PHY313 - CEI544 - Stony Brook Universityinsti.physics.sunysb.edu/itp/lectures/05-Spring/PHY313/MOM-6.pdf · steam that drives a turbine. ... field lines to spool the charged particles

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


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 (20miles). We will visit The Relativistic Heavy Ion Collider (RHIC) and its twolarge experiments, Phenix and Star. Experts will be on hand to explainresearch and equipment. We will return by about 7:30 pm to arrive back atStony 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 avalid picture ID. That’s all! The guard will go through the bus and check thepicture ID’s.

• What about private cars: You will still have to sign up and must bring apicture ID (your drivers license) to the event. You will park your car at thelab 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 signup 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 wasused.

• These neutrons need to be moderated tolow energies to be captured efficiently.

• If enough and sufficiently densenuclear fuel and enough low-energyneutrons are available the reaction canbe hypercritical and take off.

• The chain reaction can be contained oreven stopped by inserting nuclei intothe fuel that have a large capability ofabsorbing neutrons. Boron andCadmium are such nuclei.

• Fission reactors use mostly235Uranium and 239Plutonium as fuel.After a while the fission products fromthe chain reaction poison the fuel.

• Commercial nuclear reactor use light ofheavy water to moderate the neutrons,cool the fuel rods, and produce thesteam that drives a turbine.

• The fusion of deuterium and tritiumdelivers huge amounts of energy/ kg offuel, has an infinite supply of fuel, andproduces no long-lived radioactivewaste.

• However, the fusion reaction requires~100 Million degrees temperature whichposes very difficult technical problems.

• A modern fusion reactor uses magneticfield lines to spool the charged particlesof the plasma around in circles inside adough-nut shaped reactor vessel.

• The next generation Tokamac reactorITER is ready for construction andshould reach ignition.


Quarks

Cosmic Timeline for the Big BangCosmic Timeline for the Big Bang

proton, neutronsdeuterons

He nuclei(α particles)


How are the light elements produced in stars• Three minutes after the Big Bang the

universe consisted of75% Hydrogen,25% 4Heless than 0.01% of D, 3He and 7Li.

• The sun began to burn the available Hinto additional 4He, as we learned andheated itself up.

• Once there was sufficient 4He availablethe reaction4He + 4He+ 4He → 12 C + 8 MeVbecame efficient. It heated the sun upstill further


Energy from Fusion in the Sun

!+"+ HeHH312

HHHeHeHe11433++!+

!++"++eHHH

211

!++"++eHHH

211

!! +"+#+ee !! +"+

#+ee

!+"+ HeHH312

4 1H + 2 e- → 4He +2 n + 6 γ + 26.7MeV energy per reaction at ~ 100 MillionK temperature


From Helium to Carbon

• When the start has used up its hydrogen, therefraction stops and the star cools andcontracts. If the star is heavy enough thecontraction will produce enough heat near thecore where the 4He has accumulated to starthelium burning.

• Because of gravity the heavier elements alwaysaccumulate in the core of the star.

• The star now has 4 layers: at the centeraccumulates the Carbon, surrounded by a Hefusion layer, surrounded by a hydrogen fusionlayer, surrounded by a dilute inert layer ofhydrogen

CHeBe

BeHeHe

1248

844;

!+

!+


The CNO Cycle

• Once sufficient 12C is available it usesH nuclei to produce all the nuclei up to16O in a reaction cycle.

• When sufficient 16O is available and thestar has heated up much more, the starbreaks out of the CNO cycle by captureof a 4He or a proton. This forms all thenuclei up to 56Fe.

• In this process energy is produced toheat the star further because the bindingenergy/ nucleon is still increasing.

• Hans Bethe (Cornell) and Willy Fowler(Caltech) obtained Nobel Prizes forthese 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

bu

nd

an

ce


Supernova explosion produces heavy elements

• When a star has burned allits light fuel, it cools andcontracts under the gravitatio-nal pressure. It then explodes. Duringthe explosion huge numbersof neutrons are produced andcaptured rapidly by the exis-ting elements (r-process).

• Beta decay changes neutrons intoprotons and fills in the elements

• The new elements are blasted into spaceand are collected by newly formed stars.

• Binary stars which are very hot can alsoproduce the heavy elements.


