Transcript smtk00_spares - FSU High Energy Physics

Central Scintillator
Forward Scintillator
+ New Electronics, Trig, DAQ
New Solenoid, Tracking System
Si, SciFi,Preshowers
Shielding
Forward Mini-drift
chambers
D Upgrade
Luminosity and cross section
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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
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interaction rate:
dn / dt  L  s

n  s  Ldt
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
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 – first
mistaken for Yukawa’s particle
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 field to
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: t 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 at CERN (pp collider)
1983: W, Z observed at CERN (pp- collider built for
that purpose)
1995: top quark found at Fermilab (D0, CDF)
1999: indications for “neutrino oscillations” (SuperKamiokande experiment)
2000: direct evidence for tau neutrino (t) at
Fermilab (DONUT experiment)
2003: Higgs particle observed at Fermilab (?????)
Cathode ray history
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1855 German inventor Heinrich Geissler develops
mercury pump - produces first good vacuum
tubes, these tubes, as
modified by Sir William Crookes, become the
first to produce cathode rays, leading eventually
to the discovery of the
electron (and a bit farther down the road to
television).
1858 Julius Plücker shows that cathode rays bend
under the influence of a magnet suggesting that
they are connected in some way; this leads in
1897 to discovery that cathode rays are
composed of electrons.
1865 H. Sprengel improves the Geissler vacuum
pump. Plücker uses Geissler tubes to show that at
lower pressure,
the Faraday dark space grows larger. He also
finds that there is an extended glow on the walls
of the tube and that
this glow is affected by an external magnetic
field.
1869 J.W. Hittorf finds that a solid body put in
front of the cathode cuts off the glow from the
walls of the tube.
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1871 C.F. Varley is first to publish suggestion that
cathode rays are composed of particles. Crookes
proposes that
they are molecules that have picked up a negative
charge from the cathode and are repelled by it.
1874 George Johnstone Stoney estimates the
charge of the then unknown electron to be about
10-20 coulomb, close to
the modern value of 1.6021892 x 10-19 coulomb.
(He used the Faraday constant (total electric
charge per mole of
univalent atoms) divided by Avogadro's Number.
James Clerk Maxwell had recognized this method
soon after
Faraday had published, but he did not accept the
idea that electricity is composed of particles.)
Stoney also proposes
the name "electrine" for the unit of charge on a
hydrogen ion. In 1891, he changes the name to
"electron."
1876 Eugen Goldstein shows that the radiation in
a vacuum tube produced when an electric current
is forced through
the tube starts at the cathode; Goldstein
introduces the term cathode ray to describe the
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1883 Heinrich Hertz shows that cathode rays are
not deflected by electrically charged metal
plates, which would
seem to indicate (incorrectly) that cathode rays
cannot be charged particles.
1886 Eugen Goldstein observes that a cathoderay tube produces, in addition to the cathode ray,
radiation that travels
in the opposite direction - away from the anode;
these rays are called canal rays because of holes
(canals) bored in
the cathode; later these will be found to be ions
that have had electrons stripped in producing the
cathode ray.
1890 Arthur Schuster calculates the ratio of
charge to mass of the particles making up cathode
rays (today known as
electrons) by measuring the magnetic deflection
of cathode rays. Joseph John (J.J.) Thomson
first becomes interested
in the discharge of electricity through a gas a low
pressure, that is to say, cathode rays.
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1892 Heinrich Hertz who has concluded
(incorrectly) that cathode rays must be some
form of wave, shows that the
rays can penetrate thin foils of metal, which he
takes to support the wave hypothesis. Philipp von
Lenard develops a
cathode-ray tube with a thin aluminum window
that permits the rays to escape, allowing the rays
to be studied in the
open air.
1894 J.J. Thomson announces that he has found
that the velocity of cathode rays is much lower
than that of light. He
obtained the value of 1.9 x 107 cm/sec, as
compared to the value 3.0 x 1010 cm/sec for
light. This was in response to
the prediction by Lenard that cathode rays would
