INSTRUMENTATION & DETECTORS for HIGH ENERGY PHYSICS I - PowerPoint PPT Presentation

INSTRUMENTATION & DETECTORS for HIGH ENERGY PHYSICS I 05-07.11.2014 Isabelle Wingerter-Seez (LAPP-CNRS) - AEPSHEP2014 - Puri (India) 1

WHAT IS A PARTICLE DETECTOR ? An apparatus able to detect the passage of a particle and/or localise it and/or measure its momentum or energy and/or identify its nature and/or measure its time of arrival ….. 05-07.11.2014 2

HOW ARE PARTICLES DETECTED ? In order to detect a particle it must interact with the material of the detector transfer energy in some recognisable way and leave a signal. Detection of particles happens via their energy loss in the material they traverse. 05-07.11.2014 3

FOUR STEPS 1. Particles interact with matter depends on particle and material 1 n o s s e L 2. Energy loss transfer to detectable signal depends on the material 2 n o s s e L 3. Signal collection depends on signal and type of detection 3 n o s s e L 4. BUILD a SYSTEM depends on physics, experimental conditions,…. 05-07.11.2014 4

ELEMENTARY PARTICLES and FORCES 05-07.11.2014 5

PARTICLES 05-07.11.2014 6

H, + the ones we have not yet observed 05-07.11.2014 7

KNOWN PARTICLES H, HOW CAN A PARTICLE DETECTOR DISTINGUISH THE PARTICLES WE KNOW MEASURE PROPERTIES of PHYSICS PROCESSES IDENTIFY THE EXISTENCE OF A NEW PARTICLE ? + the ones we have not yet observed 05-07.11.2014 8

LIMITED SIZE DETECTOR A m o n g t h e s e 1 8 0 l i s t e d particles, 27 have a long enough lifetime such that, for GeV energies, they travel more than one micrometer Among these 27, 14 have c. τ <0.5 mm and leave a very short track in the detector 05-07.11.2014 9

THE 13 PARTICLES A DETECTOR MUST BE ABLE TO MEASURE AND IDENTIFY 05-07.11.2014 10

EXAMPLES OF INTERACTIONS 05-07.11.2014 11

HEP & SI UNITS 05-07.11.2014 12

MEASURING PARTICLES 05-07.11.2014 13

INTERACTION CROSS-SECTION 05-07.11.2014 14

FERMI GOLDEN RULE 05-07.11.2014 15

CROSS-SECTION: ORDER OF MAGNITUDE 05-07.11.2014 16

PROTON-PROTON SCATTERING CROSS-SECTION 05-07.11.2014 17

CROSS-SECTIONS AT THE LHC TRIGGER ! 05-07.11.2014 18

ELECTROMAGNETIC INTERACTION PARTICLE - MATTER In case the particle’s velocity is Interaction with the atomic larger than the velocity of light nucleus. in the medium, the resulting EM The incoming particle is Interaction with the atomic shockwave manifests itself as deflected causing multiple electrons. Cherenkov radiation. When scattering of the particle in the The incoming particle loses the particle crosses the material. energy and the atoms are boundary between two media, During this scattering a exited or ionised . there is a probability of 1% to Bremsstrahlung photon can produce an Xray photon called be emitted Transition radiation. 05-07.11.2014 19

ENERGY LOSS BY IONISATION: BETHE-BLOCH FORMULA 05-07.11.2014 20

IONISATION & EXCITATION The relativistic form of the While the charged particle is transverse electric field does not passing another charged particle change the momentum transfer. the Coulomb force is acting, The transverse field is stronger, but resulting in momentum transfer. the time of action is shorter. 05-07.11.2014 21

IONISATION & EXCITATION The incoming particle transfers The transferred energy energy mainly/only to the atomic electrons. 05-07.11.2014 22

BETHE-BLOCH FORMULA - CLASSICAL DERIVATION 05-07.11.2014 23

BETHE-BLOCH FORMULA - CLASSICAL DERIVATION 05-07.11.2014 24

BETHE-BLOCH FORMULA 05-07.11.2014 25

ENERGY LOSS of PIONS in Cu 05-07.11.2014 26

UNDERSTANDING BETHE-BLOCH 05-07.11.2014 27

UNDERSTANDING BETHE-BLOCH 05-07.11.2014 28

CHARGED PARTICLE ENERGY LOSS in MATERIALS Dependance on target element Mass A Charge Z Minimum Ionisation -dE/dx ~ 1-2 MeV g -1 cm 2 e.g. for Pb with ρ =11.35 g/cm 3 : -dE/dx ~ 13 MeV/cm 05-07.11.2014 29

