|
|
|
|
|
|
|
|
Photon Asymmetry S in g® p ® pop (Briscoe, Strakovsky) Threshold po production continues to be a topic of interest at MAMI. The early measurements of the real part of the E0+ amplitude identified a sharp break (cusp) in the energy dependence that corresponded to the opening of the p+n channel, and a value at threshold that was about half of that expected from Low-Energy Theorems of QCD. A study with linearly polarized photons has just been completed in which the complete set of P-wave amplitudes was extracted [Sch01]. The nonzero results for the photon polarization S are in agreement with predictions from Chiral Perturbation Theory [Ber01], but disagree with the prediction of essentially zero in a dispersion relation calculation [Han97]. What remains to be studied is the imaginary part of E0+. This quantity can be obtained from the target polarization T. It arises from the interference of the pop and p+n channels, and is expected to have a strong rise from the location of the cusp [Sch01]. The excellent capabilities at MAMI for low-energy photons, and the availability of a polarized target together with the Crystal Ball and TAPS, provide an outstanding opportunity for this interesting experiment. |
|
This site is best viewed in Internet Explorer 6.0 or higher.
Send mail to
Web Master with
questions or comments about this web site.
|
