PHY313 - CEI544 The Mystery of Matter From Quarks to the Cosmos Spring 2005

1
PHY313 - CEI544The Mystery of MatterFrom Quarks
to the CosmosSpring 2005

• Peter Paul
• Office Physics D-143
• www.physics.sunysb.edu PHY313

2
Information about the Trip to BNL

• When and where Thursday March 31, 2005 at 520
  pm pickup by bus (free) in the Physics Parking
  lot. We will drive to BNL and arrive around 6pm
  (20 miles). We will visit The Relativistic Heavy
  Ion Collider (RHIC) and its two large
  experiments, Phenix and Star. Experts will be on
  hand to explain research and equipment. We will
  return by about 730 pm to arrive back at Stony
  Brook by 8pm.
• What are the formalities? You need to sign up
  either in class or to my e-mail address
  ppaul_at_bnl.gov. by this Friday night. You must
  bring along a valid picture ID. Thats all! The
  guard will go through the bus and check the
  picture IDs.
• What about private cars You will still have to
  sign up and must bring a picture ID (your drivers
  license) to the event. You will park your car at
  the lab gate, join the bus for the tour on-site
  and then be driven back to your car.
• There is NO radiation hazard on site. I hope many
  or even most will sign up for a unique
  opportunity.

3
What have we learned last time

• A nuclear fission process can build up a a chain
  reaction initiated by neutrons, because each
  fission process produces 3 neutrons for every
  one that was used.
• These neutrons need to be moderated to low
  energies to be captured efficiently.
• If enough and sufficiently dense nuclear fuel and
  enough low-energy neutrons are available the
  reaction can be hypercritical and take off.
• The chain reaction can be contained or even
  stopped by inserting nuclei into the fuel that
  have a large capability of absorbing neutrons.
  Boron and Cadmium are such nuclei.
• Fission reactors use mostly 235Uranium and
  239Plutonium as fuel. After a while the fission
  products from the chain reaction poison the fuel.

• Commercial nuclear reactor use light of heavy
  water to moderate the neutrons, cool the fuel
  rods, and produce the steam that drives a
  turbine.
• The fusion of deuterium and tritium delivers huge
  amounts of energy/ kg of fuel, has an infinite
  supply of fuel, and produces no long-lived
  radioactive waste.
• However, the fusion reaction requires 100
  Million degrees temperature which poses very
  difficult technical problems.
• A modern fusion reactor uses magnetic field lines
  to spool the charged particles of the plasma
  around in circles inside a dough-nut shaped
  reactor vessel.
• The next generation Tokamac reactor ITER is ready
  for construction and should reach ignition.

4
Cosmic Timeline for the Big Bang
deuterons
Quarks
proton, neutrons
He nuclei(? particles)
5
How are the light elements produced in stars

• Three minutes after the Big Bang the universe
  consisted of
• 75 Hydrogen,
• 25 4He
• less than 0.01 of D, 3He and 7Li.
• The sun began to burn the available H into
  additional 4He, as we learned and heated itself
  up.
• Once there was sufficient 4He available the
  reaction
• 4He 4He 4He ? 12 C 8 MeV
• became efficient. It heated the sun up still
  further

6
Energy from Fusion in the Sun
4 1H 2 e- ? 4He 2 n 6 ? 26.7 MeV energy
per reaction at 100 Million K temperature
7
From Helium to Carbon

• When the start has used up its hydrogen, the
  refraction stops and the star cools and
  contracts. If the star is heavy enough the
  contraction will produce enough heat near the
  core where the 4He has accumulated to start
  helium burning.
• Because of gravity the heavier elements always
  accumulate in the core of the star.
• The star now has 4 layers at the center
  accumulates the Carbon, surrounded by a He fusion
  layer, surrounded by a hydrogen fusion layer,
  surrounded by a dilute inert layer of hydrogen

8
The CNO Cycle

• Once sufficient 12C is available it uses H nuclei
  to produce all the nuclei up to 16O in a reaction
  cycle.
• When sufficient 16O is available and the star has
  heated up much more, the star breaks out of the
  CNO cycle by capture of a 4He or a proton. This
  forms all the nuclei up to 56Fe.
• In this process energy is produced to heat the
  star further because the binding energy/ nucleon
  is still increasing.
• Hans Bethe (Cornell) and Willy Fowler (Caltech)
  obtained Nobel Prizes for these discoveries

