Related papers: Antiprotonic Helium Atoms
A few per cent fraction of antiprotons stopped in helium survives for an enormous time (up to tens of microseconds) in comparison with the usual lifetime ($10^{-12}s$) of these particles in matter. The explanation is that antiprotons are…
A consistent quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. For the four-body scattering wave function, corresponding to the initial state, as well as…
Antiprotonic helium, a neutral exotic three-body system consisting of a helium nucleus, an electron and an antiproton, is being studied at the Antiproton Decelerator of CERN by the ASAUCSA collaboration. Using laser spectroscopy of the…
Recent experiments on the laser-induced resonant annihilation provide a precise measurement of transition energies of antiprotonic helium atoms. Relativistic corrections of an order of $\alpha ^2$ to the pure Coulomb interaction will be…
A semi-classical, many-body atomic model incorporating a momentum-dependent Heisenberg core to stabilize atomic electrons is used to study antiproton capture on Helium. Details of the antiproton collisions leading to eventual capture are…
We present a new measurement of the s-wave scattering length a of spin-polarized helium atoms in the 2^3S_1 metastable state. Using two-photon photoassociation spectroscopy and dark resonances we measure the energy E_{v=14}= -91.35 +/- 0.06…
Low energy antiprotons offer excellent opportunities to study properties of fundamental forces and symmetries in nature. Experiments with them can contribute substantially to deepen our fundamental knowledge in atomic, nuclear and particle…
Exotic deuterium and helium are discussed. The S, P and D levels of antiprotonic and kaonic atoms are calculated. Absorptive, subthreshold antiproton-nucleon amplitudes are extracted from experimental data and compared to model…
Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, made entirely of antiparticles, is believed to be stable, and it is this longevity that holds the promise of precision…
We report a determination of the antiproton magnetic moment, measured in a three-body system, independent of previous experiments. We present results from a systematic study of the hyperfine (HF) structure of antiprotonic helium where we…
The main properties of the interaction of ultra low-energy antiprotons ($% E\le10^{-6}$ a.u.) with atomic hydrogen are established. They include the elastic and inelastic cross sections and Protonium (Pn) formation spectrum. The inverse…
The stopping power of antiprotons in atomic and molecular hydrogen as well as helium was calculated in an impact-energy range from 1 keV to 6.4 MeV. In the case of H2 and He the targets were described with a single-active electron model…
This talk gives an overview of the recent results on the precision spectroscopy of antiprotonic helium which was performed by the ASACUSA collaboration at the Antiproton Decelerator of CERN. The laser spectroscopy of energy levels of the…
We have measured twelve transition frequencies of the antiprotonic helium atom (pbar-He+) with precisions of 0.1--0.2 ppm using a laser spectroscopic method. The agreement between the experiment and theories was so good that we can put a…
We consider a neutralization of excited antiprotonic helium ion accompanied by antiproton transitions to lower states in collisions with helium atoms $(\bar{p}\mathrm{He}^{2+})_{nl} + \mathrm{He} \rightarrow \left[…
Recent progress in the spectroscopy of antiprotonic helium has allowed for measuring the separation between components of the hyperfine structure (HFS) of the (37,35) metastable states with an accuracy of 300 MHz, equivalent to a relative…
Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its…
Antiproton-induced reactions on nuclei at the beam energies from hundreds MeV up to several GeV provide an excellent opportunity to study interactions of the antiproton and secondary particles (mesons, baryons and antibaryons) with…
We discuss the formation of antihydrogen atoms ($\bar{\rm H}$) in an ultra-cold positron-antiproton plasma. For positron densities $n_p\agt 10^8$ cm$^{-3}$ the characteristic formation time of stable $\bar{H}$ is determined by collisional…
Using a newly developed laser-microwave-laser resonance method, we observed a pair of microwave transitions between hyperfine levels of the $(n,L)=(37,35)$ state of antiprotonic helium. This experiment confirms the quadruplet hyperfine…