Chapter 4
Structure of the Atom
4.1 Early Theories of Matter
4.2 Subatomic Particles & Nuclear Atom
4.2.5 Ultimate Structure of Matter – The
Standard Model (Not in Book)
4.3 How Atoms Differ
4.4 Unstable Nuclei & Radioactive Decay
Beyond proton/neutron/electron Picture
Textbook, page 97
“the three subatomic particles you have
just learned about have since been
found to have their own structures. That
is, they contain sub-subatomic
particles. … will not be covered …
because it is not understood if or how
they affect chemical behavior.”
Beyond proton/neutron/electron
Picture
Yes boys and girls, this is where we
leap off the deep end!
Beyond proton/neutron/electron Picture
(not in book)
To understand nucleus and how some
nuclear radiation processes occur,
need to examine both structure of
nucleons (proton, neutron) and forces
acting at nuclear distances
The standard model of physics
attempts to describe all known forces
and elementary particles
What Is Matter ?
Matter is all the “stuff” around you!
The big picture (from standard
model):
Matter
Hadrons
Baryons Mesons
Quarks
Anti-Quarks
Leptons
Charged Neutrinos
Forces
Gravity
Weak
Strong
EM
Particles
Launch Realplayer video from Fermilab Site
Produced by Fermilab
atoms proton/neutron/electron quarks antimatter
leptons wave/particle duality electron diffraction
http://vmsstreamer1.fnal.gov/VMS/VideoNews/VN77-Particles.ram
Antimatter – Paul Dirac
In 1928, wrote down equation which combined
quantum theory (developed in 1920s by
Schrodinger and Heisenberg) and special
relativity (1900s, Einstein), to describe
behavior of electron
Equation could have two solutions, one for
electron with positive energy, and one for
electron with negative energy
But in classical physics (and common sense!),
energy of particle must always be a positive
number!
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.html
Antimatter – Paul Dirac
Dirac interpreted this to mean that for every
particle that exists there is a corresponding
antiparticle, exactly matching the particle but
with opposite charge
For electron, for instance, there should be an
"antielectron" identical in every way but with a
positive electric charge
In Nobel Lecture, Dirac speculated on
existence of completely new Universe made
out of antimatter!
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.html
Paul Dirac
Antimatter – Carl Anderson
1932, young professor at Caltech, studied
showers of cosmic particles in cloud chamber;
saw track left by "something positively charged,
and with the same mass as an electron"
After nearly 1 year of effort and observation,
decided tracks were actually antielectrons, each
produced alongside an electron from impact of
cosmic rays in cloud chamber
Called antielectron "positron", for its positive
charge. discovery gave Anderson the Nobel Prize
in 1936 and proved existence of antiparticles as
predicted by Dirac
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html
Antimatter – Carl Anderson
Anderson's cloud chamber picture of cosmic
radiation from 1932 showing for first time
the existence of anti-electron
Particle enters from
bottom, strikes lead
plate in middle and loses
energy as can be seen
from greater curvature of
upper part of track
http://www.aps.org/publications/apsnews/200408/history.cfm
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html
Antimatter
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html
Anderson close to his cloud chamber
Quantum Mechanics & Antimatter
Nobel Prize, 1933 Erwin Shrodinger (Berlin U,
Germany), Paul Adrien Maurice Dirac (U
Cambridge, UK)
“for the discovery of new productive forms of atomic
theory”
Antimatter
Nobel Prize, 1936 Hess (Innsbruck U, Austria),
Anderson (Caltech)
Hess: for his discovery of cosmic radiation
Anderson: for his discovery of the positron [first
confirmation of the existence of antimatter]
Matter & Forces from Standard Model
Matter
Hadrons
Baryons Mesons
Quarks
Anti-Quarks
Leptons
Charged Neutrinos
Forces
Gravity
Weak
Strong
EM
Particles in Standard Model
Six leptons are all elementary particles –
includes the electron
“Ordinary” matter
All other particles (hadrons) are composed
of combinations of quarks (6 kinds) –
isolated quarks are not permitted
Class of hadrons called baryons composed
of 3 quarks – includes proton & neutron
Class of hadrons called mesons composed
of 2 quarks (quark + anti-quark)
Standard Model
Launch “The Standard Model” (Running time 6:36)
Launch QT Video (stream) from Web
The Standard Model
Standard Model
Four Fundamental Forces
In order of decreasing strength:
Strong – binds nucleons
Electromagnetic – “opposites attract”
Weak – involved in radioactive decay
(beta decay)
Gravity
Forces arise through exchange of a
mediating field particle (a boson)
Four Fundamental Forces
?
