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Incoherent pairs and γγ hadrons at 500 GeV and 3 TeV WG-6 meeting 17. May 2011. Dominik Dannheim, Andr é Sailer (CERN). Updated 18. May for gg hadrons : added information on hadronisation models; added 2d color plots for pt vs. theta. Geometry optimisation using incoherent pairs. - PowerPoint PPT Presentation
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Dominik Dannheim,André Sailer (CERN)
Incoherent pairs andγγ hadrons
at 500 GeV and 3 TeV
WG-6 meeting17. May 2011
Updated 18. May for gghadrons: added information on hadronisation models; added 2d color plots for pt vs. theta
215. May 2011 Backgrounds at 500 GeV
Geometry optimisation using incoherent pairs
• 1 bunch train worth of incoherent pairs• Only look at direct hits, therefore apply cuts:
• pT>8 MeV• θ > 2o
• Resulting sample sizes:• √s=3 TeV: 7.72M particles• √s=500 GeV: 2.75M particles
• Fast simulation of direct hits: follow particles on heliceswith CLIC_ILD geometry and B-field
• Move straight section of beam pipe closer to IP for 500 GeV,keeping projective beam pipe in forward region
• New radius of beam pipe and inner vertex layer is given byconstraint that occupancies in critical regions are similarfor 500 GeV as for the 3 TeV geometry
• Critical regions are: • Edge where beam pipe becomes conical• Most forward region of innermost vertex layer
315. May 2011 Backgrounds at 500 GeV
Occupancies at 3 TeV
Critical regions
415. May 2011 Backgrounds at 500 GeV
Occupancies at 500 GeV
515. May 2011 Backgrounds at 500 GeV
Occupancies at 500 GeV and 3 TeV
Acceptable occupancies at 500 GeV in critical regions, when moving beam pipe and innermost vertex layer closer to IP by 6 mm
617. May 2011 Backgrounds at 500 GeV
γγhadrons samples
• sqrt(s)=3 TeV sample• Daniel Schulte 2010• GUINEA-PIG + Pythia• Default hadronisation parameters in Pythia• Mγγ>2 GeV• 67k events, 3.2 events / bx• Standard sample for CDR production
• sqrt(s)=500 GeV sample• Daniel Schulte 2011• GUINEA-PIG + Pythia• OPAL tuning for hadronisation parameters in Pythia• Mγγ>2 GeV• 298k events, 0.3 events / bx
717. May 2011 Backgrounds at 500 GeV
Invariant mass of final-state particles
817. May 2011 Backgrounds at 500 GeV
Transverse momentum and polar angle (3 TeV)
917. May 2011 Backgrounds at 500 GeV
Transverse momentum and polar angle (500 GeV)
1017. May 2011 Backgrounds at 500 GeV
Polar angle of charged particles
1117. May 2011 Backgrounds at 500 GeV
Momentum of charged particles
1217. May 2011 Backgrounds at 500 GeV
Number of particles per bx
1317. May 2011 Backgrounds at 500 GeV
Visible energy per bx
1417. May 2011 Backgrounds at 500 GeV
Total energy + occupancy per bx at 3 TeV===============================================================Pythia 3 TeV sample (D. Schulte) 3.2 events / bxCLIC_ILD_CDR, B = 4 T ===============================================================Section E_vis/bx [GeV] # part./bx # ch. part./bx===============================================================no cuts 1365.2 102.42 50.05 |theta| > 5.73 deg 62.1 58.69 27.60 ---------------------------------------------------------------LUMI-CAL 101.5 18.76 9.13 ---------------------------------------------------------------Pixel-Forward - 29.86 14.33 Pixel-Barrel - 42.36 19.61 Pixel-all - 54.07 25.30 ---------------------------------------------------------------CAL-PLUG+EC 59.8 41.96 18.00 CAL-Barrel 3.6 11.02 0.25 CAL-all 62.2 50.03 18.18 ---------------------------------------------------------------TRK-Forward - 41.28 15.50 TRK-Barrel - 24.58 11.85 TRK-all - 50.58 21.51 ===============================================================
Note: 70% more background now in ECAL, after including the plug with Ri=242 mm
1517. May 2011 Backgrounds at 500 GeV
Total energy + occupancy per bx at 500 GeV===============================================================Pythia 500 GeV sample (D. Schulte) 0.3 events / bxCLIC_ILD_CDR modified vertex region, B = 4 T ===============================================================Section E_vis/bx [GeV] # part./bx # ch. part./bx===============================================================no cuts 13.3 5.01 2.54 |theta| > 5.73 deg 3.5 3.89 1.91 ---------------------------------------------------------------LUMI-CAL 3.5 0.76 0.40 ---------------------------------------------------------------Pixel-Forward - 1.88 0.95 Pixel-Barrel - 3.22 1.56 Pixel-all - 3.65 1.78 ---------------------------------------------------------------CAL-PLUG+EC 3.2 2.62 1.17 CAL-Barrel 0.2 0.78 0.01 CAL-all 3.4 3.20 1.18 ---------------------------------------------------------------TRK-Forward - 2.81 1.10 TRK-Barrel - 1.50 0.77 TRK-all - 3.37 1.48 ===============================================================
~20x less energy and occupancy at 500 GeV, compared to 3 TeV
1617. May 2011 Backgrounds at 500 GeV
Cell occupancies at ECAL+plug front
• Consider only direct hits from γγhadrons• Fast simulation for CLIC_ILD_CDR geometry:
• Follow all final state particles in B-field through detector• No energy loss in material• Simplified geometry for ECAL plug cells:
ΔR x ΔRφ x Δz = 5 mm x 5 mm x 6 mm• Create one hit if particle crosses the corresponding cell overestimation of real hit rate
1717. May 2011 Backgrounds at 500 GeV
Cell occupancies at ECAL+plug front face
1817. May 2011 Backgrounds at 500 GeV
Cell occupancies at ECAL+plug bottom face
19
• Performed optimization of beam pipe and vertex region,based on direct hits from incoherent pairs
• New detector layout for 500 GeV with outer radius of central beam pipe at 24 mm, cf. André’s presentation for details
• Validated γγhadrons sample for 500 GeV• 20x less energy and occupancy in the detector, compared
to the 3 TeV sample• Up to 40% cell-occupancy per train in ECAL plug at 3 TeV
in fast simulation
15. May 2011 Backgrounds at 500 GeV
Conclusions