Polarized HD target project started
in April 2005 and lasts five years.
The first purpose of the project is to investigate
the ss-quark content of the proton and neutron
by measuring double polarization asymmetries for the φ meson
photoproduction.
In addition, the measurement of the double polarization asymmetries
gives important informations to determine the spin-parity of
the Θ+ particle.
Experiment
The experiment will be carried out at
BL33LEP
beam line of
SPring-8
which is
about 120 km distant from
RCNP Osaka university.
The circularly and linearly polarized photon beams with energies of
1.5-2.4 GeV are produced by backward Compton scattering with an
ultra-violet Ar laser from 8 GeV electrons.
We observe the γ p → φ p or
γ n → φ n reaction mainly.
Polarized HD target production and transportation
The HD molecule can be polarized and have interesting
properties.
The proton with spin 1/2 and the deuteron with spin 1 are
independently polarized and are independently reversible.
In order to achieve high polarizations of proton and deuteron
targets, we employ the static method using ``brute force''
at low temperature (10 mK) and high magnetic
field (17 Tesla).
The polarization can exceed 90% for the proton after
aging process for two months.
The polarization of 60% for the deuteron can be obtained
by transferring the proton polarization to the deuteron
by using a method commonly known as ``Adiabatic fast passage''.
The relaxation (polarization) time of about a year is achievable
by keeping the HD target at low temperature below 300 mK
with magnetic field of 1 Tesla during the experiment.
The polarization of the HD target is produced at
RCNP
and the target is transported to
SPring-8
by a truck.
During the whole process, the magnetic field above
300 Gauss is provided to keep the polarization.
Proposal for future experiment at SPring-8 (2003) ; M. Fujiwara et al.
