J. Goodman – May 2003
Ghosts in the Universe
Jordan A. Goodman
University of Maryland
Fall 2003
Jordan A. Goodman
University of Maryland
Fall 2003
The world we don’t see around us
The world we don’t see around us
J. Goodman – May 2003
Outline
• How we see particles• How we know about things we can’t see (like
neutrinos)• What is the structure of matter• What makes up most of the Universe• Neutrino mass• “” and the Dark side of the force
J. Goodman – May 2003
The early periodic table
J. Goodman – May 2003
The structure of matter
1869 - Mendeleyev – grouped elements by atomic weights1869 - Mendeleyev – grouped elements by atomic weights
J. Goodman – May 2003
How do we know about Atoms
• Brownian Motion - Einstein
J. Goodman – May 2003
Seeing Atoms
J. Goodman – May 2003
Seeing Atoms
J. Goodman – May 2003
How do we see into atoms
• Atomic Spectra– We see spectral lines– The colors and the spacing of these lines tell us about
the structure of the atoms
EE
J. Goodman – May 2003
Hydrogen Spectra
J. Goodman – May 2003
What are fundamental particles?
• We keep finding smaller and smaller things
J. Goodman – May 2003
How do we see particles?
• Most particles have electric charge– Charged particles knock electrons out of atoms– As other electrons fall in the
atoms emit light
The light from your TV is The light from your TV is from electrons hitting the from electrons hitting the screenscreen
In a sense we are In a sense we are “seeing” electrons“seeing” electrons
The light from your TV is The light from your TV is from electrons hitting the from electrons hitting the screenscreen
In a sense we are In a sense we are “seeing” electrons“seeing” electrons
J. Goodman – May 2003
The search for fundamental particles
• Proton and electron– These were known to make up the atom
• The neutron was discovered• Free neutrons were found to decay
– They decayed into protons and electrons– But it looked like something was missing
• In 1930 Pauli postulated a unseen neutral particle
• In 1933 Fermi named it the “neutrino” (little neutron)
J. Goodman – May 2003
Why do we care about neutrinos?
• Neutrinos – They only interact
weakly– If they have mass at all
– it is very small • They may be small, but there sure are a
lot of them!– 300 million per cubic meter left over from the
Big Bang– with even a small mass they could be most
of the mass in the Universe!
J. Goodman – May 2003
Facts about Neutrinos
• Neutrinos are only weakly interacting
• 40 billion neutrinos continuously hit every cm2 on earth from the Sun (24hrs/day)
• Interaction length is ~1 light-year of steel
• 1 out of 100 billion interact going through the Earth
J. Goodman – May 2003
Seeing Big Picture
J. Goodman – May 2003
Why do we think there is dark matter?
• Isn’t obvious that most of the matter in the Universe is in Stars?
Spiral GalaxySpiral Galaxy
J. Goodman – May 2003
Why do we think there is dark matter?
• In a gravitationally bound system out past most of the mass V ~ 1/r1/2
• We can look at the rotation curves of other galaxies– They should drop off
But they don’t!
J. Goodman – May 2003
Why do we think there is dark matter?
• There must be a large amount of unseen matter in the halo of galaxies– Maybe 20 times more than in the stars!– Our galaxy looks 30 kpc across but recent data
shows that it looks like it’s 200 kpc across
J. Goodman – May 2003
Measuring the energy in the Universe
• We can measure the mass of clusters of galaxies with gravitational lensing
• These measurements give mass ~0.3
• We also know (from the primordial deuterium abundance) that only a small fraction is nucleons
nucleons < ~0.04 Gravitational
lensingGravitational
lensing
J. Goodman – May 2003
What is this ghostly matter?
• Could it be neutrinos?• How much neutrino mass would it take?
– Proton mass is 938 MeV– Electron mass is 511 KeV– Neutrino mass of 2eV would solve the galaxy
rotation problem – 20eV would close the Universe
• Theories say it can’t be all neutrinos– They have difficulty forming the kinds of structure
observed. The structures they create are too large and form too late in the history of the universe
J. Goodman – May 2003
Does the neutrino have mass?
