22 Neutrino Properties • Neutrino Mass Phenomenology • Direct Neutrino Mass Experiments • Double Beta Decay Experiments • Neutrino Oscillations Bottom Line: – No Direct evidence of neutrino mass – Neutrinos almost certainly oscillate from one flavor to another ⇒ ⇒ Neutrinos have mass and mix
23 Neutrino Mass Phenomenology
24 Neutrino Mass: Theoretical Ideas • No fundamental reason why neutrinos must be massless – But why are they much lighter than other particles? � Grand Unified Theories – Dirac and Majorana Mass ⇒ See-saw Mechanism � Modified Higgs sector to accommodate neutrino mass � Extra Dimensions – Neutrinos live outside of 3 + 1 space Many of these models have at least one Electroweak isosinglet ν – Right-handed partner of the left-handed ν – Mass uncertain from light (< 1 eV) to heavy (>10 16 eV) – Would be “sterile” – Doesn’t couple to standard W and Z bosons
25 Dirac and Majorana Neutrinos • Dirac Neutrinos • Majorana Neutrinos – Neutrino and Antineutrino are – Neutrinos and Antineutrinos are the distinct particles same particle ⇒ Only difference is “handedness” • Neutrinos are left-handed ν – Lepton number conserved → µ − • Neutrino → µ − • Antineutrinos are right-handed ν • Antineutrino → µ + → µ + – Lepton number not conserved – Dirac Mass Term • Neutrino ⇔ Antineutrino with spin flip – Majorana Mass Term See-Saw Mechanism with Both Majorana and Dirac Terms:
26 Direct Neutrino Mass Measurements
27 Direct Neutrino Mass Experiments • Techniques – Electron neutrino: • Study E e end point for 3 H → 3 He + ν e + e − µ ( keV) – Muon neutrino: • Measure P µ in π→µν µ decays e ( eV) – Tau neutrino: τ ( MeV) • Study n π mass in τ→ ( n π) ν τ decays (Also, information from Supernova time-of- flight)
28 ν e Mass Measurements ν (Tritium β β -decay Searches) • Search for a distortion in the shape of the β -decay spectrum in the end-point region. 3 H → 3 He + ν e + e −
29 Next Generation β β -decay Experiment ( δ δ m ≈ ≈ 0.35 eV)
30 Muon Neutrino Mass Studies • Current best limit from studies of the kinematics of π → µ ν decay 2 + 2 = 2 + 2 − 2 2 2 ( ) / 4 p m m m m m µ µ π µ ν π • Can use π -decay: – At Rest: Mass of π is dominate uncertainty – In Flight: Resolution on p π -p µ limited experimentally • Best mass limit is from π -decay at rest < 170 keV at 95% CL (Assamagan et al. , PRD 1996) • New BNL Experiment using g-2 setup (sensitivity for > 8 keV)
31 Proposed BNL “NuMass” Experiment BNL g-2 Neutrino Mass Experiment Forward-going decay muons m( ν µ ) < 8 keV/c 2 orbit a larger diameter by ∆ ∆ D CM ν µ ν µ π µ π µ q = 29.7 MeV/c undecayed ∆ D p µ ∆ π 0.7 MeV/c 3.26 mm µ - p π D pions π 3 GeV/c 14 m D p π shrinks ∆ ∆ D non-zero m ν ν δ D -m ν δ 2 ν ∆ D ∆ D 2 q m π π decay µ µ ’s δ D depends δ on m( ν ν ) 0.04 mm for current limit
32 Direct ν ν τ τ Mass Limits • Look at tau decays near the edge of the allowed kinematic range τ − → 2π − π + ν τ and τ − → 3π − 2π + (π 0 ) ν τ • Fit to scaled visible energy vs. scaled invariant mass (e.g. hep-ex/9906015, CLEO) • Best limit is m( ν τ ) < 18.2 MeV at 95% CL (Aleph, EPJ C2 395 1998)
