Gary D. WestfallParticles, Nuclei, and the Cosmos 1 Where Have Your Atoms Been? The Big Bang The...

1Gary D. Westfall Particles, Nuclei, and the Cosmos

•Where Have Your Atoms Been?• The Big Bang• The Creation of the Elements

Particles, Nuclei, and the Particles, Nuclei, and the CosmosCosmos

Gary D. WestfallMichigan State

University


History of the UniverseHistory of the Universe


Where Have Your Atoms Where Have Your Atoms Been?Been?

• The universe was created in the big bang 13 to 15 billion years ago

• The hydrogen in the water in your body was created then• More complex atoms had to be “cooked” inside stars• Several

generation of stars had to pass with the most massive stars exploding

• Interstellar gas was enriched with heavier elements

• Interstellar dust formed containing these elements


Nuclear Physics PrimerNuclear Physics Primer• Energies are measured in electron volts

• 1 eV is the energy acquired by a particle with charge 1 accelerated across a voltage of 1 volt• keV - 1000 eV• MeV - 1,000,000 eV, 1 million eV• GeV - 1,000,000,000 eV, 1 billion eV

• Using the famous Einstein relation E = mc2, masses are also measured in eV• Mass of an electron = 511 keV = 0.511 MeV• Mass of a proton = 939 MeV = 0.939 GeV

• A nucleon is a neutron or a proton


More Nuclear Physics More Nuclear Physics PrimerPrimer

• The binding energy of a nucleus is about 8 MeV/nucleon

• Beam energies are often given in GeV/nucleon• RHIC is one nucleus with 100 GeV/nucleon colliding

with another nucleus with 100 GeV/nucleon going the opposite direction

• The size of a nucleus is 1.2A1/3 fm where A is the mass number and a fm is 10-15 m

• Nuclei are much too small to be seen with visible light• A probe is necessary to study nuclei

• In our case, we will other other nuclei


Particle PrimerParticle Primer• There are six flavors of quarks

• Up, down, strange, charm, bottom, and top• You and I are made of up and down quarks

• The nucleons in our atoms each have three quarks (proton - up, up, down)

• Pions (+, -, 0) are composed of up and down quarks as quark/anti-quark pairs

• Kaons (K+, K-, various kinds of K0) have a strange quark

• Quarks interact by exchanging gluons• Nucleons are held together by gluons

• Free quarks have never been seen• Quarks have a distinctive non-integer charge that

would make them stand out from other charged particles

• 1/3,2/3,-1/3,-2/3


The Big BangThe Big Bang• The big bang theory states that the

universe began as a gigantic explosion

• This idea has entered popular culture


BigBang

Star Formation

Star

Supernova

Planetary Nebula M < 8 M

M > 8 M


Big Bang

Time Temperature

Size Composition

10-43 s 1032K Quarks, gluons, electrons, neutrinos

1ms 12 trillion K 1.4 light days Protons and neutrons

1s 10 billion K 4 ly Proton and neutron ratio fixed

100s – 5min 1-0.4 billion K

~55 ly Nuclei are formed

500000 yr 3000 K 1.5 million ly Atoms form, photons roam freely

νe +n→ p+e−

νe +p→ n+e+

⎧ ⎨ ⎪

⎩ ⎪

⎫ ⎬ ⎪

⎭ ⎪ n↔ p


History of the Idea of the Big History of the Idea of the Big BangBang

• Georges Lemaitre proposed a big bang-like theory in the early 1920s involving fission

• In the 1940s, George Gamov proposed the a big bang model incorporating fusion

• Since that time, many astronomers and physicists have added their work to what is now known as the standard model of the big bang

• Three main ideas underlie the big bang model• The universe cools as it expands• In very early times, the universe was mostly radiation• The hotter the universe, the more energetic photons

are available to make matter and anti-matter


The Evolution of the Early The Evolution of the Early UniverseUniverse

• With the three previous ideas in mind, we can trace the evolution of the universe back to when it was 0.01 s old and had a temperature of 100 billion K

• We can go back farther but not all the way to zero time• At 10-43 s most of our physical laws become

impractical

• At times before 0.01 s, the universe was filled with quarks and gluons• Recreate with RHIC Collisions

Collision of 2 Gold Nuclei at Collision of 2 Gold Nuclei at RHICRHIC

QuickTime™ and aSorenson Video decompressorare needed to see this picture.