Standard Model
Basic Particles and Force Carriers
All 6 quarks and 6
leptons have
corresponding
antiparticles with
opposite charge
Some particles
are their own
antiparticles
“Colors” Of Quarks
Quarks are said to have colors (thought of
as charge but 3 types)
Colors – blue, red and green
3 colors of quark are attracted together
Antiquarks have cyan, magenta, yellow
Works by exchange of gluons: called strong force
Structure within Proton
(with gluons – animation)
Structure within Proton
S
0
K
-
D
D
p
-
-
p
D
o
W
+
p
+
K
L
o
+
D
++
-
p
0
K
+
What a jungle!
Dimensions of
Subatomic
Particles
Structure Within the Atom
If protons and neutrons were 10 cm across,
then quarks and electrons would be < 0.1
mm in size and entire atom would be ~ 10
km across
Space is mostly “empty space”
Atoms > 99.999% empty space
Electron
Nucleus
Protons & Neutrons are >
99.999% empty space
g
u
Proton
Quarks make up
negligible
fraction of
protons volume !!
u
d
The Universe
The universe and all the
matter in it is almost all
empty space !
(YIKES)
Why does matter appear
to be so rigid ?
Forces, forces, forces !!!!
Primarily strong and electromagnetic
forces which give matter its solid
structure
Strong force  defines nuclear size
Electromagnetic force  defines
atomic size
Standard Model Development
Developed by careful analysis of high
energy physics experiments (particle
accelerators and colliders)
Lots of heavy thinking!
Standard Model Related Nobel Prizes
1948 Blackett (Victoria U, Manchester, UK)
for his development of the Wilson cloud chamber
method, and his discoveries therewith in the fields of
nuclear physics and cosmic radiation
Standard Model Related Nobel Prizes
1949 Yukawa (Kyoto Imperial U, Japan)
for his prediction of the existence of mesons on the
basis of theoretical work on nuclear forces
Standard Model Related Nobel Prizes
1950 Powell (Bristol U, UK)
for his development of the photographic method of
studying nuclear processes and his discoveries
regarding mesons made with this method
Standard Model Related Nobel Prizes
1957 Yang (Institute for Advanced Study,
Princeton), Lee (Columbia U)
for their penetrating investigation of the so-called parity
laws which has led to important discoveries regarding
the elementary particles
Standard Model Related Nobel Prizes
1959 Segre, Chamberlain (both U Cal. Berkeley)
for their discovery of the antiproton
Standard Model Related Nobel Prizes
1963 Wigner (Princeton), Goeppert-Mayer (U Cal.
La Jolla), Jensen (U. Heidelberg, Ger.)
Wigner: for his contributions to theory of atomic nucleus
and elementary particles, particularly through discovery
and application of fundamental symmetry principles
Goeppert-Mayer, Jensen: for their discoveries
concerning nuclear shell structure
Standard Model Related Nobel Prizes
1965 Tomonaga (Tokyo U. of Education),
Schwinger (Harvard), Feynmann (Caltech)
for their fundamental work in quantum electrodynamics,
with deep-ploughing consequences for the physics of
elementary particles
Standard Model Related Nobel Prizes
1969 Gell-Mann (Caltech)
for his contributions and discoveries concerning the
classification of elementary particles and their
interactions
Proposed new quantum property of particles
he called "strangeness number." Found
even more general characteristics that
allowed him to sort particles into eight
"families" - called this grouping the eightfold
way, referring to Buddhist philosophy's eight
attributes of right living. Found that eightfold
way could best be explained by a particle,
undiscovered as yet, with 3 parts (hadrons),
each holding a fraction of a charge. [Named
and predicted existence of quarks.]
