HLT & Calibration

1. HLT & Calibration

2. HLT as Calibration Data Source • Among the main tasks of HLT (especially in the first years) • Monitoring of the detector performance • Analysing calibration data (real events and calibration triggers) • Calculation of a (first) set of calibration parameters • Applying calibration to online event reconstruction • Storing parameters in relevant databases • Procedures are being developed in collaboration with TPC, TRD, PHOS, and Dimuon detector • HLT is open for calibration tasks for all participating detectors • Compatibility w. Computing Power / Financial Budget

3. HLT & Databases • The HLT will have contact to different databases, which are for different purposes as well as under different administration. • For now, it is foreseen to have contact to three different DBs: • Configuration DB (DCS) • Condition DB (DCS) • Calibration DB (Detector Specific)

4. HLT DB Remarks • Use of dedicated HLT portal nodes to contact DBs • Redundancy of these nodes to avoid single-point-of-failures • Data of the DBs is cached (where possible) and distributed to the appropriate places inside the HLT cluster (using its publisher-subscriber framework) • Output data to DBs will be written from the global layer of the HLT cluster. • Contact to the databases will be performed via ODBC or similar techniques.

5. TPC Calibration Example (1) • Pedestal run analysis and download • Pulser runs • Accumulation of pulser events • Gain calibration and timing alignment • Map hot/dead pads • Laser runs • Online reconstruction of laser tracks • Drift velocity map • ExB map • static E-field distortion map • Electron attachment / gas contamination • Online reconstruction of particle tracks / laser tracks • Cluster charge loss per drift length

6. TPC Calibration Example (2) • Drift velocity map • Nuclear collisions • Accumulate charge per timebin • Calculate charge step at central electrode • E.g. NA49 data NA49 charge step

7. TPC Calibration Example (3) • Space charge effects • Online reconstruction of tracks • Histogram of track impact parameters • E.g. STAR TPC – fluctuations on second timescale

8. TPC Calibration Example (4) • Histogram of track residuals • E.g. STAR TPC – grid leak distortions • Ion leakage at gating grid gap

9. PHOS Calibration Example • Pedestal run analysis and download • LED runs • Accumulation of pulser events • Gain calibration and timing alignment • Map hot/dead channels • Gain/energy calibration • Nuclear collisions • Online pulse shape analysis • Timing alignment (using fastest particles) • Online reconstruction and accumulating of showers • Relative gain calibration by equalizing channels • Absolute energy calibration by monitoring pi0-peak

10. HLT Questions/Open Points To plan connections from HLT to DBs, HLT needs to know: • At which places (processing steps) in the HLT cluster is DB data needed? • What is the estimated processing budget for online calibration? • What data for or/and from which databases? • Which detector needs what data? • How large is which data? • (different for different data -> detailed list wanted) • How often is data updated? (once (caching)  regular requests to DB) • Output data • General • e.g. Drift Velocity: • Type of measurement (once, continuous spectrum, every X sec., average, ...) • Write to DB (continously, at end of run, ...) • Who has access to data (online, offline)?