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dE/dx measurement with Phobos Si-pad detectors - very first impressions (H.P Oct 17 1998)

dE/dx measurement with Phobos Si-pad detectors - very first impressions (H.P Oct 17 1998). What characterizes dE/dx in Si?. In the MIP range: measure momentum and and amplitude for which particles are minimum ionizing in thin silicon detectors In the high p range:

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dE/dx measurement with Phobos Si-pad detectors - very first impressions (H.P Oct 17 1998)

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  1. dE/dx measurement with PhobosSi-pad detectors- very first impressions(H.P Oct 17 1998)

  2. What characterizes dE/dx in Si? • In the MIP range: • measure momentum and and amplitude for which particles are minimum ionizing in thin silicon detectors • In the high p range: • measure the relativistic rise of dEdx and compare it to predictions (Bethe Bloch, Geant) • In the low p range: • measure the 1/beta-part of dE/dx for poins and kaons • characterize the energy straggling @ different momenta and particles for PID • try to measure the signal range for stopping particles

  3. What do we need for this measurement • The Silicon detector: • use final 4 planes of the spectrometer type 1 modules • small pads -> good and full tracking • high S/N -> good energy loss measurement • 8 sensors & 96 chips -> minimize systematic error, give redundancy and allow cross checks • The TOF: • provides pi/K seperation and particle identification in the low p range • Cerenkow counters: • suppress e- back ground of secondary beams • We need to do a real precision measurement! -> Use final PHOBOS calibration • allows to get very high precision dE/dx to better than 1%

  4. Our setup: • The high momentum beam line: • pi- beam from 0.5 to 8GeV/c • The low momentum beam line (The E913 beam in C6) • pi-/K- beam line from 300MeV/c to 750 MeV/c Trigger sc Cerenkow Phobos 4 planes of Spectrometer Paddle type 1 modules TOF start (Degarder) Phobos 4 planes of TOF stop Cerenkow Paddle (Trg) type 1 modules

  5. The Readout system • Based on VME analog readout system developed by HEPHY/Vienna • repeater cards inplace of FEC and sends analog signals via 20m cables to dedicated VME ADCs (0.6 to 40MHz 12-bit) • uses 40MHz ADC to digitize TOF data • readout is based on 1 Pentium II and a simple PCI-VXI interface card and LabWindows • The calibration is based on the final PHOBOS calibration card build by FH, Wr. Neustadt, Austria • uses 12 DAC voltage • switched with 20ns rise time on the calibration capacitor • linearity better than 0.5%

  6. The system performance = Excellent! • Si- system: • a 12 000 channel system • Signal/Noise was about 17:1 to 18:1 • about 60/12300 channel noisy • total efficiency about 98 % • The TOF: • largely based on the PHOBOS paddle counter • resolution about 200ps (average over 2/3 of the paddle acceptance) (TDC intrinsic resolution about 120ps) • The DAQ: • transfered RAW data in NON-SUPPRESSED mode with up to 100Hz ! • Limited only by CPU time and disk access

  7. The PHAT analysis software is ready • ALL analysis is based on standard PHAT routines • Parts implemented: • all detector data unpacking routines are prepared • the full geometry is described • ready for track fitting • a first version for signal calculation is implemented • Some parts still to go • implement calibration • tune signal calculation

  8. Let’s get to the “first impressions” on thedata quality • The high p range: • aim to determine what a “MIP” is in thin silicon detector • measure dE/dx up from 0.5 to • The beam and trigger • pi- beam • veto e- with Cerenkow • muon contents <2% • no protons • delta p/p = 0.5% • chross checked absolut energy with calorimeter - better an 4% • Recorded 50000 tracks at each energy point:= 200k hits • energies: 0.5, 0.75, 1.0, 2, 3, 4, 6, 8 GeV/c

  9. Measurement precision WITHOUT good calibration already 1-2%!

  10. The low p range and energy straggling: • aim to determine pi and K seperation • get energy straggling data at low momenta • test dE/dx PID • The beam and trigger • pi-/K- beam (60:40) • veto e- with Cerenkow • muon contents <2% • delta p/p = 4% • use energy calibration files of E913 • Recorded 50000 tracks at each energy point:= 200k hits • energies: 285, 500, 620, 750 MeV/c and 4 degrader with lower energies for pi

  11. Kaons Not yet looked at! Pions

  12. YES - we did get stopping particles ! (pi-) • use paddle counter a veto • trigger now only on small area finger counter (1cm2) • use a 4.5 inch steel degrader • energy after degrader about 80MeV/c • for cross check used detector part which is not in beam • recorded data • with veto counter to enhance stopping events (low p tail selection) • without veto counter to cross check rates • with veto as trigger (high p tail selection) • we have very limited data but can get more on monday

  13. 30MIP signal 100MIP signal

  14. Conclusion • We have beautiful data! • We measured: • the MIP point: measured • the relativistic rise: measured from 0.5 to 8GeV/c • dE/dx below one MIP: measured from 280 to 750 MeV/c for pi (500 to 750 MeV/c for K) • measured stopping particles and their signal range (try to get more statistics on Monday • We can analyse: • energy loss over two orders magnitude in momentum! • Can fully characterise straggling over the full p range • Can explore our particle identification with REAL data • Can get ideas what to do with stopping particles …

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