33 Double Beta Decay: Are Neutrinos Majorana Particles? 0 νββ Decay 2 νββ Decay • If neutrinos are Majorana then can • Double-beta decay is transition: have 0ν transitions (Z,A) → (Z+2,A) + (e - e - ν e ν e ) Double weak transition ∝ G F 4 • In certain nuclei, single β− decay is energetically not allowed ( 136 Xe → 136 Ba, 76 Ge → 76 Se , etc. • Look for 0ν signal beyond the 2ν end point Determine neutrino mass from rate which ∝ (m ν / m e ) 2
34 Double Beta Decay Neutrino Mass Searches • Proposed next steps: • Current best limit comes from – New 76 Ge experiments Heidelberg-Moscow Experiment increase from kg to tons! using 76 Ge (GENIUS, ….) ~few x 10 -3 eV m ν < 0.2 eV – New TPC technique 136 Xe → 136 Ba Track both e - e - and Ba atom! EXO Experiment ~0.01 eV
35 Supernova Neutrinos • In a super nova explosion – Neutrinos escape before the photons – Neutrinos carry away ~99% of the energy – The rate of escape for ν e is different from ν µ and ν τ (Due extra ν e CC interactions with electrons) • Neutrino mass limit can be obtained by the spread in the propagation time – t obs -t emit = t 0 (1 + m 2 /2E 2 ) – Spread in arrival times if m ≠ 0 due to ∆ E – For SN1987a assuming emission time is over 4 sec m ν < ~30 eV (All arrived within about ~13 s after traveling 180,000 light years with energies that differed by up to a factor of three. The neutrinos arrived about 18 hours before the light was seen)
36 SNEWS The SuperNova Early Warning Sytem
37 Neutrino Oscillation Phenomenology
38 Neutrino Oscillations • Direct measurements have difficulty probing small neutrino masses ⇒ Use neutrino oscillations • If we postulate: – Neutrinos have (different) mass – The Weak Eigenstates are a mixture of Mass Eigenstates Then a pure ν µ beam at t=0, will develop a ν e component with time.
39 Derivation of Oscillation Formula (A favorite graduate exam problem ) See if you can derive the 1.27 factor in the formula by recovering from the hbar = c =1.
40 Neutrino Oscillation Formalism • Most analyses assume 2-generation mixing ν ν θ θ cos sin ( ) ( ) = 1 ν → ν = θ ∆ e 2 2 2 sin 2 sin 1 . 27 / P m L E ν − θ θ ν µ sin cos e µ e • But we have 3-generations: ν e , ν µ , and ν τ (and maybe even more ….. the sterile neutrino ν s ’s ) − δ ν ν i c c s c s e 12 13 12 13 13 1 CKM-like e δ ν = − − − ν i s c c s s c c s s s e s c Mixing Matrix µ 12 23 12 23 13 12 23 12 23 13 23 13 2 ν − δ − − δ ν for Leptons i i s s c c s e c s s c s e c c τ 12 23 12 23 13 12 23 12 23 13 23 13 3 (In this 3-generation model, there are 3 ∆ m 2 ’s but only two are ∆ 2 = 2 − 2 ∆ 2 = 2 − 2 ∆ 2 = 2 − 2 , , independent.) m m m m m m m m m 12 1 2 23 2 3 31 3 1 • At each ∆ m 2 , there can be oscillations between all the neutrino flavors with different mixing angle combinations. ( ) ( ) For example: ν → ν = 4 θ 2 θ 2 ∆ 2 cos sin 2 sin 1 . 27 / P m L E ν µ →ν e at the µ τ ν 13 23 32 ( ) ( ) (3 sets of same ∆ m 2 as ν → ν = θ θ ∆ 2 2 2 2 sin sin 2 sin 1 . 27 / P m L E 3 equations µ ν 23 13 32 e ν µ →ν τ ( ) ( ) ν → ν = θ θ ∆ like these) 2 2 2 2 cos sin 2 sin 1 . 27 / P m L E τ ν 23 13 32 e
