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MiniBooNE and n Oscillations

D m 2. Sin 2 2 q m e. MiniBooNE and n Oscillations. Magnetic Focussing Horn. Neutrino Event Display. Inside View of Detector. Sensitivity to Oscillations. Outline. A short course in the physics of n oscillations What are neutrinos? Oscillations? n oscillation landscape

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MiniBooNE and n Oscillations

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  1. Dm2 Sin2 2qme MiniBooNE and n Oscillations Magnetic Focussing Horn Neutrino Event Display Inside View of Detector Sensitivity to Oscillations

  2. Outline • A short course in the physics of n oscillations • What are neutrinos? Oscillations? • n oscillation landscape • Experimental results Neutrinos are surprising! • MiniBooNE • An experiment in progress • Experiment description • Neutrino data • Oscillation sensitivity • Can we improve statistics?

  3. Neutrinos 101 • Particle physics is described by: • The Standard Model • Matter: Fermions • Quarks and leptons • Doublets • Bound vs. free • Three generations of each • Force Carriers: Bosons • EM: Photon • Strong force: Gluon • Weak force: W,Z • Neutrinos are the lightest leptons • Massless in the standard model • Interact only via weak force

  4. nm nm Z0 NC nm m- W+ CC Neutrinos 102 • Neutrinos are created as weak-flavor eigenstates • e, m, t • Neutral Current Interactions • Z exchange • Neutrino in, neutrino out • Charged Current Interactions • W exchange • Mix within the doublets • Neutrino in, negative lepton out • Antineutrino in, positive lepton out • That's how we know a neutrino's flavor Feynman Diagrams

  5. nm nm Z0 Neutrinos 111 • The weak force is weak • s(ne) ~ 10-40cm2 • s(nN) ~ 10-36cm2 • For comparison: s(pp) ~ 10-25cm2 • 11-15 orders of magnitude difference! • Reason: W,Z are heavy: • 80, 91 GeV/c2 • As an example: • A ~10 MeV neutrino from the sun has a mean free path of several light years in lead • Hundreds of billions of neutrinos from the sun pass through every square inch of you each second

  6. Neutrinos 112 • Detecting neutrinos is very difficult! • Needed: • Intense sources • The sun • Cosmic rays • Nuclear reactors • Particle accelerators • Large detectors • Many targets • Patience Neutrino Source Neutrino Detector

  7. Neutrinos 121: • Neutrinos are seen by collider expts only as missing energy • Careful analysis of missing energy in Z0 decays reveals an interesting result: • Only three generations of light neutrinos! Invisible width of the Z0 measured by LEP expts

  8. Neutrinos 122: Mass? • In the standard model, neutrinos are massless • But it's difficult to confirm this • Direct mass searches yield limits • ne: tritium decay: m < 3 eV • nm: pion decay: m < 0.2 MeV • nt: tau decay: m < 18 MeV • Compare to hadron masses: • pions ~ 140 Mev • kaons ~ 500 MeV • protons ~ 1 GeV • neutrons ~ 1 GeV • Indirect mass searches use quantum mechanics ... and indicate non-zero neutrino mass!

  9. nm n2 q ne q n1 n2 ne nm cosqsinq -sinqcosq n1 = Neutrinos 201: Oscillations • IF: • Neutrinos have (different) masses Weak states are a mixture of the mass states • THEN: • A neutrino created as one specific flavor may later be detected as a neutrino of a different flavor • Why? Neutrinos propagate as mass eigenstates nm ne p- e- X m- n detector n source

  10. n 202: Oscillation Probability • Oscillation probability between two flavor states depends on: • Two fundamental parameters • Dm2=m12-m22 - "period" • mass difference between states • sin22q - "amplitude" • mixing between flavors • Oscillations don't measure the absolute mass scale • Two experimental parameters • L: distance from source to detector • E: neutrino energy • Two possible experiments in this example: • nmdisappearance • P(nmnm) • neappearance • P(nmne)

  11. n 211: Detecting Oscillations • Consider nmne oscillations • Disappearance • Detect fewer nmevents than expected • Should have a characteristic energy signature – oscillation probability depends on E! • Appearance • Detect more ne events than expected • Oscillation depends on E: the events that disappeared in the blue plot are related to those appearing in the red plot • Goal: Determine Dm2, sin22q Disappearance N nm Expected Detected nmEnergy (MeV) N ne Appearance Detected Expected neEnergy (MeV)

