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CAL CALIBRATION Overview and Stability

CAL CALIBRATION Overview and Stability. Thomas Sch örner-Sadenius Hamburg University ESCALE Meeting DESY, 7 June 2005. INTRODUCTION TO THE ZEUS UCAL Depleted Uranium for calibration and compensation. Principle.

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CAL CALIBRATION Overview and Stability

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  1. CAL CALIBRATION Overview and Stability Thomas Schörner-SadeniusHamburg University ESCALE Meeting DESY, 7 June 2005

  2. INTRODUCTION TO THE ZEUS UCALDepleted Uranium for calibration and compensation Principle Depleted Uranium – scintillator calorimeter; analog pipelinedPMT readout. Analog electronics on front-end cards on detector;digital electronics in 3rd floor of rucksack. Division in F/B/RCAL with 2172/2592/1154 cells, 2 PMTs per cell EM cell size: 520 (1020) cm2 in F/BCAL (RCAL) HA cell size: 2020 cm2. Resolution: (e)/E=17%/E, (h)/E=35%/E Claim: absolute energy scale known to 1%. 98.1% 238U,  decay to 234Th,  decays to 234PA and then 234U,  cascades in between. Emax()=2.3 MeV, E()=10-1000keV (U)=4.5 Gy (Giga-years)  rather stable signal of ZEUS lifetime. Use UNO (Uranium noise) signal to monitor CAL behaviour with time Calibration Uranium Idea TSS: CAL Calibration

  3. 20ms integration time over UNO current IUNO shaper shaper pipeline pipeline buffer buffer Qhigh Qlow To trigger VDAC Vref DAC Vref=1.67V 55pC READOUT OVERVIEW Necessary for understanding of calibration constants. Digitalelectronics PMT UNO Energy Q Current IPMT Charge Q Voltage V ADC counts Necessary: Calibration of particle/jet energy to ADC counts TSS: CAL Calibration

  4. CALIBRATION IDEA Use stable Uranium noise as calibration signal Assumption 1 Uranium activity stable in time. UNO signal stable in time to about 1% (CERN testbeam)e/UNO or h/UNO for given Ee, Eh stable in time (studying the ratio cancels some uncertainties  more precise result e,h response linear in energy (CERN testbeam) Assumption 2 Assumption 3 Assumption 4 Keep UNO signal stable trimming of HV settings  UNO scale factors (offline GAFs) From known and linear e/UNO (h/UNO) then estimate energy of e,h. • UNO[ADC] fixed • e(E)[ADC]/UNO[ADC]: CERN! • then e[ADC]e[GeV] STEP A STEP B One of the many complications: UNO signal and (fast) physics signal go through different signal paths on front-end card! TSS: CAL Calibration

  5. “1%” CALIBRATION Refers to rather different things 1% - the first Intermodule/interregion calibration After UNO calibration: compare various modules in their response to well-defined input energies (test beam) spread of various modules ~ 1% 1% - the second Determination of absolute scale E(particle)  ADC: after UNO calibration (UNO gives precise ADC count): absolute scale delivered by (using the test beam results): ‘one-to-one relation betweenADC and energy. Within onemodule response from towersis gaussian with width ~1%! in testbeam fix scale to 1%! Two important questions/tasks here: -- Keep the UNO signal to the nominal as closely as possible (UNO scale factors, but also other smaller corrections for front-end, signal path etc.) -- Derive offline correction factors from physics data (kin. Peak, E-pz, etc.) TSS: CAL Calibration

  6. UNO SCALE FACTORSCAL offline GAFs – the one that always stop the reconstruction For all CAL regionsmeans within fewpermille around 1.Widths below 1%. Channel-by-channel comp-arison of two UNO GAFs from 010305 and 080505.Means ~1permille.Widths ~0.5%. Several HV adjustmentsbetween the two dates. No systematic trends, distributions gaussian absolute calibration preserved at 1%-level! TSS: CAL Calibration

  7. UNO SCALE FACTORSModule by Module comparisons of relative UNO differences No significant changes between modules  intermodule calibration still at 1%-level! TSS: CAL Calibration

  8. FURTHER OFFLINE CORRECTIONS Motivated by physics; take into account dead material etc. PHANTOM routine escale03.fpp (default in ORANGE) applies corrections for F/B/RCAL, separately for EMC and HAC; in addition cell corrections for some RCAL cells FEMC: 1.024FHAC: 0.941 BEMC: 1.003*1.05BHAC: 1.044*1.05 REMC: 1.022RHAC: 1.022 Corrections derived from kinematic peakevents and DA measurements. -- repeat in newer data?-- dependence on physics case?-- any manpower currently involved? TSS: CAL Calibration

  9. SUMMARY and possible outlook Started to look into long-term stability of CAL calibration (UNO scale factors). absolute calibration seems stable to within 1% over time.  intermodule calibration within about 1%  if initial absolute energy calibration good to 1%, then this quality is probably preserved until today. Needed: Better understand of calibration in detail; only then can judge on quality of calibration. Important:  control of offline CAL regional (caltru) correction factors  use physics events for that (kin. peak, E-pz, DA method etc.) TSS: CAL Calibration

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