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

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

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

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

ES Clusters EEndcap SC = Σ(Ebci+Epreshi) Epresh = γ(EPlaneX+EPlaneY) 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)

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

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

ES Cosmic Ray Test

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

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

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

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 beam E = 50 GeV (Prelim.) S. W. Li et al 2007 H2 test beam E = 20 GeV (Prelim.)

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!!!

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