Topic
Positron
About: Positron is a research topic. Over the lifetime, 8977 publications have been published within this topic receiving 141266 citations. The topic is also known as: antielectron & positive electron.
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TL;DR: It is found that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources, and is concluded that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.
Abstract: Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium(1), which is referred to as a ' ...
2,287 citations
TL;DR: In this paper, a method for finding a real function in a finite region of a plane given its line integrals along all straight lines intersecting the region was given, and the solution found is applicable to three problems of interest for precise radiology and radiotherapy: (1) the determination of a variable x-ray absorption coefficient in two dimensions, (2) the distribution of positron annihilations when there is an inhomogeneous distribution of the positron emitter in matter, and (3) a variable density of matter with constant chemical composition, using the energy loss
Abstract: A method is given of finding a real function in a finite region of a plane given its line integrals along all straight lines intersecting the region. The solution found is applicable to three problems of interest for precise radiology and radiotherapy: (1) the determination of a variable x‐ray absorption coefficient in two dimensions; (2) the determination of the distribution of positron annihilations when there is an inhomogeneous distribution of the positron emitter in matter; and (3) the determination of a variable density of matter with constant chemical composition, using the energy loss of charged particles in the matter.
1,409 citations
TL;DR: In this article, a review of advances in the study of solid surfaces and thin films using variable-energy positron beams is presented, with more emphasis on the most recent measurements and interpretations than on the chronology of various developments.
Abstract: Recent advances in the study of solid surfaces and thin films using variable-energy positron beams are reviewed. In the first part the authors discuss the process of positron moderation and technical aspects of positron beam production and application. The second part is (roughly) organized in sections that apply to increasing time scales appropriate to the positron-solid interaction. These are (a) first encounter and scattering effects, (b) energy loss and stopping profiles, (c) diffusion of thermalized positrons, (d) positron-surface interactions, and (e) studies of defects near surfaces and interfaces. The review is written with more emphasis on the most recent measurements and interpretations than on the chronology of various developments.
1,339 citations
TL;DR: The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude, showing the existence of new physical phenomena.
Abstract: A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.
1,100 citations
919 citations