J. Goodman – Jan 2005 Smithsonian Institution Neutrinos, Dark Matter and the Cosmological Constant The Dark Side of the Universe Jordan Goodman University of Maryland

J. Goodman – Jan 2005 Smithsonian Institution Outline The Cosmological Question – the fate of the UniverseThe Cosmological Question – the fate of the Universe How do we know what the Universe is made of:How do we know what the Universe is made of: –From atoms to quarks and leptons Why do we think there is Dark MatterWhy do we think there is Dark Matter The Neutrino’s role in the UniverseThe Neutrino’s role in the Universe Data on the accelerating UniverseData on the accelerating Universe –Type Ia supernova –Cosmic Microwave Background Dark EnergyDark Energy

J. Goodman – Jan 2005 Smithsonian Institution The Big Question in Cosmology What is the ultimate fate of the Universe?What is the ultimate fate of the Universe? –Will the Universe continue to expand forever? –Or will it collapse back on itself? We were told:We were told: –The answer depends on the energy density in the Universe –   –     mass  and     is the critical density. –If  mass > 1 then the Universe is closed and it will collapse back –If  mass < 1 then the Universe is open and it will expand forever  stars = (1/2%)  stars = (1/2%) –Is this the answer? Theory says     > 1  < 1

J. Goodman – Jan 2005 Smithsonian Institution Preview

J. Goodman – Jan 2005 Smithsonian Institution Seeing Big Picture

J. Goodman – Jan 2005 Smithsonian Institution The early periodic table

J. Goodman – Jan 2005 Smithsonian Institution The structure of matter Mendeleyev – grouped elements by atomic weights

J. Goodman – Jan 2005 Smithsonian Institution Mendeleyev’s Actual 1869 Periodic Table...if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained." - Mendeleyev

J. Goodman – Jan 2005 Smithsonian Institution How do we know there really are atoms? Brownian Motion - Einstein

J. Goodman – Jan 2005 Smithsonian Institution Seeing Atoms in the 21 st Century

J. Goodman – Jan 2005 Smithsonian Institution Seeing Atoms - Iron on Copper

J. Goodman – Jan 2005 Smithsonian Institution Seeing into Atoms Atomic Spectra –We see spectral lines –The colors and the spacing of these lines tell us about the structure of the atoms E

J. Goodman – Jan 2005 Smithsonian Institution Hydrogen Spectra

J. Goodman – Jan 2005 Smithsonian Institution The structure of matter (cont.) All of this eventually gave a deeper understanding Eventually this led to Our current picture of the atom and nucleus

J. Goodman – Jan 2005 Smithsonian Institution What are fundamental particles? We keep finding smaller and smaller things

J. Goodman – Jan 2005 Smithsonian Institution How do we see particles? Most particles have electric charge –Moving charged particles knock electrons out of atoms –As other electrons fall in - the atom emits light The light from your TV is from electrons hitting the screen The light from your TV is from electrons hitting the screen In a sense we are “seeing” electrons In a sense we are “seeing” electrons

J. Goodman – Jan 2005 Smithsonian Institution The search for fundamental particles Proton and electronProton and electron –These were known to make up the atom The neutron was discoveredThe neutron was discovered Free neutrons were found to decayFree 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 particleIn 1930 Pauli postulated a unseen neutral particle In 1933 Fermi named it the “neutrino” (little neutron)In 1933 Fermi named it the “neutrino” (little neutron)

J. Goodman – Jan 2005 Smithsonian Institution How do we know about things we can’t see? Three Body Decay Two Body Particle Decay neutrino

J. Goodman – Jan 2005 Smithsonian Institution Our current view of underlying structure of matter P is uud N is udd   is ud k  is us and so on… The Standard Model } Baryons } Mesons (nucleons)

J. Goodman – Jan 2005 Smithsonian Institution Measuring the Universe

J. Goodman – Jan 2005 Smithsonian Institution Why do we think there is dark matter? Isn’t obvious that most of the matter in the Universe is in Stars? Spiral Galaxy

