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 TrackerCalorimeters

RICH-2

Coil

Muon Detector

RICH-1

LHCb detectorDesigned for comprehensive studies of CP violation with B hadrons

500 physicists

from

60 institutes

LHCb in numbersLHCb nominal Luminosity → 2x1032 cm-2 s-1

rate of p-p interactions → 2x107 per second

HLT output → 2000 Hz

RAW data per year → 2x1010 events (500 TB)

Events with b quarks → 105 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 1.5x107 background events

Signature of LHCb signals is not very bright (Pt , vertex)

LHCb calorimeter system

Sensitive Pad Detector - triggering, photons

Preshower - triggering, electrons

ECAL - triggering, photons, π0

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 monitoringsystem

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%