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Fermilab Neutrino Oscillation Program

Fermilab Neutrino Oscillation Program. Outline Introduction NuMI / Minos MiniBooNE / BooNE Muon Storage Ring n -Factory. M. Shaevitz Tropical Workshop on Particle Physics and Cosmology San Juan, Puerto Rico; May 1-6, 2000. Probing Neutrino Mass.

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Fermilab Neutrino Oscillation Program

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  1. Fermilab Neutrino Oscillation Program Outline Introduction NuMI / Minos MiniBooNE / BooNE Muon Storage Ring n-Factory M. Shaevitz Tropical Workshop on Particle Physics and Cosmology San Juan, Puerto Rico; May 1-6, 2000

  2. Probing Neutrino Mass • Neutrinos are expected to be massive but we know they are very light • Mass of electron neutrino < feweV but mass of electron is 500,000 eV • Hard to directly measure masses below 1 eV in decay experiments • For neutrino masses below 1 eV, need Neutrino Oscillation experiments • Neutrino oscillation experiments look for one type of neutrino to change into another type as the neutrino moves along its path • For a neutrino to oscillate from one type to another, one must have: • Two types of neutrino and at least one must be massiveDm2= m12 - m22> 0 • Neutrinos in nature must be mixtures of these two mass types Lepton number violation or mixing parameterized by sin22q

  3. nmne at the same Dm2 as nmnt CKM-like Mixing Matrix for Leptons Neutrino Oscillation Formalism • Most analyses assume 2-generation mixing • But we have 3-generations: ne , nm, and nt (and maybe even more ….. the sterile neutrino ns’s ) (In this 3-generation model, there are 3 Dm2’s but only two are independent.) • At each Dm2, there can be oscillations between all the neutrino flavors with different mixing angle combinations. For example:(3 sets of 3 equations like these forDm223>>Dm212 )

  4. CP Violation in Neutrino Oscillations • Disappearance measurements cannot see CP violation effect • 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. • All the terms (s12, s13, s23) must not be <<1 or effectively becomes only two component oscillation • For example, if s12 0 then s13 -s23  s12 + s31 + s23 0  To see CP violation must be sensitive to solar neutrino Dm2 10-4 - 10-10 eV2 or have large, LSND-like Dm2 1 eV2

  5. Three Hints of Oscillations Solar n’s Atmospheric n’s Los Alamos Scintillator Neutrino Detector (LSND)

  6. MiniBooNE NuMI/Minos Three Indications of Neutrino Oscillations • Questions: • Are all three indications really neutrino oscillations? • Which flavors are oscillating? • What are the oscillation parameters Dm2, sin22q ? • Fermilab Experiments • MiniBooNE  LSND Region • NuMI/Minos  Atmospheric Region

  7. Solar Neutrino Studies Future Studies: • Super-Kamiodande • Increased statistics • Lower Threshold to 4.5MeV • SNO • CC(9ev/day)/NC(3ev/day) • Flux Indep. or e  s • CC: E spectrum and D/N • Borexino • Good statistics measurement of 7Be ’s (55ev/day) • Seasonal variation if Vac. Osc. • KamLAND (Reactor Exp.) • LMA region (700 events/yr) 0.550.06 0.330.03 0.540.07

  8. Atmospheric Neutrino Oscillation Sensitivity L = 20 km, Oscillations if Dm2 >10-2eV2 SuperK n En ~ 300 MeV - 2 GeV Earth L = 104 km, Oscillations if Dm2 > few x 10-5 eV2 10-5 10-4 10-3 10-2 10-1 Dm2 Multi-GeV Sub-GeV No oscillationsZenith angle dependenceOscillations for all angles R = 1.00.5 < R < 1.0R = 0.5 if sin22q = 1

  9. Recent Super-K Results (848 days = 52 kton-yrs) SuperK Best Fit:Dm2 = 3.510-3 eV2sin22q = 1.0a = 0.06 No Osc. nmnt

  10. Reactor Experiments Limit Atmospheric nm ne Possibilities • CHOOZ, Bugey, and Palo Verde Reactor Experiments • <En> ~ 3 MeV and L ~ 1 km  Dm2  310-3eV2 CHOOZ 99

  11. What flavors are oscillating? • Dominant nm  ne: • Ruled out by CHOOZ reactor n experiment • Sub-dominant osc. possible at the sin22q < 0.10 levelSuperK could be seeing mixture of nm  ne at 10-4 eV2and nm  ntat 10-1 eV2 ? • Dominant nm  nsterile : • nsterile has no coupling to Z0 Look for n N  n N p0 • Super-K p0 - like (~NC/CC) double ratio (Data/MC)Current value is 1.11  0.06  0.26 (expect 1.00 for nt and ~0.8 for nsterile). • nsterile vs ntwill have matter effect differences at cosq = -1 • SuperK results disfavor nm  nsterile at ~2-3s level Is atmospheric results due to nm  ntoscillations ?

