[Clas_hadron] abstracts for DNP

[Igor Senderovich]

Dear Colleagues,

I would like to submit the two abstracts that follow this e-mail for the meeting of the DNP and appreciate any feedback you can offer.
Best regards,
-Igor Senderovich

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For the mini-symposium (14e. Mini-Symposium on the Excited Nucleon State Spectrum and Structure):
Title: Studies of $\eta$ photo-production in the baryon resonance excitation region with CLAS
Abstract:
Because the pseudoscalar $\eta$ meson has zero isospin, $\eta$ photo-production offers the feature of isolating N* (I=1/2) resonance states in one-step excitation processes. This ``isospin'' filter property can be very useful in helping disentangle the broad and overlapping excitations that make up the nucleon resonance spectrum. For that reason, a program of measurements on $\eta$ photo-production for the reaction $\gamma p \rightarrow \eta p$ has been conducted using the Hall B CEBAF Large Acceptance Spectrometer at Jefferson Lab. Results for the differential cross-section and for single- and double-polarization observables will be summarized. The general outlook for the ``complete experiment'' program for disentangling nucleon resonances decaying to the $p \eta$ channel will be discussed.


A general DNP submission:
Title: Double-polarization E and G observables in $\eta$ photo-production on the CLAS Frozen Spin Target
Abstract:
$\eta$ photo-production is an important tool in baryon spectroscopy, allowing isolation of N* (I=1/2) resonances in one-step excitation processes. Furthermore, it has long been recognized that due to significant overlapping of resonances in the baryon spectrum, differential cross-sections are not enough; measuring polarization observables is vital. Extensive data have been collected at Jefferson Lab in Hall B with circularly and linearly polarized tagged photon beams incident on longitudinally polarized protons provided by the Frozen Spin Target (FROST). The presentation will cover analysis and preliminary results of double-polarization observables E and G in $\eta$ photo-production - data entirely missing from the world database.