Cosmic antiprotons as a probe for supersymmetric dark matter?
L. Bergstrom, J. Edsjo, P. Ullio
TL;DR
Cosmic antiprotons are proposed as a probe of neutralino dark matter in the MSSM by computing the antiproton flux from halo annihilations across a broad model set and by revisiting the low-energy secondary background with energy loss and interstellar nuclei effects. The authors model propagation with a two-zone diffusion framework, with and without a galactic wind, and provide convenient parametrizations of antiproton yields for two-body final states. They find that, given current background uncertainties, no exotic primary component is required to explain present data, though certain MSSM scenarios can match observations if background uncertainties are exploited; the optimal SUSY signal energy can lie above several GeV rather than in the sub-GeV region. The large astrophysical uncertainties prevent exclusion of the considered MSSM models, and limits on the antiproton lifetime remain difficult due to possible neutralino-induced injection compensating decay losses. These results guide search strategies for experiments like PAMELA and AMS by highlighting energy ranges and background complexities.
Abstract
The flux of cosmic ray antiprotons from neutralino annihilations in the galactic halo is computed for a large sample of models in the MSSM (the Minimal Supersymmetric extension of the Standard Model). We also revisit the problem of estimating the background of low-energy cosmic ray induced secondary antiprotons, taking into account their subsequent interactions (and energy loss) and the presence of nuclei in the interstellar matter. We consider a two-zone diffusion model, with and without a galactic wind. We find that, given the uncertainties in the background predictions, there is no need for a primary (exotic) component to explain present data. However, allowing for a signal by playing with the uncertainties in the background estimate, we discuss the characteristic features of the supersymmetric models which give a satisfactory description of the data. We point out that in some cases the optimal kinetic energy to search for a signal from supersymmetric dark matter is above several GeV, rather than the traditional sub-GeV region. The large astrophysical uncertainties involved do not, one the other hand, allow the exclusion of any of the MSSM models we consider, on the basis of data. We present besides numerical results also convenient parameterizations of the antiproton yields of all `basic' two-body final states. We also give examples of the yield and differential energy spectrum for a set of supersymmetric models with high rates. We also remark that it is difficult to put a limit on the antiproton lifetime from present measurements, since the injection of antiprotons from neutralino annihilation can compensate the loss from decay.