Summary of E835 meeting 4/11/2000 Present: Marchetto, Negrini, Baldini, Stancari (G), Stancari (M), Pastrone, Calabrese, Bettoni, Obertino, Garzoglio, Robutti, Boca, Kasper, Seo, Graham, Gollwitzer, Joffe, Pordes The stack was at 35 mA when we started and around 39 mA when we finished. The energy of this point was request to be 3415 MeV (Ecm) Jason asked that the plans for future running be presented and distributed as soon as known. Stephen agreed that this was a good time to develop somewhat more detailed plans since we may now be in a state of stable running. The past week has been very encouraging; for the last stack, the time to recover from a store, stack 40 mA and decelerate with 94% efficiency was about 20 hrs total. We recorded data for an integrated luminosity of 2.5 pb-1 in about 36 hrs. (Note: this would give us 7.5 pb-1 in a week) IDEAS FOR RUNNING. At the group meeting it was decided to do the chi0 to the end of this month or for about 20 pb-1 which ever comes first. There was a discussion of energy points and how to assign the luminosity. A set of energy points was constructed at the meeting to allow us to measure both the chi0 gamma-gamma branching ratio and the total width. The points with their (extra) luminosities are 3370, 3385, 3450 (2.5 pb-1 each for gamma-gamma background - with 3450 the most expendable) 3416 +/-1 (peak ) 6 pb-1 (gamma-gamma assuming we get 2.5 pb-1 out of this present stack) 3409 and 3426 (2.5 pb-1 each for width measurement) for a total of 18.5 pb-1 more.. The plan for how to do these energy points depends, among other things, on the maximum stacks that can be achieved. We are presently getting about 0.1 pb-1/mA and can run at decent luminosity down to about 13 mA. An example scheme based on being able to stack 5 mA more each successive stack could start: [40 mA stack (present one) 3415] 45 mA stack 3385 2.5 pb-1, 3370 0.8 pb-1 gamma-gamma.. 50 mA stack 3426 1.8 pb-1, 3409 1.9 pb-1 width 55 mA stack 3415 3.0 pb-1, 3370 1.2 pb-1 gamma-gamma It was agreed that this be re-visited after each stack. It may be possible to achieve larger stacks - which would be a real help - or not. And it may be sensible to do at least one of the points for the width measurement sooner (ie next stack). And we will need to plan around the MI shut down. GAMMA-GAMMA ANALYSIS. Michelle reported that a very preliminary analysis of the recent data gave 25 gamma-gamma events/1.47 pb-1 at the peak and 30 events/2.52 pb-1 from the background point at 3470. These correspond to about 75% of the rate seen in the final old 835 analysis and Michelle said there could be many reasons for the difference. Stephen developed a concern for a timely pi0-pi0 analysis. PBAR PLANS Giulio said that there were plans to test the (energy mover) sequencer (ie the program which automatically moves the beam energy from one set value to another desired value) at the end of this stack (with beam). Keith mentioned that there will be studies on the stack-tail system and the delta kickers (ask Keith or Giulio) on the next stack which will take about a shift total. As per a comment from Michelle, Giulio will check on the vertical position of the beam at the target (as determined by the BPM's). RUNNING GOOD PRACTICE Giulio showed a plot summarizing the beam behavior during the last stack. The beam behaved very well. He pointed to parts of the plot here the recorded data were perfectly flat - which meant that the P77 program was stuck. This program is the one that among other things sends the information on the beam parameters to us. There is (should be) a display of the P77 output running on the console in the counting room and the online scaler display also indicates when P77 is stuck. PLEASE CALL THE MCR OR AP-10 TO REPORT SUCH A CONDITION.(sorry for using upper-case). Giulio has a memo describing all this posted by the ACNET console in AP-50. PHI-PHI-GAMMA Filter. Flavio reported on the analysis of the phi-phi filter. Using the autopass events, the online and offline agree on which triggers survive to 4 events in 1600. Using the offline, on the autopass events, he can then predict the survival rates for cuts using different numbers of CCaL blocks for the phi-phi-gamma trigger. They are: reject more than surviving triggers rate to tape at 2.5 10^31 12 5.8% 105 Hz 14 7.9% 142 Hz 16 10.5% 190 Hz 18 13.1% 236 Hz.. From the phi-phi data which shows the maximum number of blocks set to be 12 and a study of the typical number of blocks set by phi-phi-gamma type photons, 16 seems a very reasonable cut and produces an acceptable rate to tape. PBAR-P TRIGGER. Keith asked about the pbar-p trigger. In particular, it might be that with the sort of filter implemented for the phi-phi, one might achieve an acceptable rate to tape. (At present, the pbar-p is prescaled by 100 and doesn't actually include the fibers). Wander may look at the hardware side (incorporating the requirement for 1 or 2 fiber bundles) and Margherita may look at the existing pbar-p data to see what sort of calorimeter cut could be used. The pbar-p events are a very useful diagnostic for alignment if nothing else and there would be room if a reduction of 10 can be achieved. Stephen