Weekly Meeting Minutes - March 23, 2007
Meeting Agenda
Attending: P. Ambrozewicz, E. Clinton, M. Ito, I. Larin, D. McNulty, M. Wood
By phone: A. Bernstein, D. Dale, A. Gasparian, R. Miskimen, T. Rodrigues, A. Teymurazyan
Summary of Meeting Discussions:
All. Nominate secretary: (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
In preparation for Rory's seminar, each of the pi0 analyzers presented a summary of their preliminary result and errors. Links to each of the talks can be found here: Dustin, Ilya, and Eric.
1: Notable comments during Dustin's presentation:
Photon flux uncertainty should be +/- 1.1 % in systematic error table.
Discussion about incoherent models: So-called 'Glauber' model needs documentation. Analyzers need more sophisticated incoherent Monte Carlo generator. For the Cascade cross section data tables, Rory asks "Why is Tulio cutting at elasticity = 0.9?"--Tulio replies "0.9 => 500MeV loss which includes all incoherent processes". Rory says should open cut up much more.
pi0 width from the Pb target still being evaluated and important for systematic error evaluation.
preliminary result (after flux correction): 7.93 eV +/- 1.6% (stat) +/- 3.2% (syst)
2: Notable comments during Ilya's presentation:
Ilya presents study of Nuclear Coherent energy dependence. His results were difficult to interpret...He plots nuclear coherent cross section as a function of T-counter for 4 different slices of pi0 production angle. For 0 < theta < 0.5 and 0.5 < theta < 2.0, the energy (k) dep. looks ~flat, for 0.5 < theta < 1.5, the energy dependence could be consistent with k^2, and for 1.5 < theta < 2.5, the energy dependence looks ~linear (but with wrong slope). Tulio suggests that the incoherent cross section energy dependence is ~strong at 5 GeV energies and could be influencing this study (for example, Tulio says that the incoherent cross section changes by ~20% between 5 and 5.5 GeV (from 31microBarn to 36 microBarn)).
Ashot says that Sergey found that the interference phase angle should be 0.88 radian--which is precisely Ilya's result. More explaination on this point was requested.
preliminary result (after flux correction): 8.00 eV +/- 2.1% (stat) +/- 2.5% (syst)
3: Notable comments during Eric's presentation:
preliminary result (after flux correction): 7.86 eV +/- 2.2% (stat) +/- 2.0% (syst)
4: Summary of discussions:
Average preliminary result (after flux correction): 7.93 eV +/- 2.0% (stat) +/- 3.0% (syst)
Comments in support of a future PrimEx run:
We achieved 2% statistical precision, but wanted 1%.
More statistics enable more understanding of systematics.
HyCal was brand new! Best photon flux measurement ever attempted/achieved, need an iteration to refine it.
We wanted data for 3 different targets.
We learned a lot about theory this time through--for pi0 as well as Compton and Pair Production.
Calibration reaction measurements (pair prod. and Compton) are uniquely extending world data in a precise way.