Neutrino tomography: Learning about the Earth

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Neutrino tomographyLearning about the Earths
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

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Contents

• Introduction
• Requirements from geophysics and high energy
  physics
• Principles, Applications, Challenges of
• Neutrino absorption tomography
• Neutrino oscillation tomography
• Summary

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Neutrino propagation tomography
Neutrino source Neutrino propagation Neutrinodetection

Well known flux, flavor composition, etc. Well known propagation model Propagation depends on matter structure Matter structure (partly) unknown Well known detector systematics, X-sections, etc.
?
Different from geoneutrino approach!
Learn about matter structure
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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,

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Neutrino tomography Sources
Natural
?
Man-made(flux and flavor composition well known)
Neutrino oscillations
Neutrino absorption
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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)

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Requirements from high-energy physics?

• Assume that there is a possible geophysics
  application

Use existing data?Do the application in either
case!
Additional cost Additional cost Additional cost
None Low High
Use for geophysics Low X - -
Use for geophysics Medium X ? -
Use for geophysics High X X ?
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Neutrino absorption tomography (NAT)
Neutrino source Neutrino propagation Neutrinodetection

Atmospheric n (high E tail) - CosmicAGNs, Black holes, Quasars, Pulsars?- TeV neutrino beam? Weak interactions damp initial flux by absorption/deflection/regeneration Integrated effect leads to attenuation(different for muon and tau neutrinos) Depends on nucleon density 7 absorbed at 1 TeV (L2 RE) Earth opaque (nm) at about 15 TeV - Neutrino telescopes (IceCube, Antares, Nestor etc.) - Moving detectors?
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Overview Whole-Earth tomography
Isotropic flux (cosmic diffuse, atmospheric) TeV-Beam Cosmic point src
Data might be available at no additional cost - Many directions- High precisions? Isotropy of flux no problem (only time dep.)
- - Atm. n low stat. (high E) - No cosmic flux obs. yet- Isotropy of flux? - Directional resolution - Build and safely operate a TeV neutrino beam- Moving decay tunnel- Moving detectors - Moving detector or Earth rotation (IceCube not useful)- No sources obs. yet
Refs. Jain, Ralston, Frichter, 1999 Related Reynoso, Sampayo, 2004 Gonazales-Garcia, Halzen, Maltoni, 2005 De Rujula, Glashow, Wilson, Charpak, 1983 Askaryan, 1984 Borisov, Dolgoshein, Kalinovskii, 1986 Wilson, 1984Kuo, Crawford, Jeanloz, Romanowicz, Shapiro, Stevenson, 1994
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A TeV neutrino beam
Conventionaltechnique to create a n beam

• 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

Protonaccelerator
nmlt0.1 ne
Target
p
Ep
p, K
En

• Max. 4 MW believed today
• Limits pot/time x Ep

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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 (lt200m) detect
heavy materials?
Muon production in sea water under moving muon
detector
(De Rujula, Glashow, Wilson, Charpak, 1983)
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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 Earths 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)

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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 gt 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 gtgt TeV can only
  be extrapolated

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Neutrino oscillation tomography (NOT)
Neutrino source Neutrino propagation Neutrinodetection

Natural - Sun- Supernova- AtmosphereMan-made - Superbeam- n factory- b-Beam Three-flavor neutrino oscillations affected by coherent forward scattering in matter (MSW) Depends on electron density conversion in r depends on Ye electrons/nucleon 0.5 Optimal En determined byOsc. effect large and Matter effect large Depends on neutrino energysource - Water Cherenkov det.- Magnetized iron det.- Many otherpossibilities
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Neutrino oscillations Two flavors, vacuum

• Mixing and mass squared differencena
  disappearancenb appearance

Frequency
Amplitude
Baseline Source - Detector
Energy
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Picture of three-flavor oscillations
Only upper bound so far
Effective two-flavor oscillations
Oscillation name Flavors Parameters
Solar (Limit for q130)
Atmospheric (Limit for q130)
LBL, Reactor ( )
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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)
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Matter effects (two flavors, r const.)

