1. Calorimeter Occupancies University of Cambridge
Mark Thomson
University of Cambridge

2. Simulation Settings
Simulated events with entire bunchtrain of gg→hadrons background
assumed 3.2 events/BX
looked at hits out to 0.01 s
assumed energy deposits separated by 20ns would
create separate hits
applied single hit energy thresholds equivalent to
~0.3 MIPs in ECAL (c.f. 0.5 in Pandora)
~0.1 MIPs in HCAL (c.f. 0.3 in Pandora)
Plots/numbers for:
Total energy deposit in ECAL/HCAL
Time structure
Occupancy
LCD Meeting, 16/6/2011
Mark Thomson

3. Total Energy Deposit From entire bunch train 13.2 TeV in ECAL
13.7 TeV in HCAL
HCAL time structure (ECAL similar but less prominent tail)
time constant tHCAL ~2.3 ms (tECAL ~ 600 ns)
Quote numbers from first 300 ns…
LCD Meeting, 16/6/2011
Mark Thomson

4. Total Energy Deposit In 300 ns from start of bunchtrain: ECAL
Total = 11.5 TeV (490k hits)
Barrel = TeV (68k)
Endcap = TeV (420k)
HCAL
Total = TeV (115k hits)
Barrel = TeV (5k)
Endcap = 8.1 TeV (110k)
LCD Meeting, 16/6/2011
Mark Thomson

5. Occupancies Mean occupancies in endcaps (hits/cell)
Look in sampling layer with highest occupancy
ECAL (Layer 11)
HCAL (Layer 1)
ECAL structure:
square at 400mm is gap between plug and endcap
smaller squares are a binning effect
double ring due to gap at inner radius of plug
LCD Meeting, 16/6/2011
Mark Thomson

6. Occupancies cont. Occupancies vs radius Mean cell occupancy
R/mm
R/mm
LCD Meeting, 16/6/2011
Mark Thomson

7. Beam Halo Muons Use new files with Spoilers from Laurence Deacon
Assume 5 muons per BX
Integrate over whole bunchtrain
In 150 ns from start of bunchtrain:
ECAL
Total = 1.5 TeV (54k hits)
Barrel = TeV (18k)
Endcap = 0.7 TeV (36k)
HCAL
Total = TeV (128k hits)
Barrel = TeV (32k)
Endcap = TeV (96k)
LCD Meeting, 16/6/2011
Mark Thomson

8. Beam Halo Occupancies not large, due to spread in x, y. e.g. HCAL
Beam Halo Muon
c.f. gamma gamma
Mean cell occupancy
Mean cell occupancy
R/mm
R/mm
LCD Meeting, 16/6/2011
Mark Thomson

9. Summary Calorimeter occupancies not large, not also not negligible
Clear need for multi-hit capability in endcap
Need study of pair backgrounds in calorimeters
LCD Meeting, 16/6/2011
Mark Thomson