J. Goodman – Spring 2002 Colloquium – UCR Neutrinos, Dark Matter and the Cosmological Constant The Dark Side of the Universe Jordan Goodman University of Maryland

J. Goodman – Spring 2002 First Things First

“We need an AMO program to make the Basketball team proud” – Bill Phillips – 1997 Nobel Laureate First Things First

J. Goodman – Spring 2002 Outline 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 –Super-K –SNO Type Ia Supernova and the accelerating Universe Dark Energy

J. Goodman – Spring 2002 Seeing Big Picture

J. Goodman – Spring 2002 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 – Spring 2002 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

J. Goodman – Spring 2002 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 – Spring 2002 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 They don’t behave as if the mass is in stars!

J. Goodman – Spring 2002 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 – Spring 2002 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 – Spring 2002 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 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 – Spring 2002 Does the neutrino have mass?

J. Goodman – Spring 2002 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 – Spring 2002 Neutrino Oscillations 1 2 =Electron Electron 1 2 =Muon Muon

J. Goodman – Spring 2002 Super-Kamiokande

J. Goodman – Spring 2002 Super-Kamiokande

J. Goodman – Spring 2002 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 – Spring 2002 Super-K site

J. Goodman – Spring 2002 Super-K site Mozumi

J. Goodman – Spring 2002 How do we see neutrinos? muon   electron e e-

J. Goodman – Spring 2002 Cherenkov Radiation Boat moves through water faster than wave speed. Bow wave (wake)

J. Goodman – Spring 2002 Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

J. Goodman – Spring 2002 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 – Spring 2002 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 – Spring 2002 A muon going through the detector

J. Goodman – Spring 2002 A muon going through the detector

J. Goodman – Spring 2002 A muon going through the detector

J. Goodman – Spring 2002 A muon going through the detector

J. Goodman – Spring 2002 A muon going through the detector

J. Goodman – Spring 2002 A muon going through the detector

J. Goodman – Spring 2002 Stopping Muon

J. Goodman – Spring 2002 Stopping Muon – Decay Electron

J. Goodman – Spring 2002 Neutrino Production Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% :

J. Goodman – Spring 2002 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 – Spring 2002 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 – Spring 2002 Telling particles apart MuonElectron

J. Goodman – Spring 2002 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 – Spring 2002 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 – Spring 2002 Low Energy Sample No Oscillations Oscillations (1.0, 2.4x10 -3 eV 2 )

J. Goodman – Spring 2002 Moderate Energy Sample

J. Goodman – Spring 2002 Multi-GeV Sample

J. Goodman – Spring 2002 Multi-Ring Events

J. Goodman – Spring 2002 Upward Going Muons

J. Goodman – Spring 2002 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 Now the most cited exp. HEP paper Skip Tau studies

J. Goodman – Spring 2002 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 – Spring 2002 New Results

J. Goodman – Spring 2002 Neutrinos From Solar Reactions

J. Goodman – Spring 2002 Oscillation Parameter Space LMA LOW VAC SMA

J. Goodman – Spring 2002 The Solar Neutrino Problem

J. Goodman – Spring 2002 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) x Z 0 x e - e - Neutral Current (all flavors)

J. Goodman – Spring 2002 Solar Neutrinos in Super-K 1258 day sample (22.5 kiloton fiducial volume) Super-K measures: –The flux of 8 B solar neutrinos –Energy spectrum and direction of recoil electron Energy spectrum is flat from 0 to T max –The zenith angle distribution –Day / Night rates –Seasonal variations

J. Goodman – Spring 2002 Solar Neutrinos From SunToward Sun

J. Goodman – Spring 2002 Energy Spectrum Skip Solar Details

J. Goodman – Spring 2002 Energy Spectrum

J. Goodman – Spring 2002 Day / Night - BP2000+New 8 B Spectrum Preliminary

J. Goodman – Spring 2002 Seasonal/Sunspot Variation

J. Goodman – Spring 2002 Combined Results e to 

J. Goodman – Spring 2002 Combined Results e to  95% C.L allowed. - SK flux constrained w/ zenith angle energy spectrum Enlarged View 95% excluded by SK flux- independent zenith angle energy spectrum SK + Gallium + Chlorine - flux only allowed 95% C.L.

J. Goodman – Spring 2002 Combined Results e to sterile SK + Gallium+ Chlorine - 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 – Spring 2002

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 neutral current from  & 

J. Goodman – Spring 2002 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 – Spring 2002 SK & SNO Flux Measurements

J. Goodman – Spring 2002 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 – Spring 2002 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 – Spring 2002 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 – Spring 2002 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 – Spring 2002 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 – Spring 2002 Accelerating Universe

J. Goodman – Spring 2002 Accelerating Universe

J. Goodman – Spring 2002 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 – Spring 2002 Latest Results - May Boomerang Results  0 =1  nucleon mass from clusters

J. Goodman – Spring 2002 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 and accelerate

J. Goodman – Spring 2002 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 – Spring 2002 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 – Spring 2002 Md Students at Super-K

J. Goodman – Spring 2002 Super-K Disaster - Nov 12, 2001 Chain reaction destroyed 7000 OD and 1000 ID Tubes The cause is not completely understood, but it started with a lower pmt collapse. We are rebuilding!

J. Goodman – Spring 2002 Disaster (Continued)

J. Goodman – Spring 2002 Disaster (Continued)

J. Goodman – Spring 2002 Disaster (Continued)

J. Goodman – Spring 2002 Rebuild at ½ of Original Coverage