Summary of E-835 weekly tuesday meeting 5/9/00

 Present: Metreveli, Tomaradze, Obertino, Bagnasco, Lovetere, Bettoni,
          Menichetti, Gollwitzer, Garzoglio, Negrini, Baldini, Cibinetto,
          Macri, Borreani, Stancari(G), Stancari(M), Seo, Graham, Kasper, 
          Pordes

 Last Week:
  Stephen reported what he had said at the all experimenters' meeting,
 viz that we had taken more than 8.4 pb-1, finished the chi0 for a while, 
 that we were turning to the 1p1 from next three weeks, that we had taken 
 stacks of 3.6 pb-1 and 3.3 pb-1 so far, that we are dealing with the 
 statistics of small numbers and that we are a little concerned about the 
 beam momentum spread; compared to a resonance with a width (gamma) of 
 400 keV, we have had a beam width (sigma) of about 400 keV, which corresponds 
 to a beam-width (gamma) of ~1 MeV. At the meeting, Dave Mcginnis volunteered
 "we can reduce the beam-width" - the Director said "well, there you are" 
 or something like that and so..

 The stack presently in preparation:
 has been requested to be at 3526.7 and the source will try for a sigma width 
 in the lab of 1.2 MeV or less(= 1200 * 0.94/3.53 in the CM = 320 keV (sigma)
 or 760 keV (gamma)).
  Keith said that there is some concern about a narrow momentum spread beam
 and that we may be called on to turn the gas-jet off in a hurry.
 IF WE ARE CALLED BY THE OPERATORS OR AP-10 TO TURN OFF THE GAS-JET, WE ARE 
 ASKED TO RESPOND QUICKLY. THE "CLOSE THE BEAM-VALVE" IS THE PROPER BUTTON
 TO CLICK ON IN THE GAS-JET CONTROL PANEL.
 Gabriele's write-up on the jet by the jet console explains all this.
 The straws do not need to be turned off before closing the beam-valve if
 there is any rush. They should be turned off before re-opening the 
 beam-valve and then turned on when the luminosity is stable. It would also 
 be nice to pause the daq while the jet is off.
  The following stack in the current plan would be 3525.95. Stephen asked why 
 the stacking rate this afternoon had been comparatively low (typically 
 2.5 mA/hr compared to the previous typical 3.5 mA/hr). Giulio said he did 
 not know but/and that people had been working on this.


 Detector status:
  Wander recounted some of the continuing woes and work on the
 VLPC cryo system. Rich Schmitt has worked on the controls changing some of
 the "loops" and this has made for more stable temperatures but typically
 we do not make quite enough liquid helium to keep the main dewar from slowly
 emptying. Wander is in a mode where he lets the cryostat warm up a bit
 outside data taking time to allow the dewar to be replenished.

 Trigger and DAQ:
  Stephen asked if the Bombo effect (the ratio of neutral rates to charged
 rates decreases by 8% over a stack) has been further investigated. The
 answer was 'no'. We still do not know which (if either) is stable with
 the luminosity monitor. Jason said that he has not seen any problems in the
 neutral trigger thresholds. Wander reported that the trigger logic
 efficiencies as determined from the min-bias events - on disk, thankyou -
 are stable and around 95%.  There was some discussion of the pbar-p filter - 
 which needs to be carried to the actual implementation stage.
 Keith is in the process of formatting the replacemnt disk for the one which 
 failed. Stephen asked if the replacement disks could be formatted beforehand. 
 Keith would prefer not to.

 Offline:
  Diego said that the tracking is being tuned. Margherita has new calibration
 constants for the hodoscopes, including the dependence of the response with
 z position. Typically the H1 MIP channel has decreased by 10% to 20%, the H2 
 and H2' have decreased by less than 10% except for a few channels where the 
 apparent change is larger and is being investigated.
  She is also using the psi' electrons to measure the theta dependence of the
 Cerenkov response. Michelle says that the 1p1 stacks seem to have the beam
 displaced about 1mm towards the debuncher compared to the chi0 runs.

 Presentations:
  Seon-Hee showed an analysis of the two 1p1 stacks. The number of psi-gamma
 events in each stack was the same; the number of psi-pi0 events was larger
 in the second than the first.
  Gabriele showed the off-line data for the beam parameters (energy, sigmap)
 of the last stack. The baby sitter kept the energy very constant except
 when the jet was turned off and back on. Giulio emphasized that we need
 to warn the control room when we are going to turn the jet-off so they
 can deal with the beam-cooling by hand.

 Stephen 
 correction to minutes of 5/9/00

 sorry...the requested energy is 3526.5 (not 3526.7)..pursuant to the
 narrower beam..

 Stephen