move with the velocity of light. However, by 1897,
he distrusts this
measurement.
Special Note: At this time there was great rivalry
between German and British researchers. As
concerning the nature
of the cathode ray, the Germans tended to the
explanation that cathode rays were a wave (like
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In fact, J.J. Thomson will be awarded the Nobel
Prize in Physics in 1906 for proving the electron is
a particle and his
son, George Paget Thomson, will be awarded the
Nobel Prize in Physics in 1937 for showing that
the electron is a
wave.
1895 Jean-Baptiste Perrin shows that cathode
rays deposit a negative electric charge where
they impact, refuting
Hertz's concept of cathode rays as waves and
showing they are particles.
1896 Pieter P. Zeeman discovers that spectral
lines of gases placed in a magnetic field are split,
a phenomenon call
the Zeeman effect; Hendrik Antoon Lorentz
explains this effect by assuming that light is
produced by the motion of
charged particles in the atom. Lorentz uses
Zeeman's observations of the behavior of light in
magnetic field to
calculate the charge to mass ratio of the electron
in an atom, a year before electrons are
discovered and 15 years
before it is known that electron are constituents
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1869: Johann Hittorf (1824-1914) (Münster)
– determined that discharge in a vacuum tube was
accomplished by the emission of rays ( named “glow
rays” by him, later termed “cathode rays”) capable of
casting a shadow of an opaque body on the wall of the
tube.
– rays seemed to travel in straight lines and produce a
fluorescent glow where they passed through the glass.
– Rays deflected by magnetic field
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1870’s: William Crookes (1832-1919) (London):
– detailed investigation of discharges;
– Confirms Hittorf’s findings about deflection in
magnetic field
– Concludes that rays consist of particles carrying
negative charge
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1886 - 1887: Heinrich Hertz (1857-1894) (Karlsruhe)
– Built apparatus to generate and detect
electromagnetic waves predicted by Maxwell’s theory
 High voltage induction coil to cause spark discharge
between two pieces of brass; once spark forms conducting
path between two brass conductors  charge oscillated
back and forth, emitting e.m. radiation
 Circular copper wire with spark gap used as receiver;
presence of oscillating charge in receiver signaled by
spark across the spark gap
– Experiment successful –
– detected radiation up to 50 ft away
– Established that radiation had properties
reminiscent of light: was reflected and refracted as
expected, could be polarized, speed = speed of light
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1887: Heinrich Hertz:
– Unexpected new observation: when receiver
spark gap is shielded from light of transmitter
spark, the maximum spark-length became smaller
– Further investigation showed:
 Glass effectively shielded the spark
 Quartz did not
 Use of quartz prism to break up light into
wavelength components  find that wavelength
which makes little spark more powerful was in the
UV
 Hertz’ conclusion: “I confine myself at present to
communicating the results obtained, without
attempting any theory respecting the manner in
which the observed phenomena are brought about”
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1888: Wilhelm Hallwachs (1859-1922) (Dresden)
– Performs experiment to elucidate effect observed by
Hertz:
 Clean circular plate of Zn mounted on insulating stand;
plate connected by wire to gold leaf electroscope
 Electroscope charged with negative charge – stays
charged for a while; but if Zn plate illuminated with UV
light, electroscope loses charge quickly
 Electroscope charged with positive charge:
 UV light has no influence on speed of charge leakage.
– But still no explanation
– Calls effect “lichtelektrische Entladung” (lightelectric discharge)
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1894: Hertz and Philipp Lenard (1862-1947):
– Further investigations of cathode rays using
discharge tubes:
 Cathode rays penetrate through thin Al window ate
end of tube,
 Cause fluorescence over distance of few
centimeters in air
 Deflected by magnetic field
 No deflection by electric fields
(later explained due to insufficiently good
vacuum)
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1895: Wilhelm Röntgen (1845-1923)
(Würzburg)
– Uses discharge tubes designed by Hittorf and
Lenard (but improved pump) to verify Hertz’ and
Lenard’s experiments
– Discovers X-rays -- forget about cathode rays!
