-Mesonic Decays) at the D6 line.
Hyperon-nucleon scattering
We propose a series of studies of hyperon-nucleon scattering by
using the Cylindrical Detector System (CDS), which is now under
construction for E906 (Experiment
to Detect Double-Lambda Hypernuclei by Observing Characteristic
-Mesonic Decays) at the D6 line.
The 
interaction provides an interesting contrast to the
NN interaction. Because the 
and 
)
cannot exchange a 
, the long range OPE force is not present.
However, unlike the NN system, the exchange of a single strange meson is
possible. The 
system is thus more sensitive to shorter range
components of the strong force, and to different parts of the force than
the NN system. The 
system also has the advantage of
having an inelastic channel at low momentum, the production of a 
,
(
or 
) for p
of 635 MeV/c. Potential models, such as those of the Nijmegen and Jülich
groups, predict structure near this point, but each model
predicts a different structure near this point.
A comparison of 
and NN scattering should provide
a good test of any model of the baryon-baryon force.
Although numerous studies of the 
force have been made
using hypernuclei, only a small number of data exist for the free 
system. Most of the data are at low momenta, 600 events less than 300 MeV/c,
with about 250 events in the momentum range of 300-1500 MeV/c. No
spin data exist for this lower range where potential models are
applicable, and where useful comparisons with hypernuclei could be
made.
The measurement of spin observables provides a greatly increased sensitivity to any model. Unlike the cross section, which depends on the sum of the squares of each scattering amplitude (and is therefore dominated by the largest amplitudes), the spin observables depend on the interferences between amplitudes, making them much more sensitive to small amplitudes.
A unique possibility exists to measure both cross sections and some
spin parameters for 
proton scattering
in the momentum range of 450-950 MeV/c. The 
can be produced
via the 
reaction. The 
can decay to a 
allowing reconstruction of the initial
momentum. The 
can scatter in the production target
then decay to 
, with the probability of a four charged
particle final state being 21%. The decay particles, along with the
scattered proton, could be detected in a large solid angle multi-particle
spectrometer. Because the 
is produced polarized, with the
direction perpendicular to the scattering plane and as high as 90%, and is
self analyzing, spin transfer from the incident to scattered 
can be measured. The analyzing power, 
, 
, and 
could be measured.
The cross section for 
production peaks at about 0.8 mb.
About 0.1% of the 
's will scatter in the
target. With 
/s incident on a 15 cm long LH
target will give about one scattered
per second with four charged decay particles in the final
state. This is sufficient to give a statistical uncertainty of 
on the three spin transfer paramters in 1500 hours. The experiment
requires a good quality, high intensity beam, and a detector capable
of handling the high background rates.
Similar opportunities exist for the the 
and for the 
hyperons.