CLAS Meeting Minutes, February 2004

Volker Burkert gave the CLAS status summary
Andrew Hutton gave the accelerator summary. He discussed beam delivery statistics (about 100%), beam quality problems (beam shoulder problems in Hall B have been studied and we should see improvement, especially now that they have BPMs that can see the Hall B beam) and beam energy issues (Isabel cost us several cavities, but we will be able to run at 5.7 GeV in Spetember [although with a higher trip rate]. A new cryomodule will be installed in Spring 2005 that should get us to 6.0 GeV.)
CLAS business meeting:

The Physics Working Groups realignment has been approved by a vote of 27 to 5. The new PWGs are Hadron Spectroscopy, Deep Processes and Nuclear Physics. Maurik Holtrop will chair the Nuclear Physics PWG, Dave Tedeschi will chair the Hadron Spectroscopy PWG and Mauro Taiuti will chair the Deep PWG. PWG procedures, chairs, and Speakers' Committee representatives will be inherited from the previous PWGs. Elections will be held as the various terms expire. The new PWGs will take effect gradually between now and the next collaboration meeting.
We approved a bylaws change so that Full Members can be authors on CLAS publications after a 6 month probationary period. This gives full members the same authorship rights as term members.

Ludyvine Morand presented her deep omega production analysis p(e,e'w).
Marco Mirazita presented the search for theta+/lambda on d and 3He. gamma d -> theta+ lambda -> K+ (n) pi- p and gamma 3He -> theta+ lambda p -> ppp pi+ pi- pi-. These are very low statistics data. If we are allowed to combine several channels and both d and 3He targets, then the peak is 26 counts over a background of 26.
Theta+ shootout

Raffaela deVita showed the Genoa analysis of gamma p -> n K0 K+ -> K+ (n) pi+ pi- from g1 data where they see two theta+ peaks at 1.52 and 1.57 GeV. The 1.52 GeV peak is much lower statistical significance than the 1.57 GeV peak. This is now under Real Photon [or perhaps I should say Spectroscopy] PWG review.
Reinhard Schumacher has a parallel analysis with an independent particle ID algorithm. He sees different results depending on whether he plots a) the missing mass of the (pi+ pi-), b) the missing mass of the (K0) [where the K0 = pi+ pi- is forced to have the K0 mass] or, c) the invariant mass of the (n K+). He also gets a different set of events than the Genoa analysis. Further comparison is ongoing.
Ken Hicks has another parallel analysis, also with slightly different results.
One question raised in discussion is what level of confidence is needed in order to show results at conferences. This is crucial, because overly aggressive conference presentations can cause the entire collaboration to lose credibility.

Ken Hicks presented the results of his gamma p -> K+K+X looking for cascade peaks. There is some controversy over whether the peak at 1860 MeV seen by CERN NA49 is real. Ken doesn't see it in his data.
Matt Bellis presented his data on two pion photoproduction from the proton, looking for missing resonances. He fit lots of partial waves to his very comprehensive data set and does not see evidence for new states (although his results are quite sensitive to many known states).
Victor Mokeev presented his model of real and virtual two pion production from the proton. It includes many resonant and nonresonant channels. He showed that it is consistent with both Marco Ripani's electroproduction data and Matt Bellis's photoproduction data when he includes a new state (or a drastically modified existing state) at 1720 MeV. The photoproduction data is consistent with this new state since a) most of the strength in this region is nonresonant and b) there is a cancellation between the resonant terms and the interference between the resonant and nonresonant terms.
Boris Ishkanov presented plans for the CLAS data database.
Vipuli Dharmawardane presented the eg1 (polarized electrons on polarized p and d targets) results, concentrating on the inclusive channels.
Alexei Klimenko presented the results for electron scattering from a high momentum neutron in deuterium d(e,e'p_s).
Working Group Reports

Real Photon - Dave Tedeschi. two papers in PWG review, two in ad hoc review, two in collaboration review. There are significant analysis disagreements in some of the theta+ and theta++ analyses. Other analyses are undisputed but have very low statistics. We need to be very careful about presenting marginal results. 'Data should be robust against improvements to the data.' (ie: corrections intended to improve the data should make the peak broaden) Slides for conferences should be posted two weeks before the conference to allow adequate time for review. Claims should be as conservative as possible.
SoN - Mauro Taiuti: 6 analyses under review, two experiments in preparation (Bonus and g1 at low Q^2). Both will be ready in 2005.
Multhadron - Kim Egiyan: eg2 update, acceptance corrections for 3He(e,e'd)p, d(e,e'd pi+)pi- looking for double-deltas, and d(e,e'p)n search for color transparency
Offline Technical Working Group (OTWG) - Latifa: TOF and DC calibration improvements, cooking update (g7, e1-e,f,g), angular oscillations due to drift chamber L-R ambiguity, mini-torus description in GSIM, tagger calibration for g10 and g11, new detectors, partial tracking (eg: DC R1 and R2 only), etc
We need a CLAS Software Librarian and a Calibration Database Manager
Service Work Committee - Barry Berman: Need to replace 4 retiring members (including Barry). Expect 25% FTE per member. 32 institutions with 77 full and 65 term members (not including JLab).
Membership Committee - Kevin Giovanetti: 7 new term members, 7 term members pass their probationary term, 2 new Jlab staff as full members, 2 full members voted on this time, 3 full members up for vote next meeting. Members database in preparation.
Speakers Committee - Jean-Marc Laget: 62 invited and 51 contributed talks in 2003. All invited speakers need to contact the CSC!

Curtis Meyer presented his kinematical fitting routine. The idea is to use our prior knowledge of particle masses and other constraints to optimize kinematics within each event. This should improve peak widths. When applied to peaks, if it broadens the peak then something is wrong. Peaks in low statistics samples must be robust to be believed.
Cole Smith presented his Low Q^2 N -> Delta and P_11 studies. He extracted sigma_LT and sigma_TT from the data. The sigma_LT' (beam spin asymmetry) appears to be sensitive to the Roper P_11(1440) for very forward angle pions.
Simon Taylor presented the radiative decays of hyperons. The old data was sparse and/or inconsistent. Hyperon radiative decay is sensitive to the quark wave function. He extracted the radiative decay widths for cascade(1385) and lambda(1520) decays to lambda+gamma. This is a VERY difficult measurement because the statistics are poor and the backgrounds are large.
Coordinating Committee Report - Larry Weinstein:

OK'ed term members
appointed an ad hoc committee for Stavinsky's paper
we need an archivist to maintian the charter and by-laws
discussed authorship for higher level analysis of already published data. We encourage this kind of work. You don't need to include the entire CLAS membership and you don't need to go through the CLAS approval process (assuming that all the data you use is already in the public domain).
CLAS Thesis award? Good idea!
CLAS annual report? Only worth doing if done well. Need two dedicated people to organize it. Any volunteers?
Establish an outreach committee. Any volunteers?
What should we show at conferences? PWG needs to approve conference slides. Established a committee to set standards and guidelines for what should be shown. Committee to report at the next meeting. Crannell, Gilad and Meyer. No claims should be made without CLAS approval!

L. Weinstein