581 research outputs found
Experimental evidence of antiproton reflection by a solid surface
We report here experimental evidence of the reflection of a large fraction of
a beam of low energy antiprotons by an aluminum wall. This derives from the
analysis of a set of annihilations of antiprotons that come to rest in rarefied
helium gas after hitting the end wall of the apparatus. A Monte Carlo
simulation of the antiproton path in aluminum indicates that the observed
reflection occurs primarily via a multiple Rutherford-style scattering on Al
nuclei, at least in the energy range 1-10 keV where the phenomenon is most
visible in the analyzed data. These results contradict the common belief
according to which the interactions between matter and antimatter are dominated
by the reciprocally destructive phenomenon of annihilation.Comment: 5 pages with 5 figure
Investigation of two-frequency Paul traps for antihydrogen production
Radio-frequency (rf) Paul traps operated with multifrequency rf trapping
potentials provide the ability to independently confine charged particle
species with widely different charge-to-mass ratios. In particular, these traps
may find use in the field of antihydrogen recombination, allowing antiproton
and positron clouds to be trapped and confined in the same volume without the
use of large superconducting magnets. We explore the stability regions of
two-frequency Paul traps and perform numerical simulations of small,
multispecies charged-particle mixtures that indicate the promise of these traps
for antihydrogen recombination.Comment: 11 pages, 10 figure
Laser stimulated deexcitation of Rydberg antihydrogen atoms
Antihydrogen atoms are routinely formed at CERN in a broad range of Rydberg
states. Ground-state anti-atoms, those useful for precision measurements, are
eventually produced through spontaneous decay. However given the long lifetime
of Rydberg states the number of ground-state antihydrogen atoms usable is
small, in particular for experiments relying on the production of a beam of
antihydrogen atoms. Therefore, it is of high interest to efficiently stimulate
the decay in order to retain a higher fraction of ground-state atoms for
measurements. We propose a method that optimally mixes the high angular
momentum states with low ones enabling to stimulate, using a broadband
frequency laser, the deexcitation toward low-lying states, which then
spontaneously decay to ground-state. We evaluated the method in realistic
antihydrogen experimental conditions. For instance, starting with an initial
distribution of atoms within the manifolds, as formed through charge
exchange mechanism, we show that more than 80\% of antihydrogen atoms will be
deexcited to the ground-state within 100 ns using a laser producing 2 J at 828
nm.Comment: 10 page
Spin physics with antiprotons
New possibilities arising from the availability at GSI of antiproton beams,
possibly polarised, are discussed. The investigation of the nucleon structure
can be boosted by accessing in Drell-Yan processes experimental asymmetries
related to cross-sections in which the parton distribution functions (PDF) only
appear, without any contribution from fragmentation functions; such processes
are not affected by the chiral suppression of the transversity function
. Spin asymmetries in hyperon production and Single Spin Asymmetries
are discussed as well, together with further items like electric and magnetic
nucleonic form factors and open charm production. Counting rates estimations
are provided for each physical case. The sketch of a possible experimental
apparatus is proposed.Comment: Presented for the proceedings of ASI "Spin and Symmetry", Prague,
July 5-10, 2004, to be published in Czech. J. Phys. 55 (2005
A hydrogen beam to characterize the ASACUSA antihydrogen hyperfine spectrometer
The antihydrogen programme of the ASACUSA collaboration at the antiproton
decelerator of CERN focuses on Rabi-type measurements of the ground-state
hyperfine splitting of antihydrogen for a test of the combined
Charge-Parity-Time symmetry. The spectroscopy apparatus consists of a microwave
cavity to drive hyperfine transitions and a superconducting sextupole magnet
for quantum state analysis via Stern-Gerlach separation. However, the small
production rates of antihydrogen forestall comprehensive performance studies on
the spectroscopy apparatus. For this purpose a hydrogen source and detector
have been developed which in conjunction with ASACUSA's hyperfine spectroscopy
equipment form a complete Rabi experiment. We report on the formation of a
cooled, polarized, and time modulated beam of atomic hydrogen and its detection
using a quadrupole mass spectrometer and a lock-in amplification scheme. In
addition key features of ASACUSA's hyperfine spectroscopy apparatus are
discussed.
Measurement of the hyperfine structure of antihydrogen in a beam
A measurement of the hyperfine structure of antihydrogen promises one of the
best tests of CPT symmetry. We describe an experiment planned at the Antiproton
Decelerator of CERN to measure this quantity in a beam of slow antihydrogen
atoms.Comment: 5th International Symposium on Symmetries in Subatomic Physics
(SSP2012), Groningen (The Netherlands), June 18 to 22, 201
Monotonicity of quantum ground state energies: Bosonic atoms and stars
The N-dependence of the non-relativistic bosonic ground state energy is
studied for quantum N-body systems with either Coulomb or Newton interactions.
The Coulomb systems are "bosonic atoms," with their nucleus fixed, and the
Newton systems are "bosonic stars". In either case there exists some third
order polynomial in N such that the ratio of the ground state energy to the
respective polynomial grows monotonically in N. Some applications of these new
monotonicity results are discussed
Breit type equation for mesonic atoms
The finite size effects and relativistic corrections in pionic and kaonic
hydrogen are evaluated by generalizing the Breit equation for a spin-0 -
spin-1/2 amplitude with the inclusion of the hadron electromagnetic form
factors. The agreement of the relativistic corrections to the energies of the
mesonic atoms with other methods used to evaluate them is not exact, but
reasonably good. The precision values of the energy shifts due to the strong
interaction, extracted from data, are however subject to the hadronic form
factor uncertainties.Comment: 11 pages Late
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