Standard Model Related
http://www.telesio-galilei.com/L%20P%20Horwitz%20Summary%20of%20Scientific%20Contributions.pdf
Lawrence P. Horwitz
Algebraic approach to quark model
In 1964, there were many expositions on the
“quark model" of hadronic physics at CERN,
and Horwitz (then at U of Geneva) brought the
question to Yuval Ne'eman whether these
results could be explained in term of group
theory rather than the very questionable
dynamics of such strongly interacting systems.
They succeeded (with N. Cabibbo) in
developing a group theoretical model which
was very successful, and later justified its
structure in terms of the asymptotic forms Ms. Simon’s Father
proposed by Gell-Mann and his student
Melosh.
Standard Model Related Nobel Prizes
1976 Richter (Stanford Linear Accelerator Lab),
Ting (MIT)
for their pioneering work in the discovery of a heavy
elementary particle of a new kind
Standard Model Related Nobel Prizes
1979 Glashow (Harvard), Salam (Imperial
College London) & Weinberg (Harvard)
Theory of the unified weak and electromagnetic
interaction
(Weinberg coined term “standard model”)
Standard Model Related Nobel Prizes
1984 Rubbia & van der Meer (both CERN,
Geneva)
Discovery of field particles W and Z, communicators of
weak interaction
Standard Model Related Nobel Prizes
1988 Lederman (Fermilab, Batavia, IL), Schwartz
(Digital Pathways Inc, Mountain View, CA),
Steinberger (CERN, Geneva)
for neutrino beam method and demonstration of doublet
structure of leptons through discovery of muon neutrino
Standard Model Related Nobel Prizes
1990 Friedman (MIT), Kendall (MIT), Taylor
(Stanford U)
for their pioneering investigations concerning deep
inelastic scattering of electrons on protons and bound
neutrons, which have been of essential importance for
development of the quark model in particle physics
Standard Model Related Nobel Prizes
1995 Perl (Stanford), Reines (U Cal. Irvine)
for pioneering experimental contributions to lepton
physics: Perl “for the discovery of the tau lepton”; Reines
“for the detection of the neutrino”
Standard Model Related Nobel Prizes
1999 ‘t Hoof (Utrecht U., Netherlands), Veltman
(Bilthoven, Netherlands)
for elucidating the quantum structure of electroweak
interactions in physics
Standard Model Related Nobel Prizes
2004 Gross (U Cal. Santa Barbara), Politzer
(Caltech), & Wilczek (MIT)
Discovery of asymptotic freedom in the theory of the
strong interaction
Standard Model Related Nobel Prizes
2008 Nambu* (U Chicago), Kobayashi** (High Energy
Accelerator Research Org., Japan), Maskawa** (Yukawa
Institute for Theoret. Physics, Kyoto U., Japan)
*for the discovery of the mechanism of spontaneous
broken symmetry in subatomic physics
**for the discovery of the origin of the broken symmetry
which predicts the existence of at least three families of
quarks in nature
Unsolved Mysteries
The following topics are areas of active
research in the physics community
Elementary Particles if Strings Exist
(Baryons)
(Lepton)
Particle Accelerators
Charged particles, like
protons, whipped around,
bang into another high
speed particle and break
apart
Pieces don’t last long,
only 10-7 s to 10-24 s
Data used to discover
existence of quarks and
other “exotic” particles
Aerial View of Fermilab
“Doubly Strange" Particle
Sept. 3, 2008
Physicists of the DZero experiment at the
U.S. Department of Energy's Fermi National
Accelerator Laboratory have discovered a
new particle made of three quarks [baryon],
the Omega-sub-b (Ωb).
Particle contains two strange quarks and a
bottom quark (s-s-b). It is an exotic relative
of the much more common proton and
weighs about six times the proton mass.
“Doubly Strange" Particle
Combing through almost 100 trillion collision
events produced by the Tevatron particle
collider, the DZero collaboration found 18
incidents in which the particles emerging
from a proton-antiproton collision revealed
distinctive signature of the Omega-sub-b.
Once produced, the Omega-sub-b travels ~
a millimeter before it disintegrates into
lighter particles. Its decay, mediated by the
weak force, occurs in about a trillionth of a
second.
