The long road to understanding LHC data Philip Bechtle January 15th and 22nd 2010 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 1
Disclaimer I m by far not an expert on all of what I ll show, so we ll have lots of fun in the discussions P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 2
Disclaimer I m by far not an expert on all of what I ll show, so we ll have lots of fun in the discussions These are very interesting times, so if you look at this in a few months, probably a lot will be different Further Reading: ATLAS public results: https://twiki.cern.ch/twiki/bin/view/atlas/atlasresults CMS public results: http://cms-physics.web.cern.ch/cms-physics/cms Physics Result Interesting reading: Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics arxiv:0901.0512 The ATLAS Experiment at the CERN Large Hadron Collider JINST 3:S08003,2008 CMS physics: Technical design report CERN-LHCC-2006-001 Experimental prospects at the Large Hadron Collider arxiv:0905.0258 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 2
Outline 1 Why are the Detectors built as they are? 2 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 3
Outline 1 Why are the Detectors built as they are? 2 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 4
Der Large Hadron Collider Proton-Proton Kollisionen bei höchster Energie und Luminosität Umfang 27 km Schwerpunktsenergie 10 14 TeV Design-Luminosität 10 34 cm 2 s 1 Zahl der Protonpakete 2808 Abstand zwischen Kollisionen 25 ns Zahl der Wechselwirkungen pro Kollision bis zu 25 Protonen pro Paket 10 11 Zahl der Dipolmagnete 1232 Gespeicherte Energie 362MJ P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 5
The Fundamental Challenge P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 6
... at hadron machines, in contrast to others: P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 7
ATLAS P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 8
ATLAS Multi-purpose detector, largest collider detector built to date (height 25m, length 45m) Small (in spatial size) 2T solenoidal field (superconducting coil inside calorimeter) Large but only 0.5T toroidal magnetic field in the muon system Aim for high spacial granularity P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 9
CMS P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 10
CMS Multi purpose detector, very heavy (12500 tons), height 15m, length 22m Very large (6m diameter) solenoidal coil (4T inside, 2T outside): Constraint on calorimeter depth, but less material in front All tracking made of silicon detectors, aim for higher point resolution, lower granularity Overall expected performance of CMS and ATLAS trackers comparable: p T /p T < 2% for the central parts P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 11
Different Particles in CMS P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 12
ATLAS Inner Detector P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 13
ATLAS Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 14
Electromagnetic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 15
Pileup P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 16
Pileup P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 17
Pileup P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 18
Material Budget ««θ η = ln tan 2 Why did it get so much worse? Number of channels, readout speed up Power up Cooling up 70kW in through power lines and out through cooling! P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 19
Generic Requirements Radiation damage to materials and electronics in the whole experimental area > 10 16 particles (E > 1MeV)/cm 2 /year Need very precise timing and be as fast as possible: 25 ns bunch spacing, several interactions in the detector at the same time Need excellent spatial granularity to minimise pileup effects Need to identify extremely rare events: Lepton identification above huge QCD background e.g. e/jet ratio 10 5, i.e. O(100) worse than Tevatron Signal σ as low as 10 14 of σ tot Trigger rejection 10 7 Store huge data on disk ( 10 +9 events of 1.5 MB size per year) P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 20
Main specific design choices of ATLAS/CMS Size of ATLAS/CMS energies of particles produced: 1 TeV electrons (30 X 0 or 18 cm of Pb), 1 TeV pions (11 λ or 2 m Fe), 1 TeV muons outside calorimeters (optimize BL 2 ) Choice of magnet system has shaped the experiments ATLAS: separate magnet systems (small 2 T solenoid for tracker and huge toroids with large BL 2 for muon spectrometer) Pros: large acceptance in polar angle for muons and excellent muon momentum resolution without using inner tracker Cons: very expensive and largescale toroid magnet system CMS: one large 4 T solenoid with instrumented return yoke Pros: excellent momentum resolution using inner tracker and more compact experiment Cons: limited performance for standalone muon measurements (and trigger) and limited space for calorimeter inside coil P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 21
Main specific design choices of ATLAS/CMS electrons are relatively easy to measure precisely in EM calorimeters but very hard to identify (e/jet 10 5 ) muons are relatively easy to identify behind calorimeters but very hard to measure accurately at high energies ATLAS uses LAr sampling calorimeter with good energy resolution and excellent lateral and longitudinal segmentation (e/γ identification) CMS use PbWO 4 scintillating crystals with excellent energy resolution and lateral segmentation but no longitudinal segmentation signals from H γγ or H ZZ 4e should appear as narrow peaks (intrinsically much narrower in CMS) above essentially pure background from same final state (intrinsically background from fakes smaller in ATLAS) P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 22
