Analog vs. Digital Hadron Calorimetry for the ILC

Transcription

1 Analog vs. Digital Hadron Calorimetry for the ILC for the NIU/NICADD ILC detector group International Linear Collider Large Detector Meeting LLR, Paris, January 13-15,

2 Introduction We consider a hadronic calorimeter with a few thresholds (1-3). Compare gas and scintillator as live media: Single particle energy resolution, Shower width, Clustering. 2

3 Geometries Considered Scint HCal Polystyrene 5mm Steel 20mm Gas Geom1 Gas Geom2 Glass 1mm Gas 5mm Gas 1mm Steel 20mm G10 3

4 Number of cells hit by π + s of 2, 5, 10, 20, 30, 50 GeV 4

5 π + energy resolution as function of energy for different (linear) cell sizes 5

6 Energy resolution for 10 GeV π + s 9cm 2 cells σ/e=0.183 σ/n=

7 Energy resolution for 50 GeV π + s 9cm 2 cells σ/e=0.101 σ/n=

8 Nhit correlations for different cell energy thresholds 8

9 Nhit correlations for different cell energy thresholds 9

10 Nhit correlations for different cell energy thresholds 10

11 Alternatively, 11

12 Compensation Cell counting has its own version of the compensation problem (in scintillators). With multiple threshold this can be overcome by weighting cells differently (according to the threshold they passed). In MC, 3 thresholds seem to be adequate 12

13 After semi-digital treatment 13

14 Energy resolution: 50 GeV π + s σ/e=0.101 σ/e=

15 Energy resolution: 10 GeV π + s σ/e=0.183 σ/n=

16 π + energy resolution vs. energy 16

17 Time of flight 17

18 ToF dependence 18

19 Cross-talk (10% of cell E leaks equally to 4 neighbors) 19

20 Nhit vs. fraction of π + E in cells with E>10 MIP: 1cm x 1cm scintillator cells 20

21 Nhit vs. fraction of π + E in cells with E>10 MIP: Gas vs. scintillator 21

22 π + energy resolution vs. energy Multiple thresholds not used 22

23 Non-linearity Nhit/GeV varies with energy. This will introduce additional pressure on the constant term. For scintillator the non-linearity can be effectively removed by semi-digital treatment. 23

24 Density of hits Need a hierarchy in the absence of an energy measurement. Local density of hits is an obvious candidate. A simple-minded density variable: d i = Σ (1/R ij ), where R ij is the angular distance between cells i & j. 24

25 Position resolution Measured relative to the energy weighted resolutions Energy weighted unweighted Density weighted 25

26 Density vs. Energy 26

27 Width Find centroid {Σw i x i /Σw i } width = sqrt(σw i R 2 i/σw i ) Three weights were used: Unweighted (w i =1) Energy weighted (w i =E i ) Density weighted (w i =nearest-neighbor occupancy in a 5x5 window in lyrs k-1,k,k+1) 27

28 Distance to farthest cell 28

29 Density of farthest cell 29

30 Distance to farthest cell 30

31 Density of farthest cell 31

32 Backscatter 32

33 Shower width for 10GeV π ± 33

34 Shower width for 50GeV π ± 34

35 π ± angular width rms shown as bars 35

36 π ± angular width: energy weighted 36

37 π ± angular width: density weighted 37

38 Comments There is no clear cut case either way at the moment; detailed studies of assessing impact needed. Will look at cluster separability next. Need to evaluate this in the global context of calorimeter performance. 38

39 Clustering Clustering based on local density works well. It is an alternative to track-seeded clustering. Can be used in the ECal and HCal. Full PFlow implementation gives encouraging results. 39

40 10 GeV π 0 γγ Density weighted θ φ 40

41 Σ + pπ 0 pγγ Density weighted θ φ p π 0 41

42 Summary Large parameter space in the nbitsegmentation-medium plane for hadron calorimetry. Optimization through costbenefit analysis? Scintillator and Gas-based digital HCals behave differently. Need to simulate detector effects (noise, x-talk, non-linearities, etc.) Need verification in test-beam data. More studies underway. 42