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Neutrino tomography: Learning about the Earth’s interior using the propagation of neutrinos

Neutrino tomography: Learning about the Earth’s interior using the propagation of neutrinos. Neutrino sciences 2005: Neutrino geophysics University of Hawaii at Manoa December 16, 2005 Walter Winter Institute for Advanced Study, Princeton. Contents. Introduction

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Neutrino tomography: Learning about the Earth’s interior using the propagation of neutrinos

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  1. Neutrino tomography:Learning about the Earth’s interior using the propagation of neutrinos Neutrino sciences 2005: Neutrino geophysics University of Hawaii at Manoa December 16, 2005 Walter Winter Institute for Advanced Study, Princeton

  2. Contents • Introduction • Requirements from geophysics and high energy physics • Principles, Applications, Challenges of • Neutrino absorption tomography • Neutrino oscillation tomography • Summary Neutrino geophysics - Walter Winter

  3. Neutrino “propagation” tomography ? Different from geoneutrino approach! Learn about matter structure Neutrino geophysics - Walter Winter

  4. Neutrino propagation models • “Standard” • Neutrino interactions (CC/NC) leading to attenuation effects • Three-flavor neutrino oscillations; “ideal energies” (later): • Others which are affected by the presence of matter? • Mass-varying neutrinos • Non-standard interactions • Matter-induced neutrino decay, … Neutrino geophysics - Walter Winter

  5. 10-4 10-3 103 104 105 106 107 108 109 1010 1011 1012 E [eV] keV MeV GeV TeV Neutrino tomography: Sources Natural ? Man-made(flux and flavor composition well known) Neutrino oscillations Neutrino absorption

  6. Mantle: Tested very well by seismic waves However: - Uncertainties in 3D models ~ 5% (http://cfauvcs5.harvard.edu/lana/rem/mapview.htm)- Matter density derived by EOS; normal modes? InnerCore Core Mantle • Density of whole Earth: Mass+rot. inertia known • Least information on innermost parts Requirements from geophysics? • Outer core: Liquid • No seismic s-wave propagation • Less knowledge than mantle??? • Local inhomogeneities (for oil etc.): Established methods • Competitor has to be cheap and effective • Inner core: Solid? Thermal state? Anisotropies? Dynamics? • Least known part(see e.g. Steinle-Neumann et al, physics/0204055)

  7. Usefulness forgeophysics Effort for particle physics = additional cost and R&D BALANCE What is the primary purpose of the experiment?Can the geophysicsapplication be added at low additional cost? Requirements from high-energy physics? • Assume that there is a possible geophysics application: Use existing data?Do the application in either case! Neutrino geophysics - Walter Winter

  8. Scattered? Neutrino absorption tomography (NAT) Neutrino geophysics - Walter Winter

  9. Overview: Whole-Earth tomography

  10. Rule of thumb: En ~ 1/10 Ep (peak energy) Current measure: LHCEp ~ 7 TeV, En ~ 700 GeV ? ~ 5% absorption at 2 RE, 700 GeVStatistics only:~ 400 events to see this effect~ 5,000,000 events to measuredensity at percent levelThat may not be unrealistic numbers! Main challenge: Expensive.Is there other physics one needs a TeV neutrino beam for? Example: Sterile neutrino oscillation physics at long baselines for DM2 ~ 1 eV2? Use neutrino factory?But: Huge muon accelerator, huge storage ring A TeV neutrino beam Conventionaltechnique to create a n beam Protonaccelerator nm<0.1% ne Target p Ep p, K En • Max. 4 MW believed today • Limits pot/time x Ep Neutrino geophysics - Walter Winter

  11. TeV neutrino beam: Ideas Sound detection bymicrophone array? Use off-axis decetor to measure norm.: E lower, therefore absorption lower Several TeV neutrino beam Sound generation by particle shower? Muon production under surface (<200m); detect heavy materials? Muon production in sea water under moving muon detector (De Rujula, Glashow, Wilson, Charpak, 1983) Neutrino geophysics - Walter Winter

  12. NAT: Cosmic diffuse flux ~ 10 to 10000 TeV neutrinos from unresolved cosmic objects detected by km3 neutrino telescope Useful to resolve degs among seismic models in mantle? • Example for “low cost” application? • Major challenge: Solid angle of the Earth’s core is very small~ 1% of the neutrino sky seen through the inner core • Flux is small where precision needed • Also challenges: angular resolution, Isotropy of flux, … • (Jain, Ralston, Frichter, 1999) Neutrino geophysics - Walter Winter