J. Goodman – Jan 2005 Smithsonian Institution Measuring the Matter in Galaxies In a gravitationally bound system out past most of the mass V ~ 1/r 1/2In a gravitationally bound system out past most of the mass V ~ 1/r 1/2 We can look at the rotation curves of other galaxiesWe can look at the rotation curves of other galaxies –They should drop off This is evidence for invisible matter or “Dark Matter”

J. Goodman – Jan 2005 Smithsonian Institution 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 Washington

J. Goodman – Jan 2005 Smithsonian Institution Lensing

J. Goodman – Jan 2005 Smithsonian Institution Measuring the energy in the Universe We can measure the mass of clusters of galaxies with gravitational lensingWe can measure the mass of clusters of galaxies with gravitational lensing These measurements give  mass ~0.3These measurements give  mass ~0.3 We also know (from the primordial deuterium abundance) that only a small fraction is nucleons  nucleons < ~0.04We also know (from the primordial deuterium abundance) that only a small fraction is nucleons  nucleons < ~0.04 Gravitational lensing

J. Goodman – Jan 2005 Smithsonian Institution Gravitational Lensing

J. Goodman – Jan 2005 Smithsonian Institution Clusters produce distinctive tangential patterns

J. Goodman – Jan 2005 Smithsonian Institution Gravitational Lensing

J. Goodman – Jan 2005 Smithsonian Institution Movies

J. Goodman – Jan 2005 Smithsonian Institution Dark Matter

J. Goodman – Jan 2005 Smithsonian Institution Dark Matter

J. Goodman – Jan 2005 Smithsonian Institution Why do we care about neutrinos? NeutrinosNeutrinos –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!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 – Jan 2005 Smithsonian Institution Facts about Neutrinos Neutrinos are only weakly interactingNeutrinos are only weakly interacting 40 billion neutrinos continuously hit every cm 2 on earth from the Sun (24hrs/day)40 billion neutrinos continuously hit every cm 2 on earth from the Sun (24hrs/day) Interaction length is ~1 light-year of steelInteraction length is ~1 light-year of steel 1 out of 100 billion interact going through the Earth1 out of 100 billion interact going through the Earth

J. Goodman – Jan 2005 Smithsonian Institution What about neutrino mass? Could it be neutrinos?Could it be neutrinos? How much neutrino mass would it take?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 neutrinosTheories 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 – Jan 2005 Smithsonian Institution Does the neutrino have mass?

J. Goodman – Jan 2005 Smithsonian Institution 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 mixingThe rate at which they oscillate will tell us the mass difference between the neutrinos and their mixing

J. Goodman – Jan 2005 Smithsonian Institution Neutrino Oscillations 1 2 = Electron Electron 1 2 = Muon Muon

J. Goodman – Jan 2005 Smithsonian Institution Super-Kamiokande

J. Goodman – Jan 2005 Smithsonian Institution Super-Kamiokande

J. Goodman – Jan 2005 Smithsonian Institution Super-K Huge tank of water shielded by a mountain in western JapanHuge 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)(rate of muons drops from ~100k/sec to ~2/sec) 100 scientists from US and Japan100 scientists from US and Japan Data taking began in 1996Data taking began in 1996

J. Goodman – Jan 2005 Smithsonian Institution Super-K site

J. Goodman – Jan 2005 Smithsonian Institution Super-K site Mozumi

J. Goodman – Jan 2005 Smithsonian Institution How do we see neutrinos? muon   electron e e-

J. Goodman – Jan 2005 Smithsonian Institution Cherenkov Radiation Boat moves through water faster than wave speed. Bow wave (wake)

J. Goodman – Jan 2005 Smithsonian Institution Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

J. Goodman – Jan 2005 Smithsonian Institution Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

J. Goodman – Jan 2005 Smithsonian Institution Cherenkov Radiation When a charged particle moves through transparent media faster than speed of light in that media. Cherenkov radiation Cone of light

