Calorimeter Occupancies University of Cambridge Mark Thomson University of Cambridge

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

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

Total Energy Deposit In 300 ns from start of bunchtrain: ECAL Total = 11.5 TeV (490k hits) Barrel = 1.5 TeV (68k) Endcap = 10.0 TeV (420k) HCAL Total = 8.4 TeV (115k hits) Barrel = 0.3 TeV (5k) Endcap = 8.1 TeV (110k) LCD Meeting, 16/6/2011 Mark Thomson

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

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

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 = 0.8 TeV (18k) Endcap = 0.7 TeV (36k) HCAL Total = 10.8 TeV (128k hits) Barrel = 5.3 TeV (32k) Endcap = 5.5 TeV (96k) LCD Meeting, 16/6/2011 Mark Thomson

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

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