Minutes of the CALCOM analysis meeting, 26 September 1997 ========================================================= Agenda: N. Pivnyuk - Time-based tracking and straight track analysis A. Vlassov - A first look at the Cherenkov counter efficiency D. Carman - A first look at the drift chamber data J. Manak - Offline processing of 1.645 GeV data ------------------------------------------------------------------------- Next meeting: Tuesday, September 30, 3:00pm, room A110. Agenda: - time-based tracking status - a first look at the TOF data - a first look at the EC data - setting parameters (DC time windows, thresholds, B-field) for physics analysis data taking ------------------------------------------------------------------------- ====================================================================== A. Vlassov showed preliminary results of the Cherenkoiv counter efficiency analysis using the 1.645GeV data. Elastic ep scattering data were analysed to determine the #photo-electrons and the absolute efficiency of the installed 4 sectors (1,4,5,6). The absolute efficiency measurements give results for sector 6 which are consistent with the June run data. Sectors 1,4,5 seem to have higher efficiencies as inferred from the smaller number of non detected electrons in the active detector area. Only a portion of all collected calibration data were used in this study. More complete information should be available shortly (V. Burkert). ================================================================= Individfual reports: N. Pivnyuk: Time Based Reconstruction for Run 0710. ---------- Goal : investigate Time-To-Distance Relation and Spatial Resolution with B-field = 0. Input data : Run 0710 (Big Torus OFF, Mini Torus OFF, Thin target, Electron beam : Eo = GeV, Current = na). Procedure : track reconstruction in the middle plane. Superlayers 3 and 5 were taken into account only and seperatly. As a first approximation Time-to-Distant function was taken in form as it was calculated analytically on the basis of the Drift Time distribution. Flat shape of the Distance distribution was assumed. Summary : Tracks in the Superlayer 5 and tracks in the Superlayer 3 were reconstructed. Time to distance relation was obtained. It was demonstrated that spatial resolution depends on Drift time and, for the Drift time values which correspond approximately to the half of the chamber cell size, match numbers which were expected from the design and DC-Region3-Prototipe measurements ,namely, 180-220 microns. D. Carman --------- Drift Chamber Studies from the September 1997 Commissioning Run I touched briefly during my talk on five issues: 1). Drift chamber efficiency - The drift chamber efficiency has been studied as a function of voltage to map out the plateau curve. The analysis of this data was made uncertain mostly due to the fact that our measurements were carried out over the course of a three day period during the time when accelerator was having difficulty keeping beam in our Hall. Liming Qin and Rich Thompson have performed two separate analyses that were not entirely consistent except in the fact that it is apparent that our initial HV scan was not quite broad enough to accurately determine the knee of the plateau curve. However it does appear that at our nominal voltages, the drift chambers are >97% efficient in detecting electrons. 2). Discriminator Threshold Study - The number of hits per event have been studied in Region One, Two, and Three as a function of ADB threshold for both a noisy and a quiet superlayer. From these curves we determined that our initial threshold settings of -30 mV for Region One and Two and -45 mV for Region Three were acceptable settings. 3). Drift Chamber occupancies - The hit multiplicities in Region One for a good beam tune and a bad beam tune were studied under the same running conditions (1 nA on a full lH2 target). The multiplicities were reduced by nearly a factor of three in Region One for the good beam tune. As I have stressed to the collaboration in the past, a good beam tune is critical to the proper operation of the drift chambers. 4). Drift Chamber hardware - I showed two accumulation plots from CED to highlight the status of the drift chambers. The first picture was from Run 3487 in June 1997 and the second picture was from Run 6065 during the current beam time. The first thing that was clear was that we recovered a very significant portion of the drift chambers during our repair period over the summer months. I also pointed out the remaining problems with the drift chambers including areas that were turned off due to HV problems, broken wires, LV problems, and other assorted electronics problems. 5). I also talked about our use of the new epics DC high voltage control program written by Vardan Gyurjyan to control and monitor the three CAEN HV crates. Although we have encountered some minor hiccups, it is clear that this program is a great improvement over the old native CAEN control and monitor programs that we had been using. J. Manak -------- Joe Manak presented a summary of the current efforts to provide people interested in offline analysis with analyzed data. The philosophy is to provide people with analyzed data in the form of BOS banks which can then used for calibration, commissioning or offline monitoring without requiring the costly re-analysis of the data. Analyzed data sets exist on disk for runs: 5881, 5903, 5906, 5991, 6008, 6064, and 6079. For more details please consult the offline analysis web page at: http://www.cebaf.gov/~manak/offline_analysis.html In addition Joe showed the results of some analysis of these data sets, including the missing mass sqared, and the theta distribution for elastically scattered electrons by sector - these plots are also available on the web page.