9
Relative Elemental Abundances of the Solar System
.At least 4 processes generate heavier elements.
10
Supernova explosion produces heavy elements

• When a star has burned all
• its light fuel, it cools and
• contracts under the gravitatio-
• nal pressure. It then explodes. During the
  explosion huge numbers
• of neutrons are produced and
• captured rapidly by the exis-
• ting elements (r-process).
• Beta decay changes neutrons into protons and
  fills in the elements
• The new elements are blasted into space and are
  collected by newly formed stars.
• Binary stars which are very hot can also produce
  the heavy elements.

11
Location of the r-process in the nuclear mass
table
Chart of the Nuclei
Z
The r-process works its way up the mass table on
the neutron-rich side. There are other processes
on the proton rich side
N
12

• Heavy elements are also created in a slow neutron
  capture process, called the s process.
• The site for this process is in specific stage of
  stellar evolution, known as the Asymptotic Giant
  Branch(AGB) phase.
• It occurs just before an old star expels its
  gaseous envelope into the surrounding
  interstellar space and sometime thereafter dies
  as a burnt-out, dim "white dwarf
• They often produce beautiful nebulae like the
  "Dumbbell Nebula".
• Our Sun will also end its active life this way,
  probably some 7 billion years from now.

13
Quarks and Gluons

• After WW-II increasingly powerful proton
  accelerators were able to produce many new
  elementary particles of increasingly heavier
  mass M
• M Energy of the collision/c2
• These were all strongly interacting but some had
  strange characteristics indicating new quantum,
  numbers.
• It became more and more apparent that this many
  particles could not be all fundamental and there
  had to be a deeper system explaining all of this.
• In the 1970s on purely theoretical grounds
  Murray Gell-Mann introduced a new class of
  sub-nucleon particles which he called quarks.

• The Alternating Gradient proton Synchrotron at
  Brookhaven revolutionized proton acceleration,
  reaching 25 GeV in 1962
• This accelerator could produce new particles with
  mass as high as 7 GeV

14
The production of new elementary particles

• If we bombard a target of hydrogen with an
  accelerated beam, of protons, a number of things
  can happen
• Elastic scattering
• A set of different, but known particles are
  produced
• A completely unknown
• particle is produced

• The following properties are known to be
  conserved
• Energy and momentum
• Electric charge
• Baryon Number ? number of heavy particles

Bubble chamber produces vivid pictures of the
reaction
15
Bubble chamber pictures
16
Energetics of elementary particle production.

• The kinetic energy of the beam and the reaction
  products and the energy contained in all the
  masses must be conserved, i.e. must add up left
  and right for a stationary target for the three
  reactions above
• By knowing the masses and Kinetic Energy of the
  beam and target and measuring the KE of all
  participants, I can determine the mass of the new
  particle x

17
Strange behavior of new particles

• http//hyperphysics.phy-astr.gsu.edu/hbase/particl
  es/Cronin.html
• In the 1940s new particles of mass 500 MeV
  were discovered. Later confirmed at Brookhaven
• They were first called V-particles, later called
  Kaons and other particles.
• They behaved strangely
• They decayed into strongly interacting particles,
  but with a very slow life time of 10-6 to 10-9 s.
  
• They seemed to be produced in pairs
• Gell-Mann concluded that a new quantum number,
  which he called Strangeness, must prohibit (slow
  down) the decay.

18
The Particle Zoo I

• Light particles (Leptons)

• http//hyperphysics.phy-astr.gsu.edu/hbase/particl
  es/Cronin.html

Species Symbol Mass
electrons e, e- 511 keV
muons µ, µ- 105.7 MeV
neutrinos 3 ?s Very small

• Medium heavy particles (Mesons). All have
• Integer spin 0,1
• Baryon number 0

Species Symbol Life time Strangeness Mass
Pions ?, ?-, ?0 2.6 x 10-8 s 8.3 x 10-17 s S 0 S 0 139.6 MeV 135 MeV
Kaons K, K- K0 1.2 x 10-8s 5 x 10-8 , 10-10 s S 1 S 1 493.7 MeV 497.7 MeV
Etas ? 2.6 keV S 0 548.8 MeV
19
The Particle Zoo II

• Heavy particles (Baryons) These particles all
  have
• Half integer spin ½ 3/2
• Baryon number B 1.