41 CP Violation in Neutrino Oscillations • Disappearance measurements cannot see CP violation effect ( ) ( ) • ν → ν = ν → ν P P µ µ µ µ • Very, very hard to see CP violation effects in exclusive (appearance) measurements. (From B. Kayser) – Only can see CP violation effects if an experiment is sensitive to oscillations involving at least three types of neutrinos. ( ) ( ) ( ) ν → ν − ν → ν = + + * * 4 Im ( ) P P U U U U s s s µ µ e µ µ 1 1 3 3 12 23 31 e e e ( ) = δ 2 δ 2 = 2 − 2 sin 2 where s and m L E m m m ij ij ij i j – All the terms (s 12 , s 13 , s 23 ) must not be << 1 or effectively becomes only two component oscillation • For example, if s 31 ≈ 0 then s 12 ≈ − s 23 ⇒ s 12 + s 31 + s 23 ≈ 0 ⇒ ⇒ To see CP violation must be sensitive to all three neutrino oscillations i.e. the hardest is usually the lowest (solar neutrino) ∆ ∆ m 2 ≈ ≈ 10 10 −4 −4 − 10 − 10 −10 −10 eV 2
42 Oscillation Formula Parameters ( ) = θ ∆ 2 2 2 sin 2 sin 1 . 27 / P m L E Osc
43 Oscillation Phenomenology • Two types of oscillation searches: – Appearance Experiment: Look for appearance of ν e or ν τ in a pure ν µ beam vs. L and E • Need to know the backgrounds – Disappearance Experiment: Look for a change in ν µ flux as a function of L and E • Need to know the flux and cross sections • P osc = sin 2 2 θ sin 2 (1.27 ∆ m 2 L/E) sets the details of search – Mixing angle sin 2 2 θ sets the needed statistics Small ∆ ∆ m 2 (Need large L/E) Large ∆ ∆ m 2 : <sin 2 (1.27 ∆ ∆ m 2 L/E)>=1/2
44 Oscillation Plots • If you see an oscillation signal with P osc = P ± ± δ δ P then carve out an allowed region in ( ∆ m 2 ,sin 2 2 θ ) plane. • If you see no signal and limit oscillation with P osc < P @ 90% CL then carve out an excluded region in the ( ∆ m 2 ,sin 2 2 θ ) plane.
45 Current Neutrino Oscillation Signals • Three Positive Signals – Solar Neutrinos – Atmospheric Neutrinos – Low-E Accelerator Neutrinos • Many negative searches Go thru results of each area and try to fit things together
46 Solar Neutrino Oscillation Exp’s
47 Solar Neutrino Deficit Flux of solar neutrinos detected at the earth is much less than expected ⇒ Is it due to neutrino oscillations? – The “Standard Solar Model” – Wide range of measurement techniques – How does it fit into a oscillation hypothesis? • Several possible oscillation scenarios fit data – Remaining questions and future plans Super- K (Japan) image of the sun using neutrinos