MATERIAL PROPERTIES 05-07.11.2014 30

05-07.11.2014 31

STOPPING POWER AT MINIMUM IONISATION 05-07.11.2014 32

dE/dX and PARTICLE IDENTIFICATION 05-07.11.2014 33

dE/dx FLUCTUATIONS 05-07.11.2014 34

dE/dx FLUCTUATIONS - LANDAU DISTRIBUTION 05-07.11.2014 35

MEAN PARTICLE RANGE 05-07.11.2014 36

ENERGY LOSS of ELECTRONS 05-07.11.2014 37

ELECTROMAGNETIC INTERACTION PARTICLE - MATTER In case the particle’s velocity is Interaction with the atomic larger than the velocity of light nucleus. in the medium, the resulting EM Interaction with the atomic The incoming particle is shockwave manifests itself as electrons. deflected causing multiple Cherenkov radiation. When The incoming particle loses scattering of the particle in the the particle crosses the energy and the atoms are material. boundary between two media, exited or ionised . During this scattering a there is a probability of 1% to Bremsstrahlung photon can produce an Xray photon called be emitted Transition radiation. 05-07.11.2014 38

BREMSSTRAHLUNG Real photon emission in the electromagnetic field of the atomic nucleus Electric field of the nucleus + of the electrons Z(Z+1) At large radius, electrons screen the nucleus ln(183Z -1/3 ) [D.F.] where y=k/E and For a given E, the average energy lost by radiation, dE, is obtained by integrating over y. 05-07.11.2014 39

BREMSSTRAHLUNG & RADIATION LENGTH 05-07.11.2014 40

RADIATION LENGTH The radiation length is a “universal” distance, very useful to describe electromagnetic showers (electrons & photons) X 0 is the distance after which the incident electron has radiated (1-1/e) 63% of its incident energy 3 0,37 E 0 dE/dx=E/X 0 dE/E=dx/X 0 E 0 2 E=E 0 e -x/X0 1 1X 0 PbWO 4 Air Eau Al LAr Fe Pb LAr/Pb Z - - 13 18 26 82 - - X 0 (cm) 30420 36 8,9 14 1,76 0.56 0.89 1.9 05-07.11.2014 41

RADIATION LENGTH Approximation (X 0 in cm: divide by ρ [g/cm 3 ]) Energy loss by radiation γ Absorption (e + e - pair creation) : 1/ X 0 = " w j / X j For compound material w j being the relative density 05-07.11.2014 42

CRITICAL ENERGY 05-07.11.2014 43

TOTAL ENERGY LOSS FOR ELECTRONS 05-07.11.2014 44

µ + in COPPER 05-07.11.2014 45

INTERACTION OF PHOTONS WITH MATTER 05-07.11.2014 46

PHOTO-ELECTRIC EFFECT 05-07.11.2014 47

PHOTO-ELECTRIC EFFECT 05-07.11.2014 48

PAIR PRODUCTION 05-07.11.2014 49

COMPTON SCATTERING Scattered photon Atomic e - E γ ’ = h ν ’ E e =m e c 2 p γ ’=h ν ’/c θ P e ~0 Incident Photon E γ = h ν φ p γ =h ν /c scattered e - E e ’= √ m e2 c 4 +p e ’ 2 c 2 P e ’=- p γ ’ QED cross-section for γ -e scattering σ compton ∼ Z . ln(E γ )/E γ Process dominant at E γ ≃ 100 keV - 5 GeV 05-07.11.2014 50

ANGULAR DISTRIBUTION 05-07.11.2014 51

INTERACTION OF PHOTONS WITH MATTER Mass absorption coefficient λ = 1/(µ/ ρ ) [g.cm 2 ] with µ= Ν Α . σ /A 05-07.11.2014 52

INTERACTION OF PHOTONS WITH MATTER 05-07.11.2014 53

ELECTROMAGNETIC INTERACTION PARTICLE - MATTER In case the particle’s velocity is Interaction with the atomic larger than the velocity of light nucleus. in the medium, the resulting Interaction with the atomic The incoming particle is EM shockwave manifests itself electrons. deflected causing multiple as Cherenkov radiation. The incoming particle loses scattering of the particle in the When the particle crosses the energy and the atoms are material. boundary between two media, exited or ionised . During this scattering a there is a probability of 1% to Bremsstrahlung photon can produce an Xray photon called be emitted Transition radiation. 05-07.11.2014 54

CERENKOV RADIATION Particles moving in a medium with speed larger than speed of light in that medium loose energy by emitting electromagnetic radiation Charged particles polarise the medium generating an electrical dipole varying with time Every point in the trajectory emits a spherical EM wave; waves constructively interfere 05-07.11.2014 55

CERENKOV RADIATION 05-07.11.2014 56

IDENTIFYING PARTICLES with CERENKOV RADIATION 05-07.11.2014 57

CERENKOV RADIATION: MOMENTUM DEPENDENCE m π = 0.1395 GeV m K = 0.4937 GeV m p = 1 .007 GeV 05-07.11.2014 58

COSMIC RAYS 05-07.11.2014 59

HESS EXPERIMENT 05-07.11.2014 60

Transition radiation Transition radiation occurs if a relativistic particle ( large γ ) passes the boundaries between two media with different refraction indices. Intensity of radiation is logarithmically proportional to γ 05-07.11.2014 61

IDENTIFYING PARTICLES WITH TRANSITION RADIATION 05-07.11.2014 62

ATLAS TRANSITION RADIATION TRACKER 05-07.11.2014 63

IDENTIFYING PARTICLES WITH TRANSITION RADIATION 05-07.11.2014 64