Use of Isolated Charged Particles in Fast MC

1. Use of Isolated Charged Particles in Fast MC Salavat Abdullin,CERN / / ITEP (Moscow) Meeting: Isolated Charged Particle from Collision Data CMS week, June 24, 2009 S.Abdullin, Use of Isolated Charged Particles in FastSim

2. Outline FastSim e/g energy response and shower shape FastSim hadron energy response and shower shape main consumer of isolated single particle data GFlash approach within G4 framework Actual use of isolated charged tracks S.Abdullin, Use of Isolated Charged Particles in FastSim

3. Single e/g Response in FastSim Energy response Input particle energy (at ECAL surface) is taken Local NxN Xtals matrix considered Containment corrections/ noise / Selective Readout Shower simulation – H1 GFLASH For more details http://indico.cern.ch/contributionDisplay.py?contribId=47&confId=28808 (F.Beaudette’s talk) Limited e/g samples for tests/checks/validation S.Abdullin, Use of Isolated Charged Particles in FastSim

4. Single-Hadron Response in FastSim Non-linear inhomogeneous ECAL+HCAL Currently uses MC data CMSSW_218 with some limited ad-hoc after-tuning Needs to be re-evaluated with CMSSW_310 E (15 knots), h (50 knots) mean and s Caveat: response is not necessarily Gaussian (low-e, HF) ! Massive MC samples 1GeV - 3 TeV, 75-150k ev each (1,2,3,5,9,15,20,30,50,100,150,225,300,1000,3000) ~ 4000 numbers used for interpolation (incl. e/g in HF !) Separately: MIP/non-MIP in ECAL Quite special (MC) data required No interactions before Calo, no noise, no ZS (these effects are simulated in FastSim itself) S.Abdullin, Use of Isolated Charged Particles in FastSim

5. Hadron Shower Shape in FastSim • Simulation of the hadron shower in both ECAL and HCAL • “a la” GFLASH H1@ HERA: G.Grindhammer, M.Rudowitz and S.Peters, Nuclear Instruments and Methods in Physics Research A290 (1990) 469-488 • Longitudinal “sliced” parameterization, including 1 step in ECAL (1+10 slices) • Transverse shower profiles, using original param. expressed in l, rm and x0 • Additional (w.r.t. GFLASH parameters) handles and parameters to tune on CMS MC, for instance ECAL energy fluctuations and longitudinal “stretching” GAP S.Abdullin, Use of Isolated Charged Particles in FastSim

6. GFLASH “Shortcut” in G4 FastSim shower description is not quite precise Attempt to use available TB data for the shower shape tuning was not successful Hope is to profit (adapt) from GFLASH approach developed by Carnegie Mellon group within G4 A lot of efforts invested last couple of years in tuning of the response and shape against general G4 MC, specialized TB MC and TB data; good results demonstrated Direct import attempt might not work given very tight CPU time constraints in FastSimulation; adapting/simplification work might be needed S.Abdullin, Use of Isolated Charged Particles in FastSim

7. Use of Isolated Tracks in Fast MC “At the beginning” mostly low-to-medium-pT isolated tracks are available Medium-pT via dedicated triggers Low-pT in *any* non-ZS events (using iso filtering) Major constituents of “typical” (with accessible cross section) jets See talk of A.Nikitenko Fast MC “centaur” (half-MC, half-data) Collision data (low-pT, 1-20 GeV/c): response (&shape) Adapted TB (higher pT, 30-300 GeV/c): mostly response MC (high pT > 300 GeV/c, |h|>2.4): shape and response S.Abdullin, Use of Isolated Charged Particles in FastSim