“Doubly Strange" Particle
"The observation of the doubly strange b
baryon is yet another triumph of the quark
model," said DZero cospokesperson Dmitri
Denisov, of Fermilab. "Our measurement of
its mass, production and decay properties
will help to better understand the strong
force that binds quarks together.“
“Doubly Strange" Particle
According to the quark model, invented in
1961 by theorists Murray Gell-Mann and
Yuval Ne'eman as well as George Zweig,
the four quarks up, down, strange and
bottom can be arranged to form 20 different
spin-1/2 baryons. Scientists now have
observed 13 of these combinations.
“Doubly Strange" Particle
DZero is an international experiment of
about 600 physicists from 90 institutions in
18 countries. It is supported by the U.S.
Department of Energy, the National Science
Foundation and a number of international
funding agencies.
Some DZero
Scientists in
Front of the
DZero
Detector
Links for Those Who Want More
Fermilab Physics For Everyone Lectures
“Particle Physics: The World of Matter, Space,
and Time” November 14, 2000 00:47:04
http://vmsstreamer1.fnal.gov/Lectures/Physics4Every/Quigg/index.htm
Fermilab Physics Videos Main Search Page
Choose “General Interest” or “Student” levels or
specific series (e.g. “Physics for Everyone”) or
other topics of interest
Link to main Video Search
Particle Physics at CERN
Launch Video from Nova Science Now
http://media.pbs.org/asxgen/general/windows/wgbh/nov
a/nsn-3410-02-350.wmv.asx
12 min 20 sec
Particle Physics at CERN
http://www.pbs.org/wgbh/nova/sciencenow/3410/02.html
CERN – Large Hadron Collider LHC
Launch Video from Misc
LHC (CERN) Rap (by Alpinekat)
See YouTube
LHC
Technology Review (MIT) May/June 2008 By Jerome Friedman
The recently completed Large Hadron Collider,
the world's most powerful particle accelerator and
most ambitious scientific instrument, is being
readied to address some of the deepest
questions in physics.
Hundreds of feet below the surface of the earth,
straddling the Swiss-French border near Geneva,
it will smash counter-rotating, seventrillionelectron-volt beams of protons against one
another in a 27-kilometer ring of superconducting
magnets.
LHC
With this immense energy, the LHC will be
capable of producing new types of particles that
are thousands of times heavier than the proton.
And it will enable physicists to study phenomena
at one-ten-billionth the scale of the atom.
The science will be carried out with five
multisystem particle detectors, the most massive
of which are Atlas and CMS. Atlas is comparable
in size to a seven-story building, 135 feet long
and 75 feet wide; CMS, a somewhat smaller but
heavier detector, weighs more than one and a
half times as much as the Eiffel Tower.
Compact Muon Solenoid
CMS (high energy
particle physics detector)
at CERN lab (Geneva)
Will be largest solenoid
ever built
Maximum magnetic field
4 Tesla (~100,000 x
strength of Earth’s field)
Amount of iron used
roughly equivalent to that
used to build Eiffel Tower
Very Large Solenoid (CMS)
Very Large Solenoid (CMS)
Higgs Boson - Fermilab vs CERN
http://www.thetriplehelix.org/uncategorized/928
4/2/08
Fermilab is perhaps best known for its particle
accelerator, the Tevatron. Currently the largest and
most powerful accelerator in the world, the
Tevatron’s name originates from how it can
accelerate protons and antiprotons to energy levels
as high as one trillion electron volts, or one TeV.
Its position will soon be usurped, however, by the
Large Hadron Collider (LHC) at CERN in Geneva,
Switzerland. A multi-million dollar effort by the
European Union, the LHC is expected to officially
begin operations in May 2008.
Higgs Boson - Fermilab vs CERN
Fermilab makes its own antiprotons to be used in
Tevatron, and prevents them from interacting with
matter by holding them in place with magnetic fields.
LHC, in contrast, will use proton-proton collisions, a
decision influenced by difficulty of obtaining
antimatter—one million protons are required to
generate an average of 10 antiprotons.
Both Tevatron and LHC have one main objective: to
obtain grand prize of particle physics, the Higgs
boson. In the Standard Model of particle physics that
describes three of the four fundamental forces in the
universe, only gravity, or the origin of mass, remains
unexplained.
