Particle Detectors Summer Student Lectures 2007 Werner Riegler, - - PowerPoint PPT Presentation

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Particle Detectors Summer Student Lectures 2007 Werner Riegler, - - PowerPoint PPT Presentation

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Particle Detectors Summer Student Lectures 2007 Werner Riegler, CERN, werner.riegler@cern.ch History of Instrumentation History of Particle Physics The Real World of Particles Interaction of Particles with Matter, Tracking

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Particle Detectors

  • History of Instrumentation ↔ History of Particle Physics
  • The ‘Real’ World of Particles
  • Interaction of Particles with Matter, Tracking detectors
  • Resistive Plate Chambers, Calorimeters, Particle Identification
  • Detector Systems

Summer Student Lectures 2007

Werner Riegler, CERN, werner.riegler@cern.ch

  • W. Riegler/CERN

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SLIDE 2
  • W. Riegler/CERN

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Gas Detectors with internal Electron Multiplication

Parallel Plate Avalanche Chamber (PPAC) Resistive Plate Chamber

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SLIDE 3

Resistive Plate Chambers (RPCs)

Keuffel ‘Spark’ Counter:

High voltage between two metal plates. Charged particle leaves a trail of electrons and ions in the gap and causes a discharge (Spark). Excellent Time Resolution(<100ps). Discharged electrodes must be recharged Dead time of several ms.

Parallel Plate Avalanche Chambers (PPAC):

At more moderate electric fields the primary charges produce avalanches without forming a conducting channel between the electrodes. No Spark induced signal on the electrodes. Higher rate capability. However, the smalles imperfections on the metal surface cause sparcs and breakdown. Very small (few cm2) and unstable devices. In a wire chamber, the high electric field (100- 300kV/cm) that produces the avalanche exists

  • nly close to the wire. The fields on the cathode

planes area rather small 1-5kV/cm.

  • W. Riegler/CERN

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SLIDE 4

Resistive Plate Chambers (RPCs)

Place resistive plates in front of the metal electrodes.

No spark can develop because the resistivity together with the capacitance (tau ~ e*ρ) will only allow a very localized ‘discharge’. The rest of the entire surface stays completely unaffected. Large area detectors are possible ! Resistive plates from Bakelite (ρ = 1010-1012 Ωcm) or window glass (ρ = 1012-1013 Ωcm). Gas gap: 0.25-2mm. Elektric Fields 50-100kV/cm. Time resolutions: 50ps (100kV/cm), 1ns(50kV/cm) Application: Trigger Detectors, Time of Flight (TOF) Resistivity limits the rate capability: Time to remove avalanche charge from the surface of the resistive plate is (tau ~ e*ρ) = ms to s. Rate limit of kHz/cm2 for 1010 Ωcm.

  • W. Riegler/CERN

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SLIDE 5

130 mm active area 70 mm M5 nylon screw to hold fishing-line spacer honeycomb panel (10 mm thick) external glass plates 0.55 mm thick internal glass plates (0.4 mm thick) connection to bring cathode signal to central read-out PCB Honeycomb panel (10 mm thick) PCB with cathode pickup pads 5 gas gaps

  • f 250 micron

PCB with anode pickup pads Silicon sealing compound PCB with cathode pickup pads Flat cable connector Differential signal sent from strip to interface card Mylar film (250 micron thick)

Several gaps to increase efficiency. Stack of glass plates. Small gap for good time resolution: 0.25mm. Fishing lines as high precision spacers ! Large TOF systems with 50ps time resolution made from window glass and fishing lines ! Before RPCs Scintillators with very special photomultipliers – very

  • expensive. Very large systems are

unafordable.

ALICE TOF RPCs

  • W. Riegler/CERN

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SLIDE 6

Elektro-Magnetic Interaction of Charged Particles with Matter

1) Energy Loss by Excitation and Ionization 2) Energy Loss by Bremsstrahlung 3) Cherekov Radiation and 4) Transition Radiation are only minor contributions to the energy loss, they are however important effects for particle identification. Classical QM

  • W. Riegler/CERN

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SLIDE 7

A charged particle of mass M and charge q=Z1e is deflected by a nucleus of Charge Ze. Because of the acceleration the particle radiated EM waves energy loss. Coulomb-Scattering (Rutherford Scattering) describes the deflection

  • f the particle.

