Monitoring system of the LHCb electromagnetic calorimeter NEC’2007, Varna, Bulgaria Ivan Korolko (ITEP Moscow)

Outline LHCb detector LHCb CALO monitoring system

Yoke Vertex Shielding Tracker Calorimeters RICH-2 Coil Muon Detector RICH-1 LHCb detector Designed for comprehensive studies of CP violation with B hadrons 500 physicists from 60 institutes

LHCb in numbers LHCb nominal Luminosity→ 2x10 32 cm -2 s -1 rate of p-p interactions→ 2x10 7 per second HLT output→ 2000 Hz RAW data per year→ 2x10 10 events (500 TB) Events with b quarks → 10 5 per second (!) acceptance for b-events → 5-10% Br. for CP channels → ~10 -5 Number of CP channels → ~50 ~5 signal events in every second of LHCb operation – GREAT! Have to select them from 1.5x10 7 background events Signature of LHCb signals is not very bright (P t, vertex)

LHCb calorimeter system Sensitive Pad Detector - triggering, photons Preshower - triggering, electrons ECAL - triggering, photons, π 0 HCAL - triggering Participating (in CALO) Russian institutes: IHEP, INR, ITEP

LHCb calorimeter system Construction of CALO system is finished. Commissioning phase

Monitoring system We have to measure small CP effects Stability of trigger algorithms Effective reconstruction (S/B ratio) Robust monitoring is vital for LHCb operation Temperature variations Radiation induced degradation HV instability

Monitoring system PHENIX –laser based monitoring HERA-B-LED based monitoring LHCb-LEDs controlled with PiN diodes Long term stability Possibility to calibrate CALO system with MIPs LHCb grid system for Monte-Carlo simulation and analysis

Monitoring system 24 hours of data taking Black - 50 GeV electron Green – LED seen by PiN diode RED - LED seen by PMT Blue - corrected with monitoring system

Monitoring system (ECAL) Light splitting scheme and LED grouping for outer and middle ECAL sections (1/4 of ECAL)

Monitoring system (ECAL) ~6000 ECAL channels are monitored with 536 LEDs controlled with 128 PiN diodes long term stability – better than 0.3%