J. Goodman – Jan 2005 Smithsonian Institution Cherenkov Radiation

J. Goodman – Jan 2005 Smithsonian Institution Detecting neutrinos Electron or muon track Cherenkov ring on the wall The pattern tells us the energy and type of particle We can easily tell muons from electrons

J. Goodman – Jan 2005 Smithsonian Institution A muon going through the detector

J. Goodman – Jan 2005 Smithsonian Institution A muon going through the detector

J. Goodman – Jan 2005 Smithsonian Institution A muon going through the detector

J. Goodman – Jan 2005 Smithsonian Institution A muon going through the detector

J. Goodman – Jan 2005 Smithsonian Institution A muon going through the detector

J. Goodman – Jan 2005 Smithsonian Institution A muon going through the detector

J. Goodman – Jan 2005 Smithsonian Institution Stopping Muon

J. Goodman – Jan 2005 Smithsonian Institution Stopping Muon – Decay Electron

J. Goodman – Jan 2005 Smithsonian Institution Neutrino Production Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% :

J. Goodman – Jan 2005 Smithsonian Institution Atmospheric Oscillations about 13,000 km about 15 km Neutrinos produced in the atmosphere We look for transformations by looking at s with different distances from production SK

J. Goodman – Jan 2005 Smithsonian Institution Atmospheric Neutrino Interactions Reaction Thresholds Electron: ~1.5 MeV Muon: ~110 MeV Tau: ~3500 MeV Charged Current Neutral Current e  e n p W +

J. Goodman – Jan 2005 Smithsonian Institution Telling particles apart MuonElectron

J. Goodman – Jan 2005 Smithsonian Institution Atmospheric Oscillations about 13,000 km about 15 km Neutrinos produced in the atmosphere We look for transformations by looking at s with different distances from production SK

J. Goodman – Jan 2005 Smithsonian Institution Moderate Energy Sample

J. Goodman – Jan 2005 Smithsonian Institution Neutrinos have mass Oscillations imply neutrinos have mass!Oscillations imply neutrinos have mass! We can estimate that neutrino mass is probably <0.2 eV – (we measure  M 2 )We can estimate that neutrino mass is probably <0.2 eV – (we measure  M 2 ) Neutrinos can’t make up much of the dark matter –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 – Jan 2005 Smithsonian Institution Hubble Law

J. Goodman – Jan 2005 Smithsonian Institution The expanding Universe

J. Goodman – Jan 2005 Smithsonian Institution The expanding Universe The Universe is expandingThe Universe is expanding Everything is moving away from everythingEverything is moving away from everything Hubble’s law says the faster things are moving away the further they are awayHubble’s law says the faster things are moving away the further they are away

J. Goodman – Jan 2005 Smithsonian Institution Supernova

J. Goodman – Jan 2005 Smithsonian Institution Actually Ia’s are “standardizable” candles

J. Goodman – Jan 2005 Smithsonian Institution Supernova Cosmology Project Set out to directly measure the deceleration of the UniverseSet out to directly measure the deceleration of the Universe Measure distance vs brightness of a standard candle (type Ia Supernova)Measure distance vs brightness of a standard candle (type Ia Supernova) The Universe seems to be accelerating!The Universe seems to be accelerating! Doesn’t fit Hubble Law (at 99% c.l.)Doesn’t fit Hubble Law (at 99% c.l.)

J. Goodman – Jan 2005 Smithsonian Institution Energy Density in the Universe    may be made up of 2 parts a mass term and a “dark energy”  term (Cosmological Constant)    mass  energy Einstein invented  to keep the Universe staticEinstein invented  to keep the Universe static He later rejected it when he found out about Hubble expansionHe later rejected it when he found out about Hubble expansion He called it his “biggest blunder”He called it his “biggest blunder”  m   

J. Goodman – Jan 2005 Smithsonian Institution The expanding Universe

J. Goodman – Jan 2005 Smithsonian Institution The Cosmological Constant

J. Goodman – Jan 2005 Smithsonian Institution What is the “Shape” of Space? Closed Universe   >1Closed Universe   >1 – C < 2  R Open Universe   <1Open Universe   <1 –Circumference (C) of a circle of radius R is C > 2  R Flat Universe   =1Flat Universe   =1 – C = 2  R – Euclidean space

