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SON
structure of nature march
74
Science
Undergraduate 2
05/18/2009

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Cards

Term
QM + Special relativity =?
who's theory?
what is needed to make theory work?
Definition
Relativistic QM
Paul Dirac
Need add. particle for every currently observed particle
Term
Matter and Anti Matter of basic particles
Definition

Matter                                Antimatter

p+                                     ¯p- (anti-proton)

e-                                      e+ (positron)

n                                       ¯n (anti-neutron)

 

 

Term
Positron e+ and electron e- tracks
Definition
[image]
Term
How did carl anderson discover the positron
Definition

Placed metal bar in center of detection field.

Loses energy when hits bar, can see from where it came

Because the direction of the tracks..

must be positively charged= e+

Term
Where do e+ particles come from?
Definition

From cosmic rays= emit high energy sttuff

Nature's accelerator

Term

A theory by Pukawa predicted that what mediated strong interaction

mass?

Definition

particles called pions

approx. mass of electron

Term

How was the muon discovered

What is it?

Definition

discovered in photographic emulsion that was exposed to cosmic rays.Did not interact with protons

The muon= secong gen particle that looked like a heavier electron

Term
Why do the most interesting cosmic ray events occur at high alts?
Definition
Have better chance of seeing unstable aprticles at higher alts
Term

Strange particles

How were they identified?

mass?

Definition

make "v" like tracks

produced by a new particle= k particles

mass=1/2 of proton

Term

Pauli invented what particle?

Why?

Problem with neutrino

Definition

Neutrino

to help with the problem of conserving E and P

Can't interact with EM, need new force

Term
Klein proposed what to mediate force in weak force interactions
Definition

W particle

like pions and strong force

Term
How was the neutrino discovered?
Definition
[image]
Term

What is a baryon?

what are not?

Definition

Something that consists of 3 quarks

pi, muon, electron and k particles

Term
What is strangeness?
Definition

the # of strange quarks

get more strangeness the more mass you have

Term
strange quarks are what
Definition
unstable, 2 gen quark
Term

Particle accelerators were invented to do what?

unit?

Definition

to control production of large #s of particles

to produce high-energy beams

Use E and B field combos to ramp up energy of particles.

Unit= elecron volt

Term
Name 3 accelerators
Definition

Cyclotron

Cosmotron

LHC

Term

in the 50's how did particles show up as in scatering data?

Why couldn't they see them?

Definition

Resonances (series of particles)

Particles decayed too fast~10-23 sec

Term

all types of quarks

charge and strangeness

Definition

                          q                      s

u=up               +2/3                   0

d=down           -1/3                    0

c-charm             +2/3                 

s=strange          -1/3                  -1

t-top                  +2/3

b-bottom             -1/3

Term

How was the quark model proved

what did they find

Definition

used a linear accelerator

shot electron beam at liquid hydrogen

if proton was ball of energy-expect beam to go right through=not observed

OBSERVED= back scattering-happens if had quarks

constituents.

found: 3 quark constituents

proton=uud

 

Term
Quark model (baryons and mesons)
Definition

All observable particles are either

baryons= 3 quark combo=q1 q2 q3

eg. (p,n, sigma+)

or Mesons= quark–antiquark pairs1 ¯q2

eg. (k+, pi+)

 

Term
What is confinement?
Definition
strong force is so strong that particle–antiparticle pairs are produced before quark can seperate
Term

November revolution. e- and e+ collider and SPEAR and exp. at AGS observed what?

What did this lead to?

Definition

new fairly stable particle

name= J/4

new meson w/charm quark

 

Term
3rd gen lepton
Definition

tau

leptons:         Q

tau neutrino= 0

tau          =   -1

 

Term
3rd gen quark
Definition

bottom quark

Quark         Q

T-top        = +2/3

b-bottom  = -1/3

Term
Why did it take so long to discover the top-quark
Definition

very large mtop=170 GEV

mbottom =4.7 GEV

Term
Forces (2)
Definition

electromagnetic — photons

weak — w-,w+, z0

Term
Quantum Chromodynaimcs was theorized for what
Definition

for strong interactions between quarks

used generalized photons (gluons)

Term
GCD theory needed what?
Definition

3 types of elec charge for quarks

COLORS! red, gree, blue

8-diff colored gluons in this theory

Term

rule regarding colors

 

Definition

all observable paarticles must be color neutral or white

white= 3 quarks or particle-anti particle combo

Term

problem with color theory

what was invented to fix this

Definition

theory requires all matter problems to be massless (weak interaction theory)

Invented Higgs particle to fix this and generate mass.

