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Neutrino physics with IceCube DeepCore-PINGU … and comparison with alternatives. TeVPA 2012 TIFR Mumbai, India Dec 10-14, 2012 Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Introduction Oscillation physics with Earth matter effects

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neutrino physics with icecube deepcore pingu and comparison with alternatives

Neutrino physics with IceCube DeepCore-PINGU… and comparison with alternatives

TeVPA 2012TIFR Mumbai, India

Dec 10-14, 2012Walter Winter

Universität Würzburg

TexPoint fonts used in EMF: AAAAAAAA

  • Introduction
  • Oscillation physics with Earth matter effects
  • Mass hierarchy determination with PINGU
    • Neutrino beam to PINGU?
    • Atmospheric neutrinos
  • Comparison with alternatives, and outlook
  • Summary
atmospheric neutrino anomaly
Atmospheric neutrino anomaly
  • The rate of neutrinos should be the same from below and above
  • But: About 50% missing from below
  • Neutrino change their flavor on the path from production to detection: Neutrino oscillations(Super-Kamiokande: “Evidence for oscillations of atmospheric neutrinos”, 1998)
three flavors summary
Three flavors: Summary
  • Three flavors: 6 params(3 angles, one phase; 2 x Dm2)
  • Describes solar and atmospheric neutrino anomalies, as well as reactor antineutrino disapp.!

Solaroscillations:Amplitude:q12Frequency: Dm212

Atmosphericoscillations:Amplitude:q23Frequency: Dm312

Coupling: q13

(Super-K, 1998;Chooz, 1999; SNO 2001+2002; KamLAND 2002;Daya Bay, RENO 2012)

Suppressed effect: dCP


(short baseline)

(also: T2K, Double Chooz, RENO)

consequences of large q 13
Consequences of large q13
  • q13 to be well measured by Daya Bay
  • Mass hierarchy: 3s discovery for up to 40% of all dCP possible iff ProjectX, possiblyuntil 2025
  • CP violation measurement extremely difficultNeed new facility!

Huber, Lindner, Schwetz, Winter, 2009

matter profile of the earth as seen by a neutrino
Matter profile of the Earth… as seen by a neutrino


(PREM: Preliminary Reference Earth Model)


(not to scale)

matter effect msw
Matter effect (MSW)

(Wolfenstein, 1978; Mikheyev, Smirnov, 1985)

  • Ordinary matter: electrons, but no m, t
  • Coherent forward scattering in matter: Net effect on electron flavor
  • Hamiltonian in matter (matrix form, flavor space):

Y: electron fraction ~ 0.5

(electrons per nucleon)


Parameter mapping… for two flavors

  • Oscillation probabilities invacuum:matter:

Matter resonance: In this case: - Effective mixing maximal- Effective osc. frequency minimal

For nm appearance, Dm312:- r ~ 4.7 g/cm3 (Earth’s mantle): Eres ~ 6.4 GeV- r ~ 10.8 g/cm3 (Earth’s outer core): Eres ~ 2.8 GeV

 MH

Resonance energy:

mantle core mantle profile
Mantle-core-mantle profile

(Parametric enhancement: Akhmedov, 1998; Akhmedov, Lipari, Smirnov, 1998; Petcov, 1998)

  • Probability for L=11810 km (numerical)



Parametric enhancementthrough mantle-core-mantleprofile of the Earth.Unique physics potential!

Core resonanceenergy


Naive L/E scalingdoes not apply!

Thresholdeffects expected at:

2 GeV

4-5 GeV

what is pingu precision icecube next generation upgrade
What is PINGU?(“Precision IceCube Next Generation Upgrade“)
  • Fill in IceCube/DeepCore array with additional strings
    • Drive threshold to lower energies
  • LOI in preparation
  • Modest cost ~30-50M$ (dep. on no. of strings)
  • Two season deployment anticipated: 2015/2016/2017

(PINGU, 12/2012)

pingu fiducial volume
PINGU fiducial volume?
  • A ~ Mt fiducial mass for superbeam produced with FNAL main injector protons (120 GeV)
  • Multi-Mt detector for E > 10 GeV atmospheric neutrinos
  • Fid. volume depends on trigger level (earlier Veff higher, which is used for following analyses!)

(PINGU, 12/2012)


Atm. neutrinos

mass hierarchy measurement statistical significance illustrated
Mass hierarchy measurement:statistical significance (illustrated)

Source (spectrum, solid angle)

Osc. effect (in matter)

Detector mass

Crosssection~ E




> 2 GeV

Atmospheric neutrinosarXiv:1210.5154

> 5 GeV

Measurement at threshold  application rather for future upgrades: MICA?

BeamsM. Bishai


beams to pingu
Beams to PINGU?
  • Labs and potential detector locations (stars) in “deep underground“ laboratories:

(Agarwalla, Huber, Tang, Winter, 2010)

FNAL-PINGU: 11620 kmCERN-PINGU: 11810 kmRAL-PINGU: 12020 kmJHF-PINGU: 11370 km


All these baselines cross the Earth‘s outer core!

example low intensity superbeam
Example:“Low-intensity“ superbeam?
  • Here: use most conservative assumption NuMI beam, 1021 pot (total), neutrinos only[compare to LBNE: 22+22 1020 pot without Project X ~ factor four higher exposure than the one considered here](FERMILAB-PROPOSAL-0875, NUMI-L-714)
    • Low intensity may allow for shorter decay pipe
  • Advantage: Peaks in exactly the right energy range for the parametric enhancement
  • Include all irreduciblebackgrounds (intrinsic beam, NC, hadronic cascades), 20% track mis-ID

