There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Annals of physics

We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.

/pdf/a-white-paper-on-kev-sterile-neutrino-dark-matter-1zdzsq0i37.pdf

A White Paper on keV sterile neutrino Dark Matter

The impact-induced deposition of Al13 clusters with icosahedral structure on Ni(0 0 1) surface was studied by molecular dynamics (MD) simulation using Finnis–Sinclair potentials. The incident kinetic energy (Ein) ranged from 0.01 to 30 eV per atom. The structural and dynamical properties of Al clusters on Ni surfaces were found to be strongly dependent on the impact energy. At much lower energy, the Al cluster deposited on the surface as a bulk molecule. However, the original icosahedral structure was transformed to the fcc-like one due to the interaction and the structure mismatch between the Al cluster and Ni surface. With increasing the impinging energy, the cluster was deformed severely when it contacted the substrate, and then broken up due to dense collision cascade. The cluster atoms spread on the surface at last. When the impact energy was higher than 11 eV, the defects, such as Al substitutions and Ni ejections, were observed. The simulation indicated that there exists an optimum energy range, which is suitable for Al epitaxial growth in layer by layer. In addition, at higher impinging energy, the atomic exchange between Al and Ni atoms will be favourable to surface alloying.

Nuclear instruments and methods in physics research section B : beam interactions with materials and atoms

An evaluation of A = 16{17 was published in Nuclear Physics A565 (1993), p. 1. This version of A = 16 diers from the published version in that we have corrected some errors discovered after the article went to press. It has also been slightly revised as of May 16 ,200 0t oinclud ehyperlink sfo rreference san dtables. Introductor ytables have been omitted from this manuscript. Also, Reference key numbers have been changed to the NNDC/TUNL format.

Energy Levels of Light Nuclei A =1 6

Electron- and photon-impact atomic ionisation

The question of convergence in two-center close-coupling expansions is addressed via the study of positron-hydrogen scattering. It is found that the major cross sections do converge if sufficient number of states from a complete basis, centered separately on the hydrogen atom and positronium, are used to expand the total scattering wave function. The underlying equations are computationally highly ill conditioned, and a simple, numerically efficient technique is given that alleviates the problem. Generally, we find good agreement with available experiment and some previous theory. However, calculations that only used eigenstates for the positronium center yielded cross sections for positronium formation in the $2s$ and $2p$ states that are higher than the convergent ones obtained in this work.

Two-center convergent close-coupling approach to positron-hydrogen collisions

Surface-integral formulation of scattering theory

Much progress in the theory of positron scattering on atoms has been made in the ten years since the review of Surko, Gribakin and Buckman [J. Phys. B 38, R57 (2005)]. We review this progress for few-electron targets with a particular emphasis on the two-centre convergent close-coupling and other theories which explicitly treat positronium (Ps) formation. While substantial progress has been made for Ps formation in positron scattering on few-electron targets, considerable theoretical development is still required for multielectron atomic and molecular targets.

Recent progress in the description of positron scattering from atoms using the Convergent Close-Coupling Theory

https://iopscience.iop.org/article/10.1088/0953-4075/49/22/222002/pdf

Alisher Kadyrov

Papers

Electron- and photon-impact atomic ionisation

Two-center convergent close-coupling approach to positron-hydrogen collisions

Surface-integral formulation of scattering theory

Recent progress in the description of positron scattering from atoms using the Convergent Close-Coupling Theory

Recent progress in the description of positron scattering from atoms using the convergent close-coupling theory