The ATLAS Detector - Inside Out Julia I. Hofmann

Transcription

1 The ATLAS Detector - Inside Out Julia I. Hofmann KIP Heidelberg University Outline: 1st lecture: The Detector 2nd lecture: The Trigger 3rd lecture: The Analysis (mine)

2 Motivation Physics Goals: Study Standard Model of Particle Physics find the Higgs boson 2

3 Motivation Physics Goals: Study Standard Model of Particle Physics find the Higgs boson Search for new physics processes : SUSY microscopic black holes... 3

4 Motivation Needs: High energy particle collisions x High luminosity sample x Detector to measure plenitude of final state (multi purpose) 4

5 The Large Hadron Collider Discovery Machine: proton-proton collisions no knowledge about initial state broad range of center-ofmass energy of collision 5

6 The Large Hadron Collider Discovery Machine: proton-proton collisions no knowledge about initial state broad range of center-ofmass energy of collision two concurrent detectors 6

7 The Large Hadron Collider 7

8 The Large Hadron Collider 8

9 The Large Hadron Collider 9

10 The Large Hadron Collider 10

11 Higgs Decay 11

12 Higgs branching ratios 12

13 Wishlist for Detector recording of full event: maximal coverage of the solid angle measure and distinguish different particle species electrons photons muons jets different specialized sub components 13

14 Finding the Higgs 14

15 The ATLAS Detector 15

16 Coordinate System 16

17 The ATLAS Detector 17

18 The ATLAS Detector Particle detection via their energy loss in material they traverse 18

19 The ATLAS Detector Electrons: mainly bremsstrahlung: - de / dx = E / X0 Energy down to 1/e after X0(Radiation length) want little material in front of calorimeters and thick (> 20 X0) calorimeter Examples: X0/ρ for water 36 cm, for lead 0.56 cm 19

20 The ATLAS Detector Photons: e+e pair production Mean free path 7/9 X0 20

21 The ATLAS Detector Hadrons: Characteristic scale: nuclear interaction length λ Relevant for total calorimeter depth (hadronic + electromagnetic) Examples: λ/ρ for water 83.6 cm, for steel 17 cm 21

22 The ATLAS Detector Muons: basically heavy electrons radiation length much longer 22

23 The ATLAS Detector 23

24 Magnets Needed for momentum measurement 24

25 Inner Detector Gaseous Semiconducting 25

26 Inner Detector Gaseous Semiconducting 26

27 Semi Conductiong Detectors charged particle 27

28 Tracking 28

29 Tracking from Thomas 29

30 Tracking from Thomas Pixel layers 30

31 Pileup Pile-up is multiple proton-proton collisions at the same time In 2012: up to 40 simultaneous interactions Need precise tracking information to reject this soft interactions usually low energetic

32 Finding the Higgs 32

33 Inner Detector 33

34 Pixel Detector 34

35 SemiConductor Tracker 35

36 Inner Detector Gaseous Semiconducting 36

37 Transition Radiation Tracker 37

38 Transition Radiation Tracker 38

39 Inner Detector 39

40 Calorimeters 40

41 Two Calorimeter Types Nuclear Bremsstrahlung interactions and and ionisation pair production 41

42 Two Calorimeter Types Particles in... no particles out! 42

43 Sampling Calorimeters Particles in... no particles out! 43

44 Electromagnetic Calorimeter 44

45 Hadronic Calorimeter 45

46 Granularity Particles in... no particles out! Energy measured in cells 46

47 Granularity 47

48 Granularity 48

49 Energy Imbalance Neutrinos don't interact with detector impossible to fully reconstruct processes containing neutrinos e.g. leptonic W decay or Z υυ (without knowledge about intital state) But: energy and momentum are conserved escaping particle would manifest by momentum imbalance: missing transverse energy ETmiss important to have full φ coverage 49

50 Energy Imbalance ETmiss computed by: summing all energy deposits from calibrated objects vectorially adding muons adding unmatched calorimeter clusters ETmiss = ETmiss 50

51 51

52 Muon System 52

53 Magnets Needed for momentum measurement 53

54 Muon Spectrometer Cathode Strip Chambers using the principle of multi-wire proportional chamber Anode wire Monitored Drift Tube chamber charged particle Cathode (segmented) 54

55 Muon Spectrometer 55

56 Summary ATLAS is a multi purpose particle detector measure Higgs in all channels searching for BSM particles various technologies used in order to precisely identify particles and measure their properties In operation since 2010 results for s = 2.76 TeV, 7 TeV and 8 TeV Next week: Trigger - Which events are we recording? 56

57 Thank you! 57