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Physics Opportunities at the NuMI Neutrino Beam

Physics Opportunities at the NuMI Neutrino Beam

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Physics Opportunities at the NuMI Neutrino Beam

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  1. Physics Opportunities at the NuMI Neutrino Beam • Physics Opportunities • NuMI Beam Overview • Off-axis NuMI Beam • Backgrounds and Detector Issues • Detector Possibilities • Potential NuMI Off-axis Sensitivity • Site Question • Politics, Schedule, etc Adam Para, Fermilab Neutrino Factory Working Group CERN, September 10, 2002

  2. Three outstanding questions • Neutrino mass pattern: This ? Or that? • Electron component of n3 • Complex phase of s  CP violation in a neutrino sector

  3. Neutrino Propagation in Matter • Matter effects reduce mass of ne and increase mass of ne • Matter effects increase Dm223 for normal hierarchy and reduce Dm223 for inverted hierarchy

  4. The key: nm ne oscillation experiment A. Cervera et al., Nuclear Physics B 579 (2000) 17 – 55, expansion to second order in

  5. Observations • First 2 terms are independent of the CP violating parameter d • The last term changes sign between n and n • If q13 is very small (≤ 1o) the second term (subdominant oscillation) competes with 1st • For small q13, the CP terms are proportional to q13; the first (non-CP term) to q132 • The CP violating terms grow with decreasing En (for a given L) • CP violation is observable only if all angles ≠ 0

  6. Anatomy of Bi-probability ellipses Minakata and Nunokawa, hep-ph/0108085 ~cosd d • Observables are: • P • P • Interpretation in terms of sin22q13, d and sign of Dm223 depends on the value of these parameters and on the conditions of the experiment: L and E ~sind sin22q13

  7. An example: CP and Matter Effects at 730 km Parameter correlation: even very precise determination of Pn leads to a large allowed range of sin22q23  need antineutrinos

  8. What will MINOS do? Two functionally identical neutrino detectors Det. 1 Det. 2

  9. Possible result in 2005(?) Expected event spectrum Observed event spectrum Ratio: survival probability as a function of energy Shape: disappearance mechanism . Oscillations? Decays? Other? If oscillations => precise (~10%) measurement of the parameters Mixing angle Dm2

  10. MINOS Limits on nm to neOscillations 10 kton-yr exposure, Dm2=0.003 eV2, |Ue3|2=0.01: Signal (e = 25%) - 8.5 ev ne background - 5.6 ev Other (NC,CC,nt) – 34.1 ev M. Diwan,M. Mesier, B. Viren, L. Wai, NuMI-L-714 90% CL: | Ue3|2< 0.01 Sample ofnecandidates defined using topological cuts

  11. NuMI: Flexible Neutrino Beam Expected CC Events Rates in Minos 5kt detector • High 16,000 ev/yr • Medium 7,000 ev/yr • Low 2,500 ev/yr ‘zoom’ lens: Vary the relative distances of the source and focusing elements

  12. Status of NuMI Tunnel MARCH 2002 Beam pipe is now finished and cast in concrete

  13. NuMI Horn1: testing 1st Horn under test 1 year worth of pulses

  14. Horn 2: under construction Initial weld samples Final horn being electron welded

  15. Likely NuMI Schedule • Surface Building and Outfitting contract has just been signed (mid-September) • The Underground (tunnel, caverns, and shafts) contractor should be finished in mid-November of this year (2002) • Outfitting should take about 1 year • Installation of beam technical components and Near Detector should take about 1 year • We expect first beam on NuMI target 11/04

  16. Receipe for a Better ne Appearance Experiment • More neutrinos in a signal region • Less background • Better detector (improved efficiency, improved rejection against background) • Bigger detector • Lucky coincidences: • distance to Soudan = 735 km, Dm2=0.025-0.035 eV2 • Below the tau threshold! (BR(t->e)=17%)

  17. Two body decay kinematics At this angle, 15 mrad, energy of produced neutrinos is 1.5-2 GeV for all pion energies  very intense, narrow band beam ‘On axis’: En=0.43Ep

  18. Off-axis ‘magic’ ( D.Beavis at al. BNL Proposal E-889) 1-3 GeV intense beams with well defined energyin a cone around the nominal beam direction

  19. Medium Energy Beam: Off-axis detectors Neutrino event spectra at putative detectors located at different locations Neutrinos from K decays A. Para, M. Szleper, hep-ex/0110032

  20. ne Appearance Experiment: a Primer • Know your expected flux • Know the beam contamination • Know the NC background*rejection power (Note: need to beat it down to the level of ne component of the beam only) • Know the electron ID efficiency

  21. Beam Systematics: Predict the Spectrum. Medium Energy Beam Event spectra at far detectors located at different positions derived from the single near detector spectrum using different particle production models. Four different histograms superimposed Total flux predictable to ~1-2 %.

