English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Dark matter (DM) annihilation in the galactic halo can be enhanced relativeto that in the early Universe due to the Breit-Wigner enhancement, if the DMparticles annihilate through a narrow resonance. Although the $s$-waveBreit-Wigner enhancement can provide a consistent explanation for both theobserved cosmic-ray (CR) positron excess and the DM thermal relic density, itis severely constrained by the observations of gamma rays from dwarf spheroidalsatellite galaxies (dSphs) and the cosmic microwave background (CMB), whichhave relatively lower allowed DM annihilation cross section and typical DMvelocities than that in the galactic halo. Furthermore, in the $s$-waveBreit-Wigner enhancement, the case where the resonance mass is below athreshold (twice the DM mass) is ruled out due to the monotonically increasingannihilation cross section with decreasing DM velocity. In this work, weconsider Breit-Wigner enhanced $p$-wave DM annihilation. We explore theparameter regions which can simultaneously account for the CR positron excessand DM thermal relic density without violating the constraints from dSphs gammarays and CMB. We show that the velocity-dependent cross section in thisscenario can peak around the typical DM velocity in the galactic halo for theresonance mass both above and below the threshold. Moreover, the highlysuppressed annihilation cross section at extremely low DM velocity can evadethe constraints from dSphs gamma rays and CMB easily, which results in largerallowed parameter regions than that in the $s$-wave case.

Consistent explanation for the cosmic-ray positron excess in $p$-wave Breit-Wigner enhanced dark matter annihilation