Dark matter interpretation of recent electron and positron data

Abstract: We analyze the recently released Fermi-LAT data on the sum of electrons and positrons. Compared to a conventional, pre-Fermi, background model, a surprising excess in the several hundred GeV range is found and here we analyze it in terms of dark matter models. We also compare with newly published results from PAMELA and HESS, and find models giving very good fits to these data sets as well. If this dark matter interpretation is correct, we also predict the possibility of a sharp break in the diffuse gamma ray spectrum coming from final state radiation.

• The paper analyzes the electron and positron excess in cosmic rays and finds that dark matter annihilation, especially to muon pairs, provides a compelling explanation.
• The paper employs extensive confidence region calculations to constrain dark matter particle masses between 1–4 TeV and identify suitable annihilation channels.
• The paper discusses implications for indirect detection and future research, noting potential tensions with gamma-ray and synchrotron radiation constraints.

Analysis of Dark Matter Interpretation of Recent Electron and Positron Data

The paper "Dark matter interpretation of recent electron and positron data" by Lars Bergström, Joakim Edsjö, and Gabrijela Zaharijas explores the anomalous excess observed in cosmic ray electron and positron data and suggests potential dark matter (DM) models that could account for these findings. The authors offer insights into the dark matter scenarios that align with observations from multiple datasets, namely Fermi-LAT, PAMELA, and HESS. They explore indirect DM signatures through cosmic ray data, suggesting annihilation or decay processes as plausible interpretations.

Key Observations and Data Analysis

The recent electron and positron data from the Fermi-LAT, coupled with insights from PAMELA and HESS, reveal an excess beyond conventional astrophysical background models. This anomaly appears most pronounced in the several hundred GeV energy range, prompting exploration of dark matter models as explanations. The analysis specifically targets a comparison against the pre-Fermi GALPROP conventional background model, highlighting significant deviations.

The paper utilizes extensive confidence region calculations to determine suitable dark matter model parameters, finding that some models provide remarkably high-quality fits to observed data. A critical feature of these analyses is the estimations of dark matter particle masses and annihilation channels, focusing mainly on leptonic channels. The authors hypothesize DM annihilations primarily involving $\mu^+\mu^-$, which yield good fits to the observed data spectrum, though alternative scenarios involving light scalar or vector mediators are also considered.

Dark Matter Models and Their Implications

The researchers explore two main DM model categories: direct annihilation to leptons and indirect annihilation involving light particles. This exploration includes potential theoretical models from Arkani-Hamed et al. and Nomura and Thaler, which describe mediators decaying into the $\mu^+\mu^-$ channel, a mechanism that fits the observed excess without invoking unnatural particle physics scenarios.

Among the substantial implications from the work are suggestions about the DM particle mass and characteristics. The authors indicate viable dark matter mass ranges between 1–4 TeV, alongside significant cross-sectional enhancements derived from mechanisms like the Sommerfeld enhancement. This theoretical framework posits both micro-physical and macro-structural boosts, which align with the theoretical constraints discussed in existing literature.

Constraints and Compatibility with Other Observations

The analysis further considers implications from gamma-ray and synchrotron radiation constraints, pointing out that the strongest models may encounter tension with observations in different spectral domains. This signifies the necessity of further investigations and potentially refined models.

For indirect detection signatures involving positrons and electrons, compatibility with PAMELA data is complex, as variations in halo models and propagation parameters influence predictions. The paper suggests sensitivity to the chosen diffusion model and the specific halo density profile, noting that these components need careful calibration to match PAMELA results adequately.

Prospects for Future Research

The insights provided by the paper foreshadow a substantial impact on future cosmic ray detection research and dark matter exploration. Anticipated advances with upcoming data releases and enhanced precision may validate or refute the proposed explanations, focusing particularly on gamma-ray observations with Fermi-LAT for direct experimental verification of these models.

Importantly, the speculative aspect concerning the gamma-ray final state radiation signature posits an observational discrimination between DM models and pulsar-origin scenarios. As such, these anticipated observational frameworks could serve as categorical discriminants for dark matter models against other cosmic sources.

In conclusion, the detailed analyses and broad theoretical explorations conducted in this paper add substantial depth to the dark matter research narrative, encouraging further inquiry and refinement as cosmic ray detection technologies advance. The authors' synthesis of theoretical models with empirical data, amidst recognition of model limitations and observational constraints, underscores a pressing need for continued exploration of dark matter phenomena.