********************************************************************** 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 (as an attachment to preserve formating). ---------------------------------------------------------------------- 1) NAME AND HOME INSTITUTION OF TRAVELER (INCL. E-MAIL ADDRESS) Chueng-Ryong Ji, Dept. of Physics, North Carolina State University Email: ji@ncsu.edu ---------------------------------------------------------------------- 2) POSITION OF TRAVELER (FACULTY/STAFF/POSTDOC/STUDENT) Professor ---------------------------------------------------------------------- 3) DATES OF TRAVEL February 28, 2015 - March 16, 2015 ---------------------------------------------------------------------- 4) INSTITUTIONS VISITED (LIST PLACES AND TIME SPENT THERE) 1. JGU, Mainz, 5 days (March 1 - 5) 2. RUB, Bochum, 5 days (March 5 - 9) 3. VU, Amsterdam, 6 days (March 10 - 16) ---------------------------------------------------------------------- 5) SCIENTIFIC CONTACTS AND COLLABORATORS (INDICATE NATURE OF CONTACTS, LIKE "NEW COLLABORATION," "CONTINUING COLLABORATION," "USEFUL DISCUSSION," ETC.) 1. Marc Vanderhaeghen, "USEFUL DISCUSSION, host at JGU" 2. Vladimir Pascalutsa "USEFUL DISCUSSION, co-host at JGU" 3. Nico Stefanis, "USEFUL DISCUSSION, host at RUB" 4. Evgeny Epelbaum, "USEFUL DISCUSSION, co-host at RUB" 5. Ben Bakker, "CONTINUING COLLABORATION, host at VU" ---------------------------------------------------------------------- 6) TOPICS DISCUSSED DURING VISIT 1. Chiral effective theory and application to nucleon PDFs/GPDs 2. General Tensor Structure of Virtual Compton Scattering. 3. Kinematic Issues of GPDs/CFFs in DVCS ---------------------------------------------------------------------- 7) IMPACT ON TRAVELER'S OR HOST'S RESEARCH (INCL. EXPECTED PUBLICATIONS) 1. I've discussed with Marc Vanderhaeghen and Vladimir Pascalutsa regarding on the interface between the chiral effective theory and the E-906/SeaQuest experiment probing the proton sea. In particular, we have discussed the recent PRL paper: Y.Salamu, C.-R. Ji, W. Melnitchouk and P. Wang, "dbar-ubar Asymmetry in the Proton in Chiral Effective Theory", PRL 114, 122001 (2015), where we included both the nucleon and Delta degrees of freedom using the chiral effective theory. From the discussion with Marc and Vladimir, it was clear that our result in this PRL is independent of the unphysical parameter Z in Delta diagram calculation. This helps our future calculations for the flavor asymmetry of the polarized sea and the strange-antistrange asymmetry with the SU(3) generalization of the effective chiral theory. 2. I've discussed with Stefan Scherer regarding on the renormalization scale and scheme dependence in chiral effective theory. This helps our future calculations of the chiral loop diagrams with the dimensional regularization. 3. I've discussed with Nico Stefanis regarding on the local vs. nonlocal condensates effect in the QCD sum-rule calculation of the pion distribution amplitude. This helps the consistency check of the phenomenological model calculation with chiral symmetry. 4. I've discussed with Evgeny Epelbaum about the research efforts in Bochum, in particular the impact of the chiral effective theory on their lattice computation for the light nuclei. 5. Ben Bakker and I have derived the cross section formula for the virtual Compton scattering on a scalar target, e.g. 4He, and checked our formula with other available results, in particular, A.V. Belitsky and D. Mueller, PRD79, 014017 (2009) and A. Kirchner and D. Mueller, EJPC32, 347 (2004). We verified a complete agreement between ours and the results of Belitsky, Kirchner and Mueller. This provides a good confidence on our computation of the DVCS cross section on 4He target using the general hadronic tensor for the scalar target in terms of Compton form factors (CFFs). Our work on 4He DVCS will benchmark the validity of the general hadronic tensor structures in DVCS to cover the entire kinematic regime of current and future experimental facilities. ---------------------------------------------------------------------- 8) RELEVANCE TO JEFFERSON LAB OR GSI-FAIR (LIST RELEVANT PROGRAMS) 1. Our investigation of the kinematic issues involving GPDs in DVCS is highly relevant to the 12 GeV upgrade of CEBAF at JLab and improves the formulation of GPDs to cover the actual experimental region at JLab. 2. The discussion on the chiral theory computation as well as the general tensor structure of VCS is relevant to the hadron physics program in GSI-FAIR. ---------------------------------------------------------------------- 9) SUGGESTIONS/RECOMMENDATIONS FOR PROGRAM ADMINISTRATORS (IF ANY) GAUSTEQ is an excellent nuclear physics exchange program between Germany and US, and it might be beneficial for the program to cover the nearby countries in close proximity to Germany. ---------------------------------------------------------------------- 10) SUPPORT PROVIDED BY HOSTS (INDICATE TYPE AND EXTENT OF SUPPORT, NOT EXACT AMOUNTS) 1. Hotels in Bochum for four nights (March 5-8) covered by RUB 2. Train from Bochum to Amsterdam covered by RUB 4. Hotels in Amsterdam for seven nights (March 9-15) covered by VU 5. Train from Amsterdam to Frankfurt covered by VU ---------------------------------------------------------------------- 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." The support from the GAUSTEQ program was acknowledged in our recent work ÒNuclear chromodynamics: Novel nuclear phenomena predicted by QCD,Ó B. L. G. Bakker and C.-R. Ji, Prog. Part. Nucl. Phys. 74, 1 (2014). ---------------------------------------------------------------------- updated: Nov. 2011 **********************************************************************