Lattice QCD calculations predict the transition to occur at

Quark Gluon PlasmaQuark Gluon Plasma

3/5.1~

200150~

fmGeV

MeVT

c

c

ε

−

(F. Karsch, hep-lat/0106019)

Normal Nuclear Matter Quark Gluon Plasma


The “little bang”Stages of the collisionStages of the collision

• pre-equilibrium (deposition of initial energy)

• rapid (~1 fm/c) thermalization (?)

QGP formation (?)

hadronic rescattering

hadronization transition(poorly understood)

Chemical freeze-out: end of inelastic scatteringsKinetic freeze-out: end of elastic scatterings

tim

etem

perature

“end result” looks very similarwhether a QGP was formed or not!!!


The Relativistic Heavy Ion The Relativistic Heavy Ion ColliderCollider


Actual Measurement - STAR at Actual Measurement - STAR at RHICRHIC



Particle Identification in STARParticle Identification in STAR

e+

+

K+p d

Range-energy calculation


Particle ID Techniques - Particle ID Techniques - TopologyTopology

€

K s → π++π−

Λ → p+π−

Λ → p +π+

Ξ−→ Λ+π−

Ξ +→ Λ +π+

Ω → Λ+K−

€

Λ,Λ

€

Ξ,Ξ


Azimuthal DistributionsAzimuthal Distributions

pedestal and flow subtracted

Near-side: p+p, d+Au, Au+Au similarBack-to-back: Au+Au strongly suppressed relative to p+p and d+Au

Suppression of back-to-back correlation in Au+Au is final-state effect


After 0.01 sAfter 0.01 s• Our picture after 0.01 s is that

the universe was filled with radiation and with types of matter that exist today

• Protons and neutrons• Photons and neutrinos

• The temperature was no longer hot enough to create neutrons and protons in collisions of photons

• At about 3 minutes, nuclei begin to form

• 75% hydrogen, 25% helium, some lithium


Learning from Learning from DeuteriumDeuterium

• All the deuterium in the universe was formed in the first 3 minutes

• If the universe was very hot and dense when the deuterium formed, it would have been broken up

• If the universe expanded and then out thinned out rapidly, deuterium would survive

• The density extracted from the surviving deuterium is 5 x 10-31 g/cm3

• Suggests a low enough mass that the universe is open

• Dark matter may still play a role


The Universe Becomes The Universe Becomes TransparentTransparent

• For several hundred thousand years the universe resembled the interior of a star

• After that time, atoms began to form• The universe became transparent• Radiation and matter decoupled

• 1 billion years after the big bang, stars and galaxies began to form

• The radiation from the big bang faded but it left an indelible fingerprint, the cosmic background radiation (CBR)


Problems with the Big Bang Problems with the Big Bang ModelModel

• The standard big bang model explains many things but there are remaining issues

• It does not explain why there is more matter than antimatter in the universe

• It does not explain the observed uniformity of the universe• Parts of the universe could never have been in

contact yet they show the same background temperature

• It does not explain why the density of the universe is close to the critical density


Binding energy per nucleon of stable nuclei

4Helium

Iron and Nickel


Nuclei in the Universe

Hydrogen:

Mass number = 1

Helium:

Mass number = 4

91.0%

8.9%

By weight:

75% Hydrogen

25% Helium


Gold:

79 protons + 118 neutrons

Mass number = 197

Iron:

26 protons + 30 neutrons

Mass number = 56

Nuclei in the UniverseNuclei in the Universe


The Sun• Has been emitting 3.8 x 1026 W for about 4.5 billion years• Temperature at center: 15 Million K• Density at center: 150 g/cm3

Where does this energy come from ? Early ideas:• Fossil fuels: last ~1000 years• Meteorite impacts: would change earths period by 2s/year• Slow contraction: lasts 100 Million years

1920 Sir Arthur Eddington: nuclear energy (10 billion years)

“We do not argue with the critic who urges that the stars are not hot enough for this purpose. We tell him to go and find a hotter place”


The pp chain (the main path )



Stage Duration Product Name Product Z Product N

Hydrogen burning

7 Million yr Helium 2 2

Helium burning 700,000 yr Carbon,Oxygen 6,8 6,8

Carbon burning 400 yr Oxygen, Neon 8,10 8,10

Neon burning 1 yrOxygen, Magnesium, Silicon

8,12,14 8,12,14

Oxygen burning 8 month Silicon, Sulfur 14,16 14,16

Silicon burning 1 day ~Iron, Nickel ~24-28 ~24-28

Burning stages of a 25 solar mass star


Precollapse structure of massive star

Iron core collapses and triggers supernova explosion



Tarantula Nebula in LMC (constellation Dorado, southern hemisphere) size: ~2000ly (1ly ~ 6 trillion miles), disctance: ~180000 ly


Supernova 1987A by Hubble Space Telescope Jan 1997


Supernova 1987A seen by Chandra X-ray observatory, 2000

Shock wave hits inner ring of material and creates intense X-ray radiation


HST picture

Crab nebulaSN July 1054 ADDist: 6500 lyDiam: 10 ly, pic size: 3 lyExpansion: 3 mill. Mph (1700 km/s)Optical wavelengthsOrange: HRed : NPink : SGreen : O

Pulsar: 30 pulses/s


The r process “path”So

lar r-

abun

danc

es

Known massKnown half-lifer process waiting point (ETFSI-Q)

N=82

N=126


National Superconducting Cyclotron LaboratoryNational Superconducting Cyclotron Laboratory Coupled Cyclotron Facility Coupled Cyclotron Facility


Projectile Fragmentation RB Projectile Fragmentation RB ProductionProduction

FragmentSeparator

Fragments are madeat near beam velocity

Example: 11Be from 13C at 100 MeV/A (b=.42) would have a momentum FWHM of 5% and an angular cone of 6 degrees.


The Fragment Separator The Fragment Separator PrinciplePrinciple

H. Scheit


Rare Isotope Beam Rates with the Rare Isotope Beam Rates with the CCPCCP


Science with Radioactive Science with Radioactive BeamsBeams

• The origin of the elements – quantitative understanding of astrophysical processes: r-process nuclei, X-ray bursts, begin electron capture and neutrino interaction measurements with unstable beams• The limits of nuclear stability – What combinations of neutrons and protons are particle stable? We hope to map the neutron drip line up to Z=16.• Properties of nuclei with extreme neutron to proton ratios – An extreme challenge to many-body theory. Neutrons and protons at vastly different Fermi levels in the nucleus.• Properties of bulk neutron matter and the nature of neutron stars – Study of neutron star material and toward the neutron matter equation of state. Observables in heavy-ion reactions can potentially be related to the nuclear EOS.•Study at NSCL and the proposed Rare Ion Accelerator (RIA)


Facing the FutureFacing the Future• If the mass density of the universe is high

enough, the expansion of the universe will reverse and the universe will collapse• The Big Crunch

• If the mass density of the universe is low enough, the universe will expand forever and slowly die out

• At critical density, the universe can just barely expand forever• Flat universe• Zero curvature

“The Future’s So Bright I Gotta Wear Shades!”

-Timbuk 3

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Gary D. WestfallParticles, Nuclei, and the Cosmos 1 Where Have Your Atoms Been? The Big Bang The...

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