The first Multi Purpose Spectrometer meeting has been organized by the MPS collaboration [Perdrisat, Garibaldi] with the goals of:

• move forward the MPS project;
• formulate wide physics program around it;
• strengthen the motivation for the funding requests;
• select best/strongest physics proposals for January PAC;
• eventually enlarge the MPS collaboration.

The Multi Purpose Spectrometer [Bogdan], under design and development for the GEP5 experiment, will provide 70 msr solid angle at 15 degree and 2-10 GeV/c momentum acceptance.
It will consist of a 46 cm gap, 2-3 Tesla meter dipole magnet (from BNL), and will be equipped by a combination of the following detectors:

• a high resolution (70 um) tracking system,
• 2 identical polarimeters,
• a segmented hadron calorimeter,
• a lead glass based calorimeter,
• the HERMES RICH aerogel/gas detector for hadron PID.

In the original, prelimimary definition, the tracking system is based on a Micro-Pattern Gas Detector technology (likely GEM, [Cisbani]) which supports high rate and provides high resolution (70 um) correspondig to a momentum resolution of 0.5% at 5 GeV/c and an angular resolution of 0.3 mr.
The same MPGD technology will be used for the large trackers in the polarimeters, which can be designed to be also used in the BigBite spectrometer to improve its momentum resolution and consequently to extend the maximum particle momentum.

Several hot physics cases can beneficiate from the use of the MPS equipments, combined to the 11 GeV which will be available at JLab and the high luminosity expected for the Hall A,

First of all, the nucleon form factors measurements can be extended at high Q² (GMP, GMN and GEN, in addition to GEP) thanks to the much higher rate supported by MPS, the large momentum acceptance and the availability in Hall A of polarized neutron target that can support high currents (up to 100 uA); work on the upgrade the Hall A ³He polarized target is moving in two directions: new metal (gold coated aluminium) cell and better gas mixing via convective circulation [Cates].

The improvement on the ³He target and the availability of MPS configured with the hadron PID RICH detector and BigBite with part of the GEM trackers used in GEP5, can be successfully exploited for new measurements of pion and kaon single spin asymmetry on transversely polarized neutron in the DIS region, at high Q² and in partially unexplored x (Bjorken) valence region (0.2-0.7) [Cisbani], with superior statistics.
These measurements would contribute additional data for the extraction of the Collins and Sievers asymmetries and their associated Transversity and Sivers transverse momentum distribution functions, related to the spin structure of the nucleon and the orbital angular momentum of the quark in the nucleon.

Meson Photoproduction and high Mass Resonance [Annand, Gilman]

Remarkable advantage will be offered by the MPS equipment in the extension to higher x (and one more energy scan at 11 GeV) of the already approved measurement of the A₁^N asymmetry, a crucial step in understanding valence nucleon structure [Nilanga].

Use of MPS in place of BigbBite (or BigBite equipped with the MPS GEM tracters), will improve and extend Q² to 10 GeV² the measurements of threshold pion production at high Q², complementary to the low Q² measurements recently taken in Hall A. A discussion on this direction is going on, within the threshold pion experiments promoters [Lindgren].

The measure of the charge pion form factor at high Q² [Bogdan], a proposal presented in Hall C for the 12 GeV era+, can also benefit of the larger solid angle of MPS (respect to SHMS), even at low scattering angle.

The low cross section of J/Psi (photo)production may be investigated at JLab12 (proposal submitted in HallC and LOI in HallB) thanks to the high luminosity, using the e+e- (and mu+ mu-) decay [Chudakov]. Two MPS magnets equipped for electron/positron detection at very forward angles (GEM tracking availables from GEP5) would improve significantly the statistics (or reduce the requested data taking time), however a detailed analysis should be carried on.

A coherent program of Parity Violation DIS precision measurements, with well defined kinematics over a broad Q² and x range would provide access to search charge asymmetry violation at partonic level, to measure d(x)/u(x) at x close to 1, to study higher twist effects and to probe LHC scale via weak neutral current axial-bector quark coupling [Paschke]. A solenoid spectrometer is expected to be the optimal solution, however, the relatively large MPS and Hall A high luminosity may play an interesting role.

From the different physics talks has clearly emerged the strong impact on JLab physics progam of the MPS equipments and the high luminosity expected for Hall A. Taking this into account and the achievement of the GEP5 experiment, at least three initiatives are in progress:

• MPS R&D has started immediately after the approval of the GEP5 proposal (Summer 2007). INFN funding has been obtained for a preliminary prototype of GEM tracker [Garibaldi] which is almost completed and will be possibly tested during the Transversity experiment in October-December 2008 (as parassitic runs).
  
• Application of MRI, attempted in January 2008, for the development of a new technique for large area GEM for the polarimeter, failed due to administrative reasons [Punjabi].
  
• Finally initial R&D activity on GEM development for the tracker by the Glasgow group has been funded from various agencies [Annand].