TileCal Level-1 trigger studies at phase-2 upgrade

Introduction

The replacement of the complete read-out electronics of TileCal is planned for the second long shutdown of LHC (Phase-2). More info about the red-out electronics development and prototypes can be found here.
At Phase-2, the current Level-1 (L1) online trigger system with:

• Energy precision of 1 GeV^? and
• A detector granularity of Δη x Δφ = 0.1x0.1), called Trigger Tower (TT)

will profit from full TileCal detector granularity (radial direction: 3 layers) and energy resolution (at the cell level, i.e. cell noise ~ 20 MeV^?). The Electromagnetic (EM) Liquid Argon (LAr) calorimeter will use a TT energy precision of 256 MeV^? since Phase-1.

The motivation of these studies is improving the present Level-1 trigger system of the ATLAS experiment, to be able to keep an acceptable trigger rate, while keeping the current p_T thresholds for single and isolated objects.

The goal is to check if a better precision (below the current 1 GeV^?) with digital Trigger Towers, scheduled at phase-2, could be relevant for trigger and physics.

D3PD production

Different official ATLAS Monte Carlo (MC) datasets are processed to obtain private D3PDs for the L1 trigger upgrade studies. Here there are 2 jobOptions to produce D3PDs from RDO and ESD MC datasets by using the ATHENA release version 17.2.3:

• SVN D3PD production jobOptions

These jobOptions add into the D3PD info about:

• L1 Trigger Towers
• L1, L2 and Event Filter (EF) triggers
• TileCal cells
• Electrons, muons and taus
• Missing transverse energy (Etmiss)
• Jets

These D3PDs are stored at one TileCal IFIC UI: tilecalui01.ific.uv.es, under the path /scratch1/march/:

• Ntuple_D3PD_Tile_MB_17_2_0
• Ntuple_D3PD_Electron_17_2_3
• Ntuple_D3PD_mc12_8TeV_147913_JZ3W_Release_17_2_3_new
• Ntuple_D3PD_MB_8TeV_17_2_3
• mc11_14TeV.108351.Pythia8_minbias_Inelastic_17_2_3
• mc10_14TeV.105568.ttbar_Pythia.recon.ESD.e662_s1107_d459_r2037_17_2_3
• mc12_14TeV.147806.PowhegPythia8_AU2CT10_Zee.recon.D3PD.e1564_s1499_s1504_r4033_17_2_3
• mc10_14TeV.106052.PythiaZtautau.recon.D3PD.e921_s1322_d570_r2661_17_2_3

Jets

The L1 Trigger Tower studies performed on a J3 MC dataset sample:

• SVN jet TT studies code

This code computes:

• The TileCal Trigger Towers by using the TileCal cell offline energies and compare them with the ones from L1Calo, with L1Calo TT energies > 1 GeV^?
• The offline reconstructed, matched EF and L1 jets according to the following selection and trigger matching cuts:
  • Offline jet: p_T >30GeV, 0<|η|<1.37 & 1.52<|η|<1.7
    
  • Event Filter (EF) jet trigger: ΔR (offline, EF trigger)<0.4 & passed EF_j40
    
  • L1 jet trigger: ΔR (offline, L1 trigger)<0.4 & E_T (8x8 TTs) > 20 (40 and 70, respectively) GeV^?.
• The turn-on efficiency (jet efficiency vs p_T) plots for different L1 jet trigger items: L1_J20, L1_J40 and L1_J70.

L1_J20 (L1_J40 and L1_J70, respectively) is defined as a L1 jet trigger window of 8x8 Trigger Towers and the total E_T>20 GeV^? (E_T>40 GeV^? and E_T>70, respectively). The EM LAr Trigger Towers are taken with the current 1 GeV^? precision.

In this particular case, for all L1 jet trigger items is used the EF_j40 as Event Filter jet trigger, which corresponds to the trigger chain: EF_j40->L2_j35->L1_J20. Since there is only one more EF trigger item: EF_j300, which is too high for this study.
A Monte Carlo data sample has been used for this study:
mc10_14TeV.105568.ttbar_Pythia.recon.ESD.e662_s1107_d459_r2037
which contains 10k events with <μ> ~ 46.

Electrons

The L1 Trigger Tower studies performed on a Z->ee MC dataset sample:

• SVN electron TT studies code

This code computes: 

• The TileCal Trigger Towers by using the TileCal cell offline energies and compare them with the ones from L1Calo, with L1Calo TT energies > 1 GeV^?
• The offline reconstructed, matched EF and L1 electrons according to the following selection and trigger matching cuts:
  • Offline electron: p_T >10GeV, 0<|η|<1.37 & 1.52<|η|<1.6, mediumPP, author==1 or 3, associated truth
    
  • Event Filter (EF) electron trigger: ΔR (offline, EF trigger)<0.15 & passed EF_e18_medium1
    
  • L1 electron trigger: ΔR (offline, L1 trigger)<0.15 & total E_T (2x1 or 1x2 TTs) > 12 GeV^?.
• The turn-on efficiency (jet efficiency vs p_T) plots for different L1 jet trigger items: L1_EM12, L1_EM14VH

L1_EM12 is defined as a L1 EM trigger cluster of 2x1 or 1x2 Trigger Towers and the total E_T>12 GeV^?. The EM LAr Trigger Towers are taken with the current 1 GeV^? precision.
The L1 EM trigger algorithm is based upon a 4x4 array of 0.1x0.1 TTs in the EM and hadronic calorimeters. Within the central 2x2 EM towers, 4 clusters are formed from the sums of the 2 horizontal and 2 vertical pairs of Trigger Towers. The trigger condition is then at least 1 of the 4 clusters is above the cluster threshold.

A Monte Carlo data sample has been used for this study:
mc12_14TeV.147806.PowhegPythia8_AU2CT10_Zee.recon.RDO.e1564_s1499_s1504_r4033
which contains 5k events with <μ> ~ 40.

-- LuisMarch - 10 Jun 2013