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                              GAUSTEQ
           Germany and U.S. Nuclear Theory Exchange Program
                 for QCD Studies of Hadrons and Nuclei

*************************** VISITOR REPORT ***************************

Please use the following template to prepare your report in plain text 
format.  Short, itemized answers are preferred.

Send your report by E-mail to <gausteq@jlab.org> (as an attachment to
preserve formating).

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

Ian Cloet
Argonne National Laboratory
icloet@anl.gov

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

Staff

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3) DATES OF TRAVEL

13th - 29th July 2013

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

14-16 July    University of Regensburg
16-17 July    Technische Universitat Darmstadt
18-29 July    Forschungszentrum Julich 

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5) SCIENTIFIC CONTACTS AND COLLABORATORS (INDICATE NATURE OF CONTACTS,
   LIKE "NEW COLLABORATION," "CONTINUING COLLABORATION,"
   "USEFUL DISCUSSION," ETC.)

Jacques Bloch     - new collaboration
Vladimir Braun    - useful discussion
Daniel Ostermeier - useful discussion
Paula Perez-Rubio - useful discussion
Andreas Schaefer  - useful discussion
Jian Zhou         - useful discussion

Michael Buballa   - useful discussion
Jens Braun        - useful discussion
Markus Huber      - useful discussion
Jochen Wambach    - useful discussion

Lei Chang         - continuing collaboration
Christoph Hanhart - useful discussion
Timo Lahde        - useful discussion
Sebastian Schmidt - new collaboration

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6) TOPICS DISCUSSED DURING VISIT

* transverse momentum dependent parton distribution functions (TMDs)
  - definition
  - factorization
  - relation to PDFs
  - QCD evolution

* pion distribution amplitude
  - asymptotic limit
  - lattice calculations
  - Gegenbauer expansion
  - relation to pion and pi -> gamma gamma form factors

* QCD inspired approaches to matter at finite density and temperature
  - renormalization group techniques
  - neutron star equation of state
  - beyond mean field theory
  - pion contributions to Dyson-Schwinger Equation (DSE) kernels
  - density functional theory for nuclei

* TMDs and generalized parton distribution functions (GPDs)
  - how to define these objects within the DSE framework
  - how to treat the gauge link
  - Q^2 evolution within DSE framework
  - connection to orbital angular momentum

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

- perturbative treatment of TMDs
  While visiting Regensburg I had numerous discussions concerning TMDs,
  in particular, their treatment within perturbative QCD. These 
  discussions were enlightening and will have an important impact on
  our approach to calculating TMDs within the DSE framework.
  
- matter at finite density and temperature
  During the visit to Darmstadt I learnt about powerful techniques,
  based on the renormalization group, that can be used to go beyond 
  the mean-field approximation in many-body calculations. These 
  discussions may materially impact future work regarding our quark 
  based description of nuclei.

- non-perturbative calculations of TMDs and GPDs
  The visit to Julich enabled the necessary ground work to be completed
  that will result in the calculation of PDFs, TMDs and GPDs within the 
  DSE approach. Near term publications, which are a direct results of
  the GAUSTEQ, will included papers on pion TMDs and GPDs.

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

A large fraction of allocated running time at Jefferson Lab 12 GeV 
is devoted to the measurement of TMDs and GPDs. The research started 
and collaborations formed during this GAUSTEQ has resulted in a more 
focused research effort to determined nucleon TMDs and GPDs within
the DSE framework. The outcome of this research has the potential 
to have an important impact on the TMD and GPD programs at Jefferson 
Lab 12 GeV.

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


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10) SUPPORT PROVIDED BY HOSTS (INDICATE TYPE AND EXTENT OF SUPPORT,
    NOT EXACT AMOUNTS)

Office space was provided by hosts, but no financial support.

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11) ACKNOWLEDGMENTS

Please acknowledge support from the GAUSTEQ program in any publication
benefiting from the results of your visit, by including the following
text in your acknowledgments:

"This work was supported partially through GAUSTEQ (Germany and U.S. 
Nuclear Theory Exchange Program for QCD Studies of Hadrons and Nuclei) 
under contract number DE-SC0006758." 
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updated: Nov. 2011

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