  12. n 212: Presenting Oscillations • L and E determine the Dm2 sensitivity region • sin22q gives amplitude of oscillations • No signal: exclusion regions • Above and to the right excluded • Below and to the left cannot be ruled out • Signal: allowed regions • Shown by shaded areas specifying Dm2 and sin2 2q • Size of allowed region determined by experimental uncertainties

  13. Ue1 Ue2 Ue3 Um1 Um2 Um3 Ut1 Ut2 Ut3 ne nm nt n1 n2 n3 = u d,s W+ CC ~10.20.006 0.2~10.04 0.0050.04~1 CKM: small mixing angles n868: 3 generations • There are actually three generations of neutrinos that can oscillate into each other • MNSP matrix describes neutrino mixing • Analogous to CKM matrix for quarks • Except for the values of the matrix elements! 0.80.5? 0.40.60.7 0.40.6 0.7 MNS: large mixing angles

  14. Current Oscillation Picture • Three different oscillation signals observed (so far...) • Allowed regions indicated • Note: The true answers are actually single points! • Solar neutrinos: Dm2~10-5eV2 • Atmospheric: Dm2~10-3eV2 • LSND: Dm2~1eV2 • Yet to be confirmed • Only mass differences, not absolute scale Reactor Limit LSND nmne

  15. Neutrinos from the Sun • The sun is fueled by fusion reactions • 41H + 2e-4He + 2ne + 6g • More reaction chains follow... • Neutrinos are produced copiously • Note all produce ne, below ~10MeV • But when expts were built to search for them, they found too few! • Many techniques • All looking for CC reactions (ne) • Are the solar models wrong? Are the experiments wrong?

  16. hep-ex/0406035 Solar nResults • SNO had the ability to see neutral current (nn) as well as charged current (nl) reactions • They can see all flavors--- • Oscillations! • Solution: • Mixing angle q=32° • Dm2 = 8.210-5eV2 • KamLAND: reactor antineutrinos • Confirm solar result • Spectral distortion! • n vs. n • The experiments were right! KamLAND En KamLAND Results

  17. Atmospheric Neutrinos • Neutrinos produced by cosmic ray induced air showers • nm and nm, ne and ne • High energy cosmic rays are isotropic • Same rates on this side of the Earth as the other • Super-K measures a difference in flux as a function of zenith angle • nm,nm disappearance

  18. Atmospheric n Oscillations • L/E characteristic of oscillations • Best fit to data: • Mixing angle ~45° (Maximal!) • Quite unexpected! • Dm2 = 2.410-3eV2 • Mix of n and n • This result is confirmed by other experiments: Soudan, MACRO • K2K send n from KEK accelerator to Super-K • Compare fluxes in near detectors (200m) to fluxes at Super-K (250km) • See evidence for nm disappearance • Similar oscillation parameters hep-ex/0404034 http://neutrino.kek.jp/news/2004.06.10/index-e.html

  19. Atmospheric n Oscillations • L/E characteristic of oscillations • Best fit to data: • Mixing angle ~45° (Maximal!) • Quite unexpected! • Dm2 = 2.410-3eV2 • Mix of n and n • This result is confirmed by other experiments: Soudan, MACRO • K2K send n from KEK accelerator to Super-K • Compare fluxes in near detectors (200m) to fluxes at Super-K (250km) • See evidence for nm disappearance • Similar oscillation parameters hep-ex/0404034

  20. Atmos n in the future • MINOS will be able to measure the atmospheric oscillation parameters much better • Can run inn and n mode • Taking data right now! MINOS sensitivity

  21. Accelerator Neutrinos • Many null result accelerator neutrino experiments • Positive result: LSND Experiment at LANL • Beam:m+decay at rest • L/E ~ 1m/MeV • L ~ 30m • 20< En< 55 MeV • nmne ? • Appearance search • Clean detection signal • Inverse b decay p+m+nm m+ e+nmne

