********************************************************************** 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) Andreas Metz Temple University metza@temple.edu ---------------------------------------------------------------------- 2) POSITION OF TRAVELER (FACULTY/STAFF/POSTDOC/STUDENT) Faculty ---------------------------------------------------------------------- 3) DATES OF TRAVEL June 2 - June 8 (Regensburg) June 30 - July 5 (GSI) (The trips to Regensburg and GSI took place during a long-term stay in Europe.) ---------------------------------------------------------------------- 4) INSTITUTIONS VISITED (LIST PLACES AND TIME SPENT THERE) University of Regensburg (June 3 - June 7) GSI Darmstadt (July 1 - July 5) ---------------------------------------------------------------------- 5) SCIENTIFIC CONTACTS AND COLLABORATORS (INDICATE NATURE OF CONTACTS, LIKE "NEW COLLABORATION," "CONTINUING COLLABORATION," "USEFUL DISCUSSION," ETC.) Andreas Schaefer: continuing collaboration Jian Zhou: continuing collaboration Peter Braun-Munzinger and GSI ALICE group: useful discussion and new collaboration ---------------------------------------------------------------------- 6) TOPICS DISCUSSED DURING VISIT - Transverse single-spin asymmetry in pp -> hX in the forward region - Longitudinal-transverse double-spin asymmetry in pp -> gammaX - Hyperon polarization in unpolarized pp and pA collisions - Distribution of linearly polarized gluons in pp and pA collisions ---------------------------------------------------------------------- 7) IMPACT ON TRAVELER'S OR HOST'S RESEARCH (INCL. EXPECTED PUBLICATIONS) - Transverse single-spin asymmetry in pp -> hX in the forward region: Together with Andreas Schaefer and Jian Zhou, I made a first attempt to compute this asymmetry in small-x kT-factorization, which may well be the appropriate approach for the very forward region where the largest asymmetries have been observed. After several days we found out that the frequently used Lipatov approximation does not work for the single-spin asymmetries. We started to look for alternatives, but did not yet conclude on this. - Longitudinal-transverse double-spin asymmetry in pp -> gammaX: I discussed a numerical estimate of this asymmetry with Andreas Schaefer and Jian Zhou, as well as Vladimir Braun, Alexander Manashov and Bjoern Pirnay. The latter have a model for the relevant twist-3 correlation functions. A publication is expected. - Hyperon polarization in unpolarized pp and pA collisions: I discussed with Peter Braun-Munzinger and his group the possibility to measure hyperon polarization in unpolarized pp and pA collisions at the LHC, and in particular with the ALICE detector. Various final states were considered, all of which should be accessible with ALICE. The experimentalists want to study in more detail the feasibility. The discussion also stimulated me to consider the calculation of pp -> LambdaX, where the Lambda is transversely polarized. Such a calculation could be performed based on some recent developments at Temple University. - Distribution of linearly polarized gluons in pp and pA collisions: The distribution of linearly polarized gluons in unpolarized hadrons is expected to be very large at small x. I discussed with Peter Braun-Munzinger and his group the possibility to measure this distribution in unpolarized pp and pA collisions at the LHC through azimuthal asymmetries for different final states. It turns out that ALICE most likely is not well suited for such studies, but ATLAS and CMS may well be, for instance through the already measured Z-jet final state. A new theory paper on this topic would be in order. - Talk: At the GSI, I was able to present my field of research, which is closely related to spin physics at RHIC and at JLab. Mainly people working on LHC physics were in the audience. ---------------------------------------------------------------------- 8) RELEVANCE TO JEFFERSON LAB OR GSI-FAIR (LIST RELEVANT PROGRAMS) In general, the topics discussed/worked on during the two visits aim at a deeper understanding of (transverse) spin asymmetries in hard semi-inclusive reactions. Studies of such spin asymmetries already played a key role at JLab-6, and they will be an important part of the physics program at JLab-12. They will also be studied in the future at GSI-FAIR. ---------------------------------------------------------------------- 9) SUGGESTIONS/RECOMMENDATIONS FOR PROGRAM ADMINISTRATORS (IF ANY) ---------------------------------------------------------------------- 10) SUPPORT PROVIDED BY HOSTS (INDICATE TYPE AND EXTENT OF SUPPORT, NOT EXACT AMOUNTS) Office space was provided by hosts, but no financial support. ---------------------------------------------------------------------- 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." ---------------------------------------------------------------------- updated: Nov. 2011 **********************************************************************