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This dissertation explores the impact of dark matter on the early universe and cosmological observables, with a focus on dark matter annihilation effects on thermal history and dark matter annihilation at the small scales, including the formation of the first stars and galaxies. Dark matter annihilation, enhanced by cosmic inhomogeneities, reshapes the gas temperature and ionization history of the early universe. Annihilation injects energy into the IGM, raising the gas temperature and ionization fraction. This process can either suppress or accelerate the star formation. This study examines the effects of dark matter annihilation on the minimum cooling mass of halos at different redshifts. Notably, this work presents the first combined calculation of dark matter annihilation and dark matter baryon velocity offsets, which have previously been treated separately. Our detailed calculations reveal the non-trivial effects of interplay between dark matter annihilation and dark matter baryon velocity offsets affects the evolution of structure formation. To explore these effects further, we extend existing models to include both molecular and atomic cooling halos, allowing star formation to occur in lower-mass halos and offering insights into how dark matter annihilation, streaming velocity, and cooling mechanisms shape early observable signals. Our study calculates the sky-averaged brightness temperature of the high-redshift 21cm absorption signal against the cosmic microwave background, also known as the “global 21cm signal”, including the effects of both dark matter annihilation and velocity offsets. These factors create distinct features in the 21cm signal, providing potential observational signatures of dark matter properties. We also examine energy transfer processes within dark matter halos, including inverse Compton scattering, photoionization, and pair production. By applying a refined Monte Carlo energy-transfer calculation code, we link single-particle simulations to energy deposition fractions. These developments will be crucial for connecting small-scale effects with large- scale galaxy formation models and ultimately interpreting observational data from the early universe.
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Measurement of anti-3He nuclei absorption in matter and impact on their propagation in the Galaxy
Abstract In our Galaxy, light antinuclei composed of antiprotons and antineutrons can be produced through high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of dark-matter particles that have not yet been discovered. On Earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators. Although the properties of elementary antiparticles have been studied in detail, the knowledge of the interaction of light antinuclei with matter is limited. We determine the disappearance probability of $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ when it encounters matter particles and annihilates or disintegrates within the ALICE detector at the Large Hadron Collider. We extract the inelastic interaction cross section, which is then used as an input to the calculations of the transparency of our Galaxy to the propagation of $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ stemming from dark-matter annihilation and cosmic-ray interactions within the interstellar medium. For a specific dark-matter profile, we estimate a transparency of about 50%, whereas it varies with increasing $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ momentum from 25% to 90% for cosmic-ray sources. The results indicate that $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ nuclei can travel long distances in the Galaxy, and can be used to study cosmic-ray interactions and dark-matter annihilation.
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- PAR ID:
- 10422493
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Nature Physics
- Volume:
- 19
- Issue:
- 1
- ISSN:
- 1745-2473
- Page Range / eLocation ID:
- 61 to 71
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41567-022-01804-8