  22. Inside LSND Remember these PMTs! (photo- multiplier tubes)

  23. KARMEN2 and LSND collaborators performed joint analysis on both data sets - allowed regions remain! Dm2 ~ 1eV2, q ~ 2° The LSND signal 3.8s excess! • nmne oscillation probability: 0.264±0.067±0.045% hep-ex/0203023 hep-ex/0104049

  24. Dm223 Dm213 Dm212 Current Oscillation Summary • Problem: That's too many Dm2 regions! • Should find: Dm212 + Dm223 = Dm213 LSND Dm2 ~ 1eV2 q ~ 2° Atmospheric oscillations Dm2 ~ 10-3eV2 q ~ 45° Solar oscillations Dm2 ~ 10-5 eV2 q ~ 32° 10-5 + 10-3 1

  25. The 3Dm2 Problem • LSND signal not oscillations? • Anomalous muon decay: m+e+ nenm • New TWIST result rules out • hep-ex/0409063, hep-ex/0410045 • If it is oscillations, it indicates that our model is incomplete • Sterile Neutrinos • nmnsand then nsne • LEP results require these extra ns have no weak coupling • LSND needs to be confirmed experimentally! u NEW physics beyond the standard model

  26. Resolving LSND: MiniBooNE • Want sensitivity to the same oscillation parameters as LSND • Different systematic errors • Choose similar L/E • Higher E • Longer L • First look for nmne oscillations • Experiment description • Neutrino data • Analysis progress • Oscillation sensitivity

  27. MiniBooNE Collaboration Y. Liu, I. Stancu Alabama S. Koutsoliotas Bucknell R.A. Johnson, J.L. RaafCincinnati T. Hart, R. Nelson, M. Wilking, E.D. ZimmermanColorado A. Aguilar-Arevalo, L.Bugel, J.M. Conrad, J. Link, J. Monroe, D. Schmitz, M.H. Shaevitz, M. Sorel, G.P. Zeller Columbia D. Smith Embry Riddle L.Bartoszek, C. Bhat, S J. Brice, B.C. Brown, D.A. Finley, R. Ford, F.G.Garcia, P. Kasper, T. Kobilarcik, I. Kourbanis, A. Malensek, W. Marsh, P. Martin, F. Mills, C. Moore, P. Nienaber, E. Prebys, A.D. Russell, P. Spentzouris, R. Stefanski, T. Williams Fermilab D. C. Cox, T. Katori, H.-O. Meyer, C. Polly, R. Tayloe Indiana G.T. Garvey, A. Green, C. Green, W.C. Louis G.McGregor, S.McKenney, G.B. Mills, H. Ray, V.Sandberg, B. Sapp, R. Schirato, R.G.VandeWater, D.H. White Los Alamos R. Imlay, W. Metcalf, S.A. Ouedraogo, M. Sung, M.O. WasckoLouisiana State University J. Cao, Y. Liu, B.P. Roe, H. Yang Michigan A.O. Bazarko, P.D. Meyers, R.B. Patterson, F.C. Shoemaker, H.A.Tanaka Princeton P. Nienaber Saint Mary's of Minnesota E.A. Hawker Western Illinois A. Curioni, B.T. Fleming Yale

  28. MiniBooNE Overview • 8 GeV protons from Fermilab Booster • Beryllium target • Magnetic horn to focus mesons • Over 96M pulses - a world record! • Reversible polarity - n mode • 50 m decay region • >99% pure nm,nm beam • ~500 m dirt • nmne? • 800 ton mineral oil detector • 1520 PMTs (1280+240 veto)

  29. p+ p beryllium Neutrino Flux nm m+ • Use external meson production data to predict rates • Accelerator neutrino jargon: POT = proton on target • 99.5% are muon neutrinos • nm and nm p+/K+ m+nm p-/K- m- nm K+/K0Lpene m+ e+ ne nm

  30. MiniBooNE Detector • 800 tons of pure mineral oil • 6m radius steel sphere • ~2m earth overburden • 1520 8" PMTs • 1280 in main tank (sphere) • 240 in veto region (shell) • LSND PMTs/New PMTs • DAQ records t,Q • “Hits”

  31. nm m- nm nm W+ Z0 n p p p nm nm Z0 p0 p,n p,n nm m- W+ p+ n n Neutrinos in oil A neutrino can do many things in mineral oil... About 75% CC, 25 % NC

