ABSTRACT A deep survey of the Large Magellanic Cloud at ∼0.1–100 TeV photon energies with the Cherenkov Telescope Array is planned. We assess the detection prospects based on a model for the emission of the galaxy, comprising the four known TeV emitters, mock populations of sources, and interstellar emission on galactic scales. We also assess the detectability of 30 Doradus and SN 1987A, and the constraints that can be derived on the nature of dark matter. The survey will allow for fine spectral studies of N 157B, N 132D, LMC P3, and 30 Doradus C, and half a dozen other sources should be revealed, mainly pulsar-powered objects. The remnant from SN 1987A could be detected if it produces cosmic-ray nuclei with a flat power-law spectrum at high energies, or with a steeper index 2.3–2.4 pending a flux increase by a factor of >3–4 over ∼2015–2035. Large-scale interstellar emission remains mostly out of reach of the survey if its >10 GeV spectrum has a soft photon index ∼2.7, but degree-scale 0.1–10 TeV pion-decay emission could be detected if the cosmic-ray spectrum hardens above >100 GeV. The 30 Doradus star-forming region is detectable if acceleration efficiency is on the order of 1−10 per cent of the mechanical luminosity and diffusion is suppressed by two orders of magnitude within <100 pc. Finally, the survey could probe the canonical velocity-averaged cross-section for self-annihilation of weakly interacting massive particles for cuspy Navarro–Frenk–White profiles.
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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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- NSF-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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ABSTRACT Reticulum II (Ret II) is a satellite galaxy of the Milky Way (MW) and presents a prime target to investigate the nature of dark matter (DM) because of its high mass-to-light ratio. We evaluate a dedicated INTEGRAL observation campaign data set to obtain γ-ray fluxes from Ret II and compare those with expectations from DM. Ret II is not detected in the γ-ray band 25–8000 keV, and we derive a flux limit of ${\lesssim}10^{-8}\, \mathrm{erg\, cm^{-2}\, s^{-1}}$. The previously reported 511 keV line is not seen, and we find a flux limit of ${\lesssim}1.7 \times 10^{-4}\, \mathrm{ph\, cm^{-2}\, s^{-1}}$. We construct spectral models for primordial black hole (PBH) evaporation and annihilation/decay of particle DM, and subsequent annihilation of e+s produced in these processes. We exclude that the totality of DM in Ret II is made of a monochromatic distribution of PBHs of masses ${\lesssim}8 \times 10^{15}\, \mathrm{g}$. Our limits on the velocity-averaged DM annihilation cross section into e+e− are $\langle \sigma v \rangle \lesssim 5 \times 10^{-28} \left(m_{\rm DM} / \mathrm{MeV} \right)^{2.5}\, \mathrm{cm^3\, s^{-1}}$. We conclude that analysing isolated targets in the MeV γ-ray band can set strong bounds on DM properties without multi-year data sets of the entire MW, and encourage follow-up observations of Ret II and other dwarf galaxies.more » « less
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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
