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New Results from MINOS

New Results from MINOS. Patricia Vahle, for the MINOS collaboration College of William and Mary. The MINOS Experiment. Long base-line neutrino oscillation experiment Neutrinos from NuMI beam line L/E ~ 500 km/ GeV atmospheric Δm 2. Far Detector 735 km from Source.

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New Results from MINOS

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  1. New Results from MINOS Patricia Vahle, for the MINOS collaboration College of William and Mary

  2. The MINOS Experiment • Long base-line neutrino oscillation experiment • Neutrinos from NuMI beam line • L/E ~ 500 km/GeV • atmospheric Δm2 Far Detector 735 km from Source • Two detectors mitigate • systematic effects • beam flux mis- • modeling • neutrino interaction • uncertainties Near Detector 1 km from Source

  3. MINOS Physics Goals • Measure νμ disappearance as a function of energy • Δm232and sin2(2θ23) • test oscillations vs. decay/decoherence Δm232 Δm221

  4. MINOS Physics Goals • Measure νμ disappearance as a function of energy • Δm232and sin2(2θ23) • test oscillations vs. decay/decoherence • Mixing to sterile neutrinos? Δm232 Δm221 Δm214

  5. MINOS Physics Goals • Measure νμ disappearance as a function of energy • Δm232and sin2(2θ23) • test oscillations vs. decay/decoherence • Mixing to sterile neutrinos? • Study νμ→νemixing • measure θ13 Δm232 Δm221

  6. MINOS Physics Goals • Measure νμ disappearance as a function of energy • Δm232and sin2(2θ23) • look for differences between neutrino and anti-neutrinos Δm232 Δm221

  7. MINOS Physics Goals • Measure νμ disappearance as a function of energy • Δm232and sin2(2θ23) • look for differences between neutrino and anti-neutrinos • More MINOS analyses: • atmospheric neutrinos (See A. Blake poster) • cross section measurements • Lorentz invariance tests • cosmic rays Δm232 Δm221

  8. The Detectors Magnetized, tracking calorimeters 5.4 ktFar Detector— look for changes in the beam relative to the Near Detector 1 ktNear Detector— measure beam before oscillations 735 km from source 1 km from source

  9. Detector Technology 2.54 cm Fe • Tracking sampling calorimeters • steel absorber 2.54 cm thick (1.4 X0) • scintillator strips 4.1 cm wide (1.1 Moliere radii) • 1 GeVmuons penetrate 28 layers • Magnetized • muon energy from range/curvature • distinguish μ+ fromμ- • Functionally equivalent • same segmentation • same materials • same mean B field (1.3 T) Extruded PS scint. 4.1 x 1 cm2 U V planes +/- 450 WLS fiber Clear Fiber cables Multi-anode PMT

  10. Making a neutrino beam

  11. Making a neutrino beam • Production • bombard graphite target with 120 GeVp+ from Main Injector • 2 interaction lengths • 310 kW typical power • produce hadrons, mostly π and K

  12. Making a neutrino beam • Focusing • hadrons focused by 2 magnetic focusing horns • sign selected hadrons • forward current, (+) for standard neutrino beam runs • reverse current, (–) for anti-neutrino beam

  13. Making a neutrino beam • Decay • 2 m diameter decay pipe • result: wide band beam, peak determined by target/horn separation • secondary beam monitored (see L. Loiacono poster)

  14. Beam Performance Total Protons (x1020) Protons per week (x1018) Date

  15. Beam Performance 1021 POT! Total Protons (x1020) Protons per week (x1018) Date

  16. Beam Performance Previously published analyses Total Protons (x1020) Protons per week (x1018) Date

  17. Beam Performance Data set for today’s report Total Protons (x1020) Protons per week (x1018) Anti- neutrino running Date High energy running

  18. Events in MINOS • νμCharged Current events: • long μtrack, with hadronic activity at vertex • neutrino energy from sum of muon energy (range or curvature) and shower energy Simulated Events CC νe Event e- Transverse position (m) Depth (m) CC νμ Event NC Event ν μ-

  19. Events in MINOS • Neutral Current events: • short, diffuse shower event • shower energy from calorimetric response Simulated Events CC νe Event e- Transverse position (m) Depth (m) CC νμ Event NC Event ν μ-

  20. Events in MINOS • νeCharged Current events: • compact shower event with an EM core • neutrino energy from calorimetric response Simulated Events CC νe Event e- Transverse position (m) Depth (m) CC νμ Event NC Event ν μ-

  21. π+ Target p FD Decay Pipe ND Near to Far • Neutrino energy depends on angle wrt original pion direction and parent energy • higher energy pions decay further along decay pipe • angular distributions different between Near and Far Far spectrum without oscillations is similar, but not identical to the Near spectrum!

