Transcript Particle Physics Experiments

Particle Physics
Outline:
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Why do particle physics?
Standard model
particle physics is high energy physics
accelerators
detectors
triggers, data recording
analysis
interpretation
Webpages of interest
 http://www-d0.fnal.gov (Fermilab homepage)
 http://sg1.hep.fsu.edu/~wahl/Quarknet/index.html
(has links to many particle physics sites)
 http://www.fnal.gov/pub/tour.html
(Fermilab particle physics tour)
 http://ParticleAdventure.org/
(Lawrence Berkeley Lab.)
 http://www.cern.ch (CERN -- European Laboratory
for Particle Physics)
Goals of particle physics
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particle physics or high energy physics
•  is looking for the smallest constituents of
matter (the “ultimate building blocks”) and for
the fundamental forces between them;
 aim is to find description in terms of the
smallest number of particles and forces
(“interactions”)
 at given length scale, it is useful to describe
matter in terms of specific set of
constituents which can be treated as
fundamental;
at shorter length scale, these fundamental
constituents may turn out to consist of smaller
parts (be “composite”).
in 19th century, atoms were considered smallest
building blocks,
early 20th century research: electrons,
protons, neutrons;
now evidence that nucleons have substructure quarks;
going down the size ladder: atoms -- nuclei -nucleons -- quarks -- preons ???... ???
Issues of High Energy Physics
Why?
 To understand more organized forms of matter
 To understand the origin and destiny of the
universe.
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Basic questions:
 Are there irreducible building blocks?
Are there few or infinitely many?
What are they?
What are their properties?
 What is mass?
 What is charge?
 What is flavor?
 How do the building blocks interact?
 Why are there 3 forces?
gravity, electroweak, strong
(or are there more?)
Standard Model
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A theoretical model of interactions
of elementary particles
Symmetry:
SU(3) x SU(2) x U(1)
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“Matter particles”
quarks
up, down, charm,strange, top bottom
leptons
electron, muon, tau, neutrinos
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“Force particles”
Gauge Bosons
 (electromagnetic force)
W, Z (weak, elctromagnetic)
g gluons (strong force)
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Higgs boson
spontaneous symmetry breaking of
SU(2)
mass
Standard Model
Building Blocks
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Fundamental Forces: Bosons
Force
ravity
E-M
Weak
trong
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Boson
G?

W
Z0
g(rgb)
Mass(GeV)
?
0
80.42
91.188
0
Strength
51039
1/137
10-5
0: r0
: r
Point-like Particles: Fermions
Particle
Leptons
e