Examples for the most important processes: Higgs P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 23
Examples for the most important processes: Higgs P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 24
Examples for the most important processes: Higgs P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 25
Examples for the most important processes: Higgs P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 26
Examples for the most important processes: SUSY For fastest possible discovery: Use inclusive spectra Very challenging because detector needs to be understood very well with little data (ca. L 1fb 1 ) M eff = i p T,i + E Tmiss P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 27
Examples for the most important processes: SUSY For fastest possible discovery: Use inclusive spectra Very challenging because detector needs to be understood very well with little data (ca. L 1fb 1 ) Is it really SUSY? Which particles, which masses, which couplings, which quantum numbers? kinematic edges mass information P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 27
Expectations: Tracking P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 28
Expectations: Muons P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 29
Expectations: Hadronic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 30
Expectations: EM Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 31
Outline 1 Why are the Detectors built as they are? 2 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 32
Check the operational status of all channels P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 33
First: We ve got data now! P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 34
Not so unimportant: Inspect the data! P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 35
Not so unimportant: Inspect the data! P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 36
Triggers µ P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 37
Triggers P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 38
Triggers P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 39
Triggers: What to do and to measure Timing Efficiencies Resolutions in comparison with offline Deadtime Configuration correct?... P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 40
Number of recorded events P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 41
Luminosity P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 42
Luminosity Measurement P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 43
What s a collision, anyway? P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 44
What s a collision, anyway? P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 45
So what s the event rate? P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 46
Silicon System P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 47
Silicon Sensors P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 48
Silicon Sensors P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 49
Silicon Sensors P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 50
Silicon Sensors P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 51
Silicon Sensors: What to do and to measure Incredibly complex: e.g. ATLAS Pixel system: within r < 20 cm: 80M channels in 1744 modules Dead and hot channels Noise Alignment! Timing Lorentz Angle Spacial resolutions of single hits Track resolutions & vertex resolution Hit & track efficiencies P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 52
Why are the Detectors built as they are? Inner Detector Performance Y [mm] Scatter Plot of Hits on Tracks ATLAS preliminary 1000 real data run 141811 500 0-500 -1000-1000 P. Bechtle: -500 The long road to understanding LHC data 0 500 SFB Lecture 01/2010 1000 X [mm] 53
Pixel Detector Timing and Clusters Fraction of clusters 1 0.8 0.6 0.4 0.2 ATLAS Preliminary Pixel timing Minimum Bias Stream Solenoid on runs 141749 to 142154 Clusters off track Clusters on track 0 0 2 4 6 8 10 12 14 Bunch crossing Mean cluster width (number of pixels) 3.5 3 2.5 2 1.5 simulation run 141811 (solenoid on) ATLAS Preliminary run 141994 (solenoid off) 1 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 track incidence angle (rad) Number of Pixel clusters 0.16 de/dx Pixel 0.14 Data 900 GeV 0.12 MC 900 GeV 0.1 0.08 ATLAS Preliminary 0.06 0.04 0.02 0 0 20 40 60 80 100 120 de/dx [ke] P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 54
TRT Timing and Resolutions Track to wire distance (mm) 2 1.8 1.6 ATLAS preliminary 1.4 1.2 1 0.8 0.6 0.4 0.2 8000 6000 4000 TRT barrel RT 2000 Cosmic TRT barrel RT 0 0 10 20 30 40 50 TRT drift time (ns) 10000 Number of hits (run 141749) Number of hits on tracks 1000 800 600 µ=0 µm, σ=165 µm ATLAS preliminary TRT Barrel Combined ID Tracks 400 200 0-1 -0.5 0 0.5 1 Residual [mm] P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 55
TRT Timing Average trailing edge time [ns] 70 Run 140541, event 140973 65 60 55 50 45 40 ATLAS preliminary 35-3000 -2000-1000 0 1000 2000 3000 z [mm] Average trailing edge time [ns] 70 Run 140541, event 171897 65 60 55 50 45 40 ATLAS preliminary 35-3000 -2000-1000 0 1000 2000 3000 z [mm] P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 56