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Röntgen and X-rays:
Hand of Anna Röntgen
From Life magazine,6
April 1896
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1895: Jean Perrin (1870-1942) (Paris):
– Modifies cathode ray tube – adds “Faraday cup” which
is connected to electrometer
– Shows that cathode rays carry negative charge
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1896: Hendrik A Lorentz (1853-1928) (Leiden)
– Formulates atomistic interpretation of Maxwell’s
equations in terms of electrically charged particles
(called “ions” by him)
– “Lorentz force” = force exerted by magnetic field on
moving charged particles
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1896: Pieter A. Zeeman (1865-1943) (Amsterdam)
– Observes broadening of Na D line in magnetic field
– measures broadening vs field strength
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1896: Explanation of this effect by Lorentz:
 based on light emitted by “ions” orbiting within Na atom
 Calculates expected broadening f  (e/m)B
 By comparing with measured line broadening, obtains
estimate of e/m of “ions” in Na atom:
e/m  107 emu/g  1011 C/kg
(cf modern value of 1.76x10 C11/kg)
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1897: three experiments measuring e/m, all with
improved vacuum:
– Emil Wiechert (1861-1928) (Königsberg)
 Measures e/m – value similar to that obtained by Lorentz
 Assuming value for charge = that of H ion, concludes that
“charge carrying entity is about 2000 times smaller than
H atom”
 Cathode rays part of atom?
 Study was his PhD thesis, published in obscure journal –
largely ignored
– Walther Kaufmann (1871-1947) (Berlin)
 Obtains similar value for e/m, points out discrepancy, but
1897: Joseph John Thomson (1856-1940)
(Cambridge)
– Improves on tube built by Perrin with Faraday cup
to verify Perrin’s result of negative charge
– Conclude that cathode rays are negatively charged
“corpuscles”
– Then designs other tube with electric deflection
plates inside tube, for e/m measurement
– Result for e/m in agreement with that obtained by
Lorentz, Wiechert, Kaufmann, Wien
– Bold conclusion: “we have in the cathode rays matter
in a new state, a state in which the subdivision of
matter is carried very much further than in the
ordinary gaseous state: a state in which all matter...
is of one and the same kind; this matter being the
substance from which all the chemical elements are
built up.“
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1899: J.J. Thomson: studies of
photoelectric effect:
– Modifies cathode ray tube: make metal surface
to be exposed to light the cathode in a cathode
ray tube
– Finds that particles emitted due to light are the
same as cathode rays (same e/m)
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1902: Philipp Lenard
– Studies of photoelectric effect
 Measured variation of energy of emitted
photoelectrons with light intensity
 Use retarding potential to measure energy of
ejected electrons: photo-current stops when
retarding potential reaches Vstop
 Surprises:
– Vstop does not depend on light intensity
– energy of electrons does depend on color
(frequency) of light
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1905: Albert Einstein (1879-1955) (Bern)
– Gives explanation of observation relating to
photoelectric effect:
 Assume that incoming radiation consists of “light quanta”
of energy hf
(h
= Planck’s constant, f=frequency)
  electrons will leave surface of metal with energy
E = hf – W
W = “work function” = energy necessary to
get electron out of the metal
 When cranking up retarding voltage until current stops,
the highest energy electrons must have had energy eVstop
on leaving the cathode
 Therefore
eVstop = hf – W
  Minimum light frequency for a given metal, that for
which quantum of energy is equal to work function
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1906 – 1916 Robert Millikan (1868-1963) (Chicago)
– Did not accept Einstein’s explanation
– Tried to disprove it by precise measurements
– Result: confirmation of Einstein’s theory,
measurement of h with 0.5% precision
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1923: Arthur Compton (1892-1962)(St.Louis):
– Observes scattering of X-rays on electrons
Neutrino
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.
Particle detectors,

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)

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,

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.

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,

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.

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.

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.