Species Symbol Life time Strangeness Mass
Nucleons p n0 gt1035 yrs 898 s S 0 S 0 938.3 MeV 939.6 MeV
Hypernuclei ?0 ? ?0 ?- 2.6 x 10-10 s 0.8 x 10-10 5.8 x 10-20 1.5 x 10-10 S - 1 S - 1 S - 1 S - 1 1116 MeV 1189 MeV 1192 MeV 1197 MeV
20
Gell-Mann and the Eight-fold Way

• In 1961 Gell-Mann and Neeman proposed a new
  clasification scheme to bring simplicity into
  this complex zoo.
• Some observations
• The Mesons and Barayions interact via the strong
  interaction Hadrons
• The mesons have between 1/3 to ½ the mass of the
  Baryons. They have interger spin (0 and 1)
• The Baryons are the ehaviest group, they have
  half-integer spin (1/2, 3/2)
• The mesons and the Baryons seem to be separate
  groups (B0 and B1)
• They all have normal units of positive and
  negative charges, or 0 charge.

• These and other systematic observations could be
  exxplainbed bya mathematical classification
  scheme based on the mathematical symmetry group
  SU(3). It introduced quarks as a mathematical
  concept.

21
Quarks as building blocks of Hadrons

• If Quarks are building blocks of mesons and
  Baryons must have the following properties
• They must have spin ½ the 2 quarks can make spin
  0 or 1, 3 quarks can make ½ and 3/2
• They must have charges that have 1/3 or 2/3 the
  normal charge of an electron!
• There must be at least 3 different types up,
  down, and strange
• We need quarks and antiquarks

B 1/3 S 0 Q 2/3
1/3 0 -1/3
1/3 -1 -1/3
B -1/3 S 0 Q -2/3
-1/3 0 1/3
-1/3 1 1/3
22
Simple Quark configurations of hadrons

• Proton uud Q 2/32/3-1/3 1 S 0
  B 1
• Neutron udd Q 2/3 -1/3 - 1/3 0 S 0
  B 1
• ?0 uds Q 2/3 - 1/3-1/3 0 S
  -1 B 1
• ? uus Q 2/32/3 -1/3 1
  S -1 B 1
• ?0 uds Q 2/3 -1/3 1/3
  0 S -1 B 1
• ?- dds Q -1/3-1/3-1/3
  -1 S -1 B 1
• ? udbar Q 2/3 1/3 1
  S0 B 0
• ?0 uubar ddbar
• ?- dubar
• K usbar Q 2/31/3 1
  S 1 B 0

Here is a problem
We neglected the fact that quarks with spin ½ are
subject to the Pauli Principle
23
The Omega Particle

• This quark model predicts that there should be
  one particle that has the simple configuration
  sss
• This particle has Strangeness S -3,
• Charge Q -1
• Baryon Number -1
• When this particle was found in one bubble
  chamber picture in 1964 it clinched the quark
  model.
• The reaction was complicated
• (S -1) (S 0) ? (S -3) (S1) (S1)
• The ? - and the rest then decayed into many
  secondary particles.

24
Feynman Diagrams

• http//www2.slac.stanford.edu/vvc/theory/feynman.h
  tml
• Richard P. Feyman invented a pictorial way to
  describe the time evolution of a reaction based
  on the exchange of force particles
• In thees diagrams time is moving forward from
  left to right.
• The processes here are scattering of electrons
  and positrons with emission of a photon

• Feynman was one
• of the most inventive
• physicists always
• ready for a joke
• The process below is the annihilation of a
  particle (e-) and its antiparticle (e) with
  emission of a photon. The time axis for an
  antiparticle runs backwards.