  12. Super-K Matter Effects • Interactions with matter in earth changes nm  nsterile oscillation probability since nsterile has no NC interactions with quarks • Matter effect provides a difference between nm  nm vs. nm  nsterile • Large effect for cosq = -1 (upgoing) where long path through earth Look for deviation of high energy events at cosq = -1

  13. KEK to SuperK (K2K) Experiment • Low energy, E>=1.4 GeV, beam sent from KEK to SuperK (250 km) • Several front detectors at 100m and beam monitors • Running now but expect low statistics (Only ~350 events expected in 3yrs.)

  14. 2002 2004 K2K Sensitivity • K2K Data Run in June and Nov. • Near detector:Data/MC = ~0.85  0.01  0.10 • Far Detector: • Fiducial VolumeData = 3.0 events obs.No osc = 12.4 expected310-3 eV2 = 8.0 ‘’510-3 eV2 = 5.4 ‘’ • Expected events far detector for 1020 pots (~3 to 4yrs) • Expected no. of 1-ring m-like No osc: 94 events 310-3 eV2 : 50 events 510-3 eV2 : 31 events • Only 90% CL regions  Need 4-5s for a definitive measurment

  15. The MINOS Beamline Two Detector Neutrino Oscillation Experiment (Start 2003) Far Detector (5.4 ktons, magnetized) Det. 2 Det. 1

  16. MINOS Far Detector CC Events Rates in MINOS 5kt detector High Energy Beam 10,000/yr Medium Energy Beam 5,000/yr Low Energy Beam 700/yr

  17. 90% CL 3.5s MINOS Dm2 Sensitivity Minos will cover full SuperK region with 3.5s sensitivity

  18. 90% CL Contours Dm2(eV2) 0.005 0.003 0.002 MINOS Measurement Capability Minos can measure Dm2 and sin22q with good precision for Dm2 > 0.003 eV2

  19. 4s Separation Region MINOS Oscillation Mode Sensitivity( Discriminate nm vs. nmsterile ) • Use CC/NC Ratio to distinguish between oscillations to ntor nsterile • For nm , CC production of t’s will look like NC ~80% of the time CC/NC  down • For nmsterile , both CC and NC will be suppressed. CC/NC stays ~ constant

  20. CERN Competition: CERN to Gran Sasso n Osc. Program (CNGS) • CERN has approved a program for a neutrino beam from CERN to Gran Sasso (750km) • Beam similar to Minos with nt rate factor of two lower • Unlikely that a near detector hall would be built • Emphasis on appearance experiments with ntand ne identification • Opera Experiment: Emulsion detector • ICANOE Experiment: Liquid argon plus fine grain calorimetry  Start Operation in 2005+

  21. OPERA Sensitivity • Emulsion bricks interspersed with electronic trackers • 1.5 kton hybrid target • efficiency: ~10 % • Very low background • Can confirm oscillations with few events but hard to measure parameters. • For five year exposure(2.251020 pot) • ~ 20 nm ntosc. events @ Dm2=3.510-3 eV2 • ~ 0.5 events background (5 year exposure)

  22. Only 90% CL Limits ICANOE Oscillation Sensitivity • Merging of liquid argon calorimeter with magnetized fine grain solid calorimeter • Liq Ar: 4 @ 1250 = 5000 tons • Solid: 4 @ 625 = 2500 tons • Detect and identify all neutrino species • CERN-NGS neutrinos • nt appearance search • Fine grain detector • Kinematical selection like NOMAD • ne appearance search • Good electron ID • Bkgnd from beam ne and nm nt  t  e

  23. MiniBooNE MiniBooNE (nme)Experiment at Fermilab • If LSND result is correct, it will change completely our assumptions about oscillations: • Sterile n’s may be needed since we will have three different Dm2 • One Dm2 must be large, ~ 1 eV2 • CP violation studies become much more possible

