References - Bogoliubov Laboratory of Theoretical Physics - JINR

Suggestion of the experiments
for measuring the polarization transfer
from protons to antiprotons at AGS.
On the scheme (see Fig. 2)
the initial slow extracted polarized
proton beam strikes on
the BTL-1 (Beam transfer line-
1) the external production target.
Since the polarization is
normal to the orbital plane we
should rotate it to the longitudinal
direction by the Spin Rotator
-1 (SR-1). It was found
that the transfer of polariza-
Figure 3: Suggestion of the experiment (a)
tion from longitudinally polarized
protons to the longitudinally polarized neutrons was most effective [4] so we expect
that this method will be applicable to the production of polarized antiprotons. The polarized
antiprotons will be transported by the BTL-2 to the polarimeter. Before reaching
the polarimeter the longitudinal antiproton polarization should be rotated to transverse
polarization. This is done because in strong interaction we can measure only transverse
components of the polarization. The preferable direction of the antiproton polarization
is the normal to the horizontal plane. So SR-2 makes this function. We have estimated
yields of p for three different momenta. This is 6.5 GeV/c, where the maximum of yield
of p is expected. And two other momenta, 1.5 GeV/c and 15.5 GeV/c, where the yields
of p is smaller by one order of magnitude. So we have two possibilities to work with
polarized antiprotons: A and B. A includes the measurements of the antiproton polarization
in the momentum range 1.5 GeV/c to 3.1 GeV/c. This is because we would like to
use the (g-2) storage ring at AGS. This is useful because we can essentially suppress the
pion and kaon backgrounds to the antiproton beam. B includes the measurements of the
antiproton polarization in the momentum range 3.1 GeV/c to 15.5 GeV/c. In this case
we deal with antiproton beam containing huge backgrounds of pions and kaons. In this
case we have to identify the particles in beam by using the Cherenkov counters. For this
case the counting rates will be limited by the background particles (mostly by pions). In
both cases we use the polarimeter based on the polarized proton target (PPT). So we will
use as the analyzing reaction the antiproton-proton elastic scattering. We will use the
PPT in polarimeter for two reasons: 1) There are no in literature the data with sufficient
precisions on the antiprotons analyzing power in p − p and p − A-elastic scattering in
the hole momentum range of our interest. So using PPT we can measure the analyzing
power of the pbar-p-elastic scattering with needed accuracy at any energy. 2) Using the
polarized target we can simultaneously measure the analyzing power and the polarization
of antiprotons. We suggest to use the propane-diol polarized target [7]. Table presents
the counting rate per cycle and the time needed for accumulation of the scattered events
for each energy. In calculations we used [9]. To achieve the 1% precision in asymmetry
measurement, one needs 104 scattering events. For accumulating this statistics we should
use the net beam time of order indicated in the table. The detection of scattered particles
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