Term
How does the Higgs particle work/fix prob
Definition

At very high temps=higgs behaves as force mediator

at low energies, Higgs field freezes out=generates mass.

Term
Force carrier particles (4)
Definition

QED=electromagnetic — photons

?=Weak Force — w+,w-, z0

QCD=Strong force — gluons

Higgs — H

Term
Neutrino physics: solar neutrino problem encountered
Definition

discrepancy btwn solar Ve production and the # of neutrinos observed from sun.

saw only 1/2 of predicted particles

reason: Neutrinos can cause oscillations=mass

Term
Edwin Hubble: discovery
Definition
certain cloud like gases=galaxies
Term
luminosity
Definition
intrinsic brightness or power of star to emit light
Term
Cepheid variable stars
Definition

a particular type of star that varied in brightness over time.

Period of oscillation realted to luminosity-standard candle

 

Term
Steller Parallox
Definition

measure distance that the stat moves during the year

Variable star brightness: the shorter the period, the dimmer the star

the longer the period, the brighter the star.

Term

How to measure distance to star

what did hubble realize

Definition

use star luminosity which is gained from stellar parallox

this allowed hubble to see that the cloud of gas he saw was 100 x further away than any star in our galaxy=universe is huge

Term

To test motion of a star:

what did this show

Definition

Doppler effect, a star in motion and its light wavelength shift corresponds to color shift.

For star moving away, spectrum is red-shifted.

showed that galaxies are moving away from us

Term
Einstein's biggest blunder
Definition

was developing general relativity, found equation had no time independent solutions. Always found either contration or expansion of space. Decided to include an extra term to get rid static solution.

w/out the constant he had redicted the expanding universe

Term
hubble constant:
Definition

71(km/s)/ mpc

mega=3 million light years

1 par sec=3.26 light years

Term
what happened about 8 bil. yrs ago
Definition

sun and planets begin to form

when stars collapse, they create all the elements and as it explodes, elements shoot off and end in gases where gravity pulls dense objects togther

Term

Timeline of early galaxy

8 bil

6 bil

1 bil

300,00

3 mins

10-6sec

10-12sec

Definition

8 bil yrs old=sun and planets begin to form

6 bil yrs old=milky way galaxy is in forming

1 bil yrs old = first stars are forming structure formation

300,000 yrs old= entire univ=one big molecule

-light did not propogate -as sson as light was emitted it was absorbed by another atom

at 3 mins old=entire univ was one giant nucleus

at 10-6 sec= univ=one gigantic nucleon (quarks and gluons)

at 10-12sec= Higgs particle melts-all particles are massless prior to 10-12 sec.

get restoration of symmetry btwn EM and weak force

 

 

Term
What happened at 0 sec
Definition

No idea-purely theoretical

possibly grand unification-symmetry would include strong force

need to include gravity in quantum way

Term
In big bang theory what changed after 300,000 yrs
Definition

light was able to freely travel through univ for 1st time

prior to 300,000=univ=one big molecule (plasma)

after=atoms form, more space, univ transperant to light

 

Term

How was cosmic microwave background radiation discovered?

what is it?

Definition

used a radio antenna to look at sources in our galaxy

instrument was sensitive to low intensity radio and microwaves

heard random noise in the signal

thought it was pigions..but signal was still there

realized it was a real physical signal the CMBR

When an object radiates energy it does so across a variety of wavelengths

Term
How do we know the earth is not at rest
Definition
if it was you would see equal light in all directions-which we don't
Term
what happened 3 mins into the big bang
Definition

Nucleosynthesis- creation of new atomic particles from nucleoons (quarks and gluons)

which can be ued to measure the density of matter

Term
where do heavier elements come from
Definition
collapsing stars= when large stars collapse=supernova, heavier elements are created
Term
the collapse process of stars
Definition

at some point, a few billion yrs after star is formed, it burns up all the H fuel

gravity then takes over and it collapses the star material

then gets hotter and fusion begins again making heavier elements

then=BIG EXPLOSION-elements shoot off, emit light that can emit light brighter than the galaxy it is in.

Term
Dark Matter problem
Definition

- speeds of stars don't agree with calculations

pos. solutions.=

A.modify newtonian gravity-hard to do in a way that works with gen. relativity

B. Dark Matter-much more mass than is seen

-must not interact with photons or EM force

-neutrinos could work but are much too light

-motions of galaxies appear to be missing mass

Gravitational lensing=how mass cluster bend lights and affectd how we see stars-calculated mass is much larger than observed mass

 

 

Term

Problems w/ Gravitational Lensing

indicates what?