  32. nm nm Z0 p p Neutrinos in oil • A neutrino can do many things in mineral oil... • It can bounce off a nucleus and: • Eject a proton • NC elastic events ~ 16%

  33. nm m- W+ n p Neutrinos in oil • A neutrino can do many things in mineral oil... • It can bounce off a nucleus and: • Change into its charged partner • Eject a proton • CC quasi elastic events ~ 39%

  34. nm nm Z0 p0 n n Neutrinos in oil • A neutrino can do many things in mineral oil... • It can bounce off a nucleus and: • Eject an excited nuleon state • Or it can tickle a nucleus and emit a pion • NC single pion events ~ 7%

  35. nm m- W+ p+ p p Neutrinos in oil • A neutrino can do many things in mineral oil... • It can bounce off a nucleus and: • Change into its charged partner • Eject an excited nucleon • CC single pion events ~ 25%

  36. Wavefront qC Particle track light m Enlightening Mineral Oil • Charged particles passing through mineral oil produce visible light in two ways • Cherenkov radiation • Light emitted by oil if particle v > c/n • Similar to a sonic boom • Scintillation • Excited/ionized molecules emit light when electrons drop to lower E levels Molecular energy levels of oil

  37. Optics of Mineral Oil • Cherenkov light • proportional to b • Scintillation • dE/dx • time delay • Scattering (Rayleigh) • prompt • 1+cos2q • l4 • Fluorescence • isotropic • time delay • spectrum • Absorption • Michel electrons • Cosmic muons • Laser: diffuse light • Laser: pencil beam • Scintillation (IUCF) w/p+ • Scintillation (FNAL) w/m • repeated w/p+ (IUCF) • Goniometry (Princeton) • Fluorescence spectroscopy (FNAL) • Time resolved spectroscopy (JHU) • Attenuation (FNAL) • multiple devices Creation In Situ Ex Situ Propagation Work nearing completion...

  38. MiniBooNE Detector Neutrino interactions create energetic charged particle emission PMT PMTs collect photons, record t,Q Reconstruct tracks by fitting time and angular distributions

  39. Particle Images in MiniBooNE • Muons • Sharp, clear rings • Long, straight tracks • Electrons • Scattered rings • Multiple scattering • Radiative processes • Neutral Pions • Double rings • Decays to two photons • Photons pair produce

  40. Particle Images in MiniBooNE • Muons • Sharp, clear rings • Long, straight tracks • Electrons • Scattered rings • Multiple scattering • Radiative processes • Neutral Pions • Double rings • Decays to two photons • Photons pair produce

  41. Particle Images in MiniBooNE • Muons • Sharp, clear rings • Long, straight tracks • Electrons • Scattered rings • Multiple scattering • Radiative processes • Neutral Pions • Double rings • Decays to two photons • Photons pair produce

  42. Particle Images in MiniBooNE • Muons • Sharp, clear rings • Long, straight tracks • Electrons • Scattered rings • Multiple scattering • Radiative processes • Neutral Pions • Double rings • Decays to two photons • Photons pair produce

  43. Michel electrons (absolute calibration) p0 photon energies Tracker & Cubes Through-going muons energy range of oscillation signal 300 700 900 100 500 1100 MeV Detector Calibration • Why we think we understand the detector ... • PMTs calibrated with laser system • Calibration data samples span oscillation signal energy range • Electron data samples • Michel electrons • p0 photons • Cosmic Muons • Stopping, through-going • Very important: most neutrino events have muons

  44. PMT Calibration Laser light distributed to 4 flasks throughout the detector Known light source position, known light emission time

  45. Cosmic Muon Calibration

  46. Muon Energy Calibration Visible energy: electron equivalent energy

  47. Looking at Tank Data Noise Hits Stopping Through-going Stopping Muons Through-going Muons

  48. Looking at Tank Data Noise Hits Stopping Muon Cut: Veto Hits<6 Through-going Stopping Muons Through-going Muons

  49. Looking at Tank Data Putting it all together... Radioactive Decays, Instrumental Effects Stopping Michel Electrons Through-going Cosmic Muons

  50. Looking at Tank Data Putting it all together... Radioactive Decays, Instrumental Effects Stopping Michel Electrons Michel Cut: Tank Hits>200 Through-going Cosmic Muons

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