  22. Sources of the ne background All ne/nm ~0.5% At low energies the dominant background is from m+e++ne+nm decay, hence • K production spectrum is not a major source of systematics • ne background directly related to the nmspectrum at the near detector K decays

  23. Background rejection: beam + detector issue n spectrum NC (visible energy), no rejection Spectrum mismatch: These neutrinos contribute to background, but no signal ne background ne (|Ue3|2 = 0.01) NuMI low energy beam NuMI off-axis beam These neutrinos contribute to background, but not to the signal

  24. Fighting NC background:the Energy Resolution M. Messier, Harvard U. Cut around the expected signal region to improve signal/background ratio

  25. Sensitivity dependence on neefficiency and NC rejection Major improvement of sensitivity by improving ID efficiency up to ~50% Factor of ~ 100 rejection (attainable) power against NC sufficient NC background not a major source of the error, but a near detector probably desirable to measure it

  26. NuMI Beam Layout Near off-axis detector

  27. Antineutrinos are very important Antineutrinos are crucial to understanding: • Mass hierarchy • CP violation • CPT violation High energy beams experience: antineutrinos are ‘expensive’. Ingredients: s(p+)~3s(p-) (large x) For the same number of POT NuMI ME beam energies: s(p+)~1.15s(p-) (charge conservation!) Neutrino/antineutrino events/proton ~ 3 Backgrounds very similar to the neutrino case (smaller NC background) (no Pauli exclusion ~25% at 0.7 GeV)

  28. Detector(s) Challenge • Surface (or light overburden) • High rate of cosmic m’s • Cosmic-induced neutrons • But: • Duty cycle 0.5x10-5 • Known direction • Observed energy > 1 GeV LoDen R&D project • Principal focus: electron neutrinos identification • Good sampling (in terms of radiation/Moliere length) • Large mass: • maximize mass/radiation length • cheap

  29. NuMI Off-axis Detector • Different detector possibilities are currently being studied • The goal is an eventual 20 kt fiducial volume detector • The possibilities are: • Low Z target with RPC’s, drift tubes or scintillator • Liquid Argon (a large version of ICARUS) • Water Cherenkov counter

  30. An example of a possible detector Low Z tracking calorimeter Issues: • absorber material (plastic? Water? Particle board?) • longitudinal sampling (DX0)? • What is the detector technology (RPC? Scintillator? Drift tubes?) • Transverse segmentation (e/p0) • Surface detector: cosmic ray background? time resolution? • . . . NuMI off-axis detector workshop: January 2003

  31. A ‘typical’ signal event Fuzzy track = electron

  32. A ‘typical’ background event

  33. CC ne vs NC events in a tracking calorimeter: analysis example • Electron candidate: • Long track • ‘showering’ I.e. multiple hits in a road around the track • Large fraction of the event energy • ‘Small’ angle w.r.t. beam • NC background sample reduced to 0.3% of the final electron neutrino sample (for 100% oscillation probability) • 35% efficiency for detection/identification of electron neutrinos

  34. Resistive Plate Counters (Virginia Tech, BELLE) Glass electrodes are used to apply an electric field of ~4kV/mm across a 2mm gap. The gap has a mixture of argon,isobutane and HFC123a gas. An ionizing particle initiates a discharge which capacitively induces a signal on external pickup strips. 5 years of tests in Virginia Tech, 4 years operating experience in Belle

  35. Glass Spark Counters (Monolith) It is an RPC with electrodes made of standard float glass instead of Bakelite with a completely different design approach developed at LNGS. (see G.Bencivenni et al. NIM A300 (1991) 572 C.Gustavino et al. To be published on NIM ) Gas Mixture : Argon/Freon/C4H10 = 48/48/4 Spacers by injection molding (2 mm) Noryl Envelope Float Glass Resistive film End caps by injection molding Thermoplastic soldering for gas sealing Easy and fast and cheap construction Ready for mass production.

