Jet Calibration Issues in t t Events

Transcription

1 Jet Calibration Issues in t t Events Andreas Jantsch Max-Planck-Institut für Physik Munich 39. Herbstschule für Hochenergiephysik Maria Laach A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

2 Outline 1 Calorimetry 2 Jet Reconstruction 3 Jet Energy Calibration 4 Conclusion A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

3 Particle Shower Electromagnetic Shower e ±, γ pair production, bremsstrahlung A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

4 Particle Shower Electromagnetic Shower e ±, γ pair production, bremsstrahlung Electromagnetic Energy Invisible Energy Escaped Energy non EM Energy Hadronic Shower hadrons (π ±, K, p, n, hadronic τ-decays,... ) nuclear interactions em sub-shower π 0 invisible/escaped energy high fluctuations in shape A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

5 The ATLAS Calorimeters EM LAr-Pb accordion calorimeter Barrel (EMB): η < 1.4 End-cap (EMEC): < η < 3.2 Hadron Endcap Cal. Tile Cal. EM Barrel Cal. EM Endcap Cal. Forward Cal. η = ln tan ( ) θ 2 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

6 The ATLAS Calorimeters EM LAr-Pb accordion calorimeter Barrel (EMB): η < 1.4 End-cap (EMEC): < η < 3.2 Hadron calorimeters Barrel (Tile): Scint.-Steel η < 1.7 End-cap (HEC): LAr-Cu 1.5 < η < 3.2 Hadron Endcap Cal. EM Endcap Cal. Tile Cal. EM Barrel Cal. Forward Cal. η = ln tan ( ) θ 2 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

7 The ATLAS Calorimeters EM LAr-Pb accordion calorimeter Barrel (EMB): η < 1.4 End-cap (EMEC): < η < 3.2 Hadron calorimeters Barrel (Tile): Scint.-Steel η < 1.7 End-cap (HEC): LAr-Cu 1.5 < η < 3.2 Forward calorimeter (FCal) 3.2 < η < 4.9 FCal1: LAr-Cu FCal2&3: LAr-W Hadron Endcap Cal. EM Endcap Cal. η = ln tan Tile Cal. EM Barrel Cal. ( ) θ 2 Forward Cal. A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

8 Cell Clustering Cell smallest reco object ATLAS: cells reco em scale 0 Cell Tower Cluster A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

9 Cell Clustering Cell smallest reco object ATLAS: cells reco em scale 0 Cell Tower Cluster Tower fixed η φ grid contains the sum of cell (fraction) energies and the center of the grid square ( η φ) as members A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

10 Cell Clustering Cell smallest reco object ATLAS: cells reco em scale 0 Cell Tower Cluster Tower fixed η φ grid contains the sum of cell (fraction) energies and the center of the grid square ( η φ) as members Cluster formed around a seed cell fixed size ( η φ) around seed cell (sliding window) variable borders based on significance of the cells (topo cluster) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

11 Topo Cluster Algorithm (S. Menke) Cluster Making (4/2/0) form clusters around seed cells with E seed > 4σ tan(θ) sin(φ) FCal1A tan(θ) cos(φ) 2 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

12 Topo Cluster Algorithm (S. Menke) Cluster Making (4/2/0) form clusters around seed cells with E seed > 4σ expand clusters using neighbor cells with E neigh > 2σ tan(θ) sin(φ) FCal1A tan(θ) cos(φ) 2 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

13 Topo Cluster Algorithm (S. Menke) Cluster Making (4/2/0) form clusters around seed cells with E seed > 4σ expand clusters using neighbor cells with E neigh > 2σ include perimeter cells with E cell > 0σ tan(θ) sin(φ) FCal1A tan(θ) cos(φ) 2 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

14 Topo Cluster Algorithm (S. Menke) Cluster Making (4/2/0) form clusters around seed cells with E seed > 4σ expand clusters using neighbor cells with E neigh > 2σ include perimeter cells with E cell > 0σ merge clusters if they share a neighbor cell sin(φ) tan(θ) FCal1A tan(θ) cos(φ) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

15 Topo Cluster Algorithm (S. Menke) Cluster Making (4/2/0) form clusters around seed cells with E seed > 4σ expand clusters using neighbor cells with E neigh > 2σ include perimeter cells with E cell > 0σ merge clusters if they share a neighbor cell split cluster around local maxima sin(φ) tan(θ) FCal1A tan(θ) cos(φ) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

16 Topo Cluster Algorithm (S. Menke) Cluster Making (4/2/0) form clusters around seed cells with E seed > 4σ expand clusters using neighbor cells with E neigh > 2σ include perimeter cells with E cell > 0σ merge clusters if they share a neighbor cell split cluster around local maxima after clustering all cells in the signal regions are kept sin(φ) tan(θ) FCal1A tan(θ) cos(φ) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

