Radiation from matter-antimatter annihilation in the quark nugget model of dark matter

TL;DR

This paper investigates the interactions of matter with antimatter quark nuggets in the dark matter model, showing that electron-positron annihilation is suppressed and proposing alternative mechanisms for observed galactic gamma-ray signals.

Contribution

It demonstrates that the strong electric field of anti-quark nuggets prevents electron-positron annihilation, challenging previous explanations for galactic 511 keV photons and suggesting new mechanisms involving proton interactions.

Findings

Electron-positron annihilation probability is reduced by five orders of magnitude.

Electron interactions cannot explain the galactic 511 keV photon observations.

Proton annihilation and pion decay may account for observed gamma-ray signals.

Abstract

We revisit the properties of positron cloud in quark nugget (QN) model of dark matter (DM). In this model, dark matter particles are represented by compact composite objects composed of a large number of quarks or antiquarks with total baryon number $B\sim 10^{24}$. These particles have a very small number density in our galaxy which makes them "dark" to all DM detection experiments and cosmological observations. In this scenario, anti-quark nuggets play special role because they may manifest themselves in annihilation with visible matter. We study electron-positron annihilation in collisions of free electrons, hydrogen and helium gases with the positron cloud of anti-quark nuggets. We show that a strong electric field of anti-quark nuggets destroys positronium, hydrogen and helium atoms and prevents electrons from penetrating deeply in positron cloud, thus reducing the probability of the electron-positron annihilation by nearly five orders of magnitude. Therefore, electron annihilation in the positron cloud of QNs cannot explain the observed by SPI/INTEGRAL detector photons with energy 511 keV in the center of our galaxy. These photons may be explained by a different mechanism in which QN captures protons which annihilate with anti-quarks in the quark core or transform to neutrons thus reducing the QN core charge and increasing QN temperature. As a result QN loses positrons to space which annihilate with electrons there. Even more positrons are produced from charged pions resulting from the proton annihilation. Another manifestation may be emission of photons from $\pi^0$ decays.