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

J. Goodman Richtmyer Lecture – Jan Outline Matter in the Universe Why do we care about neutrinos? Why do we think there is dark matter? Could some of it be neutrinos? The search for neutrino mass Type Ia Supernova and the accelerating Universe Dark Energy

J. Goodman Richtmyer Lecture – Jan Seeing Big Picture

J. Goodman Richtmyer Lecture – Jan The early periodic table

J. Goodman Richtmyer Lecture – Jan The structure of matter Mendeleyev – grouped elements by atomic weights

J. Goodman Richtmyer Lecture – Jan The structure of matter (cont.) This lead eventually to a deeper understanding Eventually this led to Our current picture of the atom and nucleus

J. Goodman Richtmyer Lecture – Jan What are fundamental particles? We keep finding smaller and smaller things

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan Facts about Neutrinos Neutrinos are only weakly interacting Interaction length is ~1 light-year of steel 40 billion neutrinos continuously hit every cm 2 on earth from the Sun (24hrs/day) 1 out of 100 billion interact going through the Earth 1931 – Pauli predicts a neutral particle to explain energy and momentum non-conservation in Beta decay Enrico Fermi develops a comprehensive theory of radioactive decays, including Pauli's particle, Fermi calls it the neutrino (Italian: "little neutral one") Discovery of the neutrino is announced by Clyde Cowan and Fred Reines

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan The Ultimate Fate of the Universe   measures the total energy density of the Universe –If   > 1 Universe is closed –If   < 1 Universe is open   = 1 Universe (E tot =0) - Flat universe From the mass of the stars we get    Theorists say    What is the other 99.5% of the Universe?

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan Why do we think there is dark matter? In a gravitationally bound system out past most of the mass V ~ 1/r 1/2 We can look at the rotation curves of other galaxies –They should drop off But they don’t!

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan 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 < ~0.05 Gravitational lensing

J. Goodman Richtmyer Lecture – Jan 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 A neutrino mass of only 2eV would solve the galaxy rotation problem – 6 eV would close the Universe

J. Goodman Richtmyer Lecture – Jan Does the neutrino have mass?

J. Goodman Richtmyer Lecture – Jan 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

J. Goodman Richtmyer Lecture – Jan Neutrino Oscillations 1 2 =Electron Electron 1 2 =Muon Muon

J. Goodman Richtmyer Lecture – Jan Super-Kamiokande

J. Goodman Richtmyer Lecture – Jan Super-Kamiokande

J. Goodman Richtmyer Lecture – Jan Super-Kamiokande

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan Super-K site

J. Goodman Richtmyer Lecture – Jan Super-K site Mozumi

J. Goodman Richtmyer Lecture – Jan How do we see neutrinos? muon   electron e e-

J. Goodman Richtmyer Lecture – Jan Cherenkov Radiation Boat moves through water faster than wave speed. Bow wave (wake)

J. Goodman Richtmyer Lecture – Jan Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan A muon going through the detector

J. Goodman Richtmyer Lecture – Jan Stopping Muon

J. Goodman Richtmyer Lecture – Jan Stopping Muon – Decay Electron

J. Goodman Richtmyer Lecture – Jan Neutrino Production Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% :

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan Telling particles apart MuonElectron

J. Goodman Richtmyer Lecture – Jan Muon - Electron Identification PID Likelihood sub-GeV, Multi- GeV, 1-ring Monte Carlo (no oscillations) We expect about twice as many  as e

J. Goodman Richtmyer Lecture – Jan Super-K Atmospheric Data Set days of data (22.5 kilotons fiducial volume) Data Set is divided into: –Single and Multi Ring events –Electron-like and Muon-like –Energy Intervals 1.4 GeV Also E vis < 400MeV (little or no pointing) –Fully or partially contained muons (PC) –Upward going muons - stopping or through going Data is compared to Atmospheric Monte Carlo –Angle (path length through earth) –Visible energy of the Lepton

J. Goodman Richtmyer Lecture – Jan Low Energy Sample No Oscillations Oscillations (1.0, 2.4x10 -3 eV 2 )

J. Goodman Richtmyer Lecture – Jan Moderate Energy Sample

J. Goodman Richtmyer Lecture – Jan Multi-GeV Sample Oscillations (1.0, 2.4x10 -3 eV 2 ) No Oscillations  to  neutrino oscillations UP going DownUPDown

