Particle detection

Principles of detectionExamples of detectors

Interaction of particles with matter

http://physics.bu.edu/neppsr/2004/Talks/Calorimetry-Surrow.pdf

Energy loss in matter – Bethe Bloch Formula

Z of incoming particle, A of materialDensity of materialAvogadro constantmass of electron

density correction

Electricfiled ~E2

density of electron

1/v2 time(^2) of interaction

Radiative losses - bremsstrahlungIonization

T max maximal Energy transfered to electronI – mean ionisation energy

Particle Identification by measurement of ionisation (dE/dx)

e, μ

K p d

π

• dE/dx – measurement in gas chambers90% Ar : 10% C02

IONIZATION – Bethe Bloch

!!

• momentum vs velocity (β)

Mesurement of particle deflection in magnetic fieldp ⊥ to B [GeV/c] = 0.3 * B [T] * R (radius of curvature in m)

• positions of particle track measured on position sensitive detectors –wire chambers, strip detectors with precision better than 150 µm - tracking

β (v/c) = Distance/TimeOfFlight (for v=c 30cm = 1ns)• TOF measured with precision betten than 100 ps

Experiment HADES

Measurement of ionisation (dE/dx) and position in wire chamber

Positive VoltageVery thin wires(even 20 µm)

Planse of wiresNegative Voltage(or put on ground) • Primary ionisation – few tens of electron-ion pairs

• Formation of avalanche , largest amplification close to wire, additional ion –pairs, gain ~105

Particle track

• Many layers of such planes in one detector – Multiwire Chambers

Multiwire Drift Chambers (from drift time to wire position of track is reconstructed)

time

Radiative losses (bremsstrahlung)

After X0 particlelooses 1/e energy

Detection of photons

LOW Energy HIGH Energy

Pair creation

Electromagnetic showers

Similar for electrons/positrons and high Energy photons

Calorimter types

Detection of hadrons-nuclear interactions

Electromagnetic and hadronic showers

Electromagneticshower:

Principle of multiparticle detection

Bremsstrahlung(showers)– e/γ

Bremmstrahlung Ionization M>>me Mµ ~300Me

Separation of particle detectionIonisation

Cherenkov effect

Vpart < c/n

No polarization

Vpart > c/n

Polarization-emission of electromagneticwave

Vpart > c/n Mechanism of light creation: polarization of medium

Example-Threshold Ring Imaging Cherenkov detector

γ=1/√(1−β2 ), Gas mixture C4F10 : n=1.0015 !γthreshold = 18.3pπ> 2.5 GeV/c, pε> 20 MeV/c !

Detector CMS @ LHC (collider)

HCAL – hadronic calorimetrECAL – Electromagnetic calorimeterTracker (inner detector)- tracking chambers

pseduorapidity η ≅ -ln (tan (θ/2))

ECAL

Particle reconstruction in CMS

Mions

fotons

hadrons

CMS di-muon invariant mass spectrum

HADES detector (fixed target experiment)Side View

START

RICH – GAS Cherenkov detector

MDC – Multiwire Drift Chambers

TOF – Time of Flight DetectorsSHOWER – Em. Cascade Detector

AMS -first Particle Physics Experiment on ISS 2006/2011(AMS-01/02)

Temperature: T: (-180: +50o C)Vibrations (6.8 g RMS) , during start 17g maximal powerlimitation 2000 WVacuumm: < 10-10 TorrControil only from EearthData stream : 1Mbyte/sLarge flux of comsmicradiation ~1000 cm-2s-1

Discovery STS’91

AMS01

Food for MIR’a

100 h sata taking

AMS01 lunched for the firsttime in 1998 on board of Discovery 320-350 km

AMS-02 2011

AMS: Particle identification for E=300 MeV- 3TeV

B

Magnet

z x

Magnet (B=0.15T)

Tracker T1-T6

(TOF S1-S4) + Čerenkov’ a

• BR =p/(Z*e) – pmomentum via BR

• velocity via TOF, N(γ) Čerenkov’ a

• Z (chargé) via dE/dx (T1-T6),(S1-S4)

Full identyfication of particles M ,Z

δx=10 µm!

δt=50 ps!

e/p>104-105 !

B=0.9 [T]