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Hugh Gallagher Tufts University June 15, 2004 Neutrino 2004 College de France

Other Atmospheric Neutrino Experiments (past) – present – and future. Hugh Gallagher Tufts University June 15, 2004 Neutrino 2004 College de France. Introduction.

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Hugh Gallagher Tufts University June 15, 2004 Neutrino 2004 College de France

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  1. Other Atmospheric Neutrino Experiments (past) – present – and future Hugh Gallagher Tufts University June 15, 2004 Neutrino 2004 College de France

  2. Introduction • In less than two decades, atmospheric neutrinos have gone from being “anomalous” to being one of our main tools for exploration of the lepton sector. • 1980s – 1990s: Skepticism was rampant! • “Neutrino experiments are hard!” • “Cosmic ray experiments are hard!” • “Oscillation experiments are hard!” Since 1998 the experimental evidence from SuperK, MACRO and Soudan 2 for atmospheric neutrino oscillations has been overwhelming. Now that neutrino oscillations are established, is there still a role for atmospheric neutrinos to play in the experimental study of neutrino oscillations?

  3. Experimental Goals - Present • One set of experimental questions around the goal of confirming or refuting the standard picture of neutrino oscillations. • Mixing between 3 active flavors of neutrinos through neutrino oscillations. • No sterile mixing. • No CPT violation. • Majorana masses, small via see-saw mechanism. • Experimental goals: • Confirmation with multiple independent measurements • Observing “oscillations” • Confirming nm nt through nt appearance • Ruling out mixing to sterile neutrinos • Ruling out various alternative hypotheses: decoherence, neutrino decay, CPT violation in the neutrino sector, violation of Lorentz invariance… NC detection np  np J. Beacom and S. Palomares-Ruiz PRD 67 (2003)

  4. Current Experiments • These goals, as well as the measurement of Dm223 and sin2(2q23), have been the focus of the current generation of experiments. • Soudan 2 • MACRO • MINOS • SNO Final or “nearly final” analyses Preliminary analyses

  5. The experiment is located 2340 feet underground in the Soudan Underground State Park in Soudan, Minnesota. Soudan 2: The Detector 224 1m x 1m x 2.7 m modules 963 ton total mass 5.90 fiducial kton-yr exposure The detector is surrounded by a ~1700 m2 “veto shield” which provides nearly 4p coverage for the identification of charged particles entering / exiting the detector cavern.

  6. Soudan 2 Partially contained events <En> ~ 6 GeV Contained events <En> ~ 1 GeV nmmultiprong “In-down” muons <En> = 2.4 GeV Up-stopping muons < En> = 6.2 GeV • 3 flavor categories (ne CC, nm CC, NC) • 2 bins of resolution (“hi” and “low” resolution) • Data corrected for neutral backgrounds (6% • in hi-resolution samples) nequasi-elastic

  7. CEV Flavor ratio Soudan 2 Flavor tag True flavor Corrected for mis-id note scale

  8. Soudan 2 Perform a Feldman-Cousins analysis using unbinned maximum likelihood assuming nm nt. Flux normalization and background amounts (7 parameters) allowed to float at each point in (Dm2, sin2(2q)) plane. Nuisance Parameters: e-energy calibration: 7% m-energy calibration: 3% Flux shape (1 + b En): sb = 0.005 GeV-1 e/m ratio: 5% Qel/inelastic s: 20% D ln L sin2(2q) log10(Dm2) M. Sanchez et al, PRD 68, 113004 (2003)

  9. Soudan 2: Results Best Fit: m2 = 0.0052 eV2 sin22 = 0.97 fn(data/mc) = 0.90 MC  Bartol '96 Inclusion of systematic errors and application of Feldman- Cousins technique substantially increases the size of the 90% CL region.

  10. Soudan 2: Upgoing Muons A sample of 45 events entering or exiting the bottom of the detector have been isolated. Work is underway to incorporate them into the oscillation fits.

