Transcript Introduction - Department of Physics, HKU

PHYS3321 Nuclear and Particle Physics
Course coordinator
Prof. Zhang Fu-Chun
–
–
–
–
Head & Chair Professor
Department of Physics
[email protected]
Room 517 A, Chong Yuet Ming Building
Tutor
Mr. HUO Jia-wei
– Address: Room 418, Chong Yuet Ming Building (Physics
department)
– Email: [email protected]
– Phone: 95106582
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PHYS3321 Textbook
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To the late Prof. C.D. Beling
This lecture notes are based on the course
materials by the late Prof. C.D. Beling, who
taught this course over the past a few years
in the physics department of HKU.
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PHYS3321 Course Assessment
Four Assignments + mid-term test:
Examination (3 hours):
30%
70%
SCHEDULE
Tuesdays 9:30 – 11:25
Thursdays 10:30 – 11:25
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MW322
MW702
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Continuous Assessment
• Four Assignments + 1 mid-term test +
attendance
– 30% of overall weighting
Assignment Date to release
Due date
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2
3
4
Feb. 7
Feb. 16
Feb. 28
Mar. 29
Jan. 31
Feb. 9
Feb. 23
Mar. 22
Mid–term test: Mar. 1st 10:30-11:25 AM
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Course requirements
• Four Assignments + 1 mid-term test +
attendance
– 30% of overall weighting
• End of Semester Exam
– 70% of overall weighting
• Prerequisite:
– Pass in PHYS2321(Introductory
electromagnetism) and PHYS2322(Statistical
mechanics and thermodynamics) and
PHYS2323(Introduction to Quantum
Mechanics)
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PHYS3321 course schedule
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PHYS3321 course schedule
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PHYS3321 course schedule
(detailed)
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PHYS3321 course schedule
(detailed)
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Where to get the course materials
http://www.physics.hku.hk/~phys3321/
This course website will update every week
You must check this website to download
•lecture notes
•Assignment questions
•Assignment answers
•Other information…
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This course
Nuclear
physics
+
Particle
physics
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What will this course cover
Nuclear physics
• Rutherford Scattering
• Electron scattering
• Nuclear binding energy
• Liquid drop model
• Nuclear shell model
• Alpha decay
• Beta decay
• Fission
Schematic diagram of Rutherford Scattering
http://en.wikipedia.org
What will this course cover
Nuclear physics
• Rutherford Scattering
• Electron scattering
• Nuclear binding energy
• Liquid drop model
• Nuclear shell model
• Alpha decay
• Beta decay
• Fission
What will this course cover
Nuclear physics
• Rutherford Scattering
• Electron scattering
• Nuclear binding energy
• Liquid drop model
• Nuclear shell model
• Alpha decay
• Beta decay
• Fission
http://library.thinkquest.org/
What will this course cover
Nuclear physics
• Rutherford Scattering
• Electron scattering
• Nuclear binding energy
• Liquid drop model
• Nuclear shell model
• Alpha decay
• Beta decay
• Fission
http://library.thinkquest.org/
What will this course cover
Nuclear physics
• Rutherford Scattering
• Electron scattering
• Nuclear binding energy
• Liquid drop model
• Nuclear shell model
• Alpha decay
• Beta decay
• Fission
What will this course cover
Particle physics (see the next a few slides)
• Particle Classification
• Quark Composition of Hadrons
• Conservation Laws
• Particle Reactions and Decays
• The standard model
• Grand Unified Theory
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Fundamental building block
of baryons and mesons
Q
2
3
Q
1
3
Q  1
Q0
The six quarks
1
3
1

