Polarized muonic beam with variable helicity

Abstract A special mode of muonic beam with an average momentum of 21 GeV/ c and opposite helicity from 40 GeV/ c π-meson decay (the soft part of muonic spectrum corresponding to backward emission of muons in the pion rest-frame; negative polarization of muonic beam) and from 28 GeV/ c μ-meson decay (the hard part of the muonic spectrum, positive polarization of muonic beam) has been realized at the IHEP muon beam channel with the view of search for parity-nonconservation effects in deep inelastic μN -interactions. The beam channel is automatically retuned from the operational mode with one helicity to that with the opposite one in each five accelerator cycles during the time intervals between the cycles. Muonic polarization was measured with the help of the energy spectrum of electrons from μ →eνν decay in-flight. In the momentum range 19–23 GeV/ c the difference in polarization of two muonic beams was λ = 0.80±0.15.