Medium Energy Physics Seminar

Conference Room Rm B-221, Building 203,
Argonne National Laboratory
at 10:00 AM

Melissa Cummings
William and Mary
A Measurement of gp2 at Low Q2
Host: Roy Holt
2 July 2015

Jefferson Lab has been at the forefront of a program to study the polarized structure of nucleons. Measurements of the spin dependent structure functions, g1 and g2, have proven to be powerful tools in testing and understanding QCD. The neutron structure function gn2 has been measured extensively in Hall A at Jefferson Lab over a wide range of Q2, but data for gp2 remains scarce. This talk will discuss the gp2experiment, which ran in Hall A at Jefferson Lab in the spring of 2012, and will provide the first measurement of gp2 in the resonance region; covering 0.02 < Q2 < 0.2 GeV2. The 0th moment of g2 provides a test of the Burkhardt-Cottingham sum rule, which states that the integral of g2 over the Bjorken scaling variable x goes to zero. This sum rule, valid for all values of Q2, has been satisfied for the neutron, but a violation is suggested for the proton at high Q2. The 2nd moment allows for a benchmark test of χPT at low Q2. Specifically, the behavior of the longitudinally-transverse spin polarizability (δLT), as χPT calculations of this quantity deviate significantly from the measured neutron data. This talk will discuss the current status of the analysis along with preliminary results.

Kawtar Hafidi, Chairwoman (+1-630-252-4012, kawtar@anl.gov)

Debbie Beres, Secretary (+1-630-252-4100, beres@anl.gov )



Paul E. Reimer
reimer@anl.gov
1 July 2015