  13. NAT: Summary of challenges • Atmospheric n (high-E part) (Gonazales-Garcia, Halzen, Maltoni, 2005)The only detected source so far!Example IceCube: Several hundred events at > 10 TeVBut: Only O(10) events seen through inner coreRequired: ~ 17000 for per cent level measurement • TeV neutrino beam: Feasible? Direction changeable? Cost? Moving detectors? Other applications? • Cosmic point sources/diffuse fluxNo detection yetFlux known, or relative measurement? Stable (point source)? Isotropic (diffuse flux)? Backgrounds? Cross sections at >> TeV can only be extrapolated Neutrino geophysics - Walter Winter

  14. Neutrino oscillation tomography (NOT) Neutrino geophysics - Walter Winter

  15. Neutrino oscillations: Two flavors, vacuum Mixing and mass squared difference:na “disappearance”:nb “appearance”: Frequency Amplitude Baseline: Source - Detector Energy Neutrino geophysics - Walter Winter

  16. Atmosphericoscillation:Amplitude: q23Frequency: Dm312 Solaroscillation:Amplitude: q12Frequency: Dm212 Sub-leading effect: dCP Coupling strength: q13 Picture of three-flavor oscillations Only upper bound so far Effective two-flavor oscillations: Neutrino geophysics - Walter Winter

  17. Matter effects in n-oscillations (MSW) • Ordinary matter contains electrons, but no m, t • Coherent forward scattering in matter has net effect on electron flavor because of CC (rel. phase shift) • Matter effects proportional to electron density and baseline • Hamiltonian in matter: (Wolfenstein, 1978; Mikheyev, Smirnov, 1985) Y: electron fraction ~ 0.5 (electrons per nucleon) Neutrino geophysics - Walter Winter

  18. Matter effects (two flavors, r const.) • Parameter mapping (same form):Vacuum:Matter: “Matter resonance”: In this case: - Effective mixing maximal- Effective osc. frequency min.r = 4.5 g/cm3 (Earth matter)Solar osc.: E ~ 100 MeV !!!LBL osc.: E ~ 6.5 GeV Resonance energy: Neutrino geophysics - Walter Winter

  19. Numerical evaluation for three flavors • Evolution operator method:H(rj) is the Hamiltonian in constant densityNote that in general • Additional information by interference effects compared to neutrino absorption tomography Neutrino geophysics - Walter Winter

  20. Matter profile inversion problem Matter density profile Measurement (observables) Easy to calculate Generallyunsolved • Some attempts for direct inversion: • Simple models: For instance, only cavity (e.g., Nicolaidis, 1988; Ohlsson, Winter, 2002) • Linearization for low densities (e.g., Akhmedov, Tortola, Valle, 2005) • Discretization of profile with many parameters: Use non-deterministic algorithms to fit N parameters (genetic algorithms, etc.) (Ohlsson, Winter, 2001) (Ermilova, Tsarev, Chechin, 1988) Neutrino geophysics - Walter Winter

  21. NOT with solar neutrinos • Oscillation phases in matter: • Theoretical results (sun+supernova) - For arriving mass eigenstates, DP (cavity-no cavity) depends on F2, but not F1 - Damping of contributions from remote distances x2 - Solar neutrinos less sensitive to deep interior of Earth! (~factor 10 suppressed) • Statistics issues (sun) - Change in oscillation probability DP/P < 0.1%; tiny effect - Use rotation of Earth to measure effect of cavity Exposure time (cavity in line of sight sun-detector) 0 < texp < 24h (at poles) - Detector mass M ~ 130 Mt/texp [hr] >> 5 Mt (poles) - Challenges: Statistics, area of detectors > cavity, backgrounds (Ioannisian, Smirnov, 2003; Ioannisian, Smirnov, 2004; Ioannisian, Kazarian, Smirnov, Wyler, 2004) Solar neutrinos: Â << 1 “Low density medium”

  22. NOT Theory: Inversion problem(in “low density medium” = sun+supernovae) Reconstruct matter density profile from day-night regeneration effect: Now use V << 2d (“low density medium”), V L << 1 (L<1700km) and linearize f(d): Measured asfunction of E (Akhmedov, Tortola, Valle, 2005)