48 Standard Solar Model • Stellar evolution models: – Hydrodynamic equilibrium between pressure and gravity pep – Energy transport by radiation pp and convection – Energy production by nuclear reactions • Can produce ν ’s here • Many experimental and theoretical inputs: – Age, luminosity, opacity, hep abundances, radius, surface 7 Be temp, core temp, core density, diffusion parameters. 8 B • Ouput: – Temp(r), density(r) – Neutrino Flux But how big are the uncertainties
49 Solar Neutrino Spectrum • Many fusion processes in the sun lead to neutrinos • Solar model predicts flux – From solar luminosity, main pp neutrino flux known to 1% – 7 Be and 8 B neutrinos 10% to 20% uncertainties
50 Solar Neutrino Experiments • Solar neutrino cross sections …… are very, very small • At these energies σ ν ∼ 10 −45 cm 2 • With flux of 10 10 /cm 2 /s and 10 30 atoms → 1 event / day – Introduce new unit …… “The SNU” • 1 SNU = 10 -36 captures / target atom / s • Two types of experiments: – Chemical Extraction experiments • Homestake (“Chlorine”) ν e + 37 Cl → 37 Ar + e − • Sage and Gallex (“Gallium”) ν e + 71 Ga → 71 Ge + e − – Scattering experiments • SuperKamioka (Kamioka) ν x + e − → ν x + e − (Light water) • SNO ν e + d → e − + p + p (Heavy water) ν x + d → ν x + n + p
51 Chemical Extraction Experiments • Homestake: ν e + 37 Cl → 37 Ar + e − • Gallium Exps: ν e + 71 Ga → 71 Ge + e − – GALLEX (Gran Sasso, Italy) uses – Located in Lead, SD aqueous gallium chloride (101 tons) – 615 tons of C 2 Cl 4 (Cleaning fluid) – SAGE (Baksan,Russia) uses – Extraction method: metallic gallium (57 tons) • Pump in He that displaces Ar – Extraction method: • Collect Ar in charcoal traps • Synthesized into GeH 4 • Count Ar using radioactive • Inserted into Xe prop. Counters decay • Detect x-rays and Auger electrons – Systematic errors ~ 7% Sage : 67 ± 8 SNU Gallex: 78 ± 6 SNU (Expect 130 ± 1.1) (Expect 8.6 ± 1.1)
52 Super-K Experiment Η 2 Η 2 Ο Ο Cerenkov Detectors
53 Super-K Results • Super-K has good angular, energy, and time resolution – Sensitivity to seasonal variations – Sensitive to day/night variations – Ability to “see” the sun 0.465 Energy (MeV)
54 Solar Neutrino Experiments Rate measurement Reaction Obs / Theory ν e + 37 Cl → 37 Ar + e − 0.34 ± 0.03 • Homestake (US) ν e + 71 Ga → 71 Ge + e − 0.59 ± 0.06 • SAGE (Russia) ν e + 71 Ga → 71 Ge + e − 0.58 ± 0.05 • Gallex+GNO (Italy) ν x + e − → ν x + e − 0.46 ± 0.02 • Super-K (Japan) H 2 O ν e + d → p + p + e − 0.35 ± 0.03 • SNO (Canada) D 2 O
55 Sudbury Neutrino Observatory (SNO) • Advantages of Heavy vs Light Water – ν e + d → p + p + e − (D 2 O) – ν e + e − → ν e + e − (H 2 O or D 2 O) – Cross section ∝ (E cm ) 2 = s • s = 2 m target E ν ⇒ s N / s e- = M p /M e ≈ 2000 – But x5 more electrons in H 2 O than n’s SNO (1kton) 8.1 CC events/day 1000 tons D 2 O SuperK (22ktons) 25 events/day (12m Inner Vessel)
56 SNO Results ES = Elastic Scattering • ν ν e = NC + CC • ν ν µ µ or ν ν τ τ = NC only
57 SNO Physics ⇒ Solar Oscillations ⇒ not totally to sterile neutrinos
