Weekly Meeting Minutes - September 29, 2006

Attending: P. Ambrozewicz, E. Clinton, J. Feng, M. Ito, I. Larin, D. McNulty, E. Pasyuk, Y. Prok, A. Teymurazyan, M. Wood By phone: D. Dale

Summary of Meeting Discussions:

All. Nominate secretary: Dustin McNulty (next secretary: ???)

All. Approval of last meeting's minutes:

Approved. You can find the previous meeting minutes here. No comments on last weeks meeting minutes.

All. New Business: Itemized below

3: Jing gave a presentation of his double-arm Compton cross section measurements for 5% Xo C-12 target.

He analyzed runs 4943 - 4946; 4965 with ~standard Compton analysis techniques and cuts.

He characterized line-shape of bkgd events by analyzing empty target runs (5158--Empty Frame, and 4869--Big Blank). Note that these runs had very low event statistics, furthermore, the events which it did have lied mostly within the geometric region of hycal excluded from the standard, carbon-run analysis (the middle 4 vertical columns of hycal crystal channels were excluded).

Jing's total cross section results as a function of T-counter energy are in good agreement with the Klein-Nishina calculation given by Liping.

A somewhat drawn-out discussion of the meaning of Rory's "effective atomic density" number took place. Conclusion: The number 1.046E23 atoms/cm2 is ~2% less than the "real atomic density = density*thickness" of the 5% Xo C-12 target. This 2% reduction comes from photon absorption/rescattering in the target which was calculated at UMass using x-ray diffraction apparatus.

4: Ilya gave a presentation of software issues.

He introduced 4 new calDB attributes listed below (all are contained within both the "crystal" and "glass" systems).

eres_a, eres_b: Energy resolutions calculated from 1st snake scan data. He says c=0.0 for glass and c=1.02 for crystals(the latter number is from Vasily).

tdif_al: Timing alignment constants calculated from 1st snake scan data...uses trigphoton.tdiff for trigger supervisor bit 2 (HyCal total sum). Constant for each channel.

status: HyCal detector channel status; -1 = non existent, 0 = normal, 1 = dead dynode (adc ok), 2 = completely dead, and 3 = hot channel.

5: Ilya gave presentation on pi0 lifetime stability.

In this study, Ilya shows how pi0 lifetime is affected by variations in analysis methods, cuts, and calculations/simulations.

It was noted during discussion that some observed variations were unexpectedly large (for example, the variations seen w.r.t changes in elasticity cut were very large???).

Overall, this was a very impressive investigation that will take time to understand. Conclusions were not yet available.

6: Ilya gave an analysis presentation of coherent omega production off He-4

He extracts omega->pi0+gamma events from all possible data runs.

The omega 3-gamma inv. mass peak is shifted by 14 MeV from expected 782MeV. Ilya thinks this is because of inadequate shower depth coordinate correction, since vertex of omega production is in Helium bag approx. 1 - 2 meters from HyCal.

Omega->3gamma yield calculated as a function of omega production angle. Ilya says he needs He bag pressure to convert to cross section.