Unified interpretation of cosmic ray nuclei and antiproton recent measurements

Abstract

We use our numerical code, DRAGON, to study the implications of recent data on our knowledge of the propagation properties of cosmic ray nuclei in the Galaxy. We show that B/C (as well as N/O and C/O) data, including those recently taken by CREAM, andp/p data, especially including recent PAMELA results, can consistently be fitted within a unique diffusion-reacceleration model. The requirement that light nuclei andp data are consistently reproduced within experimental uncertainties places significant limits on the main propagation parameters. In particular, we find the allowed range of the diffusion coefficient spectral index to be 0.3 < δ < 0.6 at 95% confidence level and that Kraichnan type diffusion is favored with respect to Kolmogorov. While some amount of reacceleration is required, only a limited range of the Alfvèn velocity value (10 < ∼ v A < ∼ 20 km s −1 ) is allowed by a combined analysis of nuclear and antiproton data, which we perform here for the first time. If antiproton data are not used to constrain the propagation parameters, a larger set of models is allowed. In this case, we determine which combinations of the relevant parameters maximize and minimize the antiproton flux under the condition of still fitting light nuclei data at 95% C.L. These models may then be used to constrain a possible extra antiproton component arising from astrophysical or exotic sources (e.g. dark matter annihilation or decay).

Cosmic ray anomalies from the MSSM?

“…Experimentally, there are measurements of B/C and various phenomenological propagation models that are used to constrain δ given the measured data. These works have found ranges of values for δ that provide consistency with B/C measurements, some favoring lower values δ = 0.3 − 0.5 [68][69][70] and others finding that larger values δ = 0.5 − 0.8 are preferred [71][72][73]. In this work we use only propagation models that have δ = 0.33.…”

“…As δ describes the spectrum of turbulent features in the bulk magnetic field, there has been a large industry devoted to theoretical and experimental considerations of what its value should be [68][69][70][71][72][73]. Particularly well-motivated theoretical values include δ = 0.33 (Kolmogorov turbulence) and δ = 0.5 (Kraichnan turbulence).…”

Propagation of cosmic rays in the AMS-02 era

“…The annihilation of several tens of GeV dark matter particles may also be responsible for the low energy excess of antiprotons [85][86][87]. Alternatively, an empirical adjustement of the velocity-dependence of the diffusion coefficient with a β η term, i.e., the DR2 model in this work, was suggested to be able to explain the B/C and antiproton data [18]. In this treatment a larger δ value and a weaker reacceleration effect is required, which enables more production of low energy secondary particles (both Boron and antiprotons).…”

“…While the reacceleration model can fit the B/C data, it would under-predict antiprotons [43]. An adjustment of the η parameter in the diffusion coefficient was introduced to solve such a discrepancy [18]. The modification of the low energy diffusion coefficient is also physically motivated from the potential resonant interaction of CR particles and the magnetohydrodynamic (MHD) waves which results in dissipation of such waves [44].…”

“…Many works have been dedicated to using the secondary-toprimary ratios and the unstable-to-stable isotope ratios to constrain the CR propagation parameters (see e.g., [6,9,[12][13][14][15][16][17][18][19]). However, due to the large number of the model parameters and the degeneracy between different parameters, the investigation of the parameter space is incomplete and the conclusion might be biased.…”