TeVPA 2012

TIFR Mumbai, IndiaDec 10-14, 2012

Walter WinterUniversität Würzburg

Neutrino physics with IceCube DeepCore-PINGU

… and comparison with alternatives

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Contents

Introduction Oscillation physics with Earth matter

effects Mass hierarchy determination with PINGU

Neutrino beam to PINGU? Atmospheric neutrinos

Comparison with alternatives, and outlook Summary

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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)

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Three flavors: 6 params(3 angles, one phase; 2 x m2)

Describes solar and atmospheric neutrino anomalies, as well as reactor antineutrino disapp.!

Three flavors: Summary

Coupling: 13

Atmosphericoscillations:Amplitude: 23

Frequency: m312

Solaroscillations:Amplitude: 12

Frequency: m212

Suppressed

effect: CP

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

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(also: T2K, Double Chooz, RENO)

(short baseline)

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Consequences of large 13

13 to be well measured by Daya Bay

Mass hierarchy: 3 discovery for up to 40% of all CP possible iff ProjectX, possiblyuntil 2025

CP violation measurement extremely difficultNeed new facility!

Huber, Lindner, Schwetz, Winter, 2009

Oscillation physics withEarth matter effects

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Matter profile of the Earth… as seen by a neutrino

(PR

EM

: Prelim

inary R

eference E

arth M

odel)

Core

Innercore

(not to scale)

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Matter effect (MSW) Ordinary matter:

electrons, but no , 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)

(Wolfenstein, 1978; Mikheyev, Smirnov, 1985)

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Parameter mapping… for two flavors

Oscillation probabilities invacuum:matter:

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

For appearance, m312:

- ~ 4.7 g/cm3 (Earth’s mantle): Eres ~ 6.4 GeV- ~ 10.8 g/cm3 (Earth’s outer core): Eres ~ 2.8 GeV

Resonance energy:

MH

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Mantle-core-mantle profile

Probability for L=11810 km (numerical)

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

Core resonance

energy

Mantleresonance

energy

Param.enhance-

ment

Thresholdeffects

expected at:2 GeV 4-5 GeV

Naive L/E scalingdoes not apply!

Parametric enhancementthrough mantle-core-mantle

profile of the Earth.Unique physics potential!

!

Mass hierarchy determination with PINGU

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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)

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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!)

LBNE-likebeam

Atm. neutrinos

(PINGU, 12/2012)

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Mass hierarchy measurement:statistical significance (illustrated)

Source (spectrum, solid angle)

Osc. effect (in matter)

Detector mass

Crosssection

~ E

Atmospheric neutrinosarXiv:1210.5154

BeamsM. Bishai

x

> 2 GeV

> 5 GeV

x x

Coreres.

Measurement at threshold application rather for future upgrades: MICA?

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Beams to PINGU? Labs and potential detector locations (stars) in

“deep underground“ laboratories: (Agarw

alla, Hu

ber, Tang, W

inter, 2010)

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

All these baselines cross the Earth‘s outer core!

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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

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Event rates

Normal hier. Inv. hierarchy

Signal 1560 54

Backgrounds: e beam 39 59

Disapp./track mis-ID 511 750

appearance 3 4

Neutral currents 2479 2479

Total backgrounds 3032 3292

Total signal+backg. 4592 3346

(for Veff 03/2012)

>18 (stat. only)

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Mass hierarchy with a beam

Very robust mass hierarchy measurement (as long as either some energy resolution or control of systematics)

(Daya B

ay best-fit; current param

eter un

certainties includ

ed; b

ased on

Tang, W

inter, JH

EP

1202 (2012) 028 )

GLoBES 2012

All irreducible backgrounds included

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Atmospheric neutrinos

Neutrino source available “for free“

Source not flavor-clean different channels contribute and mask effect

Power law spectrum

A. Smirnov

Many different baselines at once, weighted by solid angle

Detector: angular+energy resolution required!

arXiv:1210.5154

Akhmedov, Razzaque, Smirnov, 2012

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Mass hierarchy with atmospheric neutrinos

Akhmedov, Razzaque, Smirnov, 2012

Statistical significance depends on angular and energy resolution

About 3-10 likely for reasonable values

Final proof of principle will require event reconstruction techniques (in progress)

Comparison with alternatives

… and outlook

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Mass hierarchy

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!

3, Project X and T2K with proton driver, optimized neutrino-antineutrino run plan

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

PINGU2018-2020?

Ak

hm

edov, R

azzaqu

e, Sm

irnov, 2012; v5

3

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Probabilities: CP-dependence

There is rich CP-phenomenology:

NH

L=11810 km

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Upgrade path towards CP? Measurement of CP

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!

Tang, Winter, JHEP 1202 (2012) 028

same beamto PINGU

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Matter density measurementExample: LBNE-like Superbeam

Precision ~ 0.5% (1) 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

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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 3-5?

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

BACKUP

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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

Muons,neutrinos

Possible neutrino sources

Protons

Target Selection,focusing

Pions

Decaytunnel

Absorber

Neutrinos

Superbeam

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Detector paramet.: mis-ID

misIDtracks << misID <~ 1 ?

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

misID: fraction of events of a

specific channel

mis-identified as signal

1.0?

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Want to study e- 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 + and - (normally)

Detector requirements

13, CP

13, CP

13, CP

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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 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)

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Many proposals for measuring CP violation with a neutrino beam

Require all a dedicated (new) detector + control of systematics

Measurement of CP?

Coloma, Huber, Kopp, Winter, 2012