PHYS3321 Nuclear and Particle Physics

Prof. Zhang Fu-Chun– Head & Chair Professor– Department of Physics– fuchun@hku.hk– Room 517 A, Chong Yuet Ming Building

Course coordinator

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TutorMr. HUO Jia-wei

– Address: Room 418, Chong Yuet Ming Building (Physics department)

– Email: jiaweihuo@gmail.com– Phone: 95106582

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: 30%Examination (3 hours): 70%

SCHEDULE

Tuesdays 9:30 – 11:25 MW322 Thursdays 10:30 – 11:25 MW702

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• Four Assignments + 1 mid-term test + attendance– 30% of overall weighting

Continuous Assessment

Assignment Date to release Due date

1 Jan. 31 Feb. 72 Feb. 9 Feb. 163 Feb. 23 Feb. 284 Mar. 22 Mar. 29

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Mid–term test: Mar. 1st 10:30-11:25 AM

• 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)

Course requirements

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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

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Nuclear physics

+

Particle physics

What will this course coverNuclear physics•Rutherford Scattering•Electron scattering•Nuclear binding energy•Liquid drop model•Nuclear shell model•Alpha decay•Beta decay•Fission

http://en.wikipedia.org

Schematic diagram of Rutherford Scattering

What will this course coverNuclear physics•Rutherford Scattering•Electron scattering•Nuclear binding energy•Liquid drop model•Nuclear shell model•Alpha decay•Beta decay•Fission

What will this course coverNuclear 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 coverNuclear 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 coverNuclear physics•Rutherford Scattering•Electron scattering•Nuclear binding energy•Liquid drop model•Nuclear shell model•Alpha decay•Beta decay•Fission

What will this course coverParticle 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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3

1Q

3

2Q 1Q

0Q

Fundamental building block

of baryons and mesons

3

1

3

1

3

1

3

2

3

2

3

2

The six quarks

http://www.hep.phys.soton.ac.uk/~belyaev/teaching/phys3002/notes.html

Large Hadron Collider Experiment

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!

*Slide by Tony Weidberg2012 28

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.

*Slide by Tony Weidberg

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3He magnetic resonance imaging of the lung

Non-smoker Light smoker

Mainz University and University hospital Mainz, 1999

Medical Applications

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).

*Slide by Tony Weidberg

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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

1900 – 1910 Thomson model of the atom prevailed

Proton charge evenly distributed over size of 1Å. Electrons imbedded and oscillatory.

He4

e

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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.

m1510Nuclear radius less than

Charge on nucleus = atomic number =Z

=1fm= 1 Fermi

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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

Li63 Li7

3

1 2

3Spin

During the 1920s this model came under criticism from many physicists.

(i) How could the electrons be confined

(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

E=mc2

MassEnergy

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•1931, First artificial splitting of nucleus

•Also the first transmutation using artificially accelerated particles

•And the first experimental verification of E = mc2

Ernest WaltonJohn Cockcroft

Nobel Prize 1951

Cockroft and Waltonhttp://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

Cockroft and Waltonhttp://homepage.eircom.net/~louiseboylan/Pages/Cockroft_walton.htm

Energy He He Li H 42

42

73

11

Proton + Lithium Two alpha particles + Energy

1 MeV 17.3 MeV

History of Particle Physics

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

Hideki Yukawa (1907 – 1981)

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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 – (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.

Carl Anderson (1905 – 1991)

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Pions decay into two particles, a muon and a muon neutrino or antineutrino

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 Physics1952First 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)2012 47

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 49

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 50

Particle Physics: searching for Higgs Boson

Higgs hunters: A graphic showing a collision at full power at the CMS detector control roomBBC: http://www.bbc.co.uk/news/science-environment-16116230http://www.dailymail.co.uk/sciencetech/article-2073533/Higgs-boson-First-hard-evidence-God-particle-CERN.html 51

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-higgs-boson-real-111213.html

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Particle Physics: searching for Higgs Boson

Particle PhysicsThis 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