  11. MACRO • 5.3 kton detector located in the • Gran Sasso laboratory • ~40 CR m 1989 – 2000 • 3 atmos n samples: • Up-throughgoing m • In-up going • In-down + Up-stop Scintillator layers for timing (0.5 ns) Streamer tubes for tracking (1 cm)

  12. MACRO: Up-going m Produced by neutrino interactions in rock below detector. Shape of distribution known to 5% Normalization uncertain to 25% 2 independent analyses yield consistent results. Estimate E and … MC predictions assume oscillations with the MACRO parameters: sin2(2q) = 1 , Dm2 = 0.0023 eV2

  13. MACRO: m Energy Calibration Energy estimated from muon multiple Coulomb scattering. Use drift time in streamers to get sx ~ 3 mm. Calibrated in test beam runs at the CERN PS and SPS. Muon energy estimated using a neural network with 7 inputs, 1 hidden layer and a single output. Global En resolution is 150%.

  14. MACRO 2 low energy samples InUp Identified by topological criteria and time-of-flight. Expect to be fully oscillated. UpStop + InDown Identified by topology: UpStop  fully oscillated InDown  unoscillated Ratio InUp/ (UpStop+InDown) Known to 6% FLUKA MC Prediction (no oscillation) Oscillations with MACRO parameters

  15. MACRO • Monte Carlo studies are carried out to find • the flux normalization – independent statistics • most senstive to oscillations. • Vertical (cosq<-0.7) / Horizontal (cosq>-0.4) • Upward Throughgoing muons • Nlow (En<30 GeV) / Nhigh (En>130 GeV) • InUp / (InDown + UpStop) Ambrosio et al, “Measurements of Atmospheric Muon Neutrino Oscillations”, submitted to EPJ. Ambrosio et al, Phys Lett. B 566, (2003) 35. Ambrosio et al, NIM A 492, (2002) 376.

  16. MACRO 10 bin angular distribution of up-through events Use Feldman-Cousins procedure to account for physical boundary. Best fit: sin2(2q)=1 -- Dm2=0.0023 eV2 (Nlow, Nhigh) (InDown+UpStop, InUp) a parameters normalize the data to the prediction in each category. Absolute rate of the UpThrough events is not used because of the uncertainty in the flux at high energy. Suggest increase in flux normalization of: 25% at high energy 12% at low energy Vertical / horizontal rate sensitive to matter effects: nm ns excluded at 99.8% CL

  17. MINOS: Far Detector 5.4 kton long baseline detector 2 2.7 kton “supermodules” Fermilab beam on schedule for late 2004. • Alternating 8m octagonal planes: • 1 inch thick steel • 192 4.1 cm x 1cm plastic • scintillator strips with embedded • WLS fiber … Scintillator panel veto shield Average 1.5 T magnetic field 8-fold optical multiplexing at face of 16 channel Hammamatsu PMTs. Scintillator layers rotated by + 45o for 3d tracking. 2-ended readout

  18. Time vs Z Time vs Y y x Y vs X z Y vs Z Strip vs Plane MINOS: Cosmic Ray Data First detector capable of separating n from n interactions: Contained events, up-going stopping muons, and neutrino-induced throughgoing muons. Muon energy determined by range or curvature, track direction from timing or curvature.

  19. MINOS: Atmospheric Neutrinos • Thursday’s MINOS talk will include results from 2 preliminary analyses on • data taken September 2002 – April 2004. • throughgoing muons • contained events (1.85 fiducial-kiloton years) Neutrino Sky Map: Muon direction for neutrino-induced throughgoing muons.

  20. Sudbury Neutrino Observatory SNO: Not just a solar neutrino detector… CR m, atmospheric neutrinos, spallation products Large overburden means that one can look for throughgoing muons from neutrino interactions from above the horizon.