58 Solar Neutrino Experiments Rate measurement Reaction Obs / Theory ν e + 37 Cl → 37 Ar + e − 0.34 ± 0.03 • Homestake (US) ν e + 71 Ga → 71 Ge + e − 0.59 ± 0.06 • SAGE (Russia) ν e + 71 Ga → 71 Ge + e − 0.58 ± 0.05 • Gallex+GNO (Italy) Limits ν x + e − → ν x + e − 0.46 ± 0.02 • Super-K (Japan) H 2 O osc to ν s ν e + d → p + p + e − 0.35 ± 0.03 <50% @ • SNO (Canada) D 2 O 90%CL
59 Solar Neutrino Results “Interpretations”
60 Oscillation Interpretations • “Just-So” or Vacuum Oscillations • MSW or Matter Effects in Sun (Mikheyev-Smirnov-Wolfenstein) – Mass eigenstates propagate – But these are mixtures of flavor eigenstates • They have different interactions with e’s in sun – Try to fit the results into the the oscillation formula P osc = sin 2 2 θ θ sin 2 (1.27 ∆ ∆ m 2 L/E) for L ≈ 10 11 (m) – If N = electron density then Resonance Condition: sin 2 2 θ eff = 1 if W 2 = sin 2 2 θ
61 Allowed Regions Fogli et al. hep-ph/0106247; Bahcall et al. hep-ph/0106258
62 • Matter effects can also occur in the electrons in the earth – Would cause a day/night Oscillation Interpretations effect in the Super-K data (Preliminary Super-K)
63 Putting It All Together Fogli et al. hep-ph/0106247; Bahcall et al. hep-ph/0106258
64 What’s Coming Up in Solar ν ν ’s • Kamland • Borexino Reactor neutrino exp. In solar region Go after 7 Be ν ν ’s – 1000 m 3 liquid scintillator – 300 ton liquid scintillator – 2000 17-inch phototubes – 2200 8-inch phototubes – E e > 250 keV ν from reactors (L ~ 170 km) e + + ν + → + Detect e from p e n • Detect ν e + e − → ν e + e − e = ( 1 . 8 ) MeV E – 55 events/day for SSM threshold
65 Kamland and Borexino Sensitivity Borexino Borexino
66 Atmospheric Neutrino Oscillation Exp’s
67 Atmospheric Neutrino Oscillations • Atmospheric Neutrino Flux – From π and µ decay from cosmic-ray hadronic showers in the atmosphere – Flux modeled using: • Measured cosmic-ray fluxes • Accelerator cross section measurements • Include geomagnetic effects • Some disagreements with atmospheric muon measurements (~20% level)
68 Experimental Techniques Atmospheric Neutrinos > 0.1 GeV ⇒ Interactions on protons and ⇒ neutrons in target • Water Cerenkov Detectors n p (Super-K) – Identify various event types by the Cerenkov ring configurations (single-ring e’s or µ ’s multi-ring NC and CC) n p • Sampling Calorimeters and Trackers (Sudan II and MINOS like NuTeV) – Electrons have short showers N N – Muons have penetrating tracks – Multi-particle events
69 Atmospheric Neutrino Studies cos θ Zenith = 1.0 E ν ~ 300 MeV - 2 GeV 15 km Oscillations if ∆ m 2 >10 -2 eV 2 • Flux dependence on azimuth is directly related to distance traveled – Perfect laboratory to search for oscillations 13,000 km Oscillations if ∆ m 2 >few x 10 -5 eV 2 cos θ Zenith = -1.0
70 Oscillation Survival Probability for ν ν µ µ →ν →ν τ τ • cos θ Zenith distributions for various neutrino energies, E ν (Rapid change in behavior for cos θ Z < 0 ) Note: Detector resolution will • ∆ m 2 = 5 ×10 −3 eV 2 integrate over rapid sin 2 2 θ = 1.0 oscillations and average to ½ .