e


Quarks
u
c
t
d
s
b
Charge
Mass (MeV)
0
1
<0.01
0.511
<0.17
105.6
<18
1777


300
300
1500
500
175000
4500
Matter constituents and force
carriers
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(1994 summary from the Contemporary Physics
Education Project at LBNL)
And top is very very heavy !!!
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This mass (175 GeV/c2) is ~ 40x larger than the
next most massive quark. Is this just an
“accident” or does it point to some deeper truth
about the nature of Electroweak symmetry
breaking ?
Brief History of the Standard Model
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Late 1920’s - early 1930’s: Dirac, Heisenberg, Pauli,
& others extend Maxwell’s theory of EM to include
Special Relativity & QM (QED) - but it only works
to lowest order!
1933: Fermi introduces 1st theory of weak
interactions, analogous to QED, to explain b decay.
1935: Yukawa predicts the pion as carrier of a new,
strong force to explain recently observed hadronic
resonances.
1937: muon is observed in cosmic rays
1938: heavy W as mediator of weak interactions?
(Klein)
1947: pion is observed in cosmic rays
1949: Dyson, Feynman, Schwinger, and Tomonaga
introduce renormalization into QED - most accurate
theory to date!
1954: Yang and Mills develop Gauge Theories
1950’s - early 1960’s: more than 100 hadronic
“resonances” have been observed !
1962 two neutrinos!
1964: Gell-Mann & Zweig propose a scheme whereby
resonances are interpreted as composites of 3
“quarks”. (up, down, strange)
Brief History of the Standard Model
(continued)
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1970: Glashow, Iliopoulos, Maiani: 4th quark
(charm) explains suppression of K decay into 
1964-1967:spontaneous symmetry breaking
(Higgs, Kibble)
1967: Weinberg & Salam propose a unified Gauge
Theory of electroweak interactions, introducing
the W,Z as force carriers and the Higgs fieldto
provide the symmetry breaking mechanism.
1967: deep inelastic scattering shows “Bjorken
scaling”
1969: “parton” picture (Feynman, Bjorken)
1971-1972: Gauge theories are renormalizable
(t’Hooft, Veltman, Lee, Zinn-Justin..)
1972: high pt pions observed at the CERN ISR
1973: Gell-Mann & Fritzsch propose that quarks
are held together by a Gauge-Field whose quanta,
gluons, mediate the strong force Quantum
Chromodynamics
1973: “neutral currents” observed (Gargamelle
bubble chamber at CERN)
Brief History of the Standard Model
(continued)
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1975: J/ interpreted as cc bound state
(“charmonium”)
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1974: J/ discovered at BNL/SLAC;
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1976:  lepton discovered at SLAC
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1977:  discovered at Fermilab in 1977,
interpreted as bb bound state (“bottomonium”)
 3rd generation
1979: gluon “observed” at DESY
1982: direct evidence for jets in hadron hadron
interactions
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1983: W, Z observed at CERN
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1995: top quark found at Fermilab (D0, CDF)
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2000: direct evidence for tau neutrino () at
Fermilab (DONUT experiment)
Collisions at the Tevatron
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pp Collisions  qq(g) Interact’s
Underlying
Event
g
d
u
u
q
q
d
u
Hard Scatter
Fermilab
u
Questions at the Tevatron
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The Standard Model
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Electro-Weak (EM + Weak Interact’s)
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QCD (Strong Force)
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W,Z, + quarks & leptons
Most Accurate Theory ever !
(but only for fundamental particles)
Simple Processes  Real Tests
gluons & quarks
High E  Accurate Predictions
Low E  Not a simple Theory
Range of E’s accessible for partons in proton
Properties of Particles
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All Quarks and Leptons Produced
(only place for top quark)
All Gauge Bosons………..almost
What about the Higgs?
More Questions
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The SM works great !
Why change it ?
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2 Strategies:
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Has 18 arbitrary parameters
 Where do they come from ?
Is the Higgs really what we think it should be
?
Look Harder
Get a Bigger Hammer
Precision
Energy
The Tevatron is well suited to both of
these strategies
Fermilab Upgrade
Param
ECM
[TeV]
Bunch X-ing
Freq
[kHz]
Time
[ns]
Bunches
N
p
[1010]
anti-p
[1010]
Lumi
[cm2s1]
Ldt
[pb1]
Inter’s/X-ing
Rates
Inelastic pp
PpWX
pptt
Run I
Run II
1.8
2.0
290
3500
2500
396
7500
132
66
23
5.5
21030
125
2.5
3636
121121
27
27
3
3
21032
21032
2000
5.8
2.3
100 kHz
0.04 Hz
10 Mhz
4.4 Hz
4 / hour
500 tot
D Upgrade
Sub-System
Magnets
Solenoid
Toroid
Tracking
Calorimetry
Muons
Trigger
Run I
Run II
none
2T
Drift Chambers
TRD
2T
2T
Silicon Vtx
Scint Fibers
Pre-Shower
New electronics
ULar
Cu,SSLAr
Drift Tubes
Scintillators
2 Levels
Add Chambers
3 Levels
Experimental
High Energy Physics
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Method
 Subject matter to extreme temperatures and
densities.
Energy ~ 2 trillion eV
Temperature ~ 24,000 trillion K
Density ~ 2000 x nuclear density
 Accelerate sub-atomic particles, to closer
than 100 millionth the speed of light, and
arrange for them to collide head on.
 Study the debris of particles that emerges
from the collisions.
Example
Creating Top Quarks
e   uc
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b (-1/3)
t (+2/3)
W