TRT PID High threshold probability 0.25 0.2 0.15 0.1 0.05 0 10 ATLAS preliminary Electron candidates Electron candidates Generic tracks tracks Fit Electrons to data (MC) Generic tracks (MC) 2 10 1 10 Pion momentum (GeV) γ factor 3 10 TRT end cap 4 10 1 10 Electron momentum (GeV) P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 57
Check Resolutions and Alignment number of hits on tracks 3000 2500 2000 1500 MC perfect alignment µ=0µm, σ=46µm Collision alignment µ=0µm, σ=86µm Cosmics alignment µ=-5µm, σ=122µm ATLAS Preliminary SCT ECC Run 141749+141811 1000 500 0-0.2-0.1 0 0.1 0.2 x residual [mm] P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 58
Once the Inner Detector is working... Number of offline tracks 20 18 16 14 12 10 8 6 4 2 0 ATLAS Preliminary Candidate Collision Events Run 140541 LBN < 140 LBN > 145 N TRT track hits > 10 N SCT track hits 6 d < 10 mm 0-400 -300-200 -100 0 100 200 Offline track Z 0 [mm] P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 59
Performance Goals at the beginning and at the end P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 60
Measure tracking resolutions already with cosmics ) [mm] 0 σ(d 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 ATLAS Preliminary Cosmic 08 0 1 10 Split tracks Data, full ID Data, Si only Simulation, full ID 2 10 p [GeV] T p x σ(q/p) 0.25 0.2 0.15 0.1 0.05 ATLAS Preliminary Cosmic 08 0 1 10 Split tracks Data, full ID Data, Si only Simulation, full ID 2 10 p [GeV] T P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 61
Validate tracking resolutions with first collisions P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 62
Similar for CMS... P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 63
Electromagnetic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 64
Electromagnetic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 65
Electromagnetic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 66
Hadronic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 67
Hadronic Calorimeters P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 68
Calorimeters: What to do and to measure Spacial resolution obviously not so important... Timing Noise Dead and noisy channels Calibration! Energy Resolution Response to individual particles: each object has to be calibrated separately, e.g. electrons leave a different fraction of energy in the absorber than hadrons, strongly different spatial distributions of energy deposits etc. P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 69
π 0 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 70
Again similar for CMS... P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 71
Map the detector material using conversions P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 72
Map the detector material using conversions P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 73
Muon System P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 74
Muon System P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 75
Muon System: What to do and to measure Alignment magnetic Field Noise Dead and Noisy Channels Timing Resolutions Efficiencies P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 76
Not too many muons yet... P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 77
Jets test E Tmiss, noise P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 78
Probably no τ yet, but many candidates (from jets) Entries 220 ATLAS Preliminary 200 900GeV collisions 180 Data 160 Minimum bias MC 140 120 100 80 60 40 20 0-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 EM radius Entries 120 100 80 60 40 20 ATLAS Preliminary 900GeV collisions Data Minimum bias MC 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Centrality fraction Entries/0.2GeV 3 10 2 10 ATLAS Preliminary 900GeV collisions Data Minimum bias MC Entries 120 100 80 60 ATLAS Preliminary 900GeV collisions Data Minimum bias MC 10 40 20 1 0 2 4 6 8 10 12 14 16 18 20 Cluster energy (GeV) 0 0 0.2 0.4 0.6 0.8 1 Isolation fraction P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 79
Outlook for 2010 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 80
Outlook for 2010 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 81
Outlook for your favourite physics (GeV) m 1/2 1000 800 600 400 τ 1 LSP ~ g (2.0 TeV) ~ g (1.5 TeV) ~ g (1.0 TeV) ATLAS 5 σ discovery MSUGRA tan β = 10 ~ q (1.5 TeV) 4 jets 0 lepton 4 jets 1 lepton 4 jets 2 leptons OS 1 jet 3 leptons ~ q (2.0 TeV) LLL ~ q (2.5 TeV) FITTINO SUSY SUSY SUSY 200 ~ g (0.5 TeV) ~ q (1.0 TeV) ~ q (0.5 TeV) + χ 1 (103 GeV) NO EWSB 0 0 500 1000 1500 2000 2500 3000 m 0 (GeV) msugra Entdeckungspotential mit 1fb 1 P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 82
Outlook for your favourite physics (GeV) m 1/2 1000 800 600 400 τ 1 LSP ~ g (2.0 TeV) ~ g (1.5 TeV) ~ g (1.0 TeV) ATLAS 5 σ discovery MSUGRA tan β = 10 ~ q (1.5 TeV) 4 jets 0 lepton 4 jets 1 lepton 4 jets 2 leptons OS 1 jet 3 leptons ~ q (2.0 TeV) LLL ~ q (2.5 TeV) FITTINO SUSY SUSY SUSY 200 ~ g (0.5 TeV) ~ q (1.0 TeV) ~ q (0.5 TeV) + χ 1 (103 GeV) NO EWSB 0 0 500 1000 1500 2000 2500 3000 m 0 (GeV) msugra Entdeckungspotential mit 1fb 1 Vgl. SM-Higgs mit msugra erlaubt weil leichtestes msugra-higgs extrem SM-Higgs-ähnlich Entdeckung neuer Physik wahrscheinlich lange vor Higgs-Entdeckung Brauchen Information der Higgs-Suchen bei der Interpretation neuer Physik P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 82
Outlook A lot has been achieved thanks to the incredible efforts of the machine group and the collaborations But so much remains to be done... calibrate jets, E Tmis, and so on Accumulate lots of luminosity! Find surprising and unexpected new physics! P. Bechtle: The long road to understanding LHC data SFB Lecture 01/2010 83