25
Deep inelastic scattering Whats inside a
nucleon?

• http//hyperphysics.phy-astr.gsu.edu/hbase/nuclear
  /scatele.html
• Deep inelastic scattering of energetic electrons
  is the equivalent experiment of Rutherford's
  ?-scattering.
• Energetic electrons interact with the charged
  particles (if any) inside the proton.
• The Stanford experiment found such particles in
  1967, which were called partons. Today we know
  that these are the quarks.
• They found more than the 3 expected partons in a
  proton because quark-antiquark pairs are
  constantly formed inside

quark
26
Can we see quarks? Jets!

• No free quark has ever been observed. It would
  have to have 1/3 or 2/3 charge
• But quarks and antiquarks can be seen as a shower
  of secondary particles, which are called jets.
  Ecah jet represent a quark.
• We show here a spectacular four-jet event from
  the CDF detector at Fermilab.

27
Schematic description of jet event
The jet production probability can measure the
strength of the strong force as a function of
energy
If more than 2 jets are observed they could come
from Gluons
28
Gluons

• Gluons are the exchange particles between quarks.
• They are neutral particles with spin 1
• They can be seen in 3-jet events, where a quark
  was struck by an electron, and then that quark
  knocked out a gluon.

29
The first events from the HERA facility at DESY
proving the existence of gluons inside a proton
30
The Charmed Quark

• In 1974 in a surprising result at BNL and at SLAC
  a fourth quark was found. It was named the
  Charmed Quark c
• It was much heavier and bound together with an
  chamed antiquark into a c-cbar state called J/?.
  (hidden charm)
• This discovery made quarks trukly credible.
  DSince then, two ehavier quarks have been found
  the b (bottom) quark and the heaviest, the t
  (top) quark.
• http//www.shef.ac.uk/physics/teaching/phy366/j-ps
  i_files/j-psi.pdf

Sam Ting
The J/? seen as a peak at 3.1 GeV with
high-energy electron beams ?
31
Order in the (Quark) Court!

• Today we know 3 families of quarks, and 3
  antiquark families.

Spin Charge First family Second family Third family
1/2 3/2 up (3 MeV) charm (1300 MeV) top (175,000 MeV)
1/2 -1/2 down (6 MeV) strange (100 MeV) bottom (4,300 MeV)
http//hyperphysics.phy-astr.gsu.edu/hbase/particl
es/quark.html
32
The dynamics of quarks

• In addition to their regular quantum numbers
  quarks must have other property that
  differentiates them from each other. This
  property is called Color. (See e.g. the proton
  uud
• There are 3 colors Red, Green and Blue (these
  are just stand-in names). Thus the proton looks
  like this uud or any other color combination)
• The colored Quarks interact with each other
  through the exchange of gluons. These gluons
  exchange color between the quarks (Color
  interaction).
• There are 9 color combinations but only 8 gluons.
  Their mass is exactly zero!

green- anti-green green- anti-red green- anti-blue
red- anti-red red- anti-blue red- anti-green
blue- anti-blue blue- anti-red blue- anti-green
33
Quark Confinement

• The color interaction between quarks binds the
  quarks such that no single quark can ever be
  free.
• This is different from two charged bodies bound
  by the Coulomb force, but similar to the binding
  of a magnetic north-pole and a south-pole
• Thus any quark that emerges forma proton will
  dress itself with other quarks or anti-quarks
  and emerge as a jet.
• The binding force between quarks relatively weak
  when they are close together but grows stronger
  as they are pulled apart.
• At close distances they can almost be treated as
  free Asymptotic freedom

34
Fifth Homework Set, due March 10, 2005

1. As a star burns its hydrogen and helium fuel and
   later carbon oxygen, magnesium etc, how are the
   ashes arranged inside the star?
2. How does a star produce the heavy elements past
   Fe? Describe environment and process.
3. The observed elementary particles can be grouped
   by their masses in 3 groups. What are the names
   of these groups and what are typical masses in
   each group?
4. Why are some particles called strange? Name one
   such strange particle.
5. Who invented quarks and where did the name come
   from?
6. How many quarks do we know today and what are
   their specific names?