 e    d s
P (-1)
P (+1)
t (-2/3)
W

e   uc



b (+1/3)
 e    d s
Research Program
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DØ Experiment
 To study 2 TeV proton antiproton
collisions
 Fermilab, Batavia, Illinois
 Next run begins in April 2001
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CMS Experiment
 To study 14 TeV proton antiproton
collisions
 CERN, Geneva, Switzerland
 First run begins in 2005
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Hellaz Experiment
 To study 1 MeV neutrinos from the Sun.
When?!!!
Particle physics experiments
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Particle physics experiments:
 collide particles to
produce new particles
 reveal their internal structure and laws of
their interactions by observing regularities,
measuring cross sections,...
 colliding particles need to have high energy
to make objects of large mass
to resolve structure at small distances
 to study structure of small objects:
 need probe with short wavelength: use
particles with high momentum to get short
wavelength
remember de Broglie wavelength of a particle
 = h/p
 in particle physics, mass-energy equivalence
plays an important role; in collisions, kinetic
energy converted into mass energy;
relation between kinetic energy K, total energy
E and momentum p : ___________
E = K + mc2 = (pc)2 + (mc2)c2
About Units
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Energy - electron-volt
 1 electron-volt = kinetic energy of an electron
when moving through potential difference of
1 Volt;
1 eV = 1.6 × 10-19 Joules = 2.1 × 10-6 W•s
1 kW•hr = 3.6 × 106 Joules = 2.25 × 1025 eV
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mass - eV/c2
1 eV/c2 = 1.78 × 10-36 kg
electron mass = 0.511 MeV/c2
proton mass = 938 MeV/c2
professor’s mass (80 kg)  4.5 × 1037 eV/c2
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momentum - eV/c:
1 eV/c = 5.3 × 10-28 kg m/s
momentum of baseball at 80 mi/hr
 5.29 kgm/s  9.9 × 1027 eV/c
How to do a particle physics experiment
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Outline of experiment:
 get particles (e.g. protons, antiprotons,…)
 accelerate them
 throw them against each other
 observe and record what happens
 analyse and interpret the data
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ingredients needed:
 particle source
 accelerator and aiming device
 detector
 trigger (decide what to record)
 recording device
 many people to:
 design, build, test, operate accelerator
 design, build, test, calibrate, operate, and
understand detector
analyse data
 lots of money to pay for all of this
How to get high energy -collisions
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Need Ecom to be large enough to
allow high momentum transfer (probe small
distances)
produce heavy objects (top quarks,_ Higgs
boson)
_
e.g. top_ quark production:
e+e- tt,
qq  tt, gg  tt, …
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_____ on a target (“fixed target”):
Shoot particle beam
 Ecom = 2Emc2 ~ 20 GeV for E = 100 GeV,
m = 1 GeV/c2
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Collide two particle beams (“collider :
 Ecom = 2E ~ 200 GeV for E = 100 GeV
How to make qq collisions, cont’d
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However, quarks are not found free in nature!
But (anti)quarks are elements of (anti)protons.
_ and anti-protons we should
So, if we collide protons
get some qq- collisions.
Proton structure functions give the probability that
a single quark (or gluon) carries a fraction x of the
proton momentum (which is 900 GeV/c at the
Tevatron)
Accelerator
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accelerators:
use electric fields to accelerate particles,
magnetic fields to steer and focus the beams
synchrotron:
particle beams kept in circular orbit by
magnetic field; at every turn, particles “kicked”
by electric field in accelerating station;
fixed target operation: particle beam
extracted from synchrotron, steered onto a
target
collider operation:
accelerate bunches of protons and antiprotons
moving in opposite direction in same ring; make
them collide at certain places where detectors
are installed
Fermilab accelerator complex
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ACCELERATORS
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are devices to increase the energy of
charged particles;
 use magnetic fields to shape (focus and bend)
the trajectory of the particles;
 use electric fields for acceleration.
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types of accelerators:
 electrostatic (DC) accelerators
 Cockcroft-Walton accelerator (protons up to 2
MeV)
 Van de Graaff accelerator (protons up to 10
MeV)
Tandem Van de Graaff accelerator (protons up
to 20 MeV)
 resonance accelerators
cyclotron (protons up to 25 MeV)
linear accelerators
– electron linac: 100 MeV to 50 GeV
– proton linac: up to 70 MeV
 synchronous accelerators
synchrocyclotron (protons up to 750 MeV)
proton synchrotron (protons up to 900 GeV)
electron synchrotron (electrons from 50 MeV
to 90 GeV)
 storage ring accelerators (colliders)
ACCELERATORS, cont’d
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electrostatic accelerators:
 generate high voltage between two
electrodes  charged particles move in
electric field,
energy gain = charge times voltage drop;
 Cockcroft-Walton and Van de Graaff
accelerators differ in method to achieve
high voltage.
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proton linac (drift tube accelerator):
 cylindrical metal tubes (drift tubes) along axis
of large vacuum tank
 successive drift tubes connected to opposite
terminals of AC voltage source
 no electric field inside drift tube  while in
