Bounds on Dark Matter decay from 21 cm line

The 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.Comment: 9 pages, 2 figures. v3: Improved discussion of the assumptions, matching to the published version. Bounds for different decay channels included. References adde

Stochastic Ultralight Dark Matter Fluctuations in Pulsar Timing Arrays

Metric perturbations induced by ultralight dark matter (ULDM) fields have long been identified as a potential target for pulsar timing array (PTA) observations. Previous works have focused on the coherent oscillation of metric perturbations at the characteristic frequency set by the ULDM mass. In this work, we show that ULDM fields source low-frequency stochastic metric fluctuations and that these low-frequency fluctuations can produce distinctive detectable signals in PTA data. Using the NANOGrav 12.5-year data set and synthetic data sets mimicking present and future PTA capabilities, we show that the current and future PTA observations provide the strongest probe of ULDM density within the solar system for masses in the range of $10^{-18}\;{\rm eV}-10^{-16}\;{\rm eV}$.Comment: 13 pages; 4 figure

Gluequark Dark Matter

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.Comment: 39 pages, 7 figures. v2: improved discussion of theoretical uncertainties, matching to the published version. References added and typos fixe

Dark Matter as a weakly coupled Dark Baryon

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.Comment: New version published in JHE

Detectability of Axion Dark Matter with Phonon Polaritons and Magnons

Collective excitations in condensed matter systems, such as phonons and magnons, have recently been proposed as novel detection channels for light dark matter. We show that excitation of i) optical phonon polaritons in polar materials in an ${\mathcal O}$(1 T) magnetic field (via the axion-photon coupling), and ii) gapped magnons in magnetically ordered materials (via the axion wind coupling to the electron spin), can cover the difficult-to-reach ${\mathcal O}$(1-100) meV mass window of QCD axion dark matter with less than a kilogram-year exposure. Finding materials with a large number of optical phonon or magnon modes that can couple to the axion field is crucial, suggesting a program to search for a range of materials with different resonant energies and excitation selection rules; we outline the rules and discuss a few candidate targets, leaving a more exhaustive search for future work. Ongoing development of single photon, phonon and magnon detectors will provide the key for experimentally realizing the ideas presented here.Comment: 35 pages, 5 figure

Implications of Dark Matter bound states

We present generic formulae for computing how 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 14 TeV the DM mass required to reproduce the cosmological DM abundance. 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

Bindings in the dark : bound states in dark matter phenomenology

It 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\ub450% 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 \u39bCDM 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 \ufb02aws 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 e\ufb00orts. 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. [...

Cosmological Implications of Dark Matter Bound States

We present generic formulae for computing how Sommerfeld corrections togetherwith bound-state formation affects the thermal abundance of Dark Matter withnon-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or5plet under SU(2)$_L$. In the latter case bound states raise to 14 TeV the DMmass required to reproduce the cosmological DM abundance and give indirectdetection signals such as (for this mass) a dominant $\gamma$-line around 85GeV. Furthermore, we consider DM co-annihilating with a colored particle, suchas a squark or a gluino, finding that bound state effects are especiallyrelevant in the latter case

Directional Dark Matter Detection in Anisotropic Dirac Materials

Dirac materials, because of their small {\cal O}(\mbox{meV}) band gap, are a promising target for dark photon-mediated scattering and absorption of light dark matter. In this paper, we characterize the daily modulation rate of dark matter interacting with a Dirac material due to anisotropies in their crystal structure. We show that daily modulation is an ${\cal O}(1)$ fraction of the total rate for dark matter scattering in the Dirac material ZrTe$_5$. When present, the modulation is dominated by the orientation of the material's dielectric tensor with respect to the dark matter wind, and is maximized when the crystal is oriented such that the dark matter wind is completely aligned with the largest and smallest components of the dielectric tensor at two different times of the day. Because of the large modulation, any putative dark matter scattering signal could be rapidly verified or ruled out by changing the orientation of the crystal with respect to the wind and observing how the daily modulation pattern changes.Comment: 22 pages, 6 figures, 1 table. v2: fixed error in the derivation of the dielectric tensor. Absorption rate modulation, and reach plots updated accordingl

Directional dark matter detection in anisotropic Dirac materials

Dirac materials, because of their small O(meV) band gap, are a promising target for dark photon-mediated scattering and absorption of light dark matter. In this paper, we characterize the daily modulation rate of dark matter interacting with a Dirac material due to anisotropies in their crystal structure. We show that daily modulation is an O(1) fraction of the total rate for dark matter scattering in the Dirac material ZrTe₅. When present, the modulation is dominated by the orientation of the material’s dielectric tensor with respect to the dark matter wind and is maximized when the crystal is oriented such that the dark matter wind is completely aligned with the largest and smallest components of the dielectric tensor at two different times of the day. Because of the large modulation, any putative dark matter scattering signal could be rapidly verified or ruled out by changing the orientation of the crystal with respect to the wind and observing how the daily modulation pattern changes