833 research outputs found
Polynomial Chaos Expansion method as a tool to evaluate and quantify field homogeneities of a novel waveguide RF Wien Filter
For the measurement of the electric dipole moment of protons and deuterons, a
novel waveguide RF Wien filter has been designed and will soon be integrated at
the COoler SYnchrotron at J\"ulich. The device operates at the harmonic
frequencies of the spin motion. It is based on a waveguide structure that is
capable of fulfilling the Wien filter condition ()
\textit{by design}. The full-wave calculations demonstrated that the waveguide
RF Wien filter is able to generate high-quality RF electric and magnetic
fields. In reality, mechanical tolerances and misalignments decrease the
simulated field quality, and it is therefore important to consider them in the
simulations. In particular, for the electric dipole moment measurement, it is
important to quantify the field errors systematically. Since Monte-Carlo
simulations are computationally very expensive, we discuss here an efficient
surrogate modeling scheme based on the Polynomial Chaos Expansion method to
compute the field quality in the presence of tolerances and misalignments and
subsequently to perform the sensitivity analysis at zero additional
computational cost.Comment: 12 pages, 19 figure
Beam Performance and Luminosity Limitations in the High-Energy Storage Ring (HESR)
The High-Energy Storage Ring (HESR) of the future International Facility for
Antiproton and Ion Research (FAIR) at GSI in Darmstadt is planned as an
antiproton synchrotron and storage ring in the momentum range from 1.5 to 15
GeV/c. An important feature of this new facility is the combination of phase
space cooled beams with dense internal targets (e.g. pellet targets), resulting
in demanding beam parameter of two operation modes: high luminosity mode with
peak luminosities up to 2*10^32 cm-2 s-1, and high resolution mode with a
momentum spread down to 10^-5, respectively. To reach these beam parameters
very powerful phase space cooling is needed, utilizing high-energy electron
cooling and high-bandwidth stochastic cooling. The effect of beam-target
scattering and intra-beam interaction is investigated in order to study beam
equilibria and beam losses for the two different operation modes.Comment: 8 pages, based on a talk presented at COULOMB'05, Accepted for
publication by Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipmen
Electrostatic deflector studies using small prototypes
The search for electric dipole moments of particles in storage rings requires
the development of dedicated deflector elements with electrostatic fields. In
these rings, electric deflectors shall be used as bending elements for the
charged particles. This paper presents studies on scaled-down prototypes, a few
cm in size, to investigate different deflector materials at similar electric
fields but much smaller distances than real size prototypes.Comment: 5 pages, 8 figure
Hydrogen Spectroscopy with a Lamb-shift Polarimeter - An Alternative Approach Towards Anti-Hydrogen Spectroscopy Experiments
A Lamb-shift polarimeter, which has been built for a fast determination of
the polarization of protons and deuterons of an atomic-beam source and which is
frequently used in the ANKE experiment at COSY-J\"ulich, is shown to be an
excellent device for atomic-spectroscopy measurements of metastable hydrogen
isotopes. It is demonstrated that magnetic and electric dipole transitions in
hydrogen can be measured as a function of the external magnetic field, giving
access to the full Breit-Rabi diagram for the and the
states. This will allow the study of hyperfine structure, factors and the
classical Lamb shift. Although the data are not yet competitive with
state-of-the-art measurements, the potential of the method is enormous,
including a possible application to anti-hydrogen spectroscopy.Comment: 6 pages, 7 figures, accepted by European Physical Journal
A method to polarise antiprotons in storage rings and create polarised antineutrons
An intense circularely polarised photon beam interacts with a cooled
antiproton beam in a storage ring. Due to spin dependent absorption cross
sections for the reaction gamma+antiproton > pi- + antineutron a built-up of
polarisation of the stored antiprotons takes place. Figures-of-merit around 0.1
can be reached in principle over a wide range of antiproton energies. In this
process antineutrons with Polarisation > 70% emerge. The method is presented
for the case of 300 MeV/c cooled antiproton beam
Electromagnetic Simulation and Design of a Novel Waveguide RF Wien Filter for Electric Dipole Moment Measurements of Protons and Deuterons
The conventional Wien filter is a device with orthogonal static magnetic and
electric fields, often used for velocity separation of charged particles. Here
we describe the electromagnetic design calculations for a novel waveguide RF
Wien filter that will be employed to solely manipulate the spins of protons or
deuterons at frequencies of about 0.1 to 2 MHz at the COoler SYnchrotron COSY
at J\"ulich. The device will be used in a future experiment that aims at
measuring the proton and deuteron electric dipole moments, which are expected
to be very small. Their determination, however, would have a huge impact on our
understanding of the universe.Comment: 10 pages, 10 figures, 4 table
Dilepton production near partonic threshold in transversely polarized proton-antiproton collisions
It has recently been suggested that collisions of transversely polarized
protons and antiprotons at the GSI could be used to determine the nucleon's
transversity densities from measurements of the double-spin asymmetry for the
Drell-Yan process. We analyze the role of higher-order perturbative QCD
corrections in this kinematic regime, in terms of the available fixed-order
contributions as well as of all-order soft-gluon resummations. We find that the
combined perturbative corrections to the individual unpolarized and
transversely polarized cross sections are large. We trace these large
enhancements to soft gluon emission near partonic threshold, and we suggest
that with a physically-motivated cut-off enhancements beyond lowest order are
moderated relative to resummed perturbation theory, but still significant. The
unpolarized dilepton cross section for the GSI kinematics may therefore provide
information on the relation of perturbative and nonperturbative dynamics in
hadronic scattering. The spin asymmetry turns out to be rather robust,
relatively insensitive to higher orders, resummation, and the cut-offs.Comment: 23 pages, 19 figures as eps. Some discussion and references added.
Final version to appear in Phys. Rev.
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