Transcript Introduction to P880.P20

Experimental Techniques of High Energy,
Nuclear, & AstroParticle Physics
Course Info
Office: PRB 3146
Office hours: anytime
Email: [email protected]
Class website: http://www.physics.ohio-state.edu/~kass/p880_06.html
(will post powerpoint notes)
Grading Policy:
40% muon lifetime experiment (discussed on next page)
40% Homework or YOU think up a project
(but I need to OK the project…)
20% Final Project (short presentation)
Muon Lifetime Experiment
Goals: Measure the lifetime of the muon (m) to ~1% precision
Search for unknown particle with lifetime ~2X m’s
Break up into groups of 2 or 3
Each group spends ~2 weeks on experiment
experiment is located in SM3018
Report written using LATEX
template provided
Report should include a section on:
Introduction
Apparatus
Theory
calculation of muon lifetime
Discussion of higher order correction
Lifetime of free m Vs captured m
I have a book with many good articles describing
similar experiments that measure the m lifetime
Data Analysis
Determination of average m lifetime
Possible separation into m+ and m- lifetimes
Upper limit on the amount of a particle with lifetime=4ms in data
Background estimation
Systematic errors
Conclusions
References
Reports are due before end of the winter quarter
Experimental Techniques of High Energy,
Nuclear & AstroParticle Physics
Course Outline
• Introduction to detectors
discuss a few typical experiments
• Probability, statistics, and data analysis (Leo, ch 4)
prob. 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
References
• Particle Data Book (FREE! ORDER ONE TODAY)
http://pdg.lbl.gov
• 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
• 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
• Quarks and Leptons, Halzen and Martin (oldie but still used in P880)
• Particle Physics, Martin and Shaw (P780 level)
• Introduction to Elementary Particles, Griffiths (P780 level)
Intro to HE/NE/AP Experiments
What are the ingredients of a high energy/nuclear physics/astro-particle experiment?
Consider four examples of different types of experiments:
Fixed Target (FOCUS, SELEX, E791)
Colliding Beam (BaBar, CDF, STAR)
Active Experiment (Super K, SNO)
Experiments in Space (GLAST)
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
radiation hardness
A Conceptual Experiment-I
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
use conservation of E and p to eliminate background reactions:
p-pk-k+n or k-kop
a way to record the data
A Conceptual Experiment-II
What are the important issues for this experiment?
p-pk-X+
a) How are we going to identify the p, kaon and proton?
what momentum range do we have to worry about?
b) To what precision do we need to measure the momentum of the p and k?
will need a magnet
will need to measure trajectory in magnetic field
c) Do we need to use a calorimeter to measure energy?
d) How will we know that only an X+ is produced?
e) How much space do we have for the experiment?
f) How much data do we need to collect?
what event rate is expected?
g) How long will this experiment take?
how many people will work on it?
h) How much $$$ will the cost?
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
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
strangene
ss
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
Pentaquarks !
Evidence for a Narrow S=+1 Baryon Resonance in Photoproduction from the Neutron
PRL 91, July 2003. T.Nakano et al.
Experiment studies:
gnnK+Kbut, does not measure the neutron
s
K+n=Q5=dudus
nK- is not exotic
nK+ is exotic
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
BaBar Experiment@ SLAC
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
Detector of
Internally
energy of g’s and po’s
Recflected
Must identify particles:
Cherenkov
Light (DIRC)
charged: e, m, p, k, p
neutral: g, p0, k0, L
SVT, DCH: charged particle tracking
Electromagnetic
Calorimeter
(EMC)
1.5 T Solenoid
Drift Chamber
(DCH)
 vertex &mom. resolution
EMC: electromagnetic calorimetry
 g/p0/h
DIRC, IFR, DCH: charged particle ID
 p/K/p
Instrumented
Flux Return
(IFR)
Silicon Vertex
Tracker (SVT)
BaBar
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))
BUT it discovered neutrino oscillations instead:
Prof. M. Koshiba (U. Tokyo) is awarded 2002 Nobel Prize "for pioneering contributions to
astrophysics, in particular for the detection of cosmic neutrinos."
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
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 2001: accident destroys 1/3 of phototubes
Nov. 13: Bottom of the SK detector
covered with shattered PMT glass pieces
and dynodes.
Gamma Ray Large Area Space Telescope
(GLAST)
A high energy physics experiment in space
Study g-rays from 20 MeV-300 GeV
Measure energy and direction
Dark matter annihilation
Gamma ray bursters
ACD
Active Galactic Nuclei
g
Segmented scintillator tiles
0.9997 efficiency
Si Tracker
pitch = 228 µm
8.8 105 channels
12 layers × 3% X0
+ 4 layers × 18% X0
+ 2 layers
CsI Calorimeter
Hodoscopic array
8.4 X0 8 × 12 bars
2.0 × 2.7 × 33.6 cm
 cosmic-ray rejection
 shower leakage
correction
e+
e–
size: 1.8x1.8x1m
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