Chart of theChart of theNucleiNuclei

N

Z

““MagicMagic””proton numbersproton numbers

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

““MagicMagic””neutronneutronnumbersnumbers

...+126...+126

Location of the r-process in the nuclear mass table

The r-process works its way upthe mass table on the neutron-rich side. There are otherprocesses on the proton richside


••Heavy elements are also created in a slow neutron captureHeavy elements are also created in a slow neutron captureprocess, called the process, called the ““ss”” process. process.

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

••It occurs just before an old star expels its gaseous envelopeIt occurs just before an old star expels its gaseous envelopeinto the surrounding interstellar space and sometime thereafterinto the surrounding interstellar space and sometime thereafterdies as a burnt-out, dim "white dwarfdies as a burnt-out, dim "white dwarf““

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

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


Quarks and Gluons

• After WW-II increasingly powerfulproton accelerators were able toproduce many new “elementaryparticles” of increasingly heavier massM

M = Energy of the collision/c2

• These were all strongly interacting butsome had “strange” characteristicsindicating new quantum, numbers.

• It became more and more apparent thatthis many particles could not be allfundamental and there had to be adeeper system explaining all of this.

• In the 1970’s on purely theoreticalgrounds Murray Gell-Mann introduceda new class of sub-nucleon particleswhich he called quarks.

• The Alternating Gradient protonSynchrotron at Brookhavenrevolutionized proton acceleration,reaching 25 GeV in 1962

• This accelerator could produce newparticles with mass as high as 7 GeV


The production of new elementary particles

• If we bombard a target of hydrogenwith an accelerated beam, ofprotons, a number of things canhappen:

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

particles are produced3. A completely unknown

particle is produced

• The following properties are known tobe conserved:

1. Energy and momentum2. Electric charge3. Baryon Number → number of “heavy

particles

xppp

dpp

pppp

+!+

+!+

+!+

+"

Bubblechamberproduces vividpictures of thereaction


Bubble chamber pictures


Energetics of elementary particle production.

• The kinetic energy of the beam and the reaction products and the energycontained 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 andmeasuring the KE of all participants, I can determine the mass of the newparticle 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 atBrookhaven

• They were first called V-particles, latercalled Kaons and other particles.

• They behaved strangely:1. They decayed into strongly interacting

particles, but with a very slow life time of10-6 to 10-9 s.

2. They seemed to be produced in pairs:

3. Gell-Mann concluded that a new quantumnumber, which he called Strangeness, mustprohibit (slow down) the decay.

0Kp +!"+

#$

particleneutralK !++"!+ ##0


The Particle Zoo I• Light particles (Leptons) http://hyperphysics.phy-

astr.gsu.edu/hbase/particles/Cronin.html

Very small3 ν’sneutrinos

105.7 MeVµ+, µ-muons

511 keVe+, e-electrons

MassSymbolSpecies

S = 0

S = ± 1S = ± 1

S = 0 S = 0

Strangeness

2.6 keV

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

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

Life time

548.8 MeVηEtas

493.7 MeV497.7 MeV

K+, K-

K0

Kaons

139.6 MeV135 MeV

π+, π-,π0

Pions

MassSymbolSpecies

Medium heavy particles(Mesons). All have…

• Integer spin: 0,1

• Baryon number =0


The Particle Zoo II

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

S = 0 S = 0

Strangeness

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

5.8 x 10-20

1.5 x 10-10

>1035 yrs898 s

Life time

1116 MeV1189 MeV1192 MeV1197 MeV

Λ0

Σ+

Σ0

Σ-

Hypernuclei

938.3 MeV939.6 MeV

p+

n0

Nucleons

MassSymbolSpecies

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 tobring 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 haveinterger 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 tobe separate groups (B=0 and B=1)

5. They all have normal units of positiveand negative charges, or 0 charge.

• These and other systematicobservations could be exxplainbedbya mathematical classificationscheme based on the mathematicalsymmetry group SU(3). It introduced„quarks“ as a mathematical concept.


