Efimov states for systems with negative scattering lengths

The recent experimental results showing the existence of an Efimov state (Kraemer T

Natural and unnatural parity resonance states in positron-hydrogen scattering

We present an investigation of resonances with natural and unnatural parities in positron scattering with atomic hydrogen. The complex scaling method has been used. Resonance states for natural parity pi=(-1)(J) with total angular momenta J = 0 - 2 and unnatural parity pi = (-1)(J+1) with J = 1, 2 are calculated. Resonance energies and widths are reported and compared with other theoretical calculations.AuthorCount:2;</p

A search for resonances in the p mu e system

The charge radius of the proton has recently been determined from 2s-2p spectroscopy of muonic hydrogen, giving a result which significantly deviates from earlier measurements. One hypothesis is that this discrepancy could arise because a metastable p mu e state is formed under the p mu (2s) threshold. We search for such a state by considering the three-body pex and p mu x systems, where x is a particle with charge -e and a mass which is varied between the electron and muon mass. We identify a new class of resonances, which extends the mass range allowing formation of resonances compared to an earlier work. We conclude that no p mu e resonances relevant for 2s-2p spectroscopy in muonic hydrogen can exist.AuthorCount:2;</p

Bimodal momentum distribution of laser-cooled atoms in optical lattices

International audienceWe study, numerically and experimentally, the momentum distribution of atoms cooled in optical lattices. Using semi-classical simulations, we show that this distribution is bimodal, made up of a central feature corresponding to " cold " , trapped atoms, with tails of " hot " , untrapped atoms, and that this holds true also for very shallow potentials. Careful analysis of the distribution of high-momentum untrapped atoms, both from simulations and experiments, shows that the tails of the distribution does not follow a normal law, hinting at a power-law distribution and non-ergodic behavior. We also revisit the phenomenon of décrochage , the potential depth below which the temperature of the atoms starts increasing

Near-threshold production of antihydrogen positive ion in positronium-antihydrogen collision

Near-threshold production of antihydrogen ion () in positronium–antihydrogen collisions is predicted by a rigorous four-body scattering calculation. The convergence of the cross sections for the rearrangement and for all competing reactions (elastic scattering, de/excitation and de/polarization of positronium) is carefully examined against partial waves. The multi-channel scattering solutions are composed of functions that diagonalize the four-body Hamiltonian, and scattering functions that satisfy the correct asymptotic boundary conditions. The production rates of show large discrepancies compared to more approximate calculations

A coupled rearrangemnet channel analysis of positronium antihydride PsH

Ground and resonance states of PsH are calculated with a coupled rearrangement-channel, four-body calculation. The structures of these states are examined with help of correlation functions and probabilities of finding two-body states in the total wavefunction. Asymptotic configurations of the ground and resonance states are determined from the tail behaviour of the correlation functions

Stability of hydrogen-antihydrogen mixtures at low energies

The stability of antimatter in contact with matter has been investigated. The interaction between hydrogen and antihydrogen is considered as the prototype reaction. We have focused interest on the rates for proton-antiproton and/or electron-positron annihilation during hydrogen-antihydrogen collisions at low energies. In particular, we have concentrated on the calculation of the rates for the rearrangement reaction leading to formation of protonium and positronium, ending inevitably in particle-antiparticle annihilation. The cross section for the rearrangement collision has been calculated in a fully quantum-mechanical treatment. Additionally, we have calculated cross sections for direct annihilation during the collision process, which was found to be comparable to the rearrangement cross section. The elastic cross section and its low-energy limit, given by the scattering length, have been calculated, allowing, by comparison to the inelastic processes, a prediction for the efficiency of cooling antihydrogen via collisions with ultracold hydrogen atoms.Physic

Four-body treatment of the antihydrogen-positronium system : binding, structure, resonant states and collisions

We have developed a coupled-rearrangement-channel method allowing the rigorous non-adiabatic treatment of the multi-channel scattering problem for four particles. We present the study of the binding, resonant and collisional properties of the (H) over bar -Ps system with the total angular momentum J = 0(+) (singlet positronic configuration). The binding energy, the life-times of the resonant states and the collisional cross sections are calculated and discussed. We present the preliminary cross sections for the elastic and inelastic (H) over bar -Ps scattering, notably for the excitation of Ps and for the rearrangement reaction producing the (H) over bar (+) ions