06-20,2005UH Teacher Workshop What’s New in Nu-clear Physics Ed V Hungerford University of Houston According to Pogo: “Nuclear Physics is not so new, and

06-20,200506-20,2005 UH Teacher WorkshopUH Teacher Workshop

What’s New in Nu-clear Physics

Ed V HungerfordUniversity of Houston

According to Pogo:

“Nuclear Physics is not

so new, and not so clear

either.”


The Answers to our questions are only as good as the questions

themselves

Why did the tree grow in the notch in the fence ?


75 years ago Nuclear Physics was New

•The neutron had just been discovered•The Proton and Neutron were considered elementary particles•The nuclear force was not understood•Nuclear models were primitive and based on classical liquids

Today Nuclear Physics in some sense is Mature

•Nucleons are not “elementary” but are composed of other particles called quarks•The nuclear force is understood as an exchange of field quanta called gluons•The nucleus is a VERY complicated interaction of many hadrons whose interaction is described by a theory called Quantum Chromodynamics

Nuclear P

hysics i

s the S

tudy o

f the e

ffects o

f

Many-body H

adronic

System

s inte

ract

ing

via Q

CD


The Particles and Symmetries of the Standard Model

3 Families


There are 4 known interactions in nature•One of the fundamental driving philosophies of physics is the assumption that these interactions can be “unified” •Two of these are manifestations of the same force (electroweak)•QCD is patterned after the electroweak interaction (gauge theory)•Gravity still lies outside a quantum theory•The new discovery of Dark Energy, if it is real, may imply a 5th force

FieldQCD


A Field Quanta

The interaction of B withA occurs through theabsorption of field quantaat B produced by A

Particle B

Particle A

The Interaction through Fields


QCD Features

• An interaction that becomes stronger the greater the distance and the lower the energy between interacting particles• A weak interaction at short distances and high energies • A permanently bound quarks and gluons• A self interaction between the field quanta (gluons)• A highly non-linear theory greatly complicating calculations and making intuitive predictions difficult• A symmetry of SU(3) expressed by 3 states of quarks and Gluons (color)


Gluon Field

The Quark and Gluon Constituents of the Baryon

Valence Quarks

Sea Quarks


Quantum ChromoDynamics (QCD) is the Theory of the Strong Interaction

(Nuclear Force)

Quarks and Gluons

Flux Tube Linear Potential vs distance


How do we probe a Nucleon or a NucleusTo determine its Quark Content ?

Incident Electron

Incident Hadron


Emission of a Quark Stretches the “interaction String”

When the string breaks, Quark-anti-quark pairs are produced

This is called Hadronization ofa Quark Jet

Quark Scattering

Long Range Nuclear forceCollapses to quark-antiquarkExchange (Yukawa Interaction)the “interaction String”


Chiral Symmetry, and Mass

Chiral symmetry is the fundamental symmetry of QCD

But the particle must not have mass

Right HandedVelocity

Left HandedVelocity


The QCD Condensate

Particles acquire mass through their interaction with the vacuum, i.e. the condensate of quarks and gluons in the vacuum

A nucleon in a simple visualization, is a bubble in the vacuum condensate

Interaction of these quarks with the condensate at the bubble surfacegives an “effective” mass to the system.

Chiral Symmetry is then said to be spontaneously broken


The Vacuum is NOT Empty

This Computer simulationshows the instantaneous gluon field that might be Present in a vacuum. Red Indicates bending(winding) in the field lines perhaps a precursor to quarkcondensates


We Live Here

Phase Diagram of Matter

Each of the 4 interactions is has its own impact on the existence of our Universe

The Strong (nuclear) force is responsible for the creation and stability nuclear matter


Studying the Vacuum and QCD

RelativisticCollidingNuclei

Quark Gluonplasma

Hadronization


Connecting the very large to the very small

One of the more recent advances in physics has been to connect microscopic theory to macroscopic(cosmology)

For example, stellar burning and supernovae produce the nuclei of which the Universe is composed

We can use this information to look back in time, as well as discussthe present features in ouruniverse


Mesons and baryons are composed of quarks

Flavor SU(3) SymmetryAllows Placement of lowest MesonsAnd Baryons in Symmetry Octets


The Nuclear Equation of State

Neutron Star

Nuclear Matter


A modern cut-away view of a Neutron Star


Measuring Matter Creation in the Galaxy


Proton number vs Neutron Number Stability


The Present Model of a Supernovae


Inside a SupernovaInside a Supernova

Dense core

100 km M.

3x107 km

3000 km

n*10 km M

.

>8 M evolves ~107 yrExtreme temp: photodissociates nuclei back to protons, neutrons and alphas.

Neutronisation: p+e- n+e

e++e- + ; + x + x (all flavours equally) ~ few x nuclear

Huge thermal emission of neutrinos ~5-10 seconds

Core bounces


Supernovae: Facts and FiguresSupernovae: Facts and Figures Energy release ~3x10Energy release ~3x104646 J (the J (the

gravitational binding energy of gravitational binding energy of the core), in about 10 secondsthe core), in about 10 seconds Equivalent to 1000 times the Equivalent to 1000 times the

energy emitted by the Sun in its energy emitted by the Sun in its entire lifetime.entire lifetime.

Energy density of the core is Energy density of the core is equivalent to 1MT TNT per cubic equivalent to 1MT TNT per cubic micron.micron.

99% of energy released is in the 99% of energy released is in the form of neutrinosform of neutrinos

~1% is in the KE of the exploding ~1% is in the KE of the exploding mattermatter

~0.01% is in light – and that’s ~0.01% is in light – and that’s enough to make it as bright as enough to make it as bright as an entire galaxy. an entire galaxy.

Probably site of the r-processProbably site of the r-process..

¼ MT test (Dominic Truckee, 1962)


A Computer model of a Supernovae


A Brief SummaryNuclear Science has tremendous breadth and complexity

After 75 years we have found some to the “right” questions to ask but others remain

I have purposely avoided discussion of the more traditional nuclear studies There are impressive new results and insights into nuclear matter. But these require detailed exposition and are difficult to develop to grasp without some prior knowledge.

As a mature, advanced science, there are significant applications in Including the fields of Medicine, Computing, Industrial Products, Energy, Finance, etc.

More than 50% of the Phd graduates in Nuclear Physics are employed in industry, medicine, and national defense.

Nuc

lear

Phy

sics

is a

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rant

, exc

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Documents

06-20,2005UH Teacher Workshop What’s New in Nu-clear Physics Ed V Hungerford University of Houston According to Pogo: “Nuclear Physics is not so new, and