8 research outputs found
Prospects for studies of the free fall and gravitational quantum states of antimatter
Different experiments are ongoing to measure the effect of gravity on cold
neutral antimatter atoms such as positronium, muonium and antihydrogen. Among
those, the project GBAR in CERN aims to measure precisely the gravitational
fall of ultracold antihydrogen atoms. In the ultracold regime, the interaction
of antihydrogen atoms with a surface is governed by the phenomenon of quantum
reflection which results in bouncing of antihydrogen atoms on matter surfaces.
This allows the application of a filtering scheme to increase the precision of
the free fall measurement. In the ultimate limit of smallest vertical
velocities, antihydrogen atoms are settled in gravitational quantum states in
close analogy to ultracold neutrons (UCNs). Positronium is another neutral
system involving antimatter for which free fall under gravity is currently
being investigated at UCL. Building on the experimental techniques under
development for the free fall measurement, gravitational quantum states could
also be observed in positronium. In this contribution, we review the status of
the ongoing experiments and discuss the prospects of observing gravitational
quantum states of antimatter and their implications.Comment: This work reviews contributions made at the GRANIT 2014 workshop on
prospects for the observation of the free fall and gravitational quantum
states of antimatte
Casimir interaction between a dielectric nanosphere and a metallic plane
We study the Casimir interaction between a dielectric nanosphere and a
metallic plane, using the multiple scattering theory. Exact results are
obtained with the dielectric described by a Sellmeier model and the metal by a
Drude model. Asymptotic forms are discussed for small spheres, large or small
distances. The well-known Casimir-Polder formula is recovered at the limit of
vanishingly small spheres, while an expression better behaved at small
distances is found for any finite value of the radius. The exact results are of
particular interest for the study of quantum states of nanospheres in the
vicinity of surfaces.Comment: 6 pages, 5 figure
Shaping the distribution of vertical velocities of antihydrogen in GBAR
International audienceGBAR is a project aiming at measuring the free fall acceleration of gravity for antimatter, namely antihydrogen atoms (). Precision of this timing experiment depends crucially on the dispersion of initial vertical velocities of the atoms as well as on the reliable control of their distribution. We propose to use a new method for shaping the distribution of vertical velocities of , which improves these factors simultaneously. The method is based on quantum reflection of elastically and specularly bouncing with small initial vertical velocity on a bottom mirror disk, and absorption of atoms with large initial vertical velocities on a top rough disk. We estimate statistical and systematic uncertainties, and show that the accuracy for measuring the free fall acceleration of could be pushed below under realistic experimental conditions
Composition and Distribution of Plankton Communities in the Atlantic Sector of the Southern Ocean
In recent decades, the waters off the Antarctic Peninsula and surrounding region have undergone a significant transformation due to global climate change affecting the structure and distribution of pelagic fauna. Here, we present the results of our study on the taxonomic composition and quantitative distribution of plankton communities in Bransfield Strait, Antarctic Sound, the Powell Basin of the Weddell Sea, and the waters off the Antarctic Peninsula and South Orkney Islands during the austral summer of 2022. A slight warming of the Transitional Zonal Water with Weddell Sea influence (TWW) and an increase in its distribution area was detected. Among the pelagic communities, three groups were found to be the most abundant: copepods Calanoides acutus, Metridia gerlachei, and Oithona spp., salpa Salpa thompsoni, and Antarctic krill Euphausia superba. Euphausiids were found in cases of low abundance, species diversity, and biomass. In the studied region, an increase in the amount of the salpa S. thompsoni and the euphausiid Thysanoessa macrura and the expansion of their distribution area were observed. Significant structural shifts in phytoplankton communities manifested themselves in changes in the structure of the Antarctic krill forage base. The composition and distribution of pelagic fauna is affected by a combination of environmental abiotic factors, of which water temperature is the main one. The obtained results have allowed us to assume that a further increase in ocean temperature may lead to a reduction in the number and size of the Antarctic krill population and its successive replacement by salps and other euphausiids that are more resistant to temperature fluctuations and water desalination
Composition and Distribution of Plankton Communities in the Atlantic Sector of the Southern Ocean
In recent decades, the waters off the Antarctic Peninsula and surrounding region have undergone a significant transformation due to global climate change affecting the structure and distribution of pelagic fauna. Here, we present the results of our study on the taxonomic composition and quantitative distribution of plankton communities in Bransfield Strait, Antarctic Sound, the Powell Basin of the Weddell Sea, and the waters off the Antarctic Peninsula and South Orkney Islands during the austral summer of 2022. A slight warming of the Transitional Zonal Water with Weddell Sea influence (TWW) and an increase in its distribution area was detected. Among the pelagic communities, three groups were found to be the most abundant: copepods Calanoides acutus, Metridia gerlachei, and Oithona spp., salpa Salpa thompsoni, and Antarctic krill Euphausia superba. Euphausiids were found in cases of low abundance, species diversity, and biomass. In the studied region, an increase in the amount of the salpa S. thompsoni and the euphausiid Thysanoessa macrura and the expansion of their distribution area were observed. Significant structural shifts in phytoplankton communities manifested themselves in changes in the structure of the Antarctic krill forage base. The composition and distribution of pelagic fauna is affected by a combination of environmental abiotic factors, of which water temperature is the main one. The obtained results have allowed us to assume that a further increase in ocean temperature may lead to a reduction in the number and size of the Antarctic krill population and its successive replacement by salps and other euphausiids that are more resistant to temperature fluctuations and water desalination
Study of strange matter production in the heavy ion collisions at NUCLOTRON
It is proposed to install an experimental setup in the fixed-target hall of the Nuclotron with the final goal to perform a research program focused on the production of strange matter in heavyion collisions at beam energies between 2 and 6 A GeV. The basic setup will comprise a large acceptance dipole magnet with inner tracking detector modules based on double-sided Silicon micro-strip sensors and GEMs. The outer tracking will be based on the drift chambers and straw tube detector. Particle identification will be based on the time-of-flight measurements. This setup will be sufficient perform a comprehensive study of strangeness production in heavy-ion collisions, including multi-strange hyperons, multi-strange hypernuclei, and exotic multi-strange heavy objects. These pioneering measurements would provide the first data on the production of these particles in heavy-ion collisions at Nuclotron beam energies, and would open an avenue to explore the third (strangeness) axis of the nuclear chart. The extension of the experimental program is related with the study of in-medium effects for vector mesons decaying in hadronic modes. The studies of the NN and NA reactions for the reference is assumed