3
1

3

2

3
2

3
2

3
Large Hadron Collider Experiment
http://www.hep.phys.soton.ac.uk/~belyaev/teaching/phys3002/notes.html
Particle physics:
The standard model
The standard model
The Standard Model
of elementary particles, with
the gauge bosons in the
rightmost column
From: http://en.wikipedia.org
The standard model
Summary of interactions
between particles described
by the Standard Model.
From: http://en.wikipedia.org
The Four Fundamental Forces
Practical Applications
• Nuclear fission for energy generation.
– No greenhouse gases
– Safety and storage of radioactive material.
• Nuclear fusion
– No safety issue (not a bomb)
– Less radioactive material but still some.
• Nuclear transmutation of radioactive waste
with neutrons.
– Turn long lived isotopes  stable or short
lived.
• Every physicist should have an informed
opinion on these important issues!
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*Slide by Tony Weidberg
Medical Applications
• Radiotherapy for cancer
– Kill cancer cells.
– Used for 100 years but can be improved by
better delivery and dosimetery
– Heavy ion beams can give more localised
energy deposition.
• Medical Imaging
– MRI (Nuclear magnetic resonance)
– X-rays (better detectors  lower doses)
– Positron emission tomography (PET)
– Many others…see Medical &
Environmental short option.
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*Slide by Tony Weidberg
Medical Applications
3He
magnetic resonance imaging of the lung
Non-smoker
Light smoker
Mainz University and University hospital Mainz, 1999
Other Applications
• Radioactive Dating
– C14/C12 gives ages for dead
plants/animals/people.
– Rb/Sr gives age of earth as 4.5 Gigayear (1
Gigayear= 1×109 years).
• Element analysis
– Forenesic (eg date As in hair).
– Biology (eg elements in blood cells)
– Archaeology (eg provenance via isotope
ratios).
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*Slide by Tony Weidberg
Nuclear physics history
History facts
1896 Bequerel
Discovers natural radioactivity in Uranium salts.
Conclusions – the Uranium atom is unstable
1897 J. J. Thompson
Discovers the electron in
“cathode rays” and measures
e/me
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1898 Wein - Discovers the proton in the “Canal
rays” of H2 discharge. A positive particle ~2000
times mass of electron.
1898 Mdm and Pierre Currie find new naturally
occuring radioactive atoms – Polonium and Radium.
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1899 – 1903 Discovery of the α, β and γ
components of nuclear radiation 4
He
e

