Cosmic-ray nuclei Ñuxes are expected to be measured with high precision in the near future. For instance, high-quality data on the antiproton component could give important clues about the nature of the astronomical dark matter. A very good understanding of the di †erent aspects of cosmic-ray propagation is therefore necessary. In this paper, we use cosmic-ray nuclei data to give constraints on the di †u-sion parameters. Propagation is studied with semianalytical solutions of a di †usion model, and we give new analytical solutions for radioactively produced species. Our model includes convection and reacceleration, as well as the standard energy losses. We perform a s2 analysis over B/C data for a large number of conÐgurations obtained by varying the relevant parameters of the di †usion model. A very good agreement with B/C data arises for a number of conÐgurations, all of which are compatible with sub-Fe/Fe data. Di †erent source spectra Q(E) and di †usion coefficients K(E) have been tried, but for both parameters only one form gives a good Ðt. Another important result is that models without convection or without reacceleration are excluded. We Ðnd that the various parameters, i.e., the di †usion coefficient normalization and spectral index d, the halo thickness L , the velocity and the K 0 Alfven V A , convection velocity are strongly correlated. We obtain limits on the spectral index d of the di †usion V c coefficient, and in particular we exclude a Kolmogorov spectrum (d \ 13 ).

We calculate the antiproton flux due to relic neutralino annihilations, in a two-dimensional diffusion model compatible with stable and radioactive cosmic ray nuclei. We find that the uncertainty in the primary flux induced by the propagation parameters alone is about two orders of magnitude at low energies, and it is mainly determined by the lack of knowledge on the thickness of the diffusive halo. On the contrary, different dark matter density profiles do not significantly alter the flux: a NFW distribution produces fluxes which are at most 20% higher than an isothermal sphere. The most conservative choice for propagation parameters and dark matter distribution normalization, together with current data on cosmic antiprotons, cannot lead to any definitive constraint on the supersymmetric parameter space, neither in a low-energy effective MSSM, or in a minimal SUGRA scheme. However, if the best choice for propagation parameters -corresponding to a diffusive halo of L = 4 kpc -is adopted, some supersymmetric configurations with the neutralino mass mχ < ∼ 100 GeV should be considered as excluded. An enhancement flux factor -due for instance to a clumpy dark halo or to a higher local dark matter density -would imply a more severe cut on the supersymmetric parameters.PACS numbers: 95.35.+d,98.35.Gi,98.35.Pr,98.70.Sa,11.30.Pb,12.60.Jv,95.30.Cq

No abstract

Once the energy spectrum of the secondary component is well understood, measurements of the antiproton cosmic-ray flux at the Earth will be a powerful way to indirectly probe for the existence of supersymmetric relics in the galactic halo. Unfortunately, it is still spoilt by considerable theoretical uncertainties. As shown in this work, searches for low-energy antideuterons appear in the mean time as a plausible alternative, worth being explored. Above a few GeV/n, a dozen spallation antideuterons should be collected by the future AMS experiment on board ISSA. For energies less than ∼ 3 GeV/n, theD spallation component becomes negligible and may be supplanted by a potential supersymmetric signal. If a few low-energy antideuterons are discovered, this should be seriously taken as a clue for the existence of massive neutralinos in the Milky Way.

Indirect detection signals from dark matter annihilation are studied in the positron channel. We discuss in detail the positron propagation inside the galactic medium: we present novel solutions of the diffusion and propagation equations and we focus on the determination of the astrophysical uncertainties which affect the positron dark matter signal. We find dark matter scenarios and propagation models that nicely fit existing data on the positron fraction. Finally, we present predictions both on the positron fraction and on the flux for already running or planned space experiments, concluding that they have the potential to discriminate a possible signal from the background and, in some cases, to distinguish among different astrophysical propagation models. PACS numbers: 95.35.+d,98.35.Gi,11.30.Pb,95.30.Cq