71 Super-K Atmospheric Results ( 1290 days)
72 Super-K Fits to ν ν µ µ → →ν ν τ τ
73 Reactor Experiments Limit Atmospheric ν ν µ µ → → ν ν e Possibilities • CHOOZ, Bugey, and Palo Verde Reactor Experiments – < E ν > ∼ 3 MeV and L ~ 1 km • Dominant ν µ → ν e : – Ruled out by CHOOZ reactor ν experiment – Sub-dominant osc. possible at the sin 2 2 θ < 0.10 level
74 Can atmospheric result be due to ν ν µ µ → → ν ν s oscillations ? • Interactions with matter in earth different for ν µ → ν τ vs. ν µ → ν sterile – ν sterile has no NC interactions with quarks – Mainly near cos θ = -1.0 • Also, differences for: – NC enriched multi-ring events – Upward-going thru- µ events • Exclude – Complete ν µ → ν sterile ruled out at 99% CL – ν µ → ν sterile fraction < 25% at 90% CL
75 Longbaseline Exps at Accelerators
76 Long-Baseline Experiments • Long-baseline experiments can be used to check atmospheric results with a well controlled accelerator produced ν beam • With high statistics and good control of systematics can: – Measure oscillation parameters ∆ m 2 , sin 2 2 θ more accurately – See oscillatory behavior with energy – Measure ν µ →ν e at the atmospheric ∆ m 2 – Directly observe ν τ events from ν µ →ν τ oscillations – Do further checks of possible ν µ →ν sterile • Having a near monitoring detector along with far detector is best • Current and near future experiments: K2K, MINOS, CNGS
77 KEK to SuperK (K2K) Experiment See C. Walters Talk • Low energy , < E ν >=1.4 GeV, beam sent from KEK to SuperK (250 km) • Several front detectors at 100m and beam monitors
78 K2K Results (Events)
79 K2K Results (Energy Spectrum) Monte Carlo Prediction for various oscillation scenarios Conclude: Event deficit consistent with oscillations but no oscillatory behavior and information on ∆ ∆ m 2
80 NuMI / MINOS Experiment “ Neutrinos at the Main Injector” Two Detector Neutrino Oscillation Experiment Far Detector: 5400 tons Det. 2 Det. 1 Near Detector: 980 tons
81 MINOS Far Detector
82 MINOS Energy Spectra 10 kt-yr Exposure (~700 CC events/yr) Solid lines - energy spectrum without oscillations Dashed histogram - spectrum in presence of oscillations Can measure: ∆ m 2 to ~10 - 20% sin 2 2 θ to ~ 0.10
83 MINOS ∆ ∆ m 2 Sensitivity 90% 3.5 σ CL
84 MINOS Oscillation Mode Sensitivity ( Discriminate ν ν µ µ →ν →ν τ τ vs. ν ν µ µ →ν →ν sterile ) • Use CC/NC Ratio to distinguish between oscillations to ν τ or ν sterile 4 σ Separation • For ν µ →ν τ , CC Region production of τ ’s will look like NC ~80% of the time CC/NC → down • For ν µ →ν sterile , both CC and NC will be suppressed. CC/NC stays ~ constant
85 Possible New Potential for NuMI Program Off-Axis “Minos” Detector • Goal: Measure ν µ → ν e at the atmospheric ∆ m 2 ⇒ sin 2 2 θ 13 (Current CHOOZ Limit: sin 2 2 θ 13 ≈0.10 @ 90% CL) – Backgrounds and identification are main problems • Intrinsic ν e ’s in the beam, NC/CC π 0 production • Electron decays of τ ’s from ν µ →ν τ – Key is to use energy constraint beam • Need a sharp energy distribution • Need little high energy tail – Answer is the normal NuMI beam to Minos but • Put your detector offaxis (at ~15 mr) Where does this put the detector? … Maybe Canada!