  23. Low density inversion problem: Challenges • Need to know f(d) forUse, for instance, iteration procedure to reconstruct unknown regions in integral: • Finite energy resolution “washes out” edges • Statistics: ~ 10 Mt detector? • However: Strongly sensitive to asymmetric profiles! (Courtesy E. Akhmedov) (Akhmedov, Tortola, Valle, 2005) Neutrino geophysics - Walter Winter

  24. Supernova neutrinos and statistics • Idea: Compare spectra at D1 (surface) and D2 (core shadow) for “snapshot” of the Earth’s interior • Advantage: • Results: Per cent level measurement of core density requires two Hyper-K-sized detectors (D=10 kpc, E=3 1053 ergs) • Challenges: • Relies on different temperatures of fluxes: if fluxes equal, no oscillation effect • Deviations from energy equipartition (more electron antineutrinos) unfavorable • ~0.2% precision for solar oscillation parameters prerequisite • Some knowledge on flux parameters required since all mass eigenstates arrive; unlikely to be obtained from detection of one flavor only • Matter density uncertainties in mantle might spoil core density extraction(damping of remote structures!) High energy tail: strong matter effects compared to solar nus! Dc2 = 35 (Lindner, Ohlsson, Tomas, Winter, 2002)

  25. Neutrino beams for oscillations nb? Artificial source: Accelerator na Far detector Often: Near detector to measure X-sections, control systematics, … Baseline: L ~ E/Dm2 (osc. length) Neutrino geophysics - Walter Winter

  26. Example: Neutrino factory (from: CERN Yellow Report ) • Main purpose: Measure q13, dCP, mass hierarchy, etc. • Muon decays in straight sections of storage ring • Decay ring naturally spans two baselines, typically ~ 700 – 3000 km • Technical challenges: Target power, muon cooling, maybe steep decay tunnels • Timescale: 2025? (Huber, Lindner, Rolinec, Winter, 2002-2004) Neutrino geophysics - Walter Winter

  27. Positional information for single baseline Example: 500 MeV superbeam (20 bins, 10000 events/bin, ~ 10Mt detector?) Assume:r = 1g/cm3Cavity at d0 = 300 kmsin22q13 = 0.03 Position canbe measured+- 100 kmNEW!!! Size of cavity can bemeasured ~ +- 50 km Degeneracy can onlybe resolved by suppressedthree-flavor effect For l0 < ~100 km:Cavity cannot be established (Ohlsson, Winter, 2002) Neutrino geophysics - Walter Winter

  28. Resolution of structures for single baseline Example: 20 GeV neutrino factory, L=11750 kmI=100,000 events in total, ~ factor 10-100 beyond current “typical” numbers, ~ Mt detector?Use genetic algorithm to fit N=14 layers (symmetric profile) Show some characteristic examples close to 1s, 2s, 3scontours (14 d.o.f.) Fluctuations of few hundered km cannot be resolved Edges at higher CLnot resolvable (Ohlsson, Winter, 2001) Analytically: One cannot resolve structures smaller than (Losc)matterNeutrino oscillations are sensitive to average densities on these length scales! Neutrino geophysics - Walter Winter

  29. Prop. To L2; compensated by flux prop. to 1/L2 (Term 1)(Term 2) (Term 1)2 (Term 2)2 Density measurements with three flavors Pure baseline effect!A 1: Matter resonance (Cervera et al, 2000; Freund, 2001; Akhmedov et al, 2004) Neutrino geophysics - Walter Winter

  30. Correlations with osc. Parameters? • Term 1: Depends on energy; can be matter enhanced for long L;sharp drop off the resonance • Very sensitive to density! • Term 2:Always suppressed for long L; zero at “magic baseline”(Huber, Winter, 2003) • Term 2 always suppresses CP and solar terms for very long baselines • Matter density measurement relatively correlation-free for large q13 (Dm312 = 0.0025, r=4.3 g/cm3, normal hierarchy) (Fig. from hep-ph/0510025) Neutrino geophysics - Walter Winter

  31. Core density measurement: Principles • Idea: Measure Baseline-averaged density: • Equal contribution of innermost parts. Measure least knowninnermost density! • Use “standard neutrino factory” • Em = 50 GeV • Running time: 4 years in each polarity • Detector: 50 kt magnetized iron calorimeter • 1021 useful muon decays/ year (~4 MW) • 10% prec. on solar params • Atmospheric parameters best measured by disapp. channel (Winter, 2005) (for details: Huber, Lindner, Winter, hep-ph/0204352) Neutrino geophysics - Walter Winter

