DAMPE squib? Significance of the 1.4 TeV DAMPE excess

TL;DR

This paper analyzes the DAMPE cosmic ray spectrum, confirming a significant spectral break at 1 TeV and investigating a potential 1.4 TeV excess, which shows some statistical hint but is not definitively significant.

Contribution

It provides a combined Bayesian and frequentist analysis of the DAMPE excess, assessing its significance and exploring dark matter interpretations with updated statistical methods.

Findings

Spectral break at 1 TeV is highly significant.

The 1.4 TeV excess has a local significance of 3.6σ.

Global significance of the excess is about 2.3σ, not conclusive.

Abstract

We present a Bayesian and frequentist analysis of the DAMPE charged cosmic ray spectrum. The spectrum, by eye, contained a spectral break at about 1 TeV and a monochromatic excess at about 1.4 TeV. The break was supported by a Bayes factor of about $10^{10}$ and we argue that the statistical significance was resounding. We investigated whether we should attribute the excess to dark matter annihilation into electrons in a nearby subhalo. We found a local significance of about $3.6\sigma$ and a global significance of about $2.3\sigma$, including a two-dimensional look-elsewhere effect by simulating 1000 pseudo-experiments. The Bayes factor was sensitive to our choices of priors, but favoured the excess by about 2 for our choices. Thus, whilst intriguing, the evidence for a signal is not currently compelling.