Constraints on dark matter from AMS-02 electron data

Herein we use the measurements of the AMS-02 electron flux for the first time in order to derive limits on the dark-matter annihilation cross section and lifetime for the specific final states of ${\mu }^{+}{\mu }^{-}$ and ${\tau }^{+}{\tau }^{-}$. With the well-motivated assumption that the electrons were generated from astrophysical processes, we impose strong limits on the dark-matter properties that are insensitive of propagation parameters and nucleon injection parameters when the dark matter particle mass ($m_{\chi }$) is larger than $\sim 200\mathrm{GeV}$. Specifically, our limits are stronger than those derived from the positron fraction or flux for $m_{\chi }>100\mathrm{GeV}$, and the dark-matter annihilation (or decay) origin of the AMS-02 positron anomaly is found to be disfavored.

Figure 1

Left panel: the fit of the AMS-02 electron flux data by assuming an injection spectrum hardening at the energy of $\sim 58.3\mathrm{GeV}$. Right panel: the fit of the AMS-02 positron flux data with an additional DM component; here we use the DR model and the annihilation final state is ${\mu }^{+}{\mu }^{-}$.

Figure 2

The probability distribution of parameters. The horizontal bars indicate the $1\sigma$ and $3\sigma$ standard deviations, and the vertical dot line represents the statistic-mean value. Here we use the DR model and the annihilation final state is ${\mu }^{+}{\mu }^{-}$; the best-fit results of $m_{\chi }$ and $⟨\sigma v⟩$ can be found in Table 4.

Figure 3

Upper left panel: limits on the DM annihilation cross section at 95% C.L. derived from the AMS-02 electron flux data in the case of $\chi \overline{\chi }\to {\mu }^{+}{\mu }^{-}$, where the DC and DR propagation models, respectively, have been calculated. The light-blue circles and pink squares are the best-fit DM parameters of positron flux data. The dashed gray curve in this and subsequent figures corresponds to the thermal relic cross section adopted from Steigman et al. [48]. Upper right panel: limits on the DM annihilation cross section at 95% C.L. derived from the AMS-02 electron flux data in the case of $\chi \overline{\chi }\to {\tau }^{+}{\tau }^{-}$. Lower left panel: limits on the DM decay lifetime at 95% C.L. derived from the AMS-02 electron flux data in the case of $\chi \to {\mu }^{+}{\mu }^{-}$. Lower right panel: limits on the DM decay lifetime at 95% C.L. derived from the AMS-02 electron flux data in the case of $\chi \to {\tau }^{+}{\tau }^{-}$.

Figure 4

Comparing our limits with those of Ref. [29]. Below $\sim 100\mathrm{GeV}$ our limits are weaker, while above 100 GeV our constraints are tighter. (In the case of $\chi \to {\tau }^{+}{\tau }^{-}$ our limits are generally stronger than those of Ref. [29]).

Figure 5

Left panel: the fit of the AMS-02 electron flux with an additional pulsar component; here we use the DR model. Right panel: limits on DM parameters of the two fitting scenarios, where the annihilation final state is ${\mu }^{+}{\mu }^{-}$.