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:
Ludyvine Morand presented her deep omega production analysis
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.
- 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.
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
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
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
Alexei Klimenko presented the results for electron scattering from a
high momentum neutron in deuterium d(e,e'p_s).
Working Group Reports
- 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
- Ken Hicks has another parallel analysis, also with slightly
- 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.
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
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:
- 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
- SoN - Mauro Taiuti: 6 analyses under review, two experiments in
preparation (Bonus and g1 at low Q^2). Both will be ready in
- 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
- 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!
modified: March 1 16:09:15 EST 2004
- 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!