  21. SNO • Analysis of 730+ live-days data is proceeding. Data above the horizon is unoscillated, Determines the flux normalization  Powerful lever arm for an oscillation fit. Normalization region

  22. Dm212 ~ 10-5 eV2 nm ne Dm223 ~ 10-3 eV2 nt Experimental Goals - Future The Future: Precision Measurements of the PMNS Matrix! • Experimental Questions include: • Better precision on masses and mixing angles • Is sin2(2q23) different from unity? • Determination of sin(q23 ) • Measurement of non-zero q13 • Measurement of dCP • “Normal” or “Inverted” mass hierarchy • Neutrino mass scales – Dirac or Majorana particles

  23. Ue1 Ue2 Ue3 Um1 Um2 Um3 Ut1 Ut2 Ut3 Atmospheric Neutrinos -- Future • Atmospheric neutrino experiments have sensitivity to all of the above experimental questions except those related directly to the neutrino mass. • Measurements will be of subtle effects, particularly those brought about by matter effects. • Future experiments will require reduction of experimental uncertainties through improved models of atmospheric neutrino fluxes and neutrino interaction cross sections on nuclear targets. • Future detectors will be large (100kton – Mton) and • explore multiple physics topics: • Proton decay • Long-baseline detectors • Atmospheric neutrinos • …

  24. INO: India-based Neutrino Observatory A possible design 1965 – first detection of atmospheric neutrinos in the Kolar Gold Fields Phase I: Atmospheric neutrinos Phase II: Very long baseline n detector • 30-50 kton magnetized steel • 140 layers of 6 cm thick Fe plates • 2.5 cm air gap containing RPCs • ns timing for direction resolution • 1-1.3 T magnetic field for good momentum • resolution and charge determination • 2 sites under consideration • Explore mass hierarchy through n / n

  25. UNO: Undergound Nucleon Decay and Neutrino Observatory Scales up a proven technology: 650 kton (440 fid) water Cerenkov detector. 3 60 x 60 x 60 m3 optically isolated cubes. 10%-40%-10% PMT coverage. Considering various underground sites Henderson mine is leading candidate. Proton decay at 1035 yr sensitivity Atmospheric neutrinos Astrophysical neutrino observatory Supernova relic neutrino detection Long baseline neutrino detector Possible centerpiece for a US National Underground Lab

  26. ≈3 kton of liquid Argon T600 T1200 T1200 Muon spectrometer Future: Icarus • An observation of atmospheric neutrino events with very high quality • An unbiased, mostly systematic free, observation of atmospheric neutrino events • CC/NC separation, clean e/µ discrimination, all final states accessible, excellent e/π0 separation, particle identification (p/K/π) for slow particles • An excellent reconstruction of incoming neutrino properties (energy and direction)

  27. (simulated nm event) Down-going n’s 90 cm p e m 90 cm Up-going n’s nmquasi-elastic interaction En = 370 MeV 1535 events in 5 kt  y (2 years of T3000) Pm = 250 MeV Tp = 90 MeV Future: Icarus

  28. Frejus Laboratory Considering options including: 1 Mton water Cerenkov 100 kt liquid Ar • Site considerations: • good depth (at least 4800 mwe) • good rock quality • horizontal access • good baseline for n superbeam, b beam • centrally located

  29. Hyper-Kamiokande 1 Mton water Cerenkov detector: follow-up to JHF  SuperK with 4 MW superbeam

  30. Thanks to Francesco Ronga, Tony Mann, Mayly Sanchez, Tom Kafka, Mark Thomson, Brian Rebel, Joe Formaggio, Flavio Cavanna, Luigi Mosca, Ed Kearns, Josh Klein, Chang-Kee Jung, M.V.N Murthy, Luciano Moscoso, Francis Halzen and Jerome Damet. Conclusions Good consistency between results from SuperK, Soudan 2, and MACRO. “Non-SuperK” atmospheric neutrinos now in the hands of MINOS and SNO. Future experiments will have sensitivity to more of the PMNS matrix – an independent check of results from future long baseline beams with completely different systematics. 90% CL intervals Soudan 2 MACRO SuperK

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