  24. LSND Experiment at LANL • Neutrino source from stopped p+s in the proton beam stop. • 1mA, 800 MeV protons • Cerenkov detector: 167 tons @ 30 m • p+ decay chain gives no <En>  40 MeV • Look for (1993-1998)

  25. Distributions of Excess ne Events • Spatial distribution in detector is consistent with ne 12C  e- Ng.s. events • Excess ne events have much higher energy than backgrounds

  26. Restrictions from Other Experiments • CCFR and Nomad rule out high Dm2 region • Bugey Reactor experiment rules out high sin22q and requires Dm2 > 0.2 eV2 • Karmen experiment : - Similar to LSND stopped p+ beam (200 ma) but closer distance (18m) - Sees no indication of oscillation but is not incompatible: • Expected 8 events • Observed 7.8  0.5 events Nomad Sensitivity Need decisive experiment to check LSND result and measure parameters if oscillations MiniBooNE

  27. Booster MainInjector MiniBooNE Experiment Use protons from the 8 GeV booster Neutrino Beam <En>~ 1 GeV 12m sphere filled withmineral oil and PMTslocated 500m from source

  28. MiniBooNE Status  On schedule for a Dec, 2001 start date.  Detector construction proceeding  Beam/Target Station design completed with bid awarded May, 2000  Beam and Detector complete end of 2001 Data Run during 2002 Need 1 yr to refute or confirm LSND at the > 5s level.

  29. MiniBooNE Rates and Sensitivity • Expected events/yr • 500,000 nm CC quasi-elastic • ~1000 ne if LSND correct • Decisive investigation of LSND region • LSND  >5s signal in MiniBooNE • Osc. signal has different energy than intrinsic ne • Experimental determinations of all backgrounds.

  30. MiniBooNE: Oscillation Parameter Measurements Two signal examples:

  31. MiniBooNE  BooNE • If signal is observed in MiniBooNE, then add second detector at appropriate distance  Two detector BooNE experiment Measure:Dm2 to  0.014 eV2 sin22q to  0.002

  32. Possible Future Step:Muon Storage Ring n-Factory • Muon storage ring could provide a super intense neutrino beamwith a wide range of energies. • High intensity, mixed beam allows investigation of all mixings (nenm or t) • Flavor composition/energy selectable and well understood: • Highly collimated beam • Very long baseline experiments possible Fermilab to California Fermilab to Cern/Japan

  33. Fermilab 6-month Studies • Physics Study (H. Schellman/S. Geer) • Physics motivation for a neutrino source based on a muon storage ring- beyond the current set of neutrino oscillation experiments. • The physics program that could be accomplished at a neutrino factory as a function of: • The stored muon energy, with the maximum energy taken to be 50 GeV. • The number of muon decays per year in the beam-forming straight section, taken to be in the range from 1019 to 1021 decays per year. • The presence or absence of muon polarization with the storage ring. • For oscillation experiments, the baseline length including investigations evaluating matter effects. • Accelerator Study (N. Holtkamp/D. Finley) • Design concept for a muon storage ring and associated support facilities that could support a compelling neutrino based research program. • Identification of the likely cost drivers within such a facility • Identify the R&D program required to move toward a conceptual design • Identify any specific environmental, safety, and health issues.

  34. Accelerator Study • Goal for the study • 21020 m decay/yr at 50 GeV • Fermilab to SLAC/LBNL (2900km) (N is number at 15 Hz rep rate for 2107sec/yr) • Study completed March 31, 2000 Available at: http://www.fnal.gov/projects/muon_collider/nu-factory

  35. Results of the Machine Feasibility Study “The result of this study clearly indicates that a neutrino source based on the concepts, which are presented here, is technically feasible.” • The study identifies the R&D required that would lead to a conceptual design. • proton driver and target area • induction linac • cooling channel • RF required for acceleration • Advantages of a n-Factory • Unique facility • Staged program in energy and intensity • Tune the machine and detector parameters Physics  Energy  Intensity  Mass detector

  36. Physics Study for a n-Factory • Group investigated physics reach of a n-Factory • Including detector resolution effects • As a function of Em store , m-decays/yr, and L(baseline) • For five oscillation scenarios: LAM SAM LOW Atmos/LSND Atmos/Solar/LSND