Definition

frequently indentifies dark matter

more matter needed to bend the light to agree with calcs-90% is missing

Term
What is dark matter?
Definition

don't know

but...doesn't interact with photon, if it did you would see it

3 catagories

1) Hot dark matter-ultra-relativistic speeds,close to c

2) warm darm matter: slower than hot but still relativistic

3) cold dark matter:slowly moving =, non-relativistic speeds.

Term
Some dark mater candidates
Definition

1) MACHOS-Massive compact hale objects

-small invisible objects made of ordinary matter

2) WIMPS- weakly interacting massive particles

-postulate particles that interact only via weak interactions

idea: early univ-electrons and positrons and high energy collide to produce WIMPS

 

 

Term
Gravitational lensing
Definition
when directly in front of star --get brief brightening of star when MACHO passes in front
Term
Problem with the explanation of MACHOS as dark matter
Definition

a. These events are very rare, 90% of matter should be happening more frequently

b. Nucleosynthesis-4% baryons

if this was right nucleosynthesis would be wrong (closer to one)

Term
Problem with WIMP theory
Definition
no wimps have ever been in an experiment
Term

Bar vogenesis Theories

tries to explain what?

Definition

Process that violates Baryon # conservation, these occur in grand unified theories (GUTs)

why there is anti-matter and matter in the univ.

 

Term
Naturalness problems (3)
Definition

a. Age problem or flatness prob.

-ballance btwn matter and initial kenetic energy to get univ to live longer than 14 billion yrs

b. Smoothness prob.- CMBR is uniform across sky~same temp in regions that have never been thermal contact

c. Lumpiness prob. -universe is not a symmetrical ball of gas

Term
Inflation theory
Definition

Our universe is expanding at an exponential rate

fixes prob of flatness problem=curvature naturally flattens out-universe large automatically due to inflation

fixes prob of smoothness-small bit @same temp initially

fixes prob of lumpiness-might have small quantum fluctuations of "small bit"-tiny QF's can expand to structure of univ.

Term
alt. theories to inflation
Definition

1)cyclic models for univ.-repeated expansion and contraction in cycle- univ. oscillates

-string theory

2) Cosmic strings-field at GUT scale can wrap up into sring like structures that extend across large portions of univ.-studies of CMBR don't match model

Term

Supernovae-prob with hubble law

explanations?

Definition

supernovae too dim

1)dust--bt only happens at great distances

2) universe is accelerating expansion

-dark matter may be why gravity is isn't causing deceleration as it should

 

Term
Define parameter "omega"
Definition

omega>1=energy density is large enough for recollapse

omega<1=not enough energy density for re collapse

omega=1=flat

Term
contributions to "omega"
Definition

1) luminous matter (baryons)

2) Dark matter?

3) Dark energy

Term
Scientific Method
Definition

1. initial guess-based on observations

2. compute consequences of guess

compare calculated consequences w/expts

4. if expts disagree with consequences, then theory is wrong

Term
Fullman and Zweig developed what?
Definition

Quark model-

developed substructure of all mesons and baryons

Term
Electroweak unification
Definition

generalized electromagnetic force-photon to incorporate weak force- z,w,w,gamma

needed to break smmetry using higgs to get theory to work.

Term
Strong force and Quark color
Definition

a further generalization of symmetry used in electroweak (w/out the breaking higgs)

QCD-

1 photon—8 gluons

Term
Problem with qravity and QM theory
Definition

THere are no quantum versions of theory

and cannot test...

Term

Kaluza-Klein theory

prob:

Definition

wrote down theory of gravity in 4 space dimensions in one time

not visually defined, but mathwise works fine

curled up extra demension into tiny circle that you cant see

prob:makes prediction that EM force is equal to the strength of gravity.

Term
String theory
Definition

an attempt to undrstand meson dynamics

didn't work

came back as fndamental theory of nature

quarks, leptons, photons etc=variety of string occilations

included closed string--behaves like gravity-graviton

 

Term
prob with string theory
Definition

lowest string mode for closed string was tachyon (not graviton)

tachyon= particle that always is faster than c

but don't really exist

===UNSTABLE

prob 2: need to curl up extra demensions to get theory to work in 4d

 

Term

String theory:

using supersymmetry

Definition

each observed particle must have a superpartner

photon — photino

electron — selectron

 

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