Minutes of the CALCOM analysis meeting, October 31, 1997. ======================================================== Agenda: D. Carman - Drift chamber hit occupancies and hardware status M. Mestayer - Status of drift chamber calibration (no report) K. Mikhailov - Straight track analysis and beam-related background L.C. Smith - EC calibration status B. Niczyporuk - Preliminary results on pion and proton id in SDA V. Burkert - Where are we on the CALCOM analysis project list? ------------------------------------------------------------------------- Individual reports: ================== D. Carman: --------- I presented an overview of the drift chamber hardware status history. This history showed the number of bad drift chamber channels in each region at the end of the final electron commissioning run, as of October 30, and also extrapolated to the start of the E1 physics running period in December. My goal is to have no more than 5% of the channels in each Region missing. I also showed a picture of how the problems in each Region are distributed as a function of time. These problem groupings were in terms of HV disconnects, electronics problems, LV disconnects, missing wires, unplugged signal connectors, and isolated individual missing wires. I also showed some results of my analysis of the drift chamber occupancy dependence on beam current using the 4.0 GeV data runs 6604 through 6609. We clearly see good linearity in the drift chamber occupancy as a function of the beam current. Drift chamber occupancies at 10**34 luminosity for all drift chambers were around 3%. I have not broken this down into what fraction is track-related and what fraction is non-track-related. All viewgraphs that I displayed at the CALCOM meeting have been included on my CLAS drift chamber web page (along with lots of other up-to-date studies). The URL is: http://www.phys.cmu.edu/cmu/names/carman/clas/dc.html This URL can be linked to from the official CLAS drift chamber web page. Konstantin Mikhailov -------------------- Konstantin presented results of his and Nikolai's analysis of possible background sources along the beamline. Straight tracks from the B=0 runs (6112 - 6116) with empty target as well as full target were used. Only hits in SL 5 were used and projected back to the beamline. While it appears that there are isolated sources of background when projecting all two-hit combinations, when requiring more than 3 hits, these "sources" disappear and the overwhelming number of tracks project back to the target. These results indicate that there are no significant sources of background outside of the target region. This study is now completed, and the main focus of this work will be on understanding the drift chamber alignment. (V. Burkert) L.C. Smith ---------- Absolute calibration and energy resolution of the forward angle calorimeters is being checked using data taken during the Sept. commissioning run. PMT HV were adjusted prior to the run using cosmic-ray minimum ionizing events to produce an average ADC calibration of 10 channels/MeV. Individual PMT calibrations were also extracted from cosmic-ray data. Pizeros were identified from events w/ two neutral EC reconstructed hits/sector. Electron ID was based on EC reconstructed hit matched with DC negative track. Run 6343 (4 GeV) was used for pizero events (w/TRK HBT), Run6079 (1.6 GeV) for electrons (w/SDA TBT). SEB was used for track matching. Results: Sector 1 2 3 4 5 6 pi0 cen (x100) 6.8 0.7 3.0 1.4 1.7 3.2 pi0 rms (x100) 13.7 11.4 10.3 12.8 11.7 11.1 e- cen (x100) 7.3 -2.5 3.1 -0.5 6.7 6.4 e- rms (x100) 10.1 10.5 8.5 10.8 9.6 9.5 pi0 cen: centroid of (invariant mass)/mpi0 - 1 e- cen: centroid of (ec energy/dc momentum) - 1 Further improvements can be expected as in situ attenuation lengths from cosmic ray runs are introduced (currently the original bench measurements are used). Also the effects of pedestal noise are under study. More commissioning data will be analyzed as TBT at 2.4 and 4.0 GeV becomes available. cole@apollo.phys.virginia.edu Bogdan Niczyporuk: "Preliminary results on pion & proton ID using ToF" ----------------- A progress on ToF calibration (timing constants), using the elastic scattering events, has been discussed. It has been shown that preliminary time constants allow us already to seperate effectively the ep --> ep(pi0) and ep --> epi+(n) reactions. The backgrounds under the missing mass of pi0 and neutron peaks has been substantially reduced (plots are available on request). In summary, at present the identified electrons, protons and pions from the exclusive reactions are being used to derive the time constants for each ToF photo-tube separately. bogdan@jlab.org Volker Burkert: Status of the CALCOM Analysis Tasks List -------------- 1. Absolute tracking efficiency, resolution, track reconstruction efficiency vs luminosity (F.J. Klein, L. Qin, J. Mueller) -> work in progress -> most urgent is tracking efficiency versus luminosity 2. DC B=0 straight track analysis to identify possible sources of background in beamline ( N. Pivnyuk, K. Mikhailov, A. Skabelin) -> work completed 3. Extract elastic and inclusive ep cross sections as a means of absolute normalization (A. Coleman, J. Manak, K. Joo) -> very urgent, needs immediate attention 4. Trigger studies (L.C. Smith, K. Joo, R. Thompson, V.B.) - uniformity of trigger response in EC - does the prescaling work as expected? - electron selectivity of EC, EC.CC, EC.TOF, EC.CC - efficiency of specific triggers -> very urgent, work has started 5. Is our live time measurement correct? (J. Manak) - look at FC, clock info in data stream, is # elastic event/FC(corrected) = constant (throughout a run) and independent of luminosity (for different runs, same energy, trigger, target) -> very urgent, needs immediate attention 6. Hit occupancy versus luminosity, noise versus track hits (D. Carman, Pittsburgh, TOF ?) - drift chambers - TOF (minimal ADC threshold) -> urgent, work on drift chambers started, need to start on TOF 7. Gain & time - matching for TOFs (S. Taylor, C. Loukachine) -> gain matching in progress 8. Particle id using matched tracks and ToF, SEB (L. Elouadrhiri, ..) -> progress on dE/dx -> needs extensive work on time matching 9. EC calibration using min. ion. particles & reconstructed gamma-gamma (from pi-0) (L.C. Smith) -> progress on all fronts, need to extract new attenuation lengths from cosmic ray runs or min. dE/dx 10. Checking the drift chamber alignment (N. Pivnyuk, K. Mikhailov, A. Skabelin) - straight track analysis - elastic ep scattering with B = 0, ep angle correlations - reconstruct target walls (empty target cell) -> machinery setup, work needs to proceed within RECSIS framework 12. LAEC calibration (P. Rossi, INFN) -> cosmic ray calibration well established -> beam calibration procedures need extensive studies 12. How well do we understand the Torus magnetic field (R. Minehart, K. Joo, H. Egiyan) - elastic scattering with w/o magnetic field - study correlation of kinematical invariants (W) in ep elastic, or MM in ep -> eppi0, enpi+ vs theta/phi angles -> need to establish procedures and criteria 13. Single particle acceptance functions vs px,py,pz,Q (V.Burkert) - use TBT and known DC positions & correct magnetic field to map out charged particle acceptances from minimum biased events -> work can start only after tracking and detector geometry understood After the meeting Steve Dytman gave me another list that he had prepared earlier, which partially overlaps this list, but also contains some other aspects. For the upcoming meeting I will combine these two lists.