M. Bishai

event rates
Event rates

(for Veff 03/2012)


>18s(stat. only)

mass hierarchy with a beam
Mass hierarchy with a beam
  • Very robust mass hierarchy measurement (as long as either some energy resolution or control of systematics)

GLoBES 2012

(Daya Bay best-fit; current parameter uncertainties included; based on Tang, Winter, JHEP 1202 (2012) 028 )


All irreducible backgrounds included

atmospheric neutrinos
Atmospheric neutrinos

Akhmedov, Razzaque, Smirnov, 2012

  • Neutrino source available “for free“
  • Source not flavor-clean  different channels contribute and mask effect
  • Power law spectrum


  • Many different baselines at once, weighted by solid angle
  • Detector: angular+energy resolution required!

A. Smirnov

mass hierarchy with atmospheric neutrinos
Mass hierarchy with atmospheric neutrinos
  • Statistical significance depends on angular and energy resolution
  • About 3-10s likely for reasonable values
  • Final proof of principle will require event reconstruction techniques (in progress)

Akhmedov, Razzaque, Smirnov, 2012

mass hierarchy
Mass hierarchy
  • 3s, Project X and T2K with proton driver, optimized neutrino-antineutrino run plan
  • PINGU completed by beginning of 2017?
  • No “conventional“ atm. neutrino experiment could be built on a similar timescale or at a similar cost
    • Bottleneck: Cavern!

Akhmedov, Razzaque, Smirnov, 2012; v5



Huber, Lindner, Schwetz, Winter, JHEP 11 (2009) 44

probabilities d cp dependence
Probabilities: dCP-dependence
  • There is rich dCP-phenomenology:


L=11810 km

upgrade path towards d cp
Upgrade path towards dCP?
  • Measurement of dCP in principle possible, but challenging
  • Wish list:
    • Electromagnetic shower ID (here: 1% mis-ID)
    • Energy resolution (here: 20% x E)
    • Maybe: volume upgrade(here: ~ factor two)
    • Project X
  • Currently being discussed in the context of further upgrades - MICA; requires further study
    • PINGU as R&D exp.?

= LBNE + Project X!

same beamto PINGU

Tang, Winter, JHEP 1202 (2012) 028

matter density measurement example lbne like superbeam
Matter density measurementExample: LBNE-like Superbeam
  • Precision ~ 0.5% (1s) on core density
  • Complementary to seismic waves (seismic shear waves cannot propagate in the liquid core!)

from: Tang, Winter, JHEP 1202 (2012) 028;see also: Winter, PRD72 (2005) 037302; Gandhi, Winter, PRD75 (2007) 053002; Minakata, Uchinami, PRD 75 (2007) 073013

conclusions pingu
Conclusions: PINGU
  • Megaton-size ice detector as upgrade of DeepCore with lower threshold; very cost-efficient compared to liquid argon, water
  • Unique mass hierarchy measurement through MSW effect in Earth matter
    • Atmospheric neutrinos:
      • Neutrino source for free, many different baselines
      • Requires energy and angular resolution (reconstruction work in progress)
      • PINGU to be the first experiment to discover the mass hierarchy at 3-5s?
    • Neutrino beam:
      • Requires dedicated source, with relatively low intensity
      • Proton beams from FNAL main injectior have just right energy to hit mantle-core-mantle parameteric enhancement region
      • Even possible as counting experiment, no angular resolution needed
  • Beyond PINGU: CPV and matter density measurements perhaps possible with beam to even denser array (MICA)?  PINGU as R&D experiment; worth further study!
  • Technology also being studied in water  ORCA
possible neutrino sources
Possible neutrino sources

There are three possibilities to artificially produce neutrinos

  • Beta decay:
    • Example: Nuclear reactors, Beta beams
  • Pion decay:
    • From accelerators:
  • Muon decay:
    • Muons produced by pion decays! Neutrino Factory










detector paramet mis id
Detector paramet.: mis-ID

misID: fraction of events of a specific channelmis-identified as signal


misIDtracks << misID <~ 1 ?

(Tang, Winter, JHEP 1202 (2012) 028)

detector requirements
Detector requirements

Want to study ne-nm oscillations with different sources:

  • Beta beams:
    • In principle best choice for PINGU (need muon flavor ID only)
  • Superbeams:
    • Need (clean) electron flavor sample. Difficult?
  • Neutrino factory:
    • Need charge identification of m+ and m- (normally)

q13, dCP

q13, dCP

q13, dCP

detector parameterization low intensity superbeam
Detector parameterization(low intensity superbeam)
  • Challenges:
    • Electron flavor ID
    • Systematics (efficiency, flux normalization  near detector?)
    • Energy resolution
  • Make very (?) conservative assumptions here:
    • Fraction of mis-identified muon tracks (muon tracks may be too short to be distinguished from signal) ~ 20%
    • Irreducible backgrounds (zeroth order assumption!):
      • Intrinsic beam background
      • Neutral current cascades
      • nm nt cascades (hadronic and electromagnetic cascades indistinguishable)
    • Systematics uncorrelated between signal and background
    • No energy resolution (total rates only)

(for details on parameterization: Tang, Winter, JHEP 1202 (2012) 028)

measurement of d cp
Measurement of dCP?
  • Many proposals for measuring CP violation with a neutrino beam
  • Require all a dedicated (new) detector + control of systematics

Coloma, Huber, Kopp, Winter, 2012