Antimatter as macroscopic dark matter

Eprint Arxiv 1410 2236, 2014

Dark matter is a vital component of the current best model of our universe, $\Lambda$CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. Here we consider a general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and cm$^2$, respectively -- we therefore dub these macroscopic objects as Macros. Such dark matter candidates could potentially be assembled out of Standard Model particles (quarks and leptons) in the early universe. A combination of Earth-based, astrophysical, and cosmological observations constrain a portion of the Macro parameter space. A large region of parameter space remains, most notably for nuclear-dense objects with masses in the range $55 - 10^{17}$ g and $2\times10^{20} - 4\times10^{24}$ g, although the lower mass window is closed for Macros that destabilize ordinary matter.

Physical Review D

A number of dark matter candidates have been discussed that are macroscopic, of approximately nuclear density, and scatter ordinary matter essentially elastically with approximately their geometric cross-section. A wide range of mass and geometric cross-section is still unprobed for these "macros." Macros passing through rock would melt the material in cylinders surrounding their long nearly straight trajectories. Once cooled, the resolidified rock would be easily distinguishable from its surroundings. We discuss how, by visually examining ordinary slabs of rock such as are widely available commercially for kitchen countertops, one could probe an interesting segment of the open macro parameter space.

New Journal of Physics, 2012

We review observational evidence for a matter-antimatter asymmetry in the early universe, which leads to the remnant matter density we observe today. We also discuss bounds on the presence of antimatter in the present day universe, including the possibility of a large lepton asymmetry in the cosmic neutrino background. We briefly review the theoretical framework within which baryogenesis, the dynamical generation of a matter-antimatter asymmetry, can occur. As an example, we discuss a testable minimal particle physics model that simultaneously explains the baryon asymmetry of the universe, neutrino oscillations and dark matter.

HAL (Le Centre pour la Communication Scientifique Directe), 2022

The structure and evolution of Primordial Antimatter domains and Dark matter objects are analysed. Relativistic low-density antimatter domains are described. The Relativistic FRW perfect-fluid solution is found for the characterization of i) ultra-high density antimatter domains, ii) high-density antimatter domains, and iii) dense anti-matter domains. The possible sub-domains structures is analyzed. The structures evolved to the time of galaxy formation are outlined. Comparison is given with other primordial celestial objects. The features of antistars are outlined. In the case of WIMP dark matter clumps, the mechanisms of their survival to the present time are discussed. The cosmological features of neutrino clumping due to fifth force are examined.

Dark matter is a vital component of the current best model of our universe, CDM.There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or exper-imental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. Here we consider a general class of dark matter candi-dates with characteristic masses and interaction cross-sections characterized in units of grams and cm2, respectively. we therefore dub these macroscopic objects as Macros. Such dark matter candidates could potentially be assembled out of Standard Model particles (quarks and leptons) in the early universe. A combination of Earth-based, astrophysical, and cosmological observations constrain a portion of the Macro param-eter space. A large region of parameter space remains, most notably for nuclear-dense objects with masses in the range from 2 × 10 20 to 4 × 10 24 , although the lower mass window is closed for Macros that destabilize ordinary matter.

We consider consequences of hypothetical existence of baryo-dense stars created in the very early universe within an extension of Affleck-Dine scenario of baryogenesis. New constraints on the possible number of compact antimatter objects are derived. The contemporary observational data do not exclude significant amount of antimatter in the Galaxy (and in other galaxies) in the form of the baryo-dense low-massive stars.

Nuclear Physics B - Proceedings Supplements, 1999

After a brief discussion of the theoretical specukions concerning the presence of cosmological antimatter, the status of the experimental investigations is revised. The observational programs for the next future (BESS, ISOMAX, WIZARD, WIZARD/PAMELA and AMS) are illustrated, and possible further developments discussed.

Proceedings of International Europhysics Conference on High Energy Physics — PoS(hep2001)

The whole set of astrophysical data indicates that our Universe is globally baryon asymmetrical. Nevertheless a possibility of existence of relatively small amount of sufficiently large antimatter regions is not excluded. Such regions can survive the annihilation with surrounding matter only in the case if their sizes exceed a certain scale. It is shown that quantum fluctuations of a complex scalar field caused by inflation can generate large antimatter domains progenitors, which contribute insignificantly to the total volume of the Universe. The resulting distribution and evolution of such antimatter regions could cause every galaxy to be a harbour of an anti-star globular cluster. The existence of one of such anti-star globular cluster in our Galaxy, does not contradict the observed γ-ray background, but the expected fluxes of 4 He and 3 He from such an antimatter object can be searched for in PAMELA experiment and are definitely accessible for the sensitivity of coming AMS02 experiment.

Journal of Cosmology and Astroparticle Physics, 2013

We systematically analyze the impact of current and foreseen cosmic ray antiproton measurements on the properties of Dark Matter (DM). We find that: 1) The current data from Pamela impose constraints on annihilating and decaying DM which are similar to (or even slightly stronger than) the most stringent bounds coming from Fermi gamma rays, for hadronic channels and with fiducial choices for the astrophysical parameters. 2) The upcoming data from Ams-02 have the power to improve these constraints by slightly less than one order of magnitude and even to probe the thermal relic DM in the range 30−200 GeV, for hadronic channels. However, with wider choices for the astrophysical parameters the uncertainty on the constraints spans between one and two orders of magnitude. We then explore the capabilities of early Ams-02 data to reconstruct the underlying DM properties in the case of a positive detection of a significant excess (attributed to DM annilations) over the background. For hadronic channels, we find that Ams-02 should be able to somewhat determine the DM mass and the cross-section, but not the specific annihilation channel nor the branching ratios. If other more exotic annihilation channels are allowed, the reconstruction will be more challenging.

2010