J. Goodman Richtmyer Lecture – Jan Multi-Ring Events

J. Goodman Richtmyer Lecture – Jan Upward Going Muons

J. Goodman Richtmyer Lecture – Jan Summary of Atmospheric Results Best Fit for  to  Sin 2 2  =1.0,  M 2 =2.4 x eV 2  2 min =132.4/137 d.o.f. No Oscillations  2 min =316/135 d.o.f. 99% C.L. 90% C.L. 68% C.L. Best Fit Compelling evidence for  to  atmospheric neutrino oscillations

J. Goodman Richtmyer Lecture – Jan Tau Appearance? Tau’s require greater than 3 GeV in neutrino energy –This eliminates most events Three correlated methods were used –All look for enhanced upward going multi-ring events All show slight evidence for Tau appearance None are statistically significant

J. Goodman Richtmyer Lecture – Jan The Solar Neutrino Problem

J. Goodman Richtmyer Lecture – Jan Solar Neutrinos in Super-K The ratio of NC/CC cross section is ~1/6.5 W e - e e - e - Charged Current (electron ’s only)

J. Goodman Richtmyer Lecture – Jan Solar Neutrinos in Super-K Super-K measures: –The flux of 8 B solar neutrinos (electron type) –Energy, Angles, Day / Night rates, Seasonal variations Super-K Results: –We see the image of the sun from 1.6 km underground –We observe a lower than predicted flux of solar neutrinos (45%)

J. Goodman Richtmyer Lecture – Jan Solar Neutrinos From SunToward Sun

J. Goodman Richtmyer Lecture – Jan Energy Spectrum

Day / Night - BP2000+New 8 B Spectrum Preliminary

J. Goodman Richtmyer Lecture – Jan Seasonal/Sunspot Variation

J. Goodman Richtmyer Lecture – Jan Combined Results e to  SK+Gallium+Cholrine exp’s- 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

J. Goodman Richtmyer Lecture – Jan SNO Results - Summer 2001 SNO measures just e SK measures mostly e but also other flavors (~1/6 strength) From the difference we see oscillations! } This is from  &  neutral current

J. Goodman Richtmyer Lecture – Jan Combining SK and SNO SNO measures just electron neutrinos and gets  e = (35% ± 3%)  ssm 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 SK observes:

J. Goodman Richtmyer Lecture – Jan Neutrinos have mass Oscillations imply neutrinos have mass! 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 – But they can be as massive as all the visible matter in the Universe! ~ ½ % of the closure density

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan 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 static He later rejected it when he found out about Hubble expansion He called it his “biggest blunder” m   

J. Goodman Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan 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 Richtmyer Lecture – Jan Accelerating Universe

J. Goodman Richtmyer Lecture – Jan Accelerating Universe

J. Goodman Richtmyer Lecture – Jan Measuring the energy in the Universe Studying the Cosmic Microwave radiation looks back at the radiation from the “Big Bang”. This gives a measure of  0

J. Goodman Richtmyer Lecture – Jan Latest Results - May Boomerang Results  0 =1  nucleon mass from clusters

J. Goodman Richtmyer Lecture – Jan What does all the data say? Three pieces of data come together in one region   ~ 0.7  m ~ 0.3 (uncertainty  ~0.1) Universe is expanding & won’t collapse Only ~1/6 of the dark matter is ordinary matter (baryons) A previously unknown and unseen “dark energy” pervades all of space and is causing it to expand

J. Goodman Richtmyer Lecture – Jan What do we know about “Dark Energy” It emits no light It acts like a large negative pressure P x ~ -  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  ~ Bottom line – we know very little!

J. Goodman Richtmyer Lecture – Jan Conclusion  tota l = 1 ± 0.04 –The Universe is flat! The Universe is : ~1/2% Stars ~1/2% Neutrinos ~33% Dark Matter (only 5% is ordinary matter) ~66% Dark Energy We can see ~1/2% We can measure ~1/2% We can see the effect of ~33% (but don’t know what most of it is) And we are pretty much clueless about the other 2/3 of the Universe There is still a lot of Physics to learn!

J. Goodman Richtmyer Lecture – Jan Md Students at Super-K

J. Goodman Richtmyer Lecture – Jan Super-K Disaster - Nov 11, 2001 Chain reaction destroyed 7000 OD and 1000 ID Tubes The cause is not completely understood, but it started with a lower pmt collapse. The energy release comes from a 4 T column of water falling There are plans to rebuild…

J. Goodman Richtmyer Lecture – Jan Disaster (Continued)

J. Goodman Richtmyer Lecture – Jan Disaster (Continued)