Limits on dark matter WIMPs using upward-going muons in the MACRO detector (original) (raw)

Modified dark matter: Relating dark energy, dark matter and baryonic matter

International Journal of Modern Physics D

Modified dark matter (MDM) is a phenomenological model of dark matter, inspired by gravitational thermodynamics. For an accelerating universe with positive cosmological constant ([Formula: see text]), such phenomenological considerations lead to the emergence of a critical acceleration parameter related to [Formula: see text]. Such a critical acceleration is an effective phenomenological manifestation of MDM, and it is found in correlations between dark matter and baryonic matter in galaxy rotation curves. The resulting MDM mass profiles, which are sensitive to [Formula: see text], are consistent with observational data at both the galactic and cluster scales. In particular, the same critical acceleration appears both in the galactic and cluster data fits based on MDM. Furthermore, using some robust qualitative arguments, MDM appears to work well on cosmological scales, even though quantitative studies are still lacking. Finally, we comment on certain nonlocal aspects of the quanta ...

Dark Baryons in the Universe: the Quest Goes On

We show that the high local baryonic fraction, M bar ∼ 1/3 M tot , found in groups and clusters of galaxies does not reconcile the observed cosmological baryon density with the standard Big-Bang prediction. Taking into account recent measurements on the hot-gas content and temperature functions of clusters and groups, we get Ω cg gas = 2.3 × 10 −3 h −1.5

Baryonic and Non-Baryonic Dark Matter

2000

Cosmological nucleosynthesis calculations imply that there should be both non-baryonic and baryonic dark matter. Recent data suggest that some of the non-baryonic dark matter must be "hot" (i.e. massive neutrinos) and there may also be evidence for "cold" dark matter (i.e. WIMPs). If the baryonic dark matter resides in galactic halos, it is likely to be in the form of compact objects (i.e. MACHOs) and these would probably be the remnants of a first generation of pregalactic or protogalactic Population III stars. Many candidates have been proposed-brown dwarfs, red dwarfs, white dwarfs or black holes-and at various times each of these has been in vogue. We review the many types of observations which can be used to constrain or exclude both baryonic and non-baryonic dark matter candidates.

Recent Developments in the Search for Baryonic Dark Matter

Phase Transitions in the Early Universe: Theory and Observations, 2001

Cosmological nucleosynthesis calculations imply that many of the baryons in the Universe must be dark. We discuss the likelihood that some of these dark baryons may reside in galaxies as Massive Compact Halo Objects (MACHOs), the remnants of a first generation of pregalactic or protogalactic stars. Various candidates have been proposed for such remnants and we review the many types of observations which can be used to detect or exclude them. Claims to have found positive evidence for some of the candidates have generally turned out to be spurious or questionable, so the status of the MACHO scenario remains controversial. However, it would be premature to reject MACHOs altogether and further observations are likely to resolve the issue soon.

Dark Matter Astrophysics

Astrophysics and Space Science Library, 2011

These lectures are intended to provide a brief pedagogical review of dark matter for the newcomer to the subject. We begin with a discussion of the astrophysical evidence for dark matter. The standard weakly-interacting massive particle (WIMP) scenario-the motivation, particle models, and detection techniques-is then reviewed. We provide a brief sampling of some recent variations to the standard WIMP scenario as well as some alternatives (axions and sterile neutrinos). Exercises are provided for the reader. 1 simple ("squiggly-line") arguments for the existence of dark matter in clusters and galaxies, as well as the arguments for why it is nonbaryonic. The motivation will be to provide insight into the evidence and arguments, rather than to summarize results from the latest state-of-the-art applications of the techniques. Likewise, construction of particle-physics models for dark matter has become a huge industry, accelerated quite recently, in particular, with anomalous cosmic-ray and diffuse-background results . Again, we will not attempt to survey these recent developments and focus instead primarily on the basic arguments for particle dark matter. In particular, there has developed in the theoretical literature over the past twenty years a "standard" weakly-interacting massive particle (WIMP) scenario, in which the dark-matter particle is a particle that arises in extensions (e.g., supersymmetry or universal extra dimensions ) of the standard model that are thought by many particle theorists to provide the best prospects for new-physics discoveries at the Large Hadron Collider (LHC). We therefore describe this basic scenario. More detailed reviews of weakly-interacting massive particles, the main subject of this article, can be found in Refs. .

Analytical and Observational Approach of Dark Matter

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.

Deficient reasoning for dark matter in galaxies

In this universe, not all of the matter around us can be readily seen. The further an object is away from us and the less luminous it is, the less visible it becomes. Just by looking at an object is usually difficult, if not impossible, to tell the amount of mass it contains. But astronomers have been using the measured luminosity to estimate the luminous mass of stars, based on empirically established mass-to-light ratio which seems to be only applicable to a special class of stars---the main-sequence stars---with still considerable uncertainties. Another basic tool for astronomers to determine the mass of a system of stars or galaxies comes from the study of their motion, as Newton demonstrated with his law of gravitation, which yields the gravitational mass. Because the luminous mass can at best only represent a portion of the gravitational mass, finding the luminous mass to be different or less than the gravitational mass should not be surprising. Using such an apparent discrepancy as compelling evidence for the so called dark matter, which has been believed to possess mysterious nonbaryonic properties having a dominant amount in galaxies and the universe, seems to be too far a stretch when seriously examining the facts and uncertainties in the measurement techniques. In our opinion, a galaxy with star type distribution varying from its center to edge may have a mass-to-light ratio varying accordingly. With the thin-disk model computations based on measured rotation curves, we found that most galaxies have a typical mass density profile that peaks at the galactic center and decreases rapidly within ~ 5% of the cut-off radius and then declines nearly exponentially toward the edge. The predicted mass density in the Galactic disk is reasonably within the reported range of that observed in interstellar medium. This leads us to believe that ordinary baryonic matter can be sufficient for supporting the observed galactic rotation curves; speculation of large amount of non-baryonic matter may be based on an ill-conceived discrepancy between gravitational mass and luminous mass which appears to be unjustified.

NONBARYONIC DARK MATTER IN COSMOLOGY

This paper is a broadband review of the current status of nonbaryonic dark matter (DM) research, starting from a historical overview of the evidences of existence of DM, then discussing how DM is distributed from small scale to large scale, continuing with a discussion on DM nature, DM candidates and their detection. I finally discuss some of the limits of the ΛCDM model, with particular emphasis on the small scale problems of the paradigm.