I mis-typed the E_cm for the next stack (item 5). It should be
E_cm = 3525.95 MeV. Thanks to all of the people who quickly caught
this.
				Keith


> 
> The following is the currently understood plan for the next two days:
> 
> 	1) The current stack will be dumped at 22:00 today.
> 
> 	2) The pbar vacuum group will then make an access (~4hr) to assess
> 	the vacuum situation in the 30 sector of the accumulator. There
> 	was a step function in the reported pressure this week and may 
> 	affect the beam lifetime and stacking rate.
> 
> 	3) Stack to 15-20mA and then perform beam manipulation studies 
> 	for ~4hr. 
> 
> 	4) Continue stacking to 55mA.
> 
> 	5) Decelerate to E_cm = 3526.95 MeV. This deceleration could start 
> 	as early as near the end of the Friday evening shift.
> 
> Keith
---------------------------------------------------------------------------
 Summary of thursday meeting 5/11/2000

 Present: Pordes, Kasper, Gollwitzer, Graham, Seo, Garzoglio, Menichetti,
          Borreani, Stancari(G), Stancari(M), Bagnasco.

 Announcement:
 Keith mentioned that along with the Users meeting, there is a meeting 
 organized by the Graduate Students Association called New Perspectives
 where students can give 10 to 15 minute talks on some aspect of their
 work. There is also a poster session. The NP is from the 27th to the 29th
 of June and would be a good opportunity for people to talk. We will
 encourage students' supervisors to take advantage of this.

 Present and Future Stacks:
 The present stack terminates at 9:30 pm. Technicians have been asked to
 come at 10 pm to investigate a possible vacuum leak at AP-30. The 
 investigation is expected to take from 2 to 4 hours after which stacking
 will start.
 There will be some studies done on the stack when it reaches 15 to 20 mA.
 These will take a few hours - there may be some possibility of losing the 
 stack during these (studies or hours).
 We have asked for a stack of 55 mA with small sigmap (see report from Giulio)
 at an energy of 3525.95 MeV. We might expect to start data taking again
 early Saturday morning. There are no studies foreseen between the weekend
 stack and the next, and the program of a point every 0.3 MeV around 3526.2 
 suggests that the following stack energy be at 3526.8.

 We are requesting no accesses and there are no requests for experiment 
 study time to install new filter programs.

 Presentations:
 CCAL Gain Stability and Laser Monitoring.
 Michelle expanded on the mail she had sent out about the CCaL gain change
 during the present run being less than a percent or two. (This was checked
 to try to find the reason for the factor of 2 drop in the ETOT trigger rates
 reported. Her note ruled out that a change in CCaL gain was the cause.
 More later from Jason)
 She showed some plots of the CCaL response variation through a stack.
 She uses the laser, normalizing to the witness pin-diode.
 During a given stack, blocks typically lose a fraction of a
 percent in gain - some of which is recovered by the time the next stack
 starts. (PMT's getting warm? tired?). She showed a plot of the change
 per 3 pb-1 for all the blocks for one stack and the change since the
 chi0 running started. The typical change over the running is a few percent.

 FCaL Energy and Position Resolution.
 Mat showed some plots of the FCal2000 energy and position resolution.
 The resolution is calculated on events with 6 photons, 5 in the CCaL
 and one in the FCal, which fit pbar-p to 3 pi-0's.  Mat has fitted the 
 resolution he sees as a function of energy and obtains 16%/sqrt(E) (in Gev).
 Stephen emphasized that while 16% was a bit big, this was the first time 
 we had an FCal with genuine data at all. Keith (and others) pointed out
 that this was an upper limit to the resolution and suggested doing the
 same analysis with all 6 photons in the CCal and looking at the resolution
 obtained for the 6th one.
 Seon-Hee mentioned that she now had a file with the measured x-y positions
 of all the FCal blocks which will go into the data base when it is fixed.
 
 Stack Cooling and History
 Giulio showed a plot of all the stack parameters (beam current, energy, 
 sigmap, gas-jet density, cooling power, Dow Jones, etc) and explained how 
 the sigmap below 1 MeV (lab) had been achieved. This is a great achievement 
 for us. McGinnis had some real insight into the connections between the 
 frequency of the bunching RF and of the cooling system to allow the
 cooling to work after it had seemed to hit a point of no further progress
 at sigmap of 1.4 MeV. When the beam reached a sigmap of 1 MeV, the cooling
 power had to be reduced to avoid hiccoughs in the transverse emittance;
 this reduction did not seem to hurt at all. We volunteered Giulio for the
 Monday talk at the All Experimenters' Meeting.