  22. Extrapolation Muon-neutrino and anti-neutrino analyses: beam matrix for FD prediction of track events NC and electron-neutrino analyses: Far to Near spectrum ratio for FD prediction of shower events

  23. νμ Disappearance Monte Carlo (Input parameters: sin22θ = 1.0, Δm2 = 3.35x10-3 eV2 ) νμ spectrum spectrum ratio Unoscillated Characteristic Shape Oscillated Monte Carlo

  24. νμ Disappearance Monte Carlo (Input parameters: sin22θ = 1.0, Δm2 = 3.35x10-3 eV2 ) νμ spectrum spectrum ratio Unoscillated sin2(2θ) Oscillated Monte Carlo

  25. νμ Disappearance Monte Carlo (Input parameters: sin22θ = 1.0, Δm2 = 3.35x10-3 eV2 ) νμ spectrum spectrum ratio Unoscillated Δm2 Oscillated Monte Carlo

  26. CC events in the Near Detector Show ND energy spectrum • Majority of data from low energy beam • High energy beam improves statistics in energy range above oscillation dip • Additionalexposure in other configurations for commissioning and systematics studies

  27. Analysis Improvements • Since PRL 101:131802, 2008 • Additional data • 3.4x1020 → 7.2x1020 POT • Analysis improvements • updated reconstruction and simulation • new selection with increased efficiency • no charge sign cut • improved shower energy resolution • separate fits in bins of energy resolution • smaller systematic uncertainties See C. Backhouse, J. Mitchell, and J. Ratchford, M. Strait posters

  28. Far Detector Energy Spectrum

  29. Far Detector Energy Spectrum • Oscillations fit the data well, 66% of experiments have worse χ2 • Pure decoherence† disfavored: > 8σ • Pure decay‡ disfavored: > 6σ • (7.8σif NC events included) †G.L. Fogliet al., PRD 67:093006 (2003) ‡V. Barger et al.,PRL 82:2640 (1999)

  30. Contours • Contour includes effects of dominant systematic uncertainties • normalization • NC background • shower energy • track energy

  31. Contours • Contour includes effects of dominant systematic uncertainties • normalization • NC background • shower energy • track energy † †Super-Kamiokande Collaboration (preliminary)

  32. Neutral Current Near Event Rates • Neutral Current event rate should not change in standard 3 flavor oscillations • A deficit in the Far event rate could indicate mixing to sterile neutrinos • νeCC events would be included in NC sample, results depend on the possibility of νe appearance See P. Rodrigues and A. Sousa poster

  33. Neutral Currents in the Far Detector • Expect: 757 events • Observe: 802 events • No deficit of NC events no (with) νeappearance

  34. νe Appearance • A few percent of the missing νμ could change into νedepending on value ofθ13 • Appearance probability additionally depends onδCPand mass hierarchy Normal Hierarchy Inverted Hierarchy ? ⇔

  35. Looking for electron-neutrinos • 11 shape variables in a Neural Net (ANN) • characterize longitudinal and transverse energy deposition • Apply selection to ND data to predict background level in FD • NC, CC, beam νeeach extrapolates differently • take advantage of NuMI flexibility to separate background components νe selected region BG Region See R. Toner, L. Whitehead, G. Pawloski poster • Data • MC

  36. νe Appearance Results Based on ND data, expect: 49.1±7.0(stat.)±2.7(syst.)

  37. νe Appearance Results Based on ND data, expect: 49.1±7.0(stat.)±2.7(syst.) Observe: 54 events in the FD, a 0.7σ excess

  38. νe Appearance Results arXiv:1006.0996v1 [hep-ex]

  39. Making an anti-neutrino beam Neutrino mode Horns focus π+,K+ Events νμ: 91.7% νμ: 7.0% νe+νe: 1.3% Focusing Horns Target 2 m π- νμ 120 GeVp’s from MI νμ π+ 30 m 15 m 675 m

  40. Making an anti-neutrino beam Neutrino mode Horns focus π+,K+ Anti-neutrino Mode Horns focus π-,K-enhancing theνμflux Events Events νμ: 91.7% νμ: 7.0% νe+νe: 1.3% νμ: 39.9% νμ: 58.1% νe+νe: 2.0% Focusing Horns Target 2 m π+ νμ 120 GeVp’s from MI νμ π- 30 m 15 m 675 m

  41. ND Anti-neutrino Data • Focus and select positive muons • purity 94.3% after charge sign cut • purity 98% < 6GeV • Analysis proceeds as (2008) neutrino analysis • Data/MC agreement comparable to neutrino running • different average kinematic distributions • more forward muons See J. Evans, N. Devenish poster Also A. Blake poster on atmospheric neutrinos

  42. ND Data • Data/MC agreement comparable to neutrino running

  43. FD Data • No oscillation Prediction: 155 • Observe: 97 • No oscillations disfavored at 6.3σ

  44. FD Data • No oscillation Prediction: 155 • Observe: 97 • No oscillations disfavored at 6.3σ

  45. FD Data

  46. Comparisons to Neutrinos

  47. Comparisons to Neutrinos

  48. Summary • With 7x1020 POT of neutrino beam, MINOS finds • muon-neutrinos disappear • NC event rate is not diminished • electron-neutrino appearance is limited • With 1.71x1020 POT of anti-neutrino beam • muon anti-neutrinos also disappear with • we look forward to more anti-neutrino beam!

  49. Backup Slides

  50. HE ME LE 10 Neutrino Spectrum Use flexibility of beam line to constrain hadron production, reduce uncertainties due to neutrino flux

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