Quarks as building blocks of Hadrons

• If Quarks are building blocks ofmesons and Baryons must have thefollowing properties

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

2. They must have charges that have1/3 or 2/3 the normal charge of anelectron!

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

4. We need quarks and “antiquarks”

d

-1 0S = 0

-1/3 1/3 -1/3 1/3Q = 2/3B = 1/3

+1 0S = 0

+1/3 -1/3 +1/3 -1/3Q = -2/3B = -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• Λ0 uds Q = 2/3 - 1/3-1/3 = 0 S = -1 B = 1• Σ+ uus Q = 2/3+2/3 -1/3 = +1 S = -1 B = 1• Σ0 uds Q = 2/3 -1/3 – 1/3 = 0 S = -1 B = 1• Σ- dds Q = -1/3-1/3-1/3 = -1 S = -1 B = 1

• π+ udbar Q = =2/3 + 1/3 = 1 S=0 B = 0• π0 uubar + ddbar• π- dubar• K+ usbar Q = 2/3+1/3 = 1 S = +1 B = 0

Here is aproblem

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 oneparticle 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 Ω - and the rest then decayed into many

secondary particles.

0KKpK ++!"+

+##


Feynman Diagramshttp://www2.slac.stanford.edu/vvc/theory/feyn

man.html• Richard P. Feyman invented a pictorial

way to describe the time evolution of areaction based on the exchange offorce particles

• In thees diagrams time is movingforward from left to right.

• The processes here are scattering ofelectrons and positrons with emissionof a photon

Feynman was oneof the most inventivephysicists alwaysready for a joke

• The process below is the annihilationof a particle (e-) and its antiparticle(e+) with emission of a photon. Thetime axis for an antiparticle runsbackwards.


Deep inelastic scattering: What’s inside a nucleon?

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

• Deep inelastic scattering of energeticelectrons is the equivalent experimentof Rutherford's α-scattering.

• Energetic electrons interact with thecharged particles (if any) inside theproton.

• The Stanford experiment found suchparticles in 1967, which were calledpartons. Today we know that these arethe quarks.

• They found more than the 3 expectedpartons in a proton because quark-antiquark pairs are constantly formedinside quar

k


Can we see quarks? Jets!• No free quark has ever been

observed. It would have tohave 1/3 or 2/3 charge

• But quarks and antiquarks canbe seen as a shower ofsecondary particles, which arecalled jets. Ecah jet representa quark.

• We show here a spectacularfour-jet event from the CDFdetector at Fermilab.


Schematic description of jet event

The jet production probability can measurethe strength of the strong force as a functionof energy

If more than 2 jets are observedthey could come from Gluons


Gluons

• Gluons are the exchange particlesbetween quarks.

• They are neutral particles with spin 1• They can be seen in 3-jet events,

where a quark was struck by anelectron, and then that quarkknocked out a gluon.


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


The Charmed Quark

• In 1974 in a surprising result at BNLand at SLAC a fourth quark was found.It was named the Charmed Quark c

• It was much heavier and boundtogether with an chamed antiquark intoa c-cbar state called J/Ψ. (hidden charm)

• This discovery made quarks truklycredible. DSince then, two ehavierquarks 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/Ψ seen as a peak at 3.1 GeVwith high-energy electron beams →

Sam Ting


Order in the (Quark) Court!

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

1/2

1/2

Spin

strange(100 MeV)

charm(1300 MeV)

Second family

-1/2

+3/2

Charge Third familyFirst family

bottom(4,300 MeV)

down(6 MeV)

top(175,000 MeV)

up(3 MeV)

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


The dynamics of quarks

• In addition to their regular quantumnumbers quarks must have otherproperty that differentiates them fromeach other. This property is calledColor. (See e.g. the proton = uud

• There are 3 colors : Red, Green andBlue (these are just stand-in names).Thus the proton looks like this = uud orany other color combination)

• The colored Quarks interact with eachother through the exchange of gluons.These gluons exchange color betweenthe quarks (Color interaction).

• There are 9 color combinations butonly 8 gluons. Their mass is exactlyzero!

blue-anti-green

blue-anti-red

blue-anti-blue

red-anti-green

red-anti-blue

red-anti-red

green-anti-blue

green-anti-red

green-anti-green


Quark Confinement

• The color interaction between quarksbinds the quarks such that no singlequark can ever be free.

• This is different from two chargedbodies bound by the Coulomb force,but similar to the binding of amagnetic north-pole and a south-pole

• Thus any quark that emerges formaproton will “dress itself with otherquarks or anti-quarks and emerge as ajet.

• The binding force between quarksrelatively weak when they are closetogether but grows stronger as theyare pulled apart.

• At close distances they can almost betreated 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 typicalmasses 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?

Documents

PHY313 - CEI544 - Stony Brook Universityinsti.physics.sunysb.edu/itp/lectures/05-Spring/PHY313/MOM-6.pdf · steam that drives a turbine. ... field lines to spool the charged particles