Search results for "31"
showing 10 items of 4401 documents
Retrieval of sun-induced fluorescence using advanced spectral fitting methods
2015
Abstract The FLuorescence EXplorer (FLEX) satellite mission, candidate of ESA's 8th Earth Explorer program, is explicitly optimized for detecting the sun-induced fluorescence emitted by plants. It will allow consistent measurements around the O2-B (687 nm) and O2-A (760 nm) bands, related to the red and far-red fluorescence emission peaks respectively, the photochemical reflectance index, and the structural-chemical state variables of the canopy. The sun-induced fluorescence signal, overlapped to the surface reflected radiance, can be accurately retrieved by employing the powerful spectral fitting technique. In this framework, a set of fluorescence retrieval algorithms optimized for FLEX ar…
The AD and ELENA orbit, trajectory and intensity measurement systems
2017
This paper describes the new Antiproton Decelerator (AD) orbit measurement system and the Extra Low ENergy Antiproton ring (ELENA) orbit, trajectory and intensity measurement system. The AD machine at European Organization for Nuclear Research (CERN) is presently being used to decelerate antiprotons from 3.57 GeV/c to 100 MeV/c for matter vs anti-matter comparative studies. The ELENA machine, presently under commissioning, has been designed to provide an extra deceleration stage down to 13.7 MeV/c. The AD orbit system is based on 32 horizontal and 27 vertical electrostatic Beam Position Monitor (BPM) fitted with existing low noise front-end amplifiers while the ELENA system consists of 24 \…
Translationally invariant treatment of pair correlations in nuclei: I. Spin and isospin dependent correlations
1996
We study the extension of our translationally invariant treatment of few-body nuclear systems to heavier nuclei. At the same time we also introduce state-dependent correlation operators. Our techniques are tailored to those nuclei that can be dealt with in $LS$ coupling, which includes all nuclei up to the shell closure at $A=40$. We study mainly $p$-shell nuclei in this paper. A detailed comparison with other microscopic many-body approaches is made, using a variety of schematic nuclear interactions. It is shown that our methodology produces very good energies, and presumably also wave functions, for medium mass nuclei.
The translationally-invariant coupled cluster method in coordinate space
2000
We study a formulation of the translationally-invariant coupled cluster method in coordinate space. Previous calculations in configuration space showed poor convergence, a problem that the new formulation is expected to remedy. This question is investigated for a system of bosons interacting through the Wigner part of the Afnan-Tang S3 interaction, where previous results exist.
Translationally invariant treatment of pair correlations in nuclei - II. Tensor correlations
1998
We study the extension of our translationally invariant treatment of few-body nuclear systems to include tensor forces and correlations. It is shown that a direct application of our method is not as successful for realistic V6 interactions as our previous results for V4 potentials suggested. We investigate the cause in detail for the case of $^4$He, and show that a combination of our method with that of Jastrow-correlated wave functions seems to be a lot more powerful, thereby suggesting that for mildly to strongly repulsive forces such a hybrid procedure may be an appropriate description.
The decay of $^{31}$Ar
1990
10 pages, 1 table, 4 figures.
Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry
2014
The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich $^{218m,219,229,231}\text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $\delta\langle r^{2}\rangle^{A,221}$ values for $^{218m,219}\text{Fr}$ and $^{229,231}\text{Fr}$ follow the observed increasing slope of the charge radii beyond $N~=~126$. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that $^{220}\text{Fr}$ has a weakly inverted odd-even staggering while $^{228}\text{Fr}$ has normal staggering. This sugges…
Spectroscopy with β2p and β-ν recoil shifts
2002
9 pages, 4 figures.-- Printed version published Apr 22, 2002.
331 models and grand unification: From minimal SU(5) to minimal SU(6)
2016
We consider the possibility of grand unification of the $\mathrm{ SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ model in an SU(6) gauge unification group. Two possibilities arise. Unlike other conventional grand unified theories, in SU(6) one can embed the $\mathrm{ SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ model as a subgroup such that different multiplets appear with different multiplicities. Such a scenario may emerge from the flux breaking of the unified group in an E(6) F-theory GUT. This provides new ways of achieving gauge coupling unification in $\mathrm{ SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ models while providing the radiative origin of neutrino masses. Alternatively, a sequential va…
Calculation of the two-loop heavy-flavor contribution to Bhabha scattering
2008
We describe in detail the calculation of the two-loop corrections to the QED Bhabha scattering cross section due to the vacuum polarization by heavy fermions. Our approach eliminates one mass scale from the most challenging part of the calculation and allows us to obtain the corrections in a closed analytical form. The result is valid for arbitrary values of the heavy fermion mass and the Mandelstam invariants, as long as s,t,u >> m_e^2.