[local physicists] Colloquium Announcement: (Stepan Stepanyan) 11/27/2012

[Malin, Delicia M.]

Old Dominion University
Department of Physics

Fall Colloquium Series

Tuesday November 27, 2012

"Photoproduction of e+e- pairs at JLAB"


Dr. Stepan Stepanyan
Jefferson Lab

    A broad program for studying the quark and gluon structure of hadrons, and in  particular,  probing nucleon structure using  deeply virtual  exclusive  reactions (DVER) and the formalism of Generalized Parton Distributions (GPDs) is underway at Jefferson Lab. Deeply Virtual  Compton Scattering (DVCS), ep → epγ, has been the focus of interest as it provides the cleanest tool for accessing the quark GPDs of the nucleon. Time-like DVCS, also known as Time-like Compton Scattering (TCS), is the inverse process to space- like DVCS that can be probed through the photo- production of lepton pairs (γp → γ∗p → l+l−p).  Combining space-like and time-like data thus offers additional constraints on the GPDs. These studies will allow to gain fundamental insight into the nature of the Compton process in the partonic regime, to test the universality of GPDs by comparing spacelike and timelike DVCS (TCS), and to take advantage of the straightforward access in TCS to the real part of the Compton form factors. No prior TCS measurements exist except for pilot analyses of CLAS 6 GeV data, which demonstrated  the general feasibility.   With  11 GeV beam di-lepton invariant masses of up to 3.4 GeV can be reached. This will allow, in addition to quark GPDs, to access the nucleon’s gluonic structure at large x through J/Ψ photoproduction.


Presentation: OCNPS 200 @ 3:00 pm
Refreshments: Atrium @ 2:30 pm

More details at http://sci.odu.edu/physics/
All are Welcome!


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