  32. Core density measurement: Results (Winter, 2005) • First: consider “ideal” geographical setup:Measure rIC (inner core) with L=2 RE • Combine with L=3000 km to measure oscillation parameters • Key question: Does this measurement survive the correlations with the unknown oscillation parameters? • For sin22q13 > 0.01 a precision at the per cent level is realistic • For 0.001 < sin22q13 < 0.01:Correlations much worse without 3000 km baseline (1s, 2s, 3s, dCP=0, Dashed: systematics only) Neutrino geophysics - Walter Winter

  33. Density measurement: Geography Something else than water in “core shadow”? (Winter, 2005) Inner core shadow Outer core shadow Neutrino geophysics - Walter Winter

  34. “Realistic geography” JHF BNL … and sin22q13=0.01. Examples for rIC: • There are potential detector locations! • Per cent level precision not unrealistic CERN (Winter, 2005) Inner core shadow Neutrino geophysics - Walter Winter

  35. Core density measurement: Summary • Survives realistic statistics and unknown oscillation parameters! • Potential detector locations for major laboratories • Could be implemented as a side product after a successful NF neutrino oscillation program Challenges: • How expensive? Enough use for geophysics? • So far only 1 d.o.f. measurement tested; maybe also time dependence • sin22q13 larger than about 0.01 necessary • Storage ring configuration with steep slopes? But: • This might not be the only application for a very long NF baseline: • “Magic baseline” to resolve degeneracies: L ~ 7 500 km (Huber, Winter, 2003) • Test of “parametric resonance”: L > 10 665 km (Akhmedov, 1998; Petcov, 1998) • Direct test of MSW effect independent of q13: L > 5 500 km (Winter, 2004) • Mass hierarchy for q13=0: L ~ 6 000 km (de Gouvea, Jenkins, Kayser, 2005; de Gouvea, Winter, 2005) Neutrino geophysics - Walter Winter

  36. NOT with atmospheric neutrinos? • Use magn. iron clorimeter • Measure nm disappearance • Compare neutrinos and antineutrinos sin22q13 = 0.08 • For instance: Obtain information on composition (Ye) • Challenge: Extreme statistics (Geiser, Kahle, 2002; from poster presented at Neutrino 2002) Neutrino geophysics - Walter Winter

  37. NOT: Challenges • Statistics, statistics, statisticsEarth matter effects have to be significant in terms of statistics;major challenge for most applications (e.g., solar day-night effect) • Knowledge on source Source flux and flavor composition has to be well known ormeasured “on the surface”; especially challenging for “natural sources”, such as supernova neutrinos • Oscillation parameters • Propagation model depends on six oscillation parameters, which are not yet precisely known • Size of q13 determines amplitude of ne-nm flavor transitions • Feasibility/complementarity/competitivenessRelevant geophysics application with reasonable extra-effort?Technically feasible? Neutrino geophysics - Walter Winter

  38. Excursion: Geophysics requirements for “standard” precision measurements • For instance: Measure dCP with high precision for large q13at short L ~ 3 000 km Acts as“backgrounduncertainty” 5% matter density uncertainty in mantlenot acceptable for these measurements!Has to be of the order of 1%(Fig. from Ohlsson, Winter, 2003;see also: Koike, Sato, 1999; Jacobsson et al 2001; Burguet-Castell et al, 2001; Geller, Hara, 2001; Shan, Young, Zhang, 2001; Fogli, Lettera, Lisi, 2001; Shan, Zhang, 2002; Huber, Lindner, Winter, 2002; Ota, Sato, 2002; Shan et al, 2003; Kozlovskaya , Peltoniemi, Sarkamo, 2003; others) Neutrino geophysics - Walter Winter

  39. Neutrino absorption tomography Principle: Attenuation effects through neutrino interactions Energies: > TeV Baselines (reconstruction problem): Many Sources: Cosmic, atmosphere, beam? Challenges: Sources, technical Neutrino oscillation tomography Principle: Neutrino oscillations affected by MSW effect Energies: MeV to GeV Baselines (reconstruction problem): at least one Sources: Sun, supernovae, beams,atmosphere? Challenges: Mainly statistics Neutrino tomography: Summary (1) Neutrino geophysics - Walter Winter

  40. Neutrino tomography: Summary (2) • Some applications at low/no costProblem: Probably no gain for geophysics • Others quite expensive:How much effort beyond “standard” program? • Conceptually different approaches: Reconstruction of profile, local inhomogeneities, core density measurement • What do geophysicists really need? What complementary information is useful? Neutrino geophysics - Walter Winter

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