High Energy Physics Seminars

ics Special Nuclear and High Energy
Wednesday, April 16, 2003
3:00 PM
Physics Building, Room 204
Note special time.
Prof. Xiangdong Ji [Host: Xiaotong Song]
Univ. of Maryland
"Viewing the nucleon through "color" filters"
While the form factors and parton distributions provide separately the shape of the proton in coordinate and momentum spaces, a more powerful imaging of the proton structure can be obtained through phase-space distributions. In this talk, I introduce the Wigner-type quark and gluon distributions which depict a full-3D proton at every fixed light-cone momentum, like what is seen through momentum ("color")-filters. After appropriate phase-space reductions, the Wigner distributions are related to the generalized parton distributions (GPD's) and transverse-momentum dependent parton distributions, which are measurable in high-energy experiments. The new interpretation of GPD's provides a classical way to visualize the orbital motion of the quarks, which is known to be the key to the spin and magnetic moment of the proton.

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