Private:Weekly Group 7/6/2011

= Igor =

Conference Impressions

 * Attendance: The conference seemed a bit subdued, less contentious than others I’ve seen before. Maybe this is related to many big (argumentative?) figures missing. Conspicuously missing were Barnes, Swanson, Adam, Close, Bugg, Pennington, Peters, Klempt, Sarantsev, Anisovich
 * Baryon DOF: interesting talk by Robert Edwards: quark-diquark description for DOF-reduction doesn’t seem to emerge.
 * COMPASS update: more significant phase motion now seen in π1(1600) (small dip shown earlier now much deeper). Some people upset by COMPASS not asserting this as resonance. “Fit to density matrix” (?) thought necessary before further assertions
 * XYZ mesons: many new states reported (dozens now) including light ones (<1GeV) Most new results from BES. LHC experiments confirm many states but say little new or show improvement in error bars at this stage.
 * ALICE: confirmation of RHIC distributions and an unexpected increase in tail of RAA vs pT distribution (??)
 * Palaez on light scalar mesons: sigma has largely non-qqbar behavior from large Nc and other analysis relating to pole motion.
 * LQCD overview: new FLAG group - LQCD’s PDG summarizing quality and ripeness of simulations in terms of all their extrapolation, degrees of quenching, reliance on some models etc.
 * Photoproduction of exotic states: no π1(1600) seen at CLAS (reported in new analysis by Bookwalter/Euginio) - questions raised about GlueX motivation. Paul cites need to understand production mechanism, understand whether Pomeron exhcnage is necessary as a way to excite glue and hopes to do analysis with Delta++ formation as a way to ensure  π- transfer for comparison.

Work on understanding angular amplitudes
I have been going over the PWA formalism more seriously in an attempt to write down my amplitudes for generating proper X->b1pi distributions and then later, hopefully, fitting to them. Specifically, I went in detail through Chung's "Spin Formalism" and Richman's "An Experimenter's Guide to the Helicity Formalism" I was hoping to be able to reconcile the 2-body decay as I see in these different sources and what has been coded into the (simplified) 2-pseudoscalar decay class TwoPSAngles in sim-recon tree, but I am not there yet. The broad features all make sense, but the details of summed over indices and some coefficients these terms pick up is not yet clear. In particular I am not connecting the coefficients I see in the reflectivity basis with those in the helicity basis.

Discussion:
 * momentum terms
 * phase space included in amplitudes in Chung's normalization?
 * qL terms in ThreePiAngles
 * funny terms in summation over helicity in ThreePiAngles and reflectivity in TwoPSAngles

To-do list
Immediate to-do list in order of priority
 * 1) Complete and submit the prospectus (draft available)
 * 2) Dissertation: begin recording finished projects
 * 3) Implement b1&pi; angular distribution code
 * 4) Begin intro sections for diamond paper, other sections needed very soon
 * 5) Proceedings to Hadron 2011 conference (by Sept 1st)