Alternative formation model for antideuterons from dark matter

Antideuterons are a potential messenger for dark matter annihilation or decay in our own Galaxy, with very low backgrounds expected from astrophysical processes. The standard coalescence model of antideuteron formation, while simple to implement, is shown to be under considerable strain by recent data from the LHC. We suggest a new empirically based model, with only one free parameter, which is better able to cope with these data, and we explore the consequences of the model for dark matter searches.

Figure 1

Fit to experimental data for the deuteron radiative capture cross section as function of nucleon momentum difference, $k$, in the c.m. frame. Circles show the photodisintegration data, while diamonds show radiative capture data.

Figure 2

Feynman diagram for the delta resonance in radiative capture. ${\overline{N}}_i$ are antinucleons here.

Figure 3

Fits to cross section data. Left: $pn\to d{\pi }^0{\pi }^0$, middle: $pn\to d{\pi }^{+}{\pi }^{-}$, right: $pp\to d{\pi }^{+}{\pi }^0$.

Figure 4

Fits to cross sections for $np\to dX$ processes.

Figure 5

Fits to cross sections for $pp\to dX$ and $nn\to dX$ processes.

Figure 6

Number of available antinucleon pairs in $e^{+}{e}^{-}$-collisions at the $Z$ resonance in Herwig++, as a function of antinucleon momentum difference $k$ in the c.m. frame and total momentum of the pairs in the lab frame. Left: $\overline{p}\overline{n}$ pairs, middle: $\overline{p}\overline{p}$ pairs, right: $\overline{n}\overline{n}$ pairs. The plots have a shared normalization and are normalized to a maximum value of 1.

Figure 7

Antideuteron spectra at ALICE for the best fit values of $p_0$ and ${\sigma }_0$ given in Tables 7 and 8. Top: 0.9 TeV, middle: 2.76 TeV, bottom: 7 TeV. Left: Herwig++, right: Pythia 8.

Figure 8

Antiproton spectra from ALICE at 7 TeV compared to Monte Carlo models.

Figure 9

Antideuteron spectra at BABAR for the best fit values of $p_0$ and ${\sigma }_0$ given in Tables 7 and 8. Left: Herwig++, right: Pythia 8.

Figure 10

Antideuteron spectra at ISR, generated using Herwig++ with the best fit values of $p_0$ and ${\sigma }_0$ given in Table 7. Left: ${\theta }_{\text{lab}}=90°$, right: ${\theta }_{\text{lab}}=62.5°$.

Figure 11

Antideuteron spectra at ISR, generated using Pythia 8 with the best fit values of $p_0$ and ${\sigma }_0$ given in Table 8. Left: ${\theta }_{\text{lab}}=90°$, right: ${\theta }_{\text{lab}}=62.5°$.

Figure 12

Antideuteron spectra at CLEO for the best fit values of $p_0$ and ${\sigma }_0$ given in Table 7. Left: Herwig++, right: Pythia 8.

Figure 13

Antideuteron spectra at Earth from dark matter annihilation into $b\overline{b}$ (left) and $W^{+}{W}^{-}$ (right), calculated using Herwig++ with $p_0=96\mathrm{MeV}$ in the coalescence model, and $1/{\sigma }_0=0.68{\text{barn}}^{-1}$ in the cross section based model. The dashed line shows the expected astrophysical background calculated in Ref. [51].

Figure 14

Antideuteron spectra at Earth from dark matter annihilation into $b\overline{b}$ (left) and $W^{+}{W}^{-}$ (right), calculated using Pythia 8 with $p_0=140\mathrm{MeV}$ in the coalescence model, and $1/{\sigma }_0=1.18{\text{barn}}^{-1}$ in the cross section based model. The dashed line shows the expected astrophysical background calculated in Ref. [51].

Figure 15

Antideuteron spectra at Earth from dark matter annihilation into $b\overline{b}$ (left) and $W^{+}{W}^{-}$ (right), calculated using Herwig++ with $p_0=187\mathrm{MeV}$ in the coalescence model, and $1/{\sigma }_0=0.68{\text{barn}}^{-1}$ in the cross section based model. The dashed line shows the expected astrophysical background calculated in Ref. [51].