J. Goodman – Jan 2005 Smithsonian Institution What is the “Shape” of Space? Open Universe   <1 –Circumference (C) of a circle of radius R is C > 2  R Flat Universe   =1 – C = 2  R – Euclidean space Closed Universe   >1 – C < 2  R

J. Goodman – Jan 2005 Smithsonian Institution Results of SN Cosmology Project The Universe is acceleratingThe Universe is accelerating The data require a positive value of  “Cosmological Constant”The data require a positive value of  “Cosmological Constant” If    =1 then they find    ~ 0.7 ± 0.1If    =1 then they find    ~ 0.7 ± 0.1

J. Goodman – Jan 2005 Smithsonian Institution Accelerating Universe

J. Goodman – Jan 2005 Smithsonian Institution Accelerating Universe

J. Goodman – Jan 2005 Smithsonian Institution Cosmic Microwave Background

J. Goodman – Jan 2005 Smithsonian Institution 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 – Jan 2005 Smithsonian Institution Recent Results  0 =1  nucleon

J. Goodman – Jan 2005 Smithsonian Institution WMAP -2003

J. Goodman – Jan 2005 Smithsonian Institution WMAP Results

J. Goodman – Jan 2005 Smithsonian Institution WMAP

J. Goodman – Jan 2005 Smithsonian Institution

J. Goodman – Jan 2005 Smithsonian Institution Sloan Digital Sky Survey

J. Goodman – Jan 2005 Smithsonian Institution Summary of WMAP & SDSS

J. Goodman – Jan 2005 Smithsonian Institution WMAP and SDSS Varying  Total

J. Goodman – Jan 2005 Smithsonian Institution WMAP and SDSS Varying  Varying  b

J. Goodman – Jan 2005 Smithsonian Institution WMAP/SDSS and Neutrinos Varying Neutrinos  h 2 < (95%) Neutrino mass (degenerate) m<0.23 eV (95%) CMB Galaxy clustering m~0 eV m~0.3 eV m~1 eV (Spergel et al 2003)

J. Goodman – Jan 2005 Smithsonian Institution Density Fluctuations to Galaxies

J. Goodman – Jan 2005 Smithsonian Institution 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 – Jan 2005 Smithsonian Institution Expansion History of the Universe

J. Goodman – Jan 2005 Smithsonian Institution Concordance model, aka  CDM

J. Goodman – Jan 2005 Smithsonian Institution Combining All Results Universe is 13.7 billion years old with a margin of error of close to 1%Universe is 13.7 billion years old with a margin of error of close to 1% Expansion rate (Hubble constant) value: H o = 71 km/sec/Mpc (with a margin of error of about 5%)Expansion rate (Hubble constant) value: H o = 71 km/sec/Mpc (with a margin of error of about 5%) Neutrinos only contribute as much matter as starsNeutrinos only contribute as much matter as stars Content of the Universe: 4% Atoms, 23% Cold Dark Matter, 73% Dark energy.Content of the Universe: 4% Atoms, 23% Cold Dark Matter, 73% Dark energy.

J. Goodman – Jan 2005 Smithsonian Institution Puzzles We are here

J. Goodman – Jan 2005 Smithsonian Institution What’s Next SNAP - JDEMSNAP - JDEM –Look at 1000’s of Ia Supernovae –Look back further in time – Z~1.7 –2m Mirror with a Gigapixel CCD

J. Goodman – Jan 2005 Smithsonian Institution What do we know about “Dark Energy” It emits no lightIt emits no light It acts like a large negative pressureIt acts like a large negative pressure P x ~ -  x It is approximately homogenousIt 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   ~ Calculations of this pressure from first principles fail miserably – assuming it’s vacuum energy you predict a value of   ~ Bottom line – we know very little!

J. Goodman – Jan 2005 Smithsonian Institution Conclusion  tota l = 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!

J. Goodman – Jan 2005 Smithsonian Institution