 Event Yield.
 Giovanni showed preliminary numbers for the present stack. 

 ETOT fun and games.
 Jason discussed the issues with the ETOT trigger noticed after the Nim Bin
 replacement on Wednesday owl. The online symptom was that the ETOT trigger
 rates went down about a factor of 2 after the replacement; the offline 
 symptom was that Jason found an efficiency of 90% for the trigger compared to
 the usual 99+%. The bin that was changed contains only two modules relevant
 to the ETOT trigger - the Northwestern Integrator which takes the 20 ring 
 sums and sums them and a Lecroy Linear Fan-in Fan-out which provides copies 
 of the output of the integrator to the two Camac Discriminators for ETOT Lo 
 and ETOT Hi. 
 It was verified that the discriminators worked properly and were
 loaded with the correct values, that all the ring sums were present and that
 the fan-in/out was working properly. Given that all the other triggers
 were working, we did not interrupt data taking to check the gain of the 
 summer or the gain of the integrator. Jason made plots of the turn on of
 the ETOT triggers and concluded unambiguously, however, that something had 
 changed in the gain of the system and that the effective threshold was 10%
 higher than previously. He reduced the discriminator settings accordingly and
 the rates went back to normal. A plot of the turn-on now looks essentially
 identical to the plot before the troubles. It would be good to look at the 
 gain of the summer and the integrator to see what is going on - at least
 as a reference.
 
 Straw Resolutions:
 Ezio showed some plots he has been making of the straw performance using the
 pbar-p (back-to-back) events. These let him measure a variety of things.
 The phi resolution he gets from comparing the two tracks the result is a phi
 resolution of about 7 mr with some tail. He showed a plot of the distance
 sum for a pair of straws in the inner-outer layer of a chamber. Even with
 perfect resolution this sum would not be a single value because of the
 spread of the vertex. Ezio claimed to see a correlation between the distance
 sum for the two tracks - suggesting some sensitivity to the vertex.
   
 Eta-c gamma:
 Michelle showed numbers from the Monte Carlo of the probability of a
 pi-0 pi-0 or pi-0 gamma event faking an eta-c gamma. (The analysis
 would reject events with a reconstructed pi-0 but this gives an idea of the
 size of the issue). A pi-0 pi-0 has a 0.3 % chance of satisfying eta-c gamma
 and pi-0 gamma has a 3.5% chance. Multiplying by the respective cross
 sections (30 nb and 0.65 nb) gives about 100 pb fake cross section.

 Online Luminosity:
 (Long discussion - sorry - may be skipped if you aren't interested)
 Channel 13 now carries a quantity from the gas-jet mac which is meant to
 be our luminosity. It is calculated from the product of the beam current 
 and the gas-jet density. The gas jet density is inferred from the pressure
 in the recovery (R) side using measurements made in PAB on the size of the
 jet beam, on the speed of the jet and on the pumping speed on the R chamber. 
 This luminosity is about 20% low (within the uncertainty of the measurements)
 compared to the actual luminosity given by the luminosity monitor. While we
 do not actually use it in computing cross sections, it is a bee in 
 Stephen's bonnet, in particular since it is a quantity now shown to the
 world.
 The density depends quite delicately on the size of the jet-beam. The 
 pressure in the recovery side depends on the flux of hydrogen which is
 given by the speed times the cross section times the density of the jet.
 If the jet diameter is actually smaller than the 7 mm assumed in the density 
 calculation, the density for a given pressure increases as (7/d)^2 and the 
 luminosity as 7/d (provided the pbar beam is smaller than the gas-jet). 
 Gabriele will look at his data from PAB and the jet size as inferred from 
 the fibers to try to get the best value for the jet diameter.
 

 Stephen 
-----------------------------------------------------------------------------
 An addition to the minutes..

 In answer to a question from Seon-Hee...Stephen has bought a proper
 speaker-phone system for the trailers so that conference calls should
 now be possible. Yes.. it's the thing that looks like a Playstation.

 Stephen