**********************************************************************

                              GAUSTEQ

           Germany and U.S. Nuclear Theory Exchange Program

                 for QCD Studies of Hadrons and Nuclei



                          VISITOR REPORT 

The main aim of the project was to look for synergy between different GSI and Jlab  projects  







----------------------------------------------------------------------

1) NAME AND HOME INSTITUTION OF TRAVELER (INCL. E-MAIL ADDRESS)



Mark Strikman, Penn State University, strikman@phys.psu.edu

----------------------------------------------------------------------

2) POSITION OF TRAVELER (FACULTY/STAFF/POSTDOC/STUDENT)


Professor of Physics



----------------------------------------------------------------------

3) DATES OF TRAVEL

October  30 - December 15
(as part of a longer trip to Europe)
----------------------------------------------------------------------

4) INSTITUTIONS VISITED (LIST PLACES AND TIME SPENT THERE)

I was based in Mainz and did short trips to other institutes:

a) University of Mainz retreat: November 12 -15 
b) FIAS - November 22
c) Bochum - December 10-11
d) GSI _ December 12



----------------------------------------------------------------------

5) SCIENTIFIC CONTACTS: Mainz: M.Vanderhaeghen, N.Kivel, F.Maas; Bochum: E.Eppelbaum, M.Polyakov, GSI: H.Stoecker, Julich: A. Gillitzer, FIAS: A.Larionov 

----------------------------------------------------------------------

6) TOPICS DISCUSSED DURING VISIT:
At Mainz I discussed the dynamics of  large angle exclusive reactions off nucleon in photon and antiproton scattering and their possible relation as well as energy dependence of the exclusive processes at fixed momentum transfer |t|> 1 GeV^2. At the Univeristy of Mainz retreat I was asked to review the future directions of theoretical studies related to the hadronic program of PANDA. Among other things I have emphasized  importance of the color transparency measurements with PANDA as well as complementarity of the PANDA and Jlab programs of the CT studies. I discussed this topic also with A.Gillitzer. Also, together with H. Stoecker and F.Maas I was discussing possible physical program for PANDA working in the collider mode: antiproton - proton (nucleus) minicollider. I discussed with the Bochum group the role of chiral degrees of freedom in hard processes.  
Another topic related to PANDA was production of charmonium final states in low energy antiproton - nucleus collisions which I discussed with A. Larionov (FIAS) 



----------------------------------------------------------------------

7) IMPACT ON TRAVELER'S OR HOST'S RESEARCH (INCL. EXPECTED PUBLICATIONS)


a) The plan was developed together with M. Vanderhaeghen to study a range of two-body processes in the  Regge limit at large |t| as a way to study transition from soft to hard dynamics. 
b) The plan was developed together with M. Polyakov of  extending our old study of the near threshold pion production to the processes which could be studied at PANDA.

c) Planning was done for developing a  joint analysis future color transparency measurements at Jlab and PANDA.
d)  We started together with the FIAS group a new study of the charmonium production in low energy antiproton - nucleus scattering.

All these projects as well as the minicollider project mentioned in 6) may lead to publications. 

----------------------------------------------------------------------

8) RELEVANCE TO JEFFERSON LAB OR GSI-FAIR (LIST RELEVANT PROGRAMS)


Study of the exclusive processes is one of the major future activities of Jlab. Ability to compare results  for the amplitudes in s and u channels (like large angle Compton scattering - Jlab and antiproton - proton annihilation into two photons - PANDA) would allow to constrain dynamics of these processes and ultimately determine the kinematics in which hard exclusive processes can be used for studies of the GPDs. Measurements of CT for pions and nucleons and Jlab will serve as an important input for the PANDA CT studies.

Jlab program of studies of J/psi production will greatly benefit from the studies of the J/psi,… production in the antiproton - nucleus collisions with PANDA.

There is a potential for a new joint direction of Jlab - PANDA studies - high precision measurement of the Regge trajectories and testing linearity of these trajectories and the degree to which the slopes are universal.



----------------------------------------------------------------------

9) SUGGESTIONS/RECOMMENDATIONS FOR PROGRAM ADMINISTRATORS (IF ANY)





----------------------------------------------------------------------

10) SUPPORT PROVIDED BY HOSTS (INDICATE TYPE AND EXTENT OF SUPPORT,

    NOT EXACT AMOUNTS)


Office space. Local support.