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

Peter Paul 03/03/05 PHY313-CEI544 Spring-05 1

PHY313 - CEI544The Mystery of Matter

From Quarks to the CosmosSpring 2005

Peter PaulOffice Physics D-143

www.physics.sunysb.edu PHY313

mailto:[email protected]


Information about the Trip to BNL

• When and where: Thursday March 31, 2005 at 5:20 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 7:30 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 [email protected]. by this Friday night. You must bring along a valid picture ID. That’s all! The guard will go through the bus and check the picture ID’s.

• 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.



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.


Quarks

Cosmic Timeline for the Big BangCosmic Timeline for the Big Bang

proton, neutronsdeuterons

He nuclei( particles)


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 MeVbecame efficient. It heated the sun up still further


Energy from Fusion in the Sun

HeHH 312

HHHeHeHe 11433

eHHH 211 eHHH 211

ee ee

HeHH 312

4 1H + 2 e- 4He +2 n + 6 + 26.7 MeV energy per reaction at ~ 100 Million K temperature


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

CHeBe

BeHeHe1248

844 ;


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


Relative Elemental Abundances of the Solar System

.At least 4 processes generate heavier elements.

1.E-12

1.E-10

1.E-08

1.E-06

1.E-04

1.E-02

1.E+00

1.E+02

0 10 20 30 40 50 60 70 80 90 100

Z

% a

bund

ance


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 numbersof neutrons are produced andcaptured 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.

Neutron star

“normal”donor star

Accretion disk

Neutron star

“normal”donor star

Accretion disk


Chart of the Chart of the NucleiNuclei

N

Z

““Magic” proton Magic” proton numbersnumbers

2,8,20,28,50,822,8,20,28,50,82 N=Z

““Magic” Magic” neutron neutron numbersnumbers

...+126...+126

Location of the r-process in the nuclear mass table

The r-process works its way up the mass table on the neutron-rich side. There are other processes on the proton rich side


•Heavy elements are also created in a slow neutron capture Heavy elements are also created in a slow neutron capture process, called the “s” process.process, called the “s” process.

•The site for this process is in specific stage of stellar evolution, The site for this process is in specific stage of stellar evolution, known as the Asymptotic Giant Branch(AGB) phase. known as the Asymptotic Giant Branch(AGB) phase.

•It occurs just before an old star expels its gaseous envelope It occurs just before an old star expels its gaseous envelope into the surrounding interstellar space and sometime thereafter into the surrounding interstellar space and sometime thereafter dies as a burnt-out, dim "white dwarf“dies as a burnt-out, dim "white dwarf“

•They often produce beautiful nebulae like the They often produce beautiful nebulae like the "Dumbbell Nebula"..

•Our Sun will also end its active life this way, probably some 7 Our Sun will also end its active life this way, probably some 7 billion years from now.billion years from now.



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 1970’s 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


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:

1. Elastic scattering2. A set of different, but known

particles are produced3. A completely unknown

particle is produced

• The following properties are known to be conserved:

1. Energy and momentum2. Electric charge 3. Baryon Number number of “heavy

particles

xpppdpp

pppp

Bubble chamber produces vivid pictures of the reaction


Bubble chamber pictures


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

)()(2)(

)()(2)(

)()(22)(

222

222

22

pKExKEcmcMcMpKE

dKEKEcMcmcMpKE

pKEpKEcMcMpKE

xpp

dp

pP


“Strange” behavior of new particleshttp://hyperphysics.phy-astr.gsu.edu/hbase/particles/Cronin.html• In the 1940’s 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: 1. They decayed into strongly interacting

particles, but with a very slow life time of 10-6 to 10-9 s.

2. They seemed to be produced in pairs:

3. Gell-Mann concluded that a new quantum number, which he called Strangeness, must prohibit (slow down) the decay.

0Kp

particleneutralK 0

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/Cronin.html



The Particle Zoo I• Light particles (Leptons) http://hyperphysics.phy-astr.gsu.edu/hbase/par

ticles/Cronin.htmlSpecies Symbol Mass

electrons e+, e- 511 keV

muons μ+, μ- 105.7 MeV

neutrinos 3 ’s Very small

Species Symbol Life time Strangeness Mass

Pions +, -, 0

2.6 x 10-8 s8.3 x 10-17 s

S = 0 S = 0

139.6 MeV135 MeV

Kaons K+, K-

K0

1.2 x 10-8s5 x 10-8 , 10-10 s

S = ± 1S = ± 1

493.7 MeV 497.7 MeV

Etas 2.6 keV S = 0 548.8 MeV

Medium heavy particles (Mesons). All have…

• Integer spin: 0,1

• Baryon number =0




The Particle Zoo II

Species Symbol Life time Strangeness Mass

Nucleons p+

n0

>1035 yrs 898 s

S = 0 S = 0

938.3 MeV939.6 MeV

Hypernuclei 0

+

0

-

2.6 x 10-10 s0.8 x 10-10

5.8 x 10-20

1.5 x 10-10

S = - 1S = - 1S = - 1S = - 1

1116 MeV1189 MeV1192 MeV1197 MeV

Heavy particles (Baryons): These particles all have

•Half integer spin: ½; 3/2

•Baryon number B = ± 1.


Gell-Mann and the Eight-fold Way• In 1961 Gell-Mann and Ne‘eman

proposed a new clasification scheme to bring simplicity into this complex zoo.

• Some observations:1. The Mesons and Barayions interact via

the strong interaction: Hadrons2. The mesons have between 1/3 to ½ the

mass of the Baryons. They have interger spin (0 and 1)

3. The Baryons are the ehaviest group, they have half-integer spin (1/2, 3/2)

4. The mesons and the Baryons seem to be separate groups (B=0 and B=1)

5. 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.


Quarks as building blocks of Hadrons

• If Quarks are building blocks of mesons and Baryons must have the following properties

1. They must have spin ½: the 2 quarks can make spin 0 or 1, 3 quarks can make ½ and 3/2

2. They must have charges that have 1/3 or 2/3 the normal charge of an electron!

3. There must be at least 3 different types: “up”, “down”, and “strange”

4. We need quarks and “antiquarks”

dB = 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

u

u

s

d

s


Simple Quark configurations of hadrons

• Proton uud Q = 2/3+2/3-1/3 = +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 = 2/3+2/3 -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 S=0 B = 0 0 uubar + ddbar - dubar • K+ usbar Q = 2/3+1/3 = 1 S = +1 B = 0

Here is a problem

We neglected the fact that quarks with spin ½ are subject to the Pauli Principle


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) + (S=+1) + (S=+1)• The - and the rest then decayed into many

secondary particles.

0KKpK


Feynman Diagramshttp://www2.slac.stanford.edu/vvc/theory/feynman.html

• 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.

http://www2.slac.stanford.edu/vvc/theory/feynman.html




Deep inelastic scattering: What’s 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 quar

k

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/scatele.html

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/scatele.html


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.


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


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.


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


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-psi_files/j-psi.pdf

The J/ seen as a peak at 3.1 GeV with high-energy electron beams

Sam Ting




Order in the (Quark) Court!

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html

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)

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




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


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


Fifth Homework Set, due March 10, 20051. 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?

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

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