drift tube, protons move with constant
velocity
 AC frequency such that protons always find
accelerating field when reaching gap between
drift tubes
 length of drift tubes increases to keep drift
time constant
 for very high velocities, drift tubes nearly of
same length (nearly no velocity increase when
approaching speed of light)
Accelerators,
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cont’d
cyclotron
 consists of two hollow metal chambers called
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(“dees” for their shape, with open sides which are
parallel, slightly apart from each other (“gap”)
dees connected to AC voltage source - always one
dee positive when other negative  electric field in
gap between dees, but no electric field inside the
dees;
source of protons in center, everything in vacuum
chamber;
whole apparatus in magnetic field perpendicular to
plane of dees;
frequency of AC voltage such that particles always
accelerated when reaching the gap between the
dees;
in magnetic field, particles are deflected:
p = qBR p = momentum, q = charge,
B = magnetic field strength,
R = radius of curvature
radius of path increases as momentum of proton
increases time for passage always the same as long
as momentum proportional to velocity
this is not true when velocity becomes too big
(``relativistic change of mass'')
Accelerators: “relativistic effects”
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“relativistic effects”
 special relativity tells us that certain
approximations made in Newtonian mechanics
break down at very high speeds;
 relation between momentum and velocity in
“old” (Newtonian) mechanics:
p = m v becomes
________
p = mo v , with  = 1/1 - (v/c)2
mo = “rest mass”, i.e. mass is replaced by
rest mass times 
- “relativistic growth of mass”
 factor  often called “Lorentz factor”;
ubiquitous in relations from special relativity;
energy: E = moc2
 acceleration in a cyclotron is possible as long
as relativistic effects are negligibly small, i.e.
only for small speeds, where momentum is still
proportional to speed; at higher speeds,
particles not in resonance with accelerating
frequency; for acceleration, need to change
magnetic field B or accelerating frequency f
or both;
Accelerators,
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cont’d
electron linac
 electrons reach nearly speed of light at small
energies (at 2 MeV, electrons have 98% of
speed of light);
no drift tubes; use travelling e.m. wave inside
resonant cavities for acceleration.
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synchrocyclotron:
 B kept constant, f decreases;
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synchrotron :
 B increases during acceleration,
f fixed (electron synchrotron)
or varied (proton synchrotron);
radius of orbit fixed.
Particle detectors,
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cont’d
Scintillator:
 energy liberated in de-excitation and capture
of ionization electrons emitted as light ``scintillation light'’
 light channeled to photomultiplier in light
guide (e.g. optical fibers);
 scintillating materials: certain crystals (e.g.
NaI), transparent plastics with doping (fluors
and wavelength shifters)
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proportional tube:
 metallic tube with thin wire in center, filled
with gas, HV between wall (-, “cathode”) and
central wire (+,”anode”);  strong electric
field near wire;
 charged particle in gas  ionization 
electrons liberated;
 electrons accelerated in electric field  can
liberate other electrons by ionization which in
turn are accelerated and ionize  “avalanche
of electrons” moves to wire  current pulse;
current pulse amplified  electronic signal:
 gas is usually noble gas (e.g. argon), with some
additives e.g. carbon dioxide, methane,
isobutane,..) as “quenchers”;
Particle detectors,
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cont’d
multi wire proportional chamber:
 contains many parallel anode wires between two
cathode planes (array of prop.tubes with
separating walls taken out)
 operation similar to proportional tube;
 cathodes can be metal strips or wires  get
additional position information from cathode
signals.
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drift chamber:
 field shaping wires and electrodes on wall to
create very uniform electric field, and divide
chamber volume into “drift cells”, each containing
one anode wire;
 within drift cell, electrons liberated by passage
of particle move to anode wire, with avalanche
multiplication near anode wire;
 arrival time of pulse gives information about
distance of particle from anode wire; ratio of
pulses at two ends of anode wire gives position
along anode wire;
Particle detectors,
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cont’d
Cherenkov detector:
 measure Cherenkov light (amount and/or
angle) emitted by particle going through
counter volume filled with transparent gas
liquid, aerogel, or solid  get information
about speed of particle.
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calorimeter:
 “destructive” method of measuring a particle's
energy: put enough material into particle's way
to force formation of electromagnetic or
hadronic shower (depending on kind of
particle)
 eventually particle loses all of its energy in
calorimeter;
 energy deposit gives measure of original
particle energy.
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Note:
many of the detectors and techniques
developed for particle and nuclear
physics are now being used in medicine,
mostly diagnosis, but also for therapy.
Identifying particles
Particle Identification
Muon B&C
Magnet
Muon A-Layer
Hadronic
Layers
Calorimeter
EM Layers
Central Tracking
e