We present a new module of micrOMEGAs devoted to the computation of indirect signals from dark matter annihilation in any new model with a stable weakly interacting particle. The code provides the mass spectrum, cross-sections, relic density and exotic fluxes of gamma rays, positrons and antiprotons. The propagation of charged particles in the Galactic halo is handled with a new module that allows to easily modify the propagation parameters. Program summaryProgram title: micrOMEGAs2.4 Catalogue identifier: ADQR_v2_3 Program summary URL: RAM: 50 MB depending on the number of processes required Classification: 1.9, 11.6 Catalogue identifier of previous version: ADQR_v2_3 Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 747 Does the new version supersede the previous version?: Yes Nature of problem: Calculation of the relic density and detection rates of the lightest stable particle in a generic new model of particle physics. Solution method: In numerically solving the evolution equation for the density of dark matter, relativistic formulas for the thermal average are used. All tree-level processes for annihilation and coannihilation of new particles in the model are included. The cross-sections for all processes are calculated exactly with CalcHEP after definition of a model file. The propagation of the charged cosmic rays is solved within a semi-analytical two-zone model. Reasons for new version:There are many experiments that are currently searching for the remnants of dark matter annihilation. In this version we perform the computation of indirect signals from dark matter annihilation in any new model with a stable weakly interacting particle. We include the propagation of charged particles in the Galactic halo. Summary of revisions:• Annihilation cross-sections for all 2-body tree-level processes and for radiative emission of a photon for all models.• Annihilation cross-sections into polarised gauge bosons.• Annihilation cross-sections for the loop induced processes γ γ and γ Z 0 in the MSSM.• Modelling of the DM halo with a general parameterization and with the possibility of including DM clumps.• Computation of the propagation of charged particles through the Galaxy, including the possibility of modifying the propagation parameters.• Effect of solar modulation on the charged particle spectrum.• Model independent predictions of the indirect detection signals.Unusual features: Depending on the parameters of the model, the program generates additional new code, compiles it and loads it dynamically. Running time: 3 sec

Context. Secondary positrons are produced by spallation of cosmic rays within the interstellar gas. Measurements have been typically expressed in terms of the positron fraction, which exhibits an increase above 10 GeV. Many scenarios have been proposed to explain this feature, among them some additional primary positrons originating from dark matter annihilation in the Galaxy. Aims. The PAMELA satellite has provided high quality data that has enabled high accuracy statistical analyses to be made, showing that the increase in the positron fraction extends up to about 100 GeV. It is therefore of paramount importance to constrain theoretically the expected secondary positron flux to interpret the observations in an accurate way. Methods. We focus on calculating the secondary positron flux by using and comparing different up-to-date nuclear cross-sections and by considering an independent model of cosmic ray propagation. We carefully study the origins of the theoretical uncertainties in the positron flux. Results. We find the secondary positron flux to be reproduced well by the available observations, and to have theoretical uncertainties that we quantify to be as large as about one order of magnitude. We also discuss the positron fraction issue and find that our predictions may be consistent with the data taken before PAMELA. For PAMELA data, we find that an excess is probably present after considering uncertainties in the positron flux, although its amplitude depends strongly on the assumptions made in relation to the electron flux. By fitting the current electron data, we show that when considering a soft electron spectrum, the amplitude of the excess might be far lower than usually claimed. Conclusions. We provide fresh insights that may help to explain the positron data with or without new physical model ingredients. PAMELA observations and the forthcoming AMS-02 mission will allow stronger constraints to be aplaced on the cosmic-ray transport parameters, and are likely to reduce drastically the theoretical uncertainties.

The archetypal model for the recently discovered dark energy component of the universe is based on the existence of a scalar field whose dynamical evolution comes down today to a non-vanishing cosmological constant. In the past -before big-bang nucleosynthesis for that matter -that scalar field could have gone through a period of kination during which the universe has expanded at a much higher pace than what is currently postulated in the standard radiation dominated cosmology. I examine here the consequences of such a period of kination on the relic abundance of neutralinos and find that the latter could be much higher -by three orders of magnitude -than what is estimated in the canonical derivation. I shortly discuss the implications of this scenario for the dark matter candidates and their astrophysical signatures.