The present JRA aims at studying the feasibility for the production of polarized antiprotons.
This means to pursue the following objectives:

  1. Investigating the possibility of polarizing a stored beam by spin-flip as an alternative method to spin filtering
  2. Performing polarization buildup studies of protons with transverse polarization.
  3. Performing longitudinal polarization studies with protons at COSY.
  4. Transverse spin-filtering measurements with antiprotons at the Antiproton-Decelerator (AD) for Tp<70 MeV,
  5. Longitudinal spin-filtering measurements with antiprotons at the AD, and
  6. Upgrade of the AD cooler and extension of spin-filtering studies to Tp=500 MeV.

Objective I) has been accomplished in HadronPhysics2 by a dedicated spin-filtering experiment at COSY which demonstrated the impossibility of polarizing a proton beam by spin-flip  with a polarized electron beam.
Objective II) is still underway at the COSY ring and will be extended in HadronPhysics3. For this purpose a low-beta section has been installed and commissioned in the COSY ring. A polarized target and polarimeter will be installed and spin-filtering measurements will be performed.
The complete program should in addition entail the following objectives, which are not covered in the framework of the upcoming HadronPhysics3 project, and will be included in the upcoming FP8 program.


Description of work and role of partners

The complete experimental setup for the spin-filtering studies that is required for the AD ring will be commissioned at COSY according to the objectives of the new JRA. We will address the implementation and commissioning of the experimental setup for the AD followed by the first spin-filtering studies with transverse polarization using simulation studies for the AD lattice functions.
In order to guarantee safe operation of the AD machine for other users, a staged approach will be pursued for the experimental installation. Six additional quadrupole magnets would be first installed without modification of the present AD lattice (i.e., while the central AD quadrupole magnet in that section remains in place).
Subsequent machine studies to commission the low-beta section would ensure that the proposed experimental setup for the spin-filtering studies is compatible with the other physics pursued at the AD. As a second step, the central quadrupole would be removed; it would be replaced by the scattering chamber and the experimental setup. Within FP8, the complete and commissioned experimental setup would then be relocated to the AD.
The tasks described below reflect the staged approach for the commissioning of the AD experimental setup at
COSY, and the design and commissioning of a Siberian snake.

Task 1 - Management
The objective of this task is the management of the present JRA. FZJ is the leading institution; assisted by INFN-FE it will manage the JRA.

Task 2 - Development of a concept for low-β section for AD
Six quadrupole magnets shall be installed in the straight section at 3 o’clock of the AD Ring in order to provide the required small β-function to operate the polarized internal target. The lattice calculations have been already been performed and reported in the Technical Proposal submitted to the SPS Committee. In order to satisfy the requirements of the  calculations, two quadrupoles of the former CELSIUS ring in Uppsala and four spare quadrupoles of the COSY ring at Juelich are available to be installed at the AD.

Task 3 - Commissioning of the experimental setup for the AD at COSY
Task 3 is composed of two parts. During the first part, in Task 3a, once the target chamber is installed at the COSY, important machine aspects can already be addressed without the PIT installed. The second part, Task 3b, addresses first measurements using the polarized target.
Task 3a - Machine acceptance studies
It is important to determine the machine acceptance with electron cooled beam. The technique we have established for this purpose has been already developed and successfully applied at COSY. It uses a small movable frame to scrape the beam. The advantage over other methods is that it also yields a measurement of the machine acceptance angle at the location of the target. This parameter needs to be precisely measured because it plays a crucial role in the interpretation of the observed polarization build-up, as discussed elsewhere.
Task 3b - Measurement of the target polarization
These first measurements will address the determination of the target polarizations when H is injected into the storage cell. In order to accomplish this, a detection system surrounding the storage cell has to be developed.
Task 3 will require a coordinated effort of most of the groups involved in the JRA.
FZJ, FAU and INFN-FE will be responsible for the running of the polarized target and its polarimeter. FAU and INFN-FE possess large experience in spin-physics, ranging from polarized sources and targets to the leadership role in the HERMES experiment at HERA-DESY, exploring the structure of the nucleon.
FZJ, INFN-FE, GSI and Mainz will be responsible for the silicon detector system, making use of their expertise in detection systems.
Task 3 will be carried out with a new detection system using transversely polarized beam produced by spin-filtering using a transversely polarized H or D target at COSY. The groups of KTH, SINS, INFN-FE will be responsible for the data analysis. KTH has large experience in data analysis of low-energy polarization experiments.

Task 4 - Design and commissioning of the Siberian snake at the COSY ring
In parallel to the development of a detection system for the spin-filtering studies for the AD a Siberian snake will be designed and commissioned at the COSY ring. Using the new detector system together with a longitudinally polarized target, the longitudinal beam polarization will be determined at COSY.
The experience of the FZJ experts in polarized beams will be fundamental to accomplish to this task.

Task 5 - Theoretical Investigation
The main task of the theory team is to provide theoretical support for the spin-filtering experiments with protons at COSY, and antiprotons at AD. The theoretical investigations involved in this JRA will be heavily supported by the expert theory groups of FZJ and Trinity College Dublin.