei by a coherent elastic process. The ensuing physical regions in the plane of the dark matter-particle mass versus the dark matter-particle nucleon cross-section are derived for various galactic halo models and by taking into account the impact of various experimental uncertainties. It is shown that the DAMA and the CoGeNT regions agree well between each other and are well fitted by a supersymmetric model with light neutralinos which satisfies all available experimental constraints, including the most recent results from CMS and ATLAS at the CERN Large Hadron Collider.

Light neutralinos and WIMP direct searches

The predictions of our previous analyses about possible low-mass (lower than 50 GeV) relic neutralinos are discussed in the light of the most recent results from WIMP direct detection experiments. It is proved that these light neutralinos are quite compatible with the new annual-modulation data of the DAMA Collaboration; our theoretical predictions are also compared with the upper bounds of the CDMS and EDELWEISS Collaborations.

Extending the DAMA annual-modulation region by inclusion of the uncertainties in astrophysical velocities

The original annual-modulation region, singled out by the DAMA/NaI experiment for direct detection of WIMPs, is extended by taking into account the uncertainties in the galactic astrophysical velocities. Also the effect due to a possible bulk rotation for the dark matter halo is considered. We find that the range for the WIMP mass becomes 30 GeV < m_chi < 130 GeV at 1-sigma C.L. with a further extension in the upper bound, when a possible bulk rotation of the dark matter halo is taken into account. We show that the DAMA results, when interpreted in the framework of the Minimal Supersymmetric extension of the Standard Model, are consistent with a relic neutralino as a dominant component of cold dark matter (on the average in our universe and in our galactic halo). It is also discussed the discovery potential for the relevant supersymmetric configurations at accelerators of present generation.

Exploring the supersymmetric parameter space by direct search for WIMPs

Abstract It is shown that the new data of the DAMA/NaI detector, combined with recent calculations of nuclear structure functions, provide the most stringent upper bounds on the WIMP-nucleon cross-section both for spin-dependent and for scalar interactions. It is proved that, for the first time, data from an experiment of direct search for WIMPs allow the exploration of a region of the supersymmetric parameter space not yet fully investigated at accelerators.

High-energy gamma radiation from the galactic center due to neutralino annihilation

Abstract We study the NGS (Non-dissipative Gravitational Singularity) model, which successfully describes the non-linear stage of evolution of perturbations (see Gurevich and Zybin, Sov. Phys. JETP 67 (1988) 1; Berezinsky; Gurevich and Zybin, Phys. Lett. B 294 (1992) 221; and references therein). This model predicts the DM density distribution ϱ ( r )∼ r − α with α⋍1.8 which holds from very small distances r min ⋍0.01 pc up to very large distances r max ⋍5 Mpc . Assuming the neutralino to be a CDM particle, we calculate the annihilation of neutralinos in the vicinity of the singularity (Galactic Center). If neutralinos are the dominant component of DM in our Galaxy, the produced energy is enough to provide the whole observed activity of the GC. Neutralinos of the most general composition and of mass in the range 20 GeV≲ m χ ≲1 TeV are considered. We find the neutralino compositions which give the relic density needed for the Mixed Dark Matter (MDM) model and we evaluate for these compositions the high-energy ( E γ >100 Mev ) gamma-ray flux under the constraint that the radio flux is lower than the observational limit. The compositions with the detectable gamma-ray flux which we found are provided by a set of almost pure gaugino states with the neutralino mass between 100 and 500 GeV. We demonstrate that a detectable high-energy gamma-ray flux is produced by the neutralino annihilation also in the case when neutralinos provide a small fraction (down to 0.1%) of the DM in our Galaxy. The predicted flux is F γ ∼ 10 −7 −10 −8 cm −2 s −1 for E γ ≳300 MeV

Size of the neutralino–nucleon cross-section in the light of a new determination of the pion–nucleon sigma term

Abstract We discuss the implications of a new determination of the pion–nucleon sigma term for the evaluation of the neutralino–nucleon cross-section, and, in turn, for detection rates for relic neutralinos in WIMP direct experiments and in some of the indirect searches. It is shown that the new range for the pion–nucleon sigma term, taken at its face value, favours values of the neutralino–nucleon cross-sections which are sizeably larger than some of the current estimates. Implications for neutralino cosmological properties are derived.

Which fraction of the measured cosmic-ray antiprotons might be due to neutralino annihilation in the galactic halo?

We analyze the data of the low-energy cosmic-ray