J. Goodman – May 2003
Detecting Neutrino Mass
• If neutrinos of one type transform to another type they must have mass:
• The rate at which they oscillate will tell us the mass difference between the neutrinos and their mixing
GeV
kmeVxe E
LmLP
222 27.1
ins2sin;
J. Goodman – May 2003
Neutrino Oscillations
1212
=Electron =Electron
Electron
Electron
1212
=Muon =Muon
Muon Muon
J. Goodman – May 2003
Solar Neutrinos
J. Goodman – May 2003
Solar Neutrino Spectrum
J. Goodman – May 2003
Solar Neutrino Experiment History
• Homestake - Radiochemical– Huge tank of Cleaning Fluid (perchloroethylene)
e + 37Cl e- + 37Ar
– Mostly 8B neutrinos + some 7Be– 35 years at <0.5 ev/day– ~1/3 SSM– (Davis - 2002 Nobel Prize)
• Sage/Gallex - Radiochemical– “All” neutrinos
– e + 71Ga e- + 71Ge
– 4 years at ~0.75 ev /day– ~2/3 SSM
• Kamiokande-II and -III – 8B neutrinos only
– e Elastic Scattering
– 10 years at 0.44 ev /day– ~1/2 SSM– (Koshiba 2002 Nobel Prize)
J. Goodman – May 2003
The Solar Neutrino Problem
J. Goodman – May 2003
The Solar Neutrino Problem
J. Goodman – May 2003
The Solar Neutrino Problem
J. Goodman – May 2003
Neutrino OscillationsF o r t w o n e u t r i n o s p e c i e s
e a n d w e h a v e :
cossin
sincos
21
21
e
w h e r e 1 a n d
2 a r e t h e m a s s e i g e n s t a t e s .
I n a w e a k d e c a y o n e p r o d u c e s a d e f i n i t e w e a k e i g e n s t a t e
t e 0 .
.
A t a l a t e r t i m e t h e p r o b a b i l i t y o f t h e f i n a l s t a t e w i l l b e :
sincos 2121
tiEtiE eet
T h e s u r v i v a l p r o b a b i l i t y i s :
GeV
kmeVee E
LmLP
222 27.1
ins2sin1; .
J. Goodman – May 2003
Neutrino Oscillations
• Could Neutrino Oscillations solve the solar neutrino problem?– Simple oscillations would require a cosmic conspiracy– The earth/sun distance would have to be just right to get rid of
Be neutrinos
• Another solution was proposed –
Resonant Matter Oscillations in the sun (MSW- Mikheev, Smirnov, Wolfenstein)
• Because electron neutrinos “feel” the effect of electrons in matter they acquire a larger effective mass– This is like an index of refraction
J. Goodman – May 2003
MSW Oscillations
Sin 2Spring =
e
Length = Mass
When length (i.e. effective mass) are equal the couplingis enhanced.
Mechanical Analogy for Neutrino Oscillations
In theSun
In theVacuum
Resonance
(Mikheev, Smirnov, Wolfenstein)
J. Goodman – May 2003
Oscillation Parameter Space
LMA
LOW
VAC
SMA
J. Goodman – May 2003
Solar Neutrinos in Super-K
• The ratio of NC/CC cross section is ~1/6.5
J. Goodman – May 2003
Super-Kamiokande
J. Goodman – May 2003
Super-Kamiokande
J. Goodman – May 2003
Super-K
• Huge tank of water shielded by a mountain in western Japan– 50,000 tons of ultra clean water – 11,200 20in diameter PMTs– Under 1.5km of rock to reduce downward cosmic rays
• (rate of muons drops from ~100k/sec to ~2/sec)
• 100 scientists from US and Japan• Data taking began in 1996
J. Goodman – May 2003
Super-K site
MozumiMozumi
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Cherenkov Radiation
Boat moves throughwater faster than wavespeed.