86
87 How/Why Does an Offaxis Beam Work? • Neutrinos produced from π -decay • Energy cuts much more effective in reducing NC background with – Kinematics give mono- offaxis beam energetic beam at 15 mrad – NC tail from high E ν on-axis events On-Axis Off-Axis
88 Estimates of Sensitivity • Study of capabilities of various • Need to optimize: detector technologies – Baseline – Detector • Mass and Technology (Signal and Bckgnd efficiency) • Electron appearance requirements for detector – Good segmentation • Identify outgoing electrons – Good energy resolution • Separate ν e and NC events Conclusion: – Particle identification – With reasonable detector can • At the 1% or better level reach sin 2 2 θ 13 ≈ 0.02 at 3σ ( about x10 better than CHOOZ)
89 CERN to Gran Sasso ν ν Osc. Program (CNGS) • CERN has approved a program for a neutrino beam from CERN to Gran Sasso – Beam similar to Minos with ν τ rate factor of two lower – Unlikely that a near detector hall would be built • Emphasis on appearance experiments with ν τ and ν e identification – Opera Experiment : Emulsion detector – ICARUS Experiment : Liquid argon
90 OPERA Hybrid Emulsion Experiment (Oscillation Project with Emulsion-tRacking Apparatus) • Emulsion bricks interspersed with electronics trackers • See τ decay in emulsion τ • Goal: 1.5 kton hybrid target – ~ 3,600 ν µ CC events/yr × eff. – ~ 45 ν τ events/yr × efficiency • efficiency: ~10 % ? ICARUS Experiment • Use liquid argon calorimeter – Liq Ar: 4 @ 1250 = 5000 tons • Detect and identify all neutrino species
91 OPERA Sensitivity • Very low background – Can confirm oscillations to ν τ with a few events • For five year exposure ( 2.25×10 20 pot) – ~ 25 ν µ → ν τ osc. events @ ∆ m 2 =3.5 × 10 -3 eV 2 – ~ 0.5 events background
92 Oscillation Exps in the LSND Region
93 LSND, Karmen, and MiniBooNE ν µ ν µ → →ν ν e at high ∆ ∆ m 2 • LSND (LANCE) sees positive indication of oscillations – Final results • Karmen II (RAL, England) experiment sees no excess and limits the allowed LSND region – Almost final results • MiniBooNE (Fermilab) will make a definitive search for oscillations in this region
The LSND Experiment (1993-98) 94 See G. Mills Talk + → + π µ ν µ e + ν e ν µ ν Oscillations? e + ν → p e n e detect prompt e track, 20< E e <60 MeV neutron capture: Baseline 30 m np → γ Neutrino Energy d 20-55 MeV, 2.2 MeV Nearly 49,000 Coulombs of protons on target 1280 phototubes 167 tons Liquid scintillator
95 LSND Final Result • Corresponding osc. probability: LSND sees excess above backgrounds (0.264 ± 0.067 ± 0.045)% – Excess: 87.9 ± 22.4 ± 6.0 evts. • 3.3 σ evidence for oscillation. High ∆ m 2 Oscillations
96 Karmen II (1997-2001) • Pulsed 800 MeV pot (ISIS) – DAR beam (90º to target) • Almost final results – 17.6 m baseline – 11 events observed – 12.3 ± 0.6 events expected • 56 tons of liquid scintillator – 512 modules – Gd-doped (8 MeV γ ) • × 10 less statistics than LSND (less intensity & size)
97 MiniBooNE Experiment Need definitive study of ν ν µ µ → →ν ν e at high ∆ ∆ m 2 … MiniBooNE Booster Use protons from the 8 GeV booster ⇒ Neutrino Beam <Ε ν >∼ 1 GeV Main 12m sphere filled with Injector mineral oil and 1500 PMTs located 500m from source
98 MiniBooNE Neutrino Flux and Expected Events The L/E is designed to be a good Expectation for electron-like events/2yrs match to LSND at ~1 m/MeV. • Intrinsic ν e background: 1,000 events • µ mis-ID background: 500 events • π 0 mis-ID background: 500 events • LSND-based ν ν µ µ → →ν ν e : 1,000 events • Backgrounds can be separated from signal – Osc. signal has different energy spectrum than intrinsic ν – Experimental determinations of all Expected intrinsic ν e flux is small backgrounds. compared to the ν µ flux.
99 MiniBooNE is about to Start • Everything on schedule for June, 2002 Start – Detector half filled with oil – Horn tested (10 7 pulses) – Proton extraction ready Magnet Focusing Horn PMT installation completed in October.
MiniBooNE Sensitivity to LSND 100 With two years of running MiniBooNE should be able to completely include or exclude the entire LSND signal region.
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