• Parameter mapping (same form)VacuumMatter

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
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Numerical evaluation for three flavors

• Evolution operator methodH(rj) is the
  Hamiltonian in constant densityNote that in
  general
• Additional information by interference effects
  compared to neutrino absorption tomography

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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)
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NOT with solar neutrinos

• Oscillation phases in matter
• Theoretical results (sunsupernova)
• - 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 lt 0.1
  tiny effect
• - Use rotation of Earth to measure effect of
  cavity Exposure time (cavity in line of sight
  sun-detector) 0 lt texp lt 24h (at poles)
• - Detector mass M 130 Mt/texp hr gtgt 5 Mt
  (poles)
• - Challenges Statistics, area of detectors gt
  cavity, backgrounds
• (Ioannisian, Smirnov, 2003 Ioannisian, Smirnov,
  2004
• Ioannisian, Kazarian, Smirnov, Wyler, 2004)

Solar neutrinos  ltlt 1 Low density medium
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NOT Theory Inversion problem(in low density
medium sunsupernovae)
Reconstruct matter density profile from day-night
regeneration effect
Now use V ltlt 2d (low density medium), V L ltlt 1
(Llt1700km) and linearize f(d)
Measured asfunction of E
(Akhmedov, Tortola, Valle, 2005)
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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)
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Supernova neutrinos and statistics

• Idea Compare spectra at D1 (surface) and D2
  (core shadow) for snapshot of the Earths
  interior
• Advantage
• Results Per cent level measurement of core
  density requires two Hyper-K-sized detectors
  (D10 kpc, E3 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)
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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)
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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)
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Positional information for single baseline
Example 500 MeV superbeam (20 bins, 10000
events/bin, 10Mt detector?)
Assumer 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 lt 100 kmCavity cannot be established
(Ohlsson, Winter, 2002)
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Resolution of structures for single baseline
Example 20 GeV neutrino factory, L11750
kmI100,000 events in total, factor 10-100
beyond current typical numbers, Mt
detector?Use genetic algorithm to fit N14
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!
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Density measurements with three flavors
Pure baseline effect!A 1 Matter resonance
(Cervera et al, 2000 Freund, 2001 Akhmedov et
al, 2004)
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Correlations with osc. Parameters?

• Term 1 Depends on energy can be matter
  enhanced for long Lsharp drop off the resonance
• Very sensitive to density!
• Term 2Always 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, r4.3 g/cm3, normal hierarchy)
(Fig. from hep-ph/0510025)
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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)
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Core density measurement Results
(Winter, 2005)

• First consider ideal geographical
  setupMeasure rIC (inner core) with L2 RE
• Combine with L3000 km to measure oscillation
  parameters
• Key question Does this measurement survive the
  correlations with the unknown oscillation
  parameters?
• For sin22q13 gt 0.01 a precision at the per cent
  level is realistic
• For 0.001 lt sin22q13 lt 0.01Correlations much
  worse without 3000 km baseline

(1s, 2s, 3s, dCP0, Dashed systematics only)
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Density measurement Geography
Something else than water in core shadow?
(Winter, 2005)
Inner core shadow
Outer core shadow
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Realistic geography

• and sin22q130.01. Examples for rIC
• There are potential detector locations!
• Per cent level precision not unrealistic

JHF
BNL
CERN
(Winter, 2005)
Inner core shadow
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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 gt 10 665 km
  (Akhmedov, 1998 Petcov, 1998)
• Direct test of MSW effect independent of q13 L gt
  5 500 km (Winter, 2004)
• Mass hierarchy for q130 L 6 000 km (de
  Gouvea, Jenkins, Kayser, 2005 de Gouvea,
  Winter, 2005)

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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)

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NOT Challenges

• Statistics, statistics, statisticsEarth matter
  effects have to be significant in terms of
  statisticsmajor 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/competitivenessReleva
  nt geophysics application with reasonable
  extra-effort?Technically feasible?

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Excursion Geophysics requirements for standard
precision measurements

• For instance Measure dCP with high precision
  for large q13at short L 3 000 km

Acts asbackgrounduncertainty
5 matter density uncertainty in mantlenot
acceptable for these measurements!Has to be of
the order of 1(Fig. from Ohlsson, Winter,
2003see 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)
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Neutrino tomography Summary (1)

• Neutrino absorption tomography
• Principle Attenuation effects through neutrino
  interactions
• Energies gt 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

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Neutrino tomography Summary (2)

• Some applications at low/no costProblem
  Probably no gain for geophysics
• Others quite expensiveHow 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?