Maxwell’s Equations describe the radiated energy for a given momentum transfer. dE/dx

Bremsstrahlung, semi-classical:

  • W. Riegler/CERN

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SLIDE 8

Proportional to Z2/A of the Material. Proportional to Z1

4 of the incoming

particle. Proportional zu ρ of the particle. Proportional 1/M2 of the incoming particle. Proportional to the Energy of the Incoming particle E(x)=Exp(-x/X0) – ‘Radiation Length’ X0 ∝ M2A/ (ρ Z1

4 Z2)

X0: Distance where the Energy E0 of the incoming particle decreases E0Exp(-1)=0.37E0 .

  • W. Riegler/CERN

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SLIDE 9

Elektron Momentum 5 50 500 MeV/c

Critical Energy: If dE/dx (Ionization) = dE/dx (Bremsstrahlung) Myon in Copper: p ≈ 400GeV Electron in Copper: p ≈ 20MeV

  • W. Riegler/CERN

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Critical Energy

For the muon, the second lightest particle after the electron, the critical energy is at 400GeV. The EM Bremsstrahlung is therefore only relevant for electrons at energies of past and present detectors.

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SLIDE 10

For Eγ>>mec2=0.5MeV : λ = 9/7X0 Average distance a high energy photon has to travel before it converts into an e+ e- pair is equal to 9/7 of the distance that a high energy electron has to travel before reducing it’s energy from E0 to E0*Exp(-1) by photon radiation.

  • W. Riegler/CERN

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SLIDE 11
  • W. Riegler/CERN

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Electro-Magnetic Shower of High Energy Electrons and Photons

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SLIDE 12
  • W. Riegler/CERN

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SLIDE 13
  • W. Riegler/CERN

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Electro-Magnetic Shower of High Energy Electrons and Photons

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SLIDE 14
  • W. Riegler/CERN

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Calorimetry: Energy Measurement by total Absorption of Particles

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SLIDE 15
  • W. Riegler/CERN

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Calorimetry: Energy Measurement by total Absorption of Particles

Liquid Nobel Gases (Nobel Liquids) Scintillating Crystals, Plastic Scintillators (sampling)

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SLIDE 16
  • W. Riegler/CERN

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Crystals Noble Liquids

EM Calorimetry

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SLIDE 17
  • W. Riegler/CERN

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EM Calorimetry

X0= 1.85cm ρ = 4.51 g/cm3 ρM = 3.5cm X0= 4.7cm ρ = 2.41 g/cm3 ρM = 5.5cm Direct CP violation experiments NA48, KTeV Excellent EM Calorimetry for π0 measurement.

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SLIDE 18
  • W. Riegler/CERN

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Hadronic Showers

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SLIDE 19

Hadron Calorimeters

  • W. Riegler/CERN

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SLIDE 20
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Sampling Calorimeters

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SLIDE 21
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SLIDE 22

Particle Identification

  • W. Riegler/CERN

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SLIDE 23

‘average’ energy loss Measured energy loss

In certain momentum ranges, particles can be identified by measuring the energy loss.

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  • W. Riegler/CERN

dE/dx

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SLIDE 24

Time of Flight (TOF)

  • W. Riegler/CERN

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NA49 combined particle ID: TOF + dE/dx (TPC)

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SLIDE 25

Cherenkov Radiation

  • W. Riegler/CERN

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SLIDE 26

Ring Imaging Cherenkov Detector

  • W. Riegler/CERN

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SLIDE 27
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LHCb RICH

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SLIDE 28

Transition Radiation

  • W. Riegler/CERN

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SLIDE 29
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Detector Systems, Selected Experiments

Thanks to Heinrich Schindler

ALICE: Heavy Ion Experiment at CERN Donut: Neutrino Experiment at Fermilab CNGS: Long Baseline Neutrino Experiment CERN/Gran Sasso Amanda: Neutrino Experiment at the Southpole AMS: Particle Physics Experiment in Space

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SLIDE 30
  • W. Riegler/CERN

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ALICE

A heavy Ion Experiment at the LHC.