jet
 
Beam Axis
What do we actually “see”
tt e  jets
Muon
Jet-1
Jet-2
Missing energy
Electron
Detectors
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Detectors
 use characteristic effects from interaction of
particle with matter to detect, identify
and/or measure properties of particle; has
“transducer” to translate direct effect into
observable/recordable (e.g. electrical) signal
 example: our eye is a photon detector;
 “seeing” is performing a photon scattering
experiment:
light source provides photons
photons hit object of our interest -- some
absorbed, some scattered, reflected
some of scattered/reflected photons make it
into eye; focused onto retina;
photons detected by sensors in retina
(photoreceptors -- rods and cones)
transduced into electrical signal (nerve pulse)
amplified when needed
transmitted to brain for processing and
interpretation
Particle interactions with matter
 electromagnetic interactions:
excitation
ionization
Cherenkov radiation
transmission radiation
bremsstrahlung
photoelectric effect
Compton scattering
pair production
 strong interactions:
secondary hadron production,
hadronic showers
 detectors usually have some amplification
mechanism
Interaction of particles with matter
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when passing through matter,
 particles interact with the electrons and/or
nuclei of the medium;
 this interaction can be electromagnetic or
strong interaction, depending on the kind of
particle; its effects can be used to detect the
particles;

possible interactions and effects in
passage of particles through matter:
 excitation of atoms or molecules (e.m. int.):
charged particles can excite an atom or
molecule (i.e. lift electron to higher energy
state);
 subsequent de-excitation leads to emission of
photons;
 ionization (e.m. int.)
electrons liberated from atom or molecule, can
be collected, and charge is detected
 Cherenkov radiation (e.m. int.):
if particle's speed is higher than speed of light
in the medium, e.m. radiation is emitted -“Cherenkov light” or Cherenkov radiation, which
can be detected;
amount of light and angle of emission depend on
particle velocity;
Interaction of particles with matter, cont’d
 transition radiation (e.m. int.):
when a charged particle crosses the boundary
between two media with different speeds of light
(different “refractive index”), e.m. radiation is
emitted -- “transition radiation”
 amount of radiation grows with (energy/mass);
 bremsstrahlung (= braking radiation) (e.m. int.):
when charged particle's velocity changes, e.m.
radiation is emitted;
due to interaction with nuclei, particles deflected
and slowed down emit bremsstrahlung;
 effect stronger, the bigger (energy/mass) 
electrons with high energy most strongly
affected;
 pair production (e.m. int.):
 by interaction with e.m. field of nucleus, photons
can convert into electron-positron pairs
 electromagnetic shower (e.m. int.):
high energy electrons and photons can cause
“electromagnetic shower” by successive
bremsstrahlung and pair production
 hadron production (strong int.):
 strongly interacting particles can produce new
particles by strong interaction, which in turn can
produce particles,... “hadronic shower”
Examples of particle detectors
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photomultiplier:
 photomultiplier tubes convert small light
signal (even single photon) into detectable
charge (current pulse)
 photons liberate electrons from
photocathode,
 electrons “multiplied” in several (6 to 14)
stages by ionization and acceleration in high
electric field between “dynodes”, with gain 
104 to 1010
 photocathode and dynodes made from
material with low ionization energy;
 photocathodes: thin layer of semiconductor
made e.g. from Sb (antimony) plus one or more
alkali metals, deposited on glass or quartz;
 dynodes: alkali or alkaline earth metal oxide
deposited on metal, e.g. BeO on Cu (gives high
secondary emission);
Examples of particle detectors