Bow wave (wake)
J. Goodman – May 2003
Cherenkov Radiation
Faster than wave speedSlower than wave speed
J. Goodman – May 2003
Cherenkov Radiation
Aircraft moves throughair faster than speed ofsound.
Sonic boom
J. Goodman – May 2003
Cherenkov Radiation
When a charged particle moves throughtransparent media fasterthan speed of light in thatmedia.
Cherenkov radiation
Cone oflight
J. Goodman – May 2003
Cherenkov Radiation
J. Goodman – May 2003
Detecting neutrinos
Electron or
muon track
Electron or
muon track
Cherenkov ring on the
wall
Cherenkov ring on the
wall
The pattern tells us the energy and type of particle
We can easily tell muons from electrons
The pattern tells us the energy and type of particle
We can easily tell muons from electrons
J. Goodman – May 2003
A muon going through the detector
J. Goodman – May 2003
A muon going through the detector
J. Goodman – May 2003
A muon going through the detector
J. Goodman – May 2003
A muon going through the detector
J. Goodman – May 2003
A muon going through the detector
J. Goodman – May 2003
A muon going through the detector
J. Goodman – May 2003
Stopping Muon
J. Goodman – May 2003
Stopping Muon – Decay Electron
J. Goodman – May 2003
Solar Neutrinos in Super-K
• 1496 day sample (22.5 kiloton fiducial volume)• Super-K measures:
– The flux of 8B solar neutrinos– Energy spectrum and direction of recoil electron
• Energy spectrum is flat from 0 to Tmax
– The zenith angle distribution– Day / Night rates– Seasonal variations
J. Goodman – May 2003
Solar Neutrinos
)s cm 10 x (syst)0.03(stat) (2.32
ssm) (syst) %0.5%(stat) (45.1%
1-2-608.00.07
1.61.4 -
e
J. Goodman – May 2003
Energy Spectrum
J. Goodman – May 2003
Seasonal/Sunspot Variation
J. Goodman – May 2003
Combined Results e to
SK+Gallium+Cholrine - flux only allowed 95% C.L.
95% excluded by SK flux-independent zenith angle energy spectrum
95% C.L allowed. - SK flux constrained w/ zenith angle energy spectrum
(Like SK)
J. Goodman – May 2003
SNO CC Results
e= (35 ± 3 )% ssm
J. Goodman – May 2003
Combining SK and SNO
• SNO measures e= (35 ± 3 )% ssm
• SK Measures es= (47 ± .5 ± 1.6)% ssm
• If Oscillation to active neutrinos:– SNO Measures just e
• This implies that ssm (~2/3 have oscillated)
– SK measures es =(e + ( /6.5)
• Assuming osc. SNO predicts that SK will see es ~ (35%+ 65%/6.5) ssm = 45% ± 3% ssm
J. Goodman – May 2003
SNO Results (NC/CC)
• SNO Results
J. Goodman – May 2003
SNO Results
J. Goodman – May 2003
Combined SK and SNO Results
J. Goodman – May 2003
Kamland – Terrestrial Neutrinos
J. Goodman – May 2003
Reactors Contributing to Kamland
J. Goodman – May 2003
Kamland Results (Dec. 2002)
J. Goodman – May 2003
Kamland
J. Goodman – May 2003
Kamland
J. Goodman – May 2003
All Experiments Combined with Kamland
J. Goodman – May 2003
• It looks like the Solar Neutrino problem has been solved!– All Data (except LSND) is now consistent
with the large angle MSW solution – e->
– We have ruled out SMA and Low solutions– Disfavor Sterile Neutrino solutions
• Neutrinos have mass!– This confirms the atmospheric neutrino results
– The Solar mass difference ~0.003eV
• Future Experiments – – MiniBoone – LSND effect
Solar Neutrino Conclusions
J. Goodman – May 2003
Atmospheric Neutrino Production
Ratio predicted to ~ 5%
Absolute Flux Predicted to ~20% :
2
ee
J. Goodman – May 2003
Atmospheric Oscillations
about 13,000 km
about 15
km
Neutrinos produced in
the atmosphere
Neutrinos produced in
the atmosphere
We look for transformations
by looking at s with different distances from production
SK
J. Goodman – May 2003
Telling particles apart
MuonElectronMuonElectron
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Moderate Energy Sample
J. Goodman – May 2003
Multi-GeV Sample
J. Goodman – May 2003
Summary of Atmospheric Results
Best Fit for to
Sin22 =1.0,
M2=2.4 x 10-3eV2
2min=132.4/137 d.o.f.