1900 – 1910 Thomson model of
the atom prevailed
Proton charge evenly
distributed over size of 1Å.
Electrons imbedded and
oscillatory.
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1911 The Nuclear Hypothesis.
Rutherford postulated that the
positive charge of the atom lay in a “nucleus”. The electrons circulated around the
nucleus to form the atom. Moreover Rutherford and his coworkers tested this model
experimentally by scattering alpha particles from the nucleus. The data confirmed
the nuclear model and not the Thompson model.
Nuclear radius less than
15
10
m
=1fm= 1 Fermi
Charge on nucleus = atomic number =Z
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1913 Bohr publishes the first quantum theory of
the H-atom based on the nuclear model
1911 – 1932 Electron + Protons model of nucleus
During the 1920s this model
came under criticism from
many physicists.
(i) How could the electrons be
confined
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3
Spin
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Li
1
7
3
Li
3
2
(ii) How could the spins of
nuclei be accounted for?
Rutherford suggested that
there must be another
particle called the Neutron
inside the nucleus
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1932 Neutron discovered by Chadwick
1932 Heisenberg - formalizes neutron + proton
model of nucleus
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1939Discovery of Nuclear Fission – Hahn, Meitner and Strassman
1939 Liquid Drop Model completed
1942 First Controlled Fission
1945 First Fission Bomb
1947 Pi meson discovered by Powel
1949 Shell Model of Nuclear Structure completed
(Mayer, Jensen, Haxel, Suess)
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Particle physics history
Matter equates with Energy
2
E=mc
Energy
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Mass
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Cockroft and Walton
http://homepage.eircom.net/~louiseboylan/Pages/Cockroft_walton.htm
•1931, First artificial splitting
of nucleus
•Also the first transmutation
using artificially accelerated
particles
•And the first experimental
verification of E = mc2
John Cockcroft
Ernest Walton
Nobel Prize 1951
Cockroft and Walton
http://homepage.eircom.net/~louiseboylan/Pages/Cockroft_walton.htm
•1931, First artificial splitting
of nucleus
•Also the first transmutation
using artificially accelerated
particles
•And the first experimental
verification of E = mc2
1
7
4
4
1H  3 Li  2 He  2 He  Energy
1 MeV
Proton + Lithium
17.3 MeV
Two alpha particles + Energy
History of Particle Physics
Hideki Yukawa (1907 – 1981)
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1935 Hideki Yukawa published
his theory of mesons, which
explained the interaction between
protons and neutrons, and was a
major influence on research into
elementary particles.
Yukawa’s theory predicted that
there was a particle – the Pion –
that mediated the strong nuclear
force that bound neutrons and
protons together in the nucleus
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History of Particle Physics
1932 Carl Anderson working with high
altitude cloud chamber discovers the
positron (The anti-particle of the electron)
as predicted by Dirac’s theory
1936 Anderson also discovers the Muon –
Carl Anderson (1905 – 1991) (then known as the Mu-Meson) The Muon
was originally thought to be the Yukawa
particle (Pion) because it had a mass in the
right range ~ 200 me. However the Muon
did not interact with neutrons or protons. We
now know the Pion is the parent of the Muon.
Pions decay into two particles, a muon and
a muon neutrino or antineutrino
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History of Particle Physics
1947 Cecil Powell and
collaborators at Bristol University
UK finally discovered the Pion in
short tracks in nuclear emulsions.
Cecil Powell (1903 – 1969)
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History of Particle Physics
1952First Proton Synchrotron 2.3GeV (Brookhaven)
1953 First production of Strange particles
1955 Anti-proton produced
1956 Parity violation discovered (C.S. Wu)
1964 Quark model proposed (Gell-Mann, Zweig)
1967 Electroweak model proposed (Weinberg, Salam)
1974 Charm quark discovered (Richter, Ting)
1977 Bottom quark discovered (Lederman)
1983 W and Z particles discovered (CERN)
1996 Top quark discovered (Fermi Lab)
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Today’s Particle physics
Particle Physics:
searching for Higgs Boson
2011 First hard evidence of God particle (Higgs boson) was
found by CERN researchers --- yet to be confirmed in 2012
A typical 'candidate event' for the Higgs boson, including two high-energy photons whose
energy (depicted by red towers) is measured by CMS. The yellow lines are the measured
tracks of other particles produced in the collision
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Particle Physics:
searching for Higgs Boson
The CMS detector weighs a staggering 13,000 tons.
CMS is a particle detector that is designed to see a wide range of particles and
phenomena produced in high-energy collisions in the Large Hadron Collider
(LHC) . Like a cylindrical onion, different layers of detectors measure the
different particles, and use this key data to build up a picture of events at the
heart of the collision
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Particle Physics:
searching for Higgs Boson
Higgs hunters: A graphic showing a collision at full power at the CMS detector
control room
BBC: http://www.bbc.co.uk/news/science-environment-16116230
http://www.dailymail.co.uk/sciencetech/article-2073533/Higgs-boson-First-hardevidence-God-particle-CERN.html
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Particle Physics:
searching for Higgs Boson
2012 BIG QUESTION FOR 2012: IS THE HIGGS BOSON
REAL?
The existence of the Higgs particle will either be confirmed or
denied by the LHC in the next few months. 2012 will
be the year when the final piece of the Standard Model
puzzle slots into place. No more rumors, no more
"tentative glimpses"; 2012 will answer the big question:
Does the Higgs boson exist?
http://news.discovery.com/space/big-question-for-2012-higgsboson-real-111213.html
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Particle Physics
This plot basically shows the
energy of detected particles
along the bottom (x-axis) and
"confidence level" (CL) up the
side (y-axis). The dotted,
curved line (inside the green
band), is the energy of the
particles that would
theoretically be detected if the
Higgs boson doesn't exist.
However, the dark wavy line represents the particles that the ATLAS detector has
actually detected so far. As you can see, this line differs greatly from the theoretical line
-- the bump skyrockets at around the 125 GeV (Giga-electronvolts), approximately
125-times the mass-energy of a single proton -- breaking the green barrier
(representing "1-sigma") and the yellow barrier (representing "2-sigma"). In fact, this
peak represents a "2.4 sigma" result. The 2.4-sigma result represents a 98 percent
certainty that this bump is real and not experimental error. What's more, the bump lies
right around the predicted energy of a "light" Higgs boson as predicted by the Standard
Model -- the theory that governs all known particles and forces (except gravity). 53