Spark chamber
 gas volume with metal plates (electrodes);
filled with gas (noble gas, e.g. argon)
 charged particle in gas  ionization 
electrons liberated;
 string of electron - ion pairs along particle
path
 passage of particle through “trigger counters”
(scintillation counters) triggers HV
 HV between electrodes  strong electric
field;
 electrons accelerated in electric field  can
liberate other electrons by ionization which in
turn are accelerated and ionize  “avalanche
of electrons”, eventually formation of plasma
between electrodes along particle path;
 gas conductive along particle path
 electric breakdown  discharge  spark
 HV turned off to avoid discharge in whole gas
volume
Examples of particle detectors, contd

Scintillation counter:
 energy liberated in de-excitation and capture
of ionization electrons emitted as light “scintillation light”
 light channeled to photomultiplier in light
guide (e.g. piece of lucite or optical fibers);
 scintillating materials: certain crystals (e.g.
NaI), transparent plastics with doping (fluors
and wavelength shifters)

Geiger-Müller counter:
 metallic tube with thin wire in center, filled
with gas, HV between wall (-, “cathode”) and
central wire (+,”anode”);  strong electric
field near wire;
 charged particle in gas  ionization 
electrons liberated;
 electrons accelerated in electric field 
liberate other electrons by ionization which in
turn are accelerated and ionize  “avalanche
of electrons”; avalanche becomes so big that
all of gas ionized  plasma formation 
discharge
 gas is usually noble gas (e.g. argon), with some
additives e.g. carbon dioxide, methane,
isobutane,..) as “quenchers”;
The D0 detector
DØ Calorimeter

Uranium-Liquid Argon sampling calorimeter
 Linear, hermetic, and compensating

No central magnetic field!
 Rely on EM calorimeter
Central Scintillator
Forward Scintillator
+ New Electronics, Trig, DAQ
New Solenoid, Tracking System
Si, SciFi,Preshowers
Shielding
Forward Mini-drift
chambers
D Upgrade
D Upgrade Tracking

Silicon Tracker
 Four layer barrels (double/single sided)
 Interspersed double sided disks
 793,000 channels

Fiber Tracker
 Eight layers sci-fi ribbon doublets (z-u-v, or z)
 74,000 830 m fibers w/ VLPC readout
Preshowers
Central


Scintillator strips
– 6,000 channels
Forward
–
Scintillator strips
–
16,000 channels
Solenoid
–2T
superconducting
cryostat
1.1
1.7
Silicon Tracker
50 cm
1/2 of detector
3
7 barrels
12 Disks “F”
1/7 of the detector
8 Disks“H”
(large-z disks not shown)
387k ch in 4-layer double
sided Si barrel (stereo)
405k ch in interspersed
disks (double sided stereo)
and large-z disks
Silicon Tracker -Detectors

Disks
 “F” disks wedge (small diameter):
 144 double sided detectors, 12 wedges = 1disk
 50m pitch, +/-15 stereo
7.5cm long, from r=2.5 to 10cm, at
z=6,19,32,45,50,55 cm
 “H” disk (large diameter):
384 single sided detectors
50 m pitch
from r=9.5-20 cm, z= 94, 126 cm