Higgs Boson - Fermilab vs CERN
The Higgs boson, thought to give mass to other
particles, is the missing piece of the puzzle. It has
escaped detection so far, but scientists hope that
the energy levels the LHC can provide—up to 14
TeV—will be high enough to finally provide a
glimpse of the elusive particle. The pursuit of the
Higgs at Fermilab is also a race against the clock,
since the Tevatron is scheduled to shut down in
2009 .
Higgs Boson vs Graviton
http://www.physicsforums.com/showthread.php?t=78993
I hope I'm posting in the right place. I was just wondering, what is
the difference between the graviton and the higgs boson. I'm not
quite sure, I think I sort of understand it... but not really.
----------------------------------------------------------------------------------The higgs boson is the field that interacts with particles to give
them mass. Think about it as the answer to the question: Where
does mass come from? The answer is: from the interaction
between the particle and the higgs field.
The graviton, is the theoretically predicted quanta of the
gravitational field. If a quantum field theory of gravity exists, the
graviton would be the particle which mediates the gravitational
force much like the photon for QED.
Higgs Boson vs Graviton
http://www.physicsforums.com/showthread.php?t=78993
The Higgs gives particle the property of mass. Once the particle
has mass, it eminates a gravitational field. The gravitons are the
mediator of this gravitational interaction.
--------------------------------------------------------------------------------------Look the Higgs is a postulated particle. It was born as a
mathematical trick in order to solve some problems concerning
symmetry in quantum field theory. The Higgs has mass because
we defined it like that. The Higgs particle gives mass to
elementary particles via it's interaction with these particles. This
interaction can be expressed in terms of a coupling between the
higgs field and the elementary particle field. The coefficient of the
product of these fields is the mass of the elementary particle. This
is just how the QFT formalism works.
Higgs Boson vs Graviton
http://www.physicsforums.com/showthread.php?t=78993
(continued)
This is very interesting stuff but not that easy.
Also i read analogy stuff like 'the gravitons are the photons'. Do
not pay any attention to this because it is fundamentally wrong.
Gravitons are very different in nature, they indeed mediate the
gravitational force but they are different in nature because they
ARE particles of space time itself
Higgs Boson: How to Detect
http://www.physicsforums.com/showthread.php?t=203001
The Higgs is one of those particles that can't be detected directly
because it will not tend to survive long enough to hit a detector.
This is okay because we can calculate, when the particle decays,
what it decays into. So if you look in the right places, you will find
descriptions of the various paths for "production" of various kinds
of particles. The idea is that at a certain energy scale there are a
certain number of ways a Higgs could come into being, and a
certain number of things that are likely to happen when a Higgs is
produced. Since we know a lot about the Higgs, we can calculate
ahead of time what those things will be.
(continued)
Higgs Boson: How to Detect
http://www.physicsforums.com/showthread.php?t=203001
I can't find right now a description of the paths we'll likely see at
the LHC, but here's a description of how they're looking for the
Higgs at the Tevatron, from the blog of a scientist there, which
should give you a rough idea.
(continued)
Higgs Boson: How to Detect
http://www.physicsforums.com/showthread.php?t=203001
The short version of the Tevatron description as I'm reading it is:
the Tevatron particles crash, and the energy of that crash could
produce a number of things. Among the things it could produce is
a Higgs, or it could also produce a W Boson and a Higgs, or
maybe a Z Boson and also a Higgs. Meanwhile, once the Higgs
comes into being, it will last for a certain amount of time, after
which it could decay into a b-quark and a b-anti-quark, or it could
decay into a pair of W bosons. Of course, the W bosons and such
aren't directly observable either! They decay into other things...
some of which decay into other things... eventually, all this
decaying is done, and the particles that are left over are long-lived
("long-lived" meaning "long enough to travel a a few feet away to
the detector") things like neutrinos. THESE are the things that the
detector detects!
(continued)
Higgs Boson: How to Detect
http://www.physicsforums.com/showthread.php?t=203001
So basically, you're running this detector. With each collision you
get a weird smattering of particles hitting the detector, and for
each particle your detector registers things like its energy, its
angle, whatever. And you sit down with a mathematical model that
has a long, long list of all the different things that could possibly be
produced in a collision; and for each of those things that could be
produced, it has a list of "decay channels" (or in other words, a list
of final states, saying for example that after all the decaying is
done, you'll get 4 particles of this type arriving at these sorts of
angles at this time, and then 3 particles of this other type
arriving... etc). Each of these productions will have a different
probability, and each decay channel/final state will have a different
probability of resulting from its initial particle production.
