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Title: Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess

Abstract

The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large 'boost factor' to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter species over cosmological timescales. Consequently, the lighter species becomes the DM which populates the universe today. We show that annihilation of the lighter DM species with an enhanced cross-section, produced via such a non-thermal mechanism, can explain the observed AMS-02 positron flux while avoiding CMB constraints. The observed DM relic density can be correctly reproduced as well with simple s -wave annihilation cross-sections. We demonstrate that the scenario is safe from CMB constraints on late-time energy depositions during the cosmic 'dark ages'. Interestingly, structure formation constraints force us to consider small mass splittings between themore » two dark matter species. We explore possible cosmological and particle physics signatures in a toy model that realizes this scenario.« less

Authors:
; ;  [1]
  1. Department of Physics, Indian Institute of Technology - Bombay, Powai, Mumbai 400076 (India)
Publication Date:
OSTI Identifier:
22667640
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 10; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANNIHILATION; CROSS SECTIONS; DECAY; DENSITY; ENERGY ABSORPTION; ENERGY LOSSES; MASS; NONLUMINOUS MATTER; POSITRONS; RECOMBINATION; S WAVES; UNIVERSE

Citation Formats

Buch, Jatan, Ralegankar, Pranjal, and Rentala, Vikram, E-mail: jatan_buch@brown.edu, E-mail: pranjal6@illinois.edu, E-mail: rentala@phy.iitb.ac.in. Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess. United States: N. p., 2017. Web. doi:10.1088/1475-7516/2017/10/028.
Buch, Jatan, Ralegankar, Pranjal, & Rentala, Vikram, E-mail: jatan_buch@brown.edu, E-mail: pranjal6@illinois.edu, E-mail: rentala@phy.iitb.ac.in. Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess. United States. doi:10.1088/1475-7516/2017/10/028.
Buch, Jatan, Ralegankar, Pranjal, and Rentala, Vikram, E-mail: jatan_buch@brown.edu, E-mail: pranjal6@illinois.edu, E-mail: rentala@phy.iitb.ac.in. Sun . "Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess". United States. doi:10.1088/1475-7516/2017/10/028.
@article{osti_22667640,
title = {Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess},
author = {Buch, Jatan and Ralegankar, Pranjal and Rentala, Vikram, E-mail: jatan_buch@brown.edu, E-mail: pranjal6@illinois.edu, E-mail: rentala@phy.iitb.ac.in},
abstractNote = {The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large 'boost factor' to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter species over cosmological timescales. Consequently, the lighter species becomes the DM which populates the universe today. We show that annihilation of the lighter DM species with an enhanced cross-section, produced via such a non-thermal mechanism, can explain the observed AMS-02 positron flux while avoiding CMB constraints. The observed DM relic density can be correctly reproduced as well with simple s -wave annihilation cross-sections. We demonstrate that the scenario is safe from CMB constraints on late-time energy depositions during the cosmic 'dark ages'. Interestingly, structure formation constraints force us to consider small mass splittings between the two dark matter species. We explore possible cosmological and particle physics signatures in a toy model that realizes this scenario.},
doi = {10.1088/1475-7516/2017/10/028},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 10,
volume = 2017,
place = {United States},
year = {Sun Oct 01 00:00:00 EDT 2017},
month = {Sun Oct 01 00:00:00 EDT 2017}
}