A surprising method for polarising antiprotons · arXivDesk
0706.3765Jun 26, 200713 pages, 8 figures; v2: minor language and signification corrections v3: (14 pages, 12 figures) major error, nonapplicable polarisation transfer cross sections replaced by the mandatory spin-flip cross sections
A surprising method for polarising antiprotons
Th. Walcher, H. Arenhoevel, K. Aulenbacher, R. Barday, A. Jankowiak
We propose a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to the antiprotons. If the relative velocity is adjusted to v/c≈0.002 the cross section for spin-flip is as large as about 2⋅1013 barn as shown by new QED-calculations of the triple spin-cross sections. Two possibilities for providing a positron source with sufficient flux density are presented. A polarised positron beam with a polarisation of 0.70 and a flux density of approximately 1.5⋅1010
Nearby in the stack
/(mm
2
s) appears to be feasible by means of a radioactive
11
C dc-source. A more involved proposal is the production of polarised positrons by pair production with circularly polarised photons. It yields a polarisation of 0.76 and requires the injection into a small storage ring. Such polariser sources can be used at low (100 MeV) as well as at high (1 GeV) energy storage rings providing a time of about one hour for polarisation build-up of about
1010
antiprotons to a polarisation of about 0.18. A comparison with other proposals show a gain in the figure-of-merit by a factor of about ten.