Download Experiments - Ohio State University

Experimental techniques of High Energy and
Nuclear Physics
• Introduction to detectors
discuss a few typical experiments
• Probability, statistics, and data analysis (Leo, ch 4)
distributions, maximum likelihood, least squares fitting, lying
• Passage of radiation through matter (Leo, ch 2)
light and heavy charged particles and photons
• Scintillation devices (Leo, ch 7, 8, 9)
counters and calorimeters, energy measurement
• Ionization devices (Leo, ch 6)
proportional and drift chambers, momentum measurement
• Semiconductor devices (Leo, ch 10)
silicon microstrip detectors, vertexing
880.A20 Winter 2002
Richard Kass
References
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Techniques for Nuclear and Particle Physics Experiments, Leo
Particle Detectors, Grupen
The Physics of Particle Detectors, Green
Detectors for Particle Radiation, Kleinknecht
The Particle Detector BriefBook, Bock and Vasilescu
http://www.cern.ch/Physics/ParticleDetector/BriefBook
Particle Data Book (FREE! ORDER ONE TODAY) http://pdg.lbl.gov
Introduction to Experimental Particle Physics, Fernow
Statistics for Nuclear and Particle Physicists, Lyons
Probability and Statistics in Particle Physics, Frodesen, Skjeggestad, Tofe
Statistical Data Analysis, Cowen
Statistics, Barlow
880.A20 Winter 2002
Richard Kass
Intro to HEP Experiments
What are the ingredients of a high energy or nuclear physics experiment?
Consider three examples of different types of experiments:
FIXED TARGET (FOCUS, SELEX, E791)
COLLIDING BEAM (CLEO, CDF, STAR)
ACTIVE EXPERIMENT (Super K, SNO)
Some Common features:
energy/momentum measurement
particle identification
trigger system
data acquisition and storage system
software
hardworking, smart people…
Some Differences:
experiment geometry
data rate
single purpose vs multi-purpose
880.A20 Winter 2002
Richard Kass
Fixed Target Experiment
Imagine an experiment designed to search for Baryons with Strangeness=+1
These particles would violate the quark model since Baryons always have
negative strangeness in the quark model.
A candidate reaction is: p-pk-X+
Since this is a strong reaction we need to conserve:
baryon number: X has B=+1
strangeness:
X has to have +1
electric charge: X has to have Q=+1
General requirements of experiment:
we need to know that only k- and one other particle produced in final state
To achieve this we will have to:
get a beam of p-’s with well defined momentum (we need an accelerator)
get a target with lots of protons (e.g. liquid hydrogen)
identify p-’s and k-’s
eliminate background reaction: p-p p-p
measure the momentum of the p-’s and k-’s
eliminate background reactions: p-pk-k+n or k-kop
a way to record the data
880.A20 Winter 2002
Richard Kass
Simple Quark Model
1960’s
Quarks are point-like spin ½ objects.
Quarks “feel” the strong force, in addition to EM, Weak, and Gravitational forces.
Mesons: pair of quark and anti-quark
Baryons: triplets of quarks
880.A20 Winter 2002
d
u
s
c
b
t
Electric
charge
-1/3
2/3
-1/3
2/3
-1/3
2/3
Isospin Iz
-1/2
+1/2
0
0
0
0
strangeness
0
0
-1
0
0
0
charm
0
0
0
+1
0
0
bottom
0
0
0
0
-1
0
topness
0
0
0
0
0
+1
Richard Kass
Example of fixed target experiment: FOCUS
Momentum: silicon+drift chambers+PWC’s+magnet
Energy: EM+hadronic calorimeters
Particle ID: Cerenkov Counters, muon filter calorimeter
Real life view
880.A20 Winter 2002
Richard Kass
CLEO III Experiment
General purpose detector to study lots of different final states
produced by e+e- annihilations at 10 GeV cm energy
e+e-B+B-
B+*+
B-D*0pD*0 D0g
m+mD0 K- p+
*+s0p+
s0 p+p-
Must have cylindrical geometry since beams pass
through the detector
Must measure:
momentum of charged particles
energy of g’s and po’s
Must identify particles:
charged: e, m, p, k, p
neutral: g, p0, k0, L
880.A20 Winter 2002
Richard Kass
Example of active experiment: SuperKamiokande
Original purpose of experiment was to search for proton decay: pe+p0
Baryon and lepton number violation predicted by many grand unified models (e.g. SU(5))
General Requirements for experiment
Need lots of protons (decay rate of 1032 years7x103 tons of H2O)
Size: Cylinder of 41.4m (Height) x 39.3m (Diameter)
Weight: 50,000 tons of pure water
Need to identify e-’s and p0’s
Reject unwanted backgrounds (cosmic rays, natural radiation)
103m underground at the Mozumi mine
of the Kamioka Mining&Smelting Co Kamioka-cho, Japan
Inside SuperK
880.A20 Winter 2002
Richard Kass
Super Kamiokande
Closer look at experimental requirements:
Identifying p’0s tricky since p0gg thus must identify g’s
Need to measure energy or momentum of e and p0
impractical to use magnetic field  measure energy using amount of Cerenkov light
detect cerenkov light using photomultiplier tubes
11,200 photomultiplier tubes, each 50cm in diameter , the biggest size in the world
Energy Resolution: 2.5% @ 1 GeV and 16% (at 10 MeV)
Energy Threshold: 5 MeV
Need to measure direction of e and po to see if they come from common point
cerenkov light is directional
Need to measure timing of e and po to see if they were produced at common time
cerenkov light is “quick”, can to timing to few nanoseconds
BUT DON’T FORGET
CIVIL ENGINEERING!
Nov 12: accident destroys 1/3 of phototubes
Nov. 13: Bottom of the SK detector
covered with shattered PMT glass pieces
and dynodes.
880.A20 Winter 2002
Richard Kass
Particle Detection
In order to detect a particle it must interact with matter
The most important “detection” processes are electromagnetic
Energy loss due to ionization
electrons
particles heavier than electrons (e.g. m, p, k, p)
Energy loss due to photon emission
Hadrons (p,k,p) interact with matter
bremsstrahlung (mainly electrons)
via the strong interaction and create
Interaction of photons with matter
particles through inelastic collisions.
photoelectric effect
These particles lose their energy via
Compton effect
EM processes:
pair production (g e+e-)
p0ggor p+m+n,m+e+nn
Coulomb scattering (multiple scattering)
Other/combination of electromagnetic processes
cerenkov light
scintillation light
electromagnetic shower
transition radiation
Calculation of above processes involve classical EM and QED
880.A20 Winter 2002
Richard Kass