A plausible explanation for the lightness of neutrino masses is that neutrinos are massless at tree level, with their mass (typically Majorana) being generated radiatively at one or more loops. The new couplings, together with the suppression coming from the loop factors, imply that the new degrees of freedom cannot be too heavy (they are typically at the TeV scale). Therefore, in these models there are no large mass hierarchies and they can be tested using different searches, making their detailed phenomenological study very appealing. In particular, the new particles can be searched for at colliders and generically induce signals in lepton-flavor and lepton-number violating processes (in the case of Majorana neutrinos), which are not independent from reproducing correctly the neutrino masses and mixings. The main focus of the review is on Majorana neutrinos. We order the allowed theory space from three different perspectives: (i) using an effective operator approach to lepton number violation, (ii) by the number of loops at which the Weinberg operator is generated, (iii) within a given loop order, by the possible irreducible topologies. We also discuss in more detail some popular radiative models which involve qualitatively different features, revisiting their most important phenomenological implications. Finally, we list some promising avenues to pursue.

/pdf/from-the-trees-to-the-forest-a-review-of-radiative-neutrino-14d3f6zmwo.pdf

From the Trees to the Forest: A Review of Radiative Neutrino Mass Models

We present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype SuperCDMS detector having a charge resolution of 0.1 electron-hole pairs (CDMS HVeV, a 0.93 g CDMS high-voltage device). These electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1  MeV/c^{2}. We demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 g d). These results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations.

/pdf/first-dark-matter-constraints-from-a-supercdms-single-charge-20irsgg76o.pdf

First Dark Matter Constraints from a SuperCDMS Single-Charge Sensitive Detector.

We study Bose-Einstein condensation and the formation of Bose stars in virialized dark matter halos and miniclusters by universal gravitational interactions. We prove that this phenomenon does occur and it is described by a kinetic equation. We give an expression for the condensation time. Our results suggest that Bose stars may form kinetically in mainstream dark matter models such as invisible QCD axions and fuzzy dark matter.

Gravitational Bose-Einstein condensation in the kinetic regime

The ordering of the neutrino masses is a crucial input for a deep understanding of flavor physics, and its determination may provide the key to establish the relationship among the lepton masses and mixings and their analogous properties in the quark sector The extraction of the neutrino mass ordering is a data-driven field expected to evolve very rapidly in the next decade In this review, we both analyze the present status and describe the physics of subsequent prospects Firstly, the different current available tools to measure the neutrino mass ordering are described Namely, reactor, long-baseline (accelerator and atmospheric) neutrino beams, laboratory searches for beta and neutrinoless double beta decays and observations of the cosmic background radiation and the large scale structure of the universe are carefully reviewed Secondly, the results from an up-to-date comprehensive global fit are reported: the Bayesian analysis to the 2018 publicly available oscillation and cosmological data sets provides strong evidence for the normal neutrino mass ordering versus the inverted scenario, with a significance of 35 standard deviations This preference for the normal neutrino mass ordering is mostly due to neutrino oscillation measurements Finally, we shall also emphasize the future perspectives for unveiling the neutrino mass ordering In this regard, apart from describing the expectations from the aforementioned probes, we also focus on those arising from alternative and novel methods, as 21 cm cosmology, core-collapse supernova neutrinos and the direct detection of relic neutrinos

/pdf/neutrino-mass-ordering-from-oscillations-and-beyond-2018-1ugstuii6d.pdf

Neutrino Mass Ordering from Oscillations and Beyond: 2018 Status and Future Prospects

The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 108 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10000 radio antennas deployed over 10000 km2. A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.

The Giant Radio Array for Neutrino Detection (GRAND): Science and design

The EDGES 21 cm Anomaly and Properties of Dark Matter

Abstract The recently claimed anomaly in the measurement of the 21 cm hydrogen absorption signal by EDGES at z ∼ 17 , if cosmological, requires the existence of new physics. The possible attempts to resolve the anomaly rely on either (i) cooling the hydrogen gas via new dark matter-hydrogen interactions or (ii) modifying the soft photon background beyond the standard CMB one, as possibly suggested also by the ARCADE 2 excess. We argue that solutions belonging to the first class are generally in tension with cosmological dark matter probes once simple dark sector models are considered. Therefore, we propose soft photon emission by light dark matter as a natural solution to the 21 cm anomaly, studying a few realizations of this scenario. We find that the signal singles out a photophilic dark matter candidate characterised by an enhanced collective decay mechanism, such as axion mini-clusters.

/pdf/the-edges-21-cm-anomaly-and-properties-of-dark-matter-arxiv-1287au2wla.pdf

The EDGES 21 cm Anomaly and Properties of Dark Matter : arXiv

Scotogenic Inverse Seesaw Model of Neutrino Mass

We consider a model of neutrino mass with a scalar triplet $({\ensuremath{\xi}}^{++},{\ensuremath{\xi}}^{+},{\ensuremath{\xi}}^{0})$ assigned lepton number $L=0$, so that the tree-level Yukawa coupling ${\ensuremath{\xi}}^{0}{\ensuremath{\nu}}_{i}{\ensuremath{\nu}}_{j}$ is not allowed. It is generated instead through the interaction of $\ensuremath{\xi}$ and $\ensuremath{\nu}$ with dark matter and the soft breaking of $L$ to $(\ensuremath{-}1{)}^{L}$. We discuss the phenomenological implications of this model, including ${\ensuremath{\xi}}^{++}$ decay and the prognosis of discovering the dark sector at the Large Hadron Collider.

Type II Radiative Seesaw Model of Neutrino Mass with Dark Matter

Recent measurements of semileptonic B-meson decays seemingly imply violations of lepton flavor universality beyond the Standard Model predictions. With three-level explanations based on extended Higgs sectors being strongly challenged by the measurements of the $B_c^-$ lifetime, new theories invoking leptoquark or vector fields appear as the only feasible answer. However, in this work we show that simple scalar extensions of the Standard Model still offer a possible solution to the $B$ physics puzzle, owing to sizeable loop-level corrections which mimic the effects of new vector contributions. Considering a simplified model characterised by a charged and a neutral scalar particle, we verify the compatibility of the observed $R_{D^{(*)}}$ signal with the relevant collider bounds. We also study an embedding of the simplified model into a three-Higgs-doublet framework, and investigate its main phenomenological constraints.

Sean Fraser

Papers

The EDGES 21 cm Anomaly and Properties of Dark Matter

The EDGES 21 cm Anomaly and Properties of Dark Matter : arXiv

Scotogenic Inverse Seesaw Model of Neutrino Mass

Type II Radiative Seesaw Model of Neutrino Mass with Dark Matter

Towards a viable scalar interpretation of $R_{D^{(*)}}$