17 Jets Jets initiated by quarks & gluons that hadronise in jet of hadrons collection of 4-vectors based on tracks and/or calorimeter objects (cells or towers or clusters) need to be calibrated finally used for physics studies A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

18 Jet Reconstruction Algorithm Cone-Algorithm collect neighbors around a seed in a radius R merge split Cone 0.7, Cone 0.4 K -Algorithm merges particles based on radial distance and transverse momentum R parameter Jet Size K 0.4, K 0.6 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

19 Hadronic Calibration Approaches Global Jet Calibration use towers or topo clusters on EM-scale as input to jets match a truth particle jet with each reco jet fit a cell-level calibration function based on energy density to all matched jet pairs A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

20 Hadronic Calibration Approaches Global Jet Calibration use towers or topo clusters on EM-scale as input to jets match a truth particle jet with each reco jet fit a cell-level calibration function based on energy density to all matched jet pairs Local Hadron Calibration calibrate topo clusters independent of jet algorithm to hadronic scale make jets out of calibrated topo clusters A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

21 Hadronic Calibration Approaches Global Jet Calibration use towers or topo clusters on EM-scale as input to jets match a truth particle jet with each reco jet fit a cell-level calibration function based on energy density to all matched jet pairs Local Hadron Calibration calibrate topo clusters independent of jet algorithm to hadronic scale make jets out of calibrated topo clusters Final In-situ Calibration both approaches above need the final step from hadron to parton level e.g. with t t Wb W b lνj b jjj b A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

22 Local Hadron Calibration particle level calibration calibrate 3D Cell Clusters before reconstructing the jets (not depending on any Jet Reco Algorithm) based on MC information: for each cell EM energy, Escaped energy, Invisible energy, Non EM energy 1 classify the clusters to EM, Hadronic and Unknown (by shower depth and the energy weighted average over the cell densities) 2 apply weights to Hadronic clusters (as function of the cluster energy and the cell energy density) 3 apply Dead Material Correction (some energy is deposited in upstream material) 4 apply Out-of-cluster correction (some energy is deposited in cells outside clusters) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, 2007 / 20

23 Final In-situ Calibration using t t events t t production gluon fusion ( 90%) quark - antiquark annihilation ( %) σ pp t t proton - (anti)proton cross sections σ tot Tevatron LHC t t decay V tb 1 t t Wb W b leptonic 2ν :( semileptonic hadronic jet combinatorics :( σ (nb) σ b σ jet (E jet T > s/20) σ W σ Z σ jet (E jet T > 0 GeV) σ tt σ jet (E jet T > s/4) σ Higgs (M H = 150 GeV) σ Higgs (M H = 500 GeV) s (TeV) events/sec for L = 33 cm -2 s -1 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

24 Final In-situ Calibration using t t events semileptonic t t events large low luminosity W -mass well known clean trigger: isolated high p T lepton b-tagging parton level calibration t t Wb W b lνj b jjj b ν p l(e,µ) W t b t b W+ J 1 J p 2 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

25 Final In-situ Calibration using t t events m PDG W = mrec W α1 α 2 α i = E part i E jet i 1 extract mw rec from Gaussian fits to di-jet mass-distribution in bins of E jet 2 use mass constraint mw rec = mpdg W for mean values of fitted Gaussians 3 extract α i by e.g. iterative procedure α k i = α k 1 mw PDG i m k 1 i A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

26 Summary A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

27 Conclusion Jet Energy Calibration is a complex task Choice of constituents tower or cluster? Choice of Jet Algorithm Cone or K? choice of parameters R, R? Choice of Calibration Method jet-level or cluster-level? data (di-jet, top-pairs, Z/γ + jet(s)) or simulation driven? Impact of Noise, Underlying Event and Pile-Up Finally only LHC data can be used for decision Waiting for LHC start in 2008 A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

28 Backup slides Backup slides A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

29 Electronic Calibration (E. Rauter) optimal filtering to reduce noise and jitter shape known sampled measurement autocorrelation of noise from noise runs compute amplitude and timing calibration pulses injected at cell level to get ADC to na (& check electronics chain) na to MeV at em scale from test beam as well as sampling fraction A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

30 λ center r (cm) (mm) λ center z (cm) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

31 ρ cell r (cm) ) 3 > (MeV/mm <ρ cell z (cm) A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20

32 Jet Algorithm (R. Haertel) Cone IR/Col unsafe K IR/Col safe A. Jantsch (MPI für Physik) Jet Calibration Issues in t t Events Sep 06, / 20