CMS Preshower : Startup procedures: Reconstruction & calibration

1. CMS Preshower:Startup procedures: Reconstruction & calibration C-M. Kuo & D. Barney

2. Contents of presentation • Preshower reconstruction scheme • Data flow • Digits • RecHits • Clusters • Inter-calibration of silicon strips etc. • Prior to installation • In-situ • Inter-calibration with EE • Startup procedure

3. Data Flow • Detector • Front-end  ES-DCC  global DAQ • pedestal subtracted • CMN corrected • zero suppressed data • “final version” of unpacker will be ready soon • VME spy memory  local DAQ • non-zero suppressed data • pedestal, noise, dead channel

4. S2 PACE 3 Pulse Shape S3 S1 ES Digits & RecHits Estrip = W0S0+W1S1+W2S2 Apply MIP calibration at RecHit level

5. ES Clusters • See CMS IN 2001/056 (C. Palomares & D. Barney) • Use the EE basic cluster to extrapolate back to preshower planes • 4 ES clusters matching each EE basic cluster • Each ES cluster contains 5 strips Search area : 3 x 31 strips EEndcap SC = Σ(Ebci+Epreshi) Epresh = γ(EPlaneX+EPlaneY)

6. Intercalibration • Preshower is a sampling calorimeter • Only “reference point” is the minimum-ionizing particle (MIP) • Response to a MIP varies from strip to strip due to: • Silicon thickness (known) • MIP Incidence angle (~known from placement in ES) • Gain of the electronics (constant with radiation) • Charge collection efficiency – varies with radiation damage • Required accuracy of MIP calibration is about 5% (corresponds to ~0.25% contribution to overall EE+ES energy resolution as about 5% electron/photon energy deposited in ES) • Switchable gain of electronics • High Gain (0  60 MIPs dynamic range) for MIP calibration • Low Gain (0  450 MIPs dynamic range) for physics running • Need for gain inter-calibration – done with internal electronic injection pulse

7. MIP Pre-calibration • All ES modules undergo “cosmic-ray calibration” for 24 hours (also serves as a first burn-in) • Not optimum as: • cosmic-rays are asynchronous with the 40MHz clock • Range of incidence angles – but ES modules arranged in a vertical stack so “tracking” can be performed • Reference data sets taken over 4 days • MIP calibration accuracy estimated to be better than 2% for 24-hours of running

8. ES Cosmic Ray Test

9. MIP Pre-calibration: examples S. W. Li et al

10. MIP Pre-calibration: alternative method Detector capacitance (known) is a good measure of the MIP to about 2%

11. In-situ MIP calibration • Main use is to follow change of charge collection efficiency with radiation damage • Use MIPs from triggered events • MUON events • Min-bias events (charged pions) • Can use the L1 (100 kHz) triggers • See CMS-NOTE 2006/052 (I. Evangelou) • Time required depends on luminosity • At high L expect ~1 week needed

12. ES-EE inter-calibration • Start by using inter-calibration constants found from beam tests and simulations • Ideally use monochromatic electrons/photons (e.g. electrons from Z0) γ=-0.018 GeV/MIP γ=-0.019 GeV/MIP 2007 H2 test beamE = 50 GeV (Prelim.)S. W. Li et al 2007 H2 test beamE = 20 GeV (Prelim.)

13. p0 rejection training • Present p0 rejection algorithms based on Neural Networks (A. Kyriakis et al) • Require training • Use constants from simulation to start with • Low-energy p0 can be used as a starting point – also used for EE calibration • Iterative procedure • THIS PART NEEDS SOME THOUGHT!!!

14. Startup Procedure • Ensure data readout from all modules • Use charge-injection pulse • Set trigger latency (i.e. time-in the beam) using triggered events • High-gain mode • Single parameter required for all modules • Pedestal runs to measure: • Pedestals for each channel (~140000 strips) • Intrinsic noise level • Common-mode noise level •  will use “spy memory” of ES-DCC (off-detector readout) i.e. no zero-suppression • Pedestals, noise, thresholds fed-back into ES-DCC via conditions database • Start training NN and perform ES-EE inter-calibration