Barrels
 7 modular, 4 layer barrel segments
 single sided:
layers 1 , 3 in two outermost barrels.
 double sided:
layers 1, 3 have 90o stereo (mpx’d 3:1)
50 & 100m pitch, 2.1 cm wide
layers 2,4 have small angle stereo (2o)
50 & 62.5m pitch, 3.4 cm wide
12cm
two detectors
wire bonded
Trigger


Trigger = device making decision on
whether to record an event
why not record all of them?
we want to observe “rare” events;
for rare events to happen sufficiently often, need
high beam intensities  many collisions take place
e.g. in Tevatron collider, proton and antiproton
bunches will encounter each other every 132ns
at high bunch intensities, every beam crossing
gives rise to collision 
about 7 million collisions per second
we can record about 20 to (maybe) 50 per second

why not pick 10 events randomly?
We would miss those rare events that we are
really after:
e.g. top production:  1 in 1010 collisions
Higgs production:  1 in 1012 collisions
 would have to record 50 events/second for
634 years to get one Higgs event!
Storage needed for these events:
 3  1011 Gbytes

Trigger has to decide fast which events
not to record, without rejecting the
“goodies”
Sample cross sections
p
t
q
p
q
t
Process
collision
2 jets
4 jets
6 jets
W
Z
WW
tt
Higgs
s(pb)
8 x 1010
3 x 106
125,000
5,000
25,000
11,000
10
5
0.1
-1
x 100 pb
events
8 trillion
300 million
12,500,000
500,000
2,500,000
1,100,000
1000
500
10
Luminosity and cross section



Luminosity is a measure of the beam
intensity
(particles per area per second)
( L~1031/cm2/s )
“integrated luminosity”
is a measure of the amount of data
collected (e.g. ~100 pb-1)
cross section s is measure of effective
interaction area, proportional to the
probability that a given process will
occur.
1 barn = 10-24 cm2
1 pb = 10-12 b = 10-36 cm2 = 10- 40 m2

interaction rate:
dn / dt  L  s

n  s  Ldt
Trigger Configuration
Detector
L1 Trigger
7 MHz
L2 Trigger
1 kHz
10 kHz
CAL
L1CAL
L2Cal
FPS
CPS
L1PS
L2PS
CFT
L1CFT
L2CFT
Global
L2
L2STT
SMT
Muon
L1
Muon
FPD
L1FPD
L2
Muon
L1: towers, tracks
L2: Combined
objects (e, , j)
DØ Experiment

Physicists










Brian Connolly
Russell Gilmartin
Attila Gonenc
Craig Group
Jose Lazoflores
Yuri Lebedev
Sinjini Sengupta
Undergraduate student:
 Burnham Stokes
Research Interests




Graduate Students








Susan Blessing
Sharon Hagopian
Vasken Hagopian
Stephan L. Linn
Harrison B. Prosper
Horst D. Wahl
Bill Lee
Silvia Tentindo-Repond

Top quarks
Supersymmetry
Leptoquarks
Higgs
Recent Work
 Measurement of top
quark mass
 Search for
leptoquarks
 Search for
supersymmetric top
quarks
CMS Experiment

Physicists






S. Hagopian
V. Hagopian
K. Johnson
H.B. Prosper
H.D. Wahl
Undergraduate student:
 Lucas Naveira
Research Interests
 Supersymmetry
 Higgs
Engineers:
 Maurizio Bertoldi
 James Thomaston



Recent Work
 R&D of a laserbased monitoring
system for the CMS
calorimeter
 R&D of devices to
scan large
scintillating tiles.
 Coordination of test
beam experiments
at CERN
Summary

Dzero: 2000 to 2005
 Will remain the main focus of our
research program for the next seven
years.
 We have a wonderful window of
opportunity to make major contributions
to our field.

CMS:
2005 and beyond
 The LHC will vastly increase our ability
to probe Nature. We are very confident
that CMS will have a profound impact on
our understanding of particle physics.

Hellaz: 2003 (?) and beyond