(continued)
Higgs Boson: How to Detect
http://www.physicsforums.com/showthread.php?t=203001
So you try to match up the things your detector found, with these
final states. Because so much of your model is based on
probabilities, you have to do this statistically-- you have to
measure a huge number of events, and then you measure
whether the number of events of each type that you saw was
close to the number of events of each type that your model
predicts will occur on average. You ask, was the final tally of
events closer on average to what the model tells us we'd see if no
Higgs are being produced? Or is it closer to what the model tells
us we'd see if the Higgs was being produced? Or is something
else entirely happening?
Standard Model Summary
The Standard Model (SM) is our current
best description of the particles of which
matter is made and the forces which govern
these particles
SM describes 4 fundamental forces
SM describes 12 elementary particles: 6
kinds of quarks and 6 kinds of leptons (not
counting anti-particles)
Particles come in two major categories:
hadrons and leptons
Standard Model Summary
Up & down quarks (in the form of neutrons
and protons) and electrons are constituents
of ordinary matter
Other leptons and particles containing
quarks can be produced in cosmic ray
showers or in high energy particle
accelerators; these particles are all shortlived
Each particle has corresponding antiparticle
Particles in Standard Model
Six leptons are all elementary particles –
includes the electron
“Ordinary” matter
All other particles (hadrons) are composed
of combinations of quarks (6 kinds) –
isolated quarks are not permitted
Class of hadrons called baryons composed
of 3 quarks – includes proton & neutron
Class of hadrons called mesons composed
of 2 quarks (quark + anti-quark)
Matter & Forces from Standard Model
Matter
Hadrons
Baryons Mesons
Leptons
Charged Neutrinos
Quarks
Anti-Quarks
Proton & neutron
in this group
Forces
Gravity
Weak
Electron in
this group
Strong
EM
The Standard Model
Higgs Boson
(gravitron)
??
EM
Strong
Weak
Standard Model
Four Fundamental Forces
In order of decreasing strength:
Strong – binds nucleons
Electromagnetic – “opposites attract”
Weak – involved in radioactive decay
(beta decay)
Gravity
Forces arise through exchange of a
mediating field particle (a boson)
Standard Model - Forces
Neutrons and protons in nucleus held together
by strong force, which has a short range
Strong force able to overcome strong electric
repulsion of + charged protons
Electrons attracted to nucleus because of
electromagnetic force
Weak force involved in neutron decay –
involves changing one type of quark into 2nd
type with electron emission
Matter mostly empty space; forces make it
seem like it isn’t
The Nucleus
Proton Neutron
Concentrated positive charge in nucleus
Nucleus should repel and blow apart
But nucleons have a deeper structure
Forces In The Atom
Electrons held in
place by
electromagnetic
force
Nucleons held
together by
strong force
Force
Strong
Electromagnetic
Gravity
Carrier Particles
(Bosons)
Gluons
Photons
Gravitons?
Getting
weaker
The Proton
Proton made of three quarks
Two Up
Quarks
One Down
Quark
Up quark has charge +2/3 and mass of (approximately) 1/3
Down quark has charge –1/3 and mass of (approximately) 1/3
Mass = 1/3 + 1/3 + 1/3 = 1
Charge = 2/3 + 2/3 – 1/3 = +1
The Neutron
Neutron also made of three quarks
Two Down
Quarks
One Up
Quark
Mass = 1/3 + 1/3 + 1/3 = 1
Charge = 2/3 – 1/3 – 1/3 = 0
Neutrons can decay
Beta Decay In Neutron
neutron
proton
W– boson
electron
neutrino
Example of weak force, of which W– is a boson
Current Work
Large accelerator experiments at Fermilab
(Illinois) and at CERN (Switzerland/France)
continuing to search for new particles and test
Standard Model predictions
Major hot topics in physics include:
Origin of mass (Higg’s Boson)
Existence of dark matter / dark energy
Acceleration of expansion of universe
Lack of antimatter
Grand unification: theory of gravity + other forces