1,721,030 research outputs found
Bindings in the dark : bound states in dark matter phenomenology
Full text linkIt is almost a century now since data implying the presence of nonluminous matter in the Universe surfaced: in 1932 Oort [1] observed that the number of stars near the sun was 30 ́50% less than the number necessary to explain their velocities; then, in 1933, Zwicky [2] pointed out that the velocity dispersion of galaxies in the Coma cluster required 10 to 100 times more mass than the one accounted for the luminous galaxies themselves. The same Zwicky called this unseen matter dunkle materie (dark matter). These observations were practically ignored for almost four decades until a large number of new evidences corroborating the claim of Oort and Zwicky emerged. Nowadays evidences advocating the existence of Dark Matter (DM) range from the galactic scale, where DM is needed to explain the observed stellar dynamics, to cosmological scales, DM being one of the pillars of the ΛCDM model. However, despite its central role, the nature of the DM remains unknown. This ignorance, which mostly stems from our inability to detect nongravitational interactions between dark and baryonic matter, together with the fact that DM is one of the few phenomenological flaws of the Standard Model (SM) has driven a huge activity in the theoretical community.1 However, if the lack of information about the DM properties makes quite easy is to come up with plausible theoretical solutions it also makes very hard to proof or disproof them. Thus it is crucial to keep pushing the experimental frontiers in parallel with the theoretical efforts. In the following we summarize the (few) experimental informations we have about the DM, and the experimental endeavors that the community is undergoing in the attempt to unveil some of its key features. [...
Bounds on Dark Matter decay from 21 cm line
No full textThe observation of the cosmic 21-cm spectrum can serve as a probe for Dark Matter properties. We point out that the knowledge of the signal amplitude at a given redshift allows one to put conservative bounds on the DM decay rate which are independent of astrophysical parameters. These limits are valid for the vast majority of DM models, those without extra IGM cooling or additional background radiation. Using the experimental results reported by the EDGES collaboration, we derive bounds that are stronger than the ones derived from other CMB observations and competitive with the ones from indirect detection
Cosmological abundance of colored relics
Full text linkThe relic cosmological abundance of stable or long-lived, charge neutral, colored particles gets reduced by up to 4 orders of magnitude by annihilations that occur after QCD confinement. We compute the abundance and the cosmological bounds on relic gluinos. The same postconfinement effect strongly enhances coannihilations with a lighter dark matter particle, provided that their mass difference is below a few giga-electron volts. Charged colored particles (such as stops) can instead form baryons, which can be (quasi)stable in some models
Cosmological Implications of Dark Matter Bound States
No full textWe present generic formulæ for computing how Sommerfeld corrections together with bound-state formation affects the thermal abundance of Dark Matter with non-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2)L. In the latter case bound states raise to 11.5 TeV the DM mass required to reproduce the cosmological DM abundance and give indirect detection signals such as (for this mass) a dominant γ-line around 70 GeV. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant in the latter case.We present generic formulae for computing how Sommerfeld corrections together with bound-state formation affects the thermal abundance of Dark Matter with non-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2). In the latter case bound states raise to 14 TeV the DM mass required to reproduce the cosmological DM abundance and give indirect detection signals such as (for this mass) a dominant -line around 85 GeV. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant in the latter case
Beyond the standard model with strong dynamics
No full textField theoretical extensions of the Standard Model which retain its successful structural features and simplicity are analyzed and characterized. A general classification is provided, in particular, for theories with new strong dynamics where the Dark Matter candidate is an accidentally stable bound state
Gluequark dark matter
Full text linkAbstract We introduce the gluequark Dark Matter candidate, an accidentally stable bound state made of adjoint fermions and gluons from a new confining gauge force. Such scenario displays an unusual cosmological history where perturbative freeze-out is followed by a non-perturbative re-annihilation period with possible entropy injection. When the gluequark has electroweak quantum numbers, the critical density is obtained for masses as large as PeV. Independently of its mass, the size of the gluequark is determined by the confinement scale of the theory, leading at low energies to annihilation rates and elastic cross sections which are large for particle physics standards and potentially observable in indirect detection experiments
Dark Matter as a weakly coupled Dark Baryon
Full text linkDark Matter might be an accidentally stable baryon of a new confining gauge interaction. We extend previous studies exploring the possibility that the DM is made of dark quarks heavier than the dark confinement scale. The resulting phenomenology contains new unusual elements: a two-stage DM cosmology (freeze-out followed by dark condensation), a large DM annihilation cross section through recombination of dark quarks (allowing to fit the positron excess). Light dark glue-balls are relatively long lived and give extra cosmological effects, DM itself can remain radioactive.Dark Matter might be an accidentally stable baryon of a new confining gauge interaction. We extend previous studies exploring the possibility that the DM is made of dark quarks heavier than the dark confinement scale. The resulting phenomenology contains new unusual elements: a two-stage DM cosmology (freeze-out followed by dark condensation), a large DM annihilation cross section through recombination of dark quarks (allowing to fit the positron excess). Light dark glue-balls are relatively long lived and give extra cosmological effects; DM itself can remain radioactive
Colored Dark Matter
Full text linkWe explore the possibility that dark matter (DM) is the lightest hadron made of two stable color octet Dirac fermions Q. The cosmological DM abundance is reproduced for MQ≈12.5 TeV, compatibly with direct searches (the Rayleigh cross section, suppressed by 1/MQ6, is close to present bounds), indirect searches (enhanced by QQ+Q¯Q¯→QQ¯+QQ¯ recombination), and with collider searches (where Q manifests as tracks, pair produced via QCD). Hybrid hadrons, made of Q and of standard model quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is 105 times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles.We explore the possibility that Dark Matter is the lightest hadron made of two stable color octet Dirac fermions . The cosmological DM abundance is reproduced for TeV, compatibly with direct searches (the Rayleigh cross section, suppressed by , is close to present bounds), indirect searches (enhanced by recombination), and with collider searches (where manifests as tracks, pair produced via QCD). Hybrid hadrons, made of and of SM quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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