  36. Energy Resolution of Digital Sampling Calorimeter • Digital sampling calorimeter: • 1/3 X0 longitudinal • 3 cm transverse • Energy = Cx(# of hits) • DE ~ 15% @ 2 GeV • DE ~ 10% 4-10 GeV • ~15% non-linearity @ 8 GeV, no significant non-gaussian tails

  37. Constructing the detector ‘wall’ • Containment issue: need very large detector. Recall: K2K near detector – 1 kton mass, 25 tons fiducial, JHF proposal – 1 kton mass, 100 tons fiducial • Engineering/assembly/practical issues Solution: Containers ?

  38. Containers ? J. Cooper 5/3/02 1 TEU • 90% of the world’s manufactured goods (i.e. non-bulk) moves in standardized shipping containers • > 14 million units exist,leading Ports handle 15 M units / year • The most common types are: 20’ Dry Freight (x 8’ x 8’ 6”) (6.1 m x 2.44 m x 2.59 m) 40’ High Cubes (x 8’ x 9’ 6 “) (12.2 m x 2.44 m x 2.9 m) • Jargon unit is the TEU (Twenty-foot Equivalent Unit) • 1 million new TEUs built each year • This is real “mass production” • Almost all built overseas, Balance of trade helps us 2 TEU– High Cube

  39. Container Details • ISO specifications • Corner posts take load • Corner blocks for rigging • Corrugated steel sides & top • Doors on one end (or more) • Hardwood plywood floor sealed to sides • Angle/channel steel support below floor, fork pockets

  40. NuMI Beam: on and off-axis Det. 2 Det. 1 • Selection of sites, baselines, beam energies • Physcis/results driven experiment optimization

  41. Two Most Attractive Sites • Closer site, in Minnesota • About 711 km from Fermilab • Close to Soudan Laboratory • Unused former mine • Utilities available • Flexible regarding exact location • Further site, in Canada, along Trans-Canada highway • About 985 km from Fermilab • There are two possibilities: • About 3 kmto the west, south of Stewart Lodge • About 2 km to the east, at the gravel pit site, near compressor station

  42. Location of Canadian Sites Stewart Lodge Beam Gravel Pit

  43. A Closer Look Stewart Lodge Compressor station and Gravel pit

  44. Sensitivity dependence on neefficiency and NC rejection Major improvement of sensitivity by improving ID efficiency up to ~50% Factor of ~ 100 rejection power against NC sufficient NC background not a major source of the error, but a near detector probably desirable to measure it Sensitivity to ‘nominal’ |Ue3|2 at the level 0.001 (phase I) and 0.0001 (phase II)

  45. Important Reminder • Oscillation Probability (or sin22qme) is not unambigously related to fundamental parameters, q13 or Ue32 • At low values of sin22q13 (~0.01), the uncertainty could be as much as a factor of 4 due to matter and CP effects • Measurement precision of fundamental parameters can be optimized by a judicious choice of running time between n and n

  46. NuMI Of-axis Sensitivity for Phases I and II We take the Phase II to have 25 times higher POT x Detector mass Neutrino energy and detector distance remain the same

  47. Result-driven program: importance of L, E flexibility Phase I: run at 712 km, oscillation maximum Where to locate Phase II detector? Matter effects amplify the effect: increase statistics at this location Osc. Maximum induces d=0/d=p ambiguity  move to lower/higher energy Matter induces d=p/2 vs d=3p/2 ambiguity  move to the second maximum

  48. On the importance of being mobile:mammals vs dinosaurs? Sin22q13=0.05 Super-superbeam somewhere? Here we come!

  49. Determination of mass hierarchy Matter effects can amplify the effect, [sgn(Dm213=+1), d=3p/2], or reduce the effect [sgn(Dm213=+1), d=3p/2], and induce the degeneracy at smaller values of sin22q13. In the latter case a measurement at the location where matter effects are small (even with neutrinos only!) breaks the degeneracy and extends the hierarchy determination to lower values of sin22q13.  complementarity of NuMI vs JHF

  50. Recent Initiative • A Letter of Intent has been submitted to Fermilab in June expressing interest in a new n effort using off-axis detector in the NuMI beam • This would most likely be a ~15 year long, 2 phase effort, culminating in study of CP violation • The LOI was considered by the Fermilab PAC at its Aspen July, 2002, meeting