  37. Where will we be in 5-10 years? • LSND Dm2 • Definitive determination if osc. • Measure Dm2/sin22q to 5-10% • If positive  New round of experiments: nm and e nt • Atmospheric Dm2 • Know if nm ntorns • Measure Dm2/sin22q to 10% if Dm2> 210-3eV2 • Can see nmne if sin22q > ~0.01 • Solar Dm2 • Restrictions to one solar solution • Know if ne nm,torns

  38. n-Factory Physics Motivation • High intensity collimated beam  Precise long baseline experiments • Unique well-understood ne (as well as nm ) beam

  39. Advantages of m-Storage Ring vs Conventional n Beam • Neutrino CC rates higher • Minos:3000 nm CC/ kt - yr • n-Factory: 24000 nm CC/ kt - yr (21020 m decay/yr at 20 GeV • Beam angular divergence better for n-Factory especially for Em 30 GeV • Long baseline experiments possible • Beams differ in composition- Conventional Beam nmonly- n-Factory  Both nmand neexplore nenm or t • For nm  nen-Factory better - Conventional beam limited to sin22q13 0.01 • Beam ne’s at 1% level and difficulties in electron detection - n-Factory can reach sin22q13 0.001 • Can do nenm with very small backgrounds

  40. n-Factory SuperK/Minos/K2K nenm Oscillation Measurements at a n-Factory • For the atmospheric Dm2 region, need to use nenm to determine sin22q13 • By using nenm , signal becomes a search for wrong-sign muons which allows good sensitivity to low sin22q13 Low background (few  10-4)with: - Pm > 4 GeV - PT2 > 2 GeV2 • Matter effects from elastic ne CC forward scattering off electrons in matter for long baseline experiments • Measure sign of Dm322 to determine if m32 > m22

  41. Initial Observation of nenm • With the observation of only 10 nenmevents, one can measure the sign of Dm2 1019 m-decay with 20 GeV Storage Ring • Can reach sin22q13 0.001 for 21019 m-decay

  42. Measure Sign of Dm322 - Is m32 > m22 • Oscillation probability is modified depending on sign of Dm2

  43. Baseline Length Dependence • For nenm study, ~3000 km is minimum (optimal?).

  44. nent Measurements at a n-Factory • Great consistency check since sensitive to Dm322 and sin22q13But • Hard to identify t events with massive detector • Large nmntsource and nenm contributions to wrong sign events. • In scenarios where MiniBooNE confirms LSND nent very sensitive to CP violating phase d

  45. Precision Measurements of the Osc. Parameters • Global fit to right-sign m’s, wrong-sign m’s, e-like, and no-lepton events • Earth density profile also can be free parameter • Measure • Mixing angles to 10% • Dm322 to few percent 21020m decays

  46. Search for CP violating effects • Difficult measurement • Effect is small • Matter effects and other osc. parameters need to be known • Use wrong-sign rate ratio for m+vs m- running • R = Nm+ / Nm- • Curves are d = 0, d =  p/2 MatterEffect Different Curves are d = 0, d =  p/2 Error bars reflect measurement with 1021m-decays @ 20 GeV

  47. Neutrino Factory Parameters vs Physics Reach

  48. Summary of n-Factory Physics Study “A neutrino factory is a unique facility for neutrino oscillations... [that] will provide the mechanism for discoveries in the latter part of the decade.” • Experiments at a n-Factory would be able to simultaneously measure, or limit, all of the appearance modes associated with nm, nt, and ne osc. • The unique, well-understood ne component of the beam can be used to: • Determine all of the leading osc. parameters: sin22q13, sin22q23, and Dm322 • Determine the sign of Dm322 , test the MSW effect, investigate CP violation • Can stage the facility with good physics at each stage • Begin with 20 GeV@1019m-decays/yr  50 GeV@1021m-decays/yr • If LSND confirmed • Medium baseline measurements using ne beams needed • nent may be substantial and have large CP violating effects

  49. MiniBooNE BooNE n-factory LSND: MINOS CNGS K2K Atmospheric: Year: 2000 01 02 03 04 05 06 07 08 09 SuperK SNO Solar: KamLand Borexino Oscillation Experiment Timeline • NuMI/Minos and MiniBooNE are two of the key oscillation experiments to run over the next five years • It is probable that neutrino oscillations will be conclusively observed. • Pursuing a n-Factory as the next step for neutrino oscillations at Fermilab or elsewhere

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