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SLIDE 31
  • W. Riegler/CERN

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ALICE

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SLIDE 32
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0 1 2 3 4 5 p (GeV/c) 1 10 100 p (GeV/c) TPC (rel. rise) π /K/p TRD e /π PHOS γ /π0 TPC + ITS (dE/dx)

π/K π/K π/K K/p K/p K/p e /π e /π

HMPID (RICH) TOF

Alice uses ~ all known techniques!

π/K K/p

ALICE

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SLIDE 33

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ALICE TPC

STAR STAR NA49 LHC: dNch/dy = 2000 - 4000

ALICE 'worst case' scenario: dNch/dy = 8000

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  • W. Riegler/CERN
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SLIDE 35
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AMANDA

Antarctic Muon And Neutrino Detector Array

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SLIDE 36

AMANDA

South Pole

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  • W. Riegler/CERN
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SLIDE 37

AMANDA

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  • W. Riegler/CERN
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SLIDE 38

AMANDA

Look for upwards going Muons from Neutrino Interactions. Cherekov Light propagating through the ice. Find neutrino point sources in the universe !

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  • W. Riegler/CERN
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SLIDE 39

AMANDA

Up to now: No significant point sources but just neutrinos from cosmic ray interactions in the atmosphere were found . Ice Cube for more statistics ! Event Display

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  • W. Riegler/CERN
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SLIDE 40
  • W. Riegler/CERN

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DONUT

Detector for Observation of Tau Neutrino.

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SLIDE 41

DONUT

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  • W. Riegler/CERN
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SLIDE 42

DONUT

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  • W. Riegler/CERN
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SLIDE 43

DONUT

Tau lepton has very short lifetime and is therefore identified by the characteristic ‘kink’

  • n the decay point.

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  • W. Riegler/CERN
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SLIDE 44

DONUT

One of the 4 tau candidates. Emulsion resolution 0.5um !

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  • W. Riegler/CERN
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SLIDE 45
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CERN Neutrino Gran Sasso (CNGS)

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SLIDE 46
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νe ντ νμ

If neutrinos have mass:

CNGS

Muon neutrinos produced at CERN. See if tau neutrinos arrive in Italy.

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SLIDE 47
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CNGS Project

CNGS (CERN Neutrino Gran Sasso)

A long base-line neutrino beam facility (732km) send νμ beam produced at CERN detect ντ appearance in OPERA experiment at Gran Sasso

direct proof of νμ - ντ oscillation (appearance experiment)

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SLIDE 48
  • W. Riegler/CERN

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CNGS

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SLIDE 49
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For 1 day of CNGS operation, we expect: protons on target 2 x 1017 pions / kaons at entrance to decay tunnel 3 x 1017 νμ in direction of Gran Sasso 1017 νμ in 100 m2 at Gran Sasso 3 x 1012

νμ events per day in OPERA

≈ 25 per day

ντ events (from oscillation)

≈ 2 per year

Neutrinos at CNGS: Some Numbers

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SLIDE 50
  • W. Riegler/CERN

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CNGS Layout p + C → (interactions) → π+, K+ → (decay in flight) → μ+ + νμ

vacuum 800m 100m 1000m 67m 26m

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SLIDE 51
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CNGS

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SLIDE 52
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CNGS

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SLIDE 53
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  • E. Gschwendtner, CERN

typical size of a detector at Gran Sasso Flat top: 500m FWHM: 2800m

Radial Distribution of the νμ-Beam at GS

5 years CNGS operation, 1800 tons target:

  • 30000 neutrino interactions
  • ~150 ντ interactions
  • ~15 ντ identified
  • < 1 event of background
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SLIDE 54
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Lead plates: massive target Emulsions: micrometric precision 10.2 x 12.7 x 7.5 cm3 8.3kg brick Brick

Pb Couche de gélatine photographique 40 μm ν τ

1 mm

Basic unit: brick

56 Pb sheets + 56 photographic films (emulsion sheets)

Opera Experiment at Gran Sasso