No Oscillations
2min=316/135 d.o.f.
99% C.L.
90% C.L.
68% C.L.
Best Fit
Compelling evidence for to atmospheric neutrino oscillations
Now the most cited exp. HEP paper
Skip Tau studies
J. Goodman – May 2003
Neutrinos have mass
• Oscillations imply neutrinos have mass!
• We can estimate that neutrino mass is probably <0.2 eV – (we measure M2)
• Neutrinos can’t make up much of the dark matter –
• But they can be as massive as all the visible matter in the Universe!
• ~ ½% of the closure density
J. Goodman – May 2003
Supernova Cosmology Project
• Set out to directly measure the deceleration of the Universe
• Measure distance vs brightness of a standard candle (type Ia Supernova)
•The Universe seems to be accelerating!•Doesn’t fit Hubble Law (at 99% c.l.)
J. Goodman – May 2003
Energy Density in the Universe
may be made up of 2
parts a mass term and a “dark energy” term
(Cosmological Constant)
massenergy
• Einstein invented to keep the Universe static
• He later rejected it when he found out about Hubble expansion
• He called it his “biggest blunder”
m
J. Goodman – May 2003
The Cosmological Constant
J. Goodman – May 2003
What is the “Shape” of Space?
• Open Universe <1
– Circumference (C) of a circle of radius R is
C > 2R
• Flat Universe =1
– C = 2R– Euclidean space
• Closed Universe >1
– C < 2R
J. Goodman – May 2003
Results of SN Cosmology Project
• The Universe is accelerating
• The data require a positive value of “Cosmological Constant”
• If =1 then they find
~ 0.7 ± 0.1
J. Goodman – May 2003
Accelerating Universe
J. Goodman – May 2003
Accelerating Universe
J. Goodman – May 2003
Measuring the energy in the Universe
• Studying the Cosmic Microwave radiation looks back at the radiation from 400,000 years after the “Big Bang”.
• This gives a measure of 0
J. Goodman – May 2003
Recent Results - 2002
0=1 nucleon
J. Goodman – May 2003
WMAP -2003
J. Goodman – May 2003
WMAP - 2003
J. Goodman – May 2003
What does all the data say?
• Three pieces of data come together in one region
~ 0.73 m~ 0.27 (uncertainty ~0.04)
• Universe is expanding & won’t collapse
• Only ~1/6 of the dark matter is ordinary matter (atoms)
• A previously unknown and unseen “dark energy” pervades all of space and is causing it to expand and accelerate
J. Goodman – May 2003
What do we know about “Dark Energy”
• It emits no light• It acts like a large negative pressure
Px ~ - x
• It is approximately homogenous– At least it doesn’t cluster like matter
• Calculations of this pressure from first principles fail miserably – assuming it’s vacuum energy you predict a value of ~ 10120
• Bottom line – we know very little!
J. Goodman – May 2003
Conclusion
• total = 1.02 ± 0.02
– The Universe is flat!
• The Universe is : ~1/2% Stars
~1/2% Neutrinos
~27% Dark Matter (only 4% is ordinary matter)
~73% Dark Energy
• We can see ~1/2%• We can measure ~1/2%• We can see the effect of
~27% (but don’t know what most of it is)
• And we are pretty much clueless about the other 3/4 of the Universe
There is still a lot of Physics to learn!