References - Bogoliubov Laboratory of Theoretical Physics - JINR

original software packages (MC simulation, generator etc.) was developed. The SSA
asymmetries, which can be measured with SPD NICA detector are estimated to be about
5-10% and the simulations shows that the such asymmetries are be visible within the
errors at the statistics about 100K events, which corresponds to two years of data taking.
The measurements of J/ψ production processes are also very important for tests of
duality model and due to unique possibility to contribute the data in unpolarized J/ψ
production. The data on both unpolarized and polarized J/ψ production obtained with
SPD NICA can essentially improve the theoretical models of unpolarized J/ψ production.
The possibility of NICA facility to change the energy beams allows to scan different
kinematical regions and to obtain the unique information.
The preliminary design of (SPD) detector for
spin effects studies is based on the requirements
imposed by the DY and J/ψ productions studies.
These requirements are the following: almost
4π geometry for secondary particles; precise
vertex detector; precise tracking system ;
precise momentum measurement od secondary
particles; good particle identification capabilities
(μ, π, p, e, etc.) high trigger rate capabilities.
The most of these requirements are also good for
other studies mentioned above. Basing on these
requirements several possible scheme of SPD are
considered, one of them is similar to the detector
Figure 1: The design of SPD with Range
System shown at the edge of the detector. The
nagnet system is shown in red, EC- in yellow.
of PAX experiment (close to NICA in kinematics) [3] at FAIR GSI, the second one is the
SPD of limited posibilities, providing the muon pair detection only and the third is the
scheme of SPD based on so-called Muon Range System, which is considered as detector
for PANDA muon system. This scheme is shown in Fig. 1 The main parts of this scheme
is described below.
The toroid magnet of the spectrometer provides a field free region around the interaction
point and does not disturb the trajectories. The toroid magnet can consist of 8
superconducting coils symmetrically placed around the beam axis. A support ring upstream
of the target hosts the supply lines for electric power and for liquid helium. At the
downstream end, an hexagonal plate compensates the magnetic forces to hold the coils in
place. The field lines of ideal toroid magnet are always perpendicular to the path of the
particles originating from the beam line. Since the field intensity increases inversely proportional
to the radial distance: greater bending power is available for particles scattered
at smaller angles, which have higher momenta. These properties help to design a compact
spectrometer that keeps the investment costs for the detector tolerable. The production
of such a field requires the insertion of the coils into the tracking volume shadowing part
of the azimuthal acceptance. Preliminary studies show that the use of superconducting
coils, made by a Nb3Sn-Copper core surrounded by a winding of aluminum for support
and cooling, allows one to reach an azimuthal detector acceptance in excess of 85%, while
the radius of the inner magnet volume can be about 0.3 m and outer - about 0.7m, with
� BdL ∼ 0.8 − 1Tm. Several layers of double-sided Silicon strips can provide a precise
vertex reconstruction and tracking of the particles before they reach the magnet. The
design should use a small number of silicon layers to minimize the radiation length of the
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