Phenomenology of light neutralinos in view of recent results at the CERN Large Hadron Collider

We review the status of the phenomenology of light neutralinos in an effective Minimal Supersymmetric extension of the Standard Model (MSSM) at the electroweak scale, in light of new results obtained at the CERN Large Hadron Collider. First we consider the impact of the new data obtained by the CMS Collaboration on the search for the Higgs boson decay into a tau pair, and by the CMS and LHCb Collaborations on the branching ratio for the decay $B_s \rightarrow {\mu}^{+} + {\mu}^{-}$. Then we examine the possible implications of the excess of events found by the ATLAS and CMS Collaborations in a search for a SM--like Higgs boson around a mass of 126 GeV, with a most likely mass region (95% CL) restricted to 115.5--131 GeV (global statistical significance about 2.3 $\sigma$). From the first set of data we update the lower bound of the neutralino mass to be about 18 GeV. From the second set of measurements we derive that the excess around $m^{SM}_H$ = 126 GeV, which however needs a confirmation by further runs at the LHC, would imply a neutralino in the mass range 18 GeV \lsim m_{\chi} \lsim 38 GeV, with neutralino--nucleon elastic cross sections fitting well the results of the dark matter direct search experiments DAMA/LIBRA and CRESST.Comment: 10 pages, 6 figures, typeset with ReVTeX4. v2:discussion on LHC Higgs excess extended and one figure added. Matches version accepted for publication on Phys.Rev.D. A version of the paper with full resolution figures can be found at http://www.to.infn.it/~scopel/phenom_v2.pd

Positrons from dark matter annihilation in the galactic halo: uncertainties

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 show that, especially in the low energy tail of the positron spectra at Earth, the uncertainty is sizeable and we quantify the effect. Comparison of our predictions with current available and foreseen experimental data are derived.Comment: 4 pages, 4 figures, Proc. of the 30th International Cosmic Ray Conference, July 3 - 11, 2007, Merida, Yucatan, Mexico (ICRC07

Positrons from dark matter annihilation in the galactic halo: theoretical uncertainties

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.Comment: 22 pages, 15 figures. A few comments and references adde

Interpretation of AMS-02 electrons and positrons data

We perform a combined analysis of the recent AMS-02 data on electrons, positrons, electrons plus positrons and positron fraction, in a self-consistent framework where we realize a theoretical modeling of all the astrophysical components that can contribute to the observed fluxes in the whole energy range. The primary electron contribution is modeled through the sum of an average flux from distant sources and the fluxes from the local supernova remnants in the Green catalog. The secondary electron and positron fluxes originate from interactions on the interstellar medium of primary cosmic rays, for which we derive a novel determination by using AMS-02 proton and helium data. Primary positrons and electrons from pulsar wind nebulae in the ATNF catalog are included and studied in terms of their most significant (while loosely known) properties and under different assumptions (average contribution from the whole catalog, single dominant pulsar, a few dominant pulsars). We obtain a remarkable agreement between our various modeling and the AMS-02 data for all types of analysis, demonstrating that the whole AMS-02 leptonic data admit a self-consistent interpretation in terms of astrophysical contributions.Comment: 33 pages, 26 figures and 4 tables, v2: accepted for publication in JCAP, minor changes relative to v

Thermal Relics in Modified Cosmologies: Bounds on Evolution Histories of the Early Universe and Cosmological Boosts for PAMELA

Alternative cosmologies, based on extensions of General Relativity, predict modified thermal histories in the Early Universe during the pre Big Bang Nucleosynthesis (BBN) era, epoch which is not directly constrained by cosmological observations. When the expansion rate is enhanced with respect to the standard case, thermal relics typically decouple with larger relic abundances. The correct value of the relic abundance is therefore obtained for larger annihilation cross--sections, as compared to standard cosmology. A direct consequence is that indirect detection rates are enhanced. Extending previous analyses of ours, we derive updated astrophysical bounds on the dark matter annihilation cross sections and use them to constrain alternative cosmologies in the pre--BBN era. We also determine the characteristics of these alternative cosmologies in order to provide the correct value of relic abundance for a thermal relic for the (large) annihilation cross--section required to explain the PAMELA results on the positron fraction, therefore providing a "cosmological boost" solution to the dark matter interpretation of the PAMELA data.Comment: 19 pages, 27 figures, matches published versio

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.Comment: 13 pages, 7 figure