Flavor identification of astronomical high energy neutrinos and

the accuracy of mixing angles

Kim SiyeonChung-Ang University

2008 - 6 - 20

Based on the work with G.R. Hwang, arXiv:0711.3122

SUSY 08, Seoul

2008 – 6 – 20 SUSY08 K. Siyeon 2

Outline

I. Oscillation probability: degeneracy and uncertaintyII. Neutrino flux from a astronomical sourceIII. Specification of initial flux from pion decayIV. Neutrino telescope as ambiguity settlementV. Concluding remarks

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Oscillation

• The transition probability from to P = |< | (t) >|2

= i<j∑ Re(UiU*jU*

iUj) sin2 xij

i<j∑ Im(UiU*jU*

iUj) sin 2xij

xij = (mi2-mj2)L/4E = 1.27 m2L/E in unit of (eV2.km/GeV)

• Sensitive for 23

• Degenerate under 23 -> /2- 23 and under m31

2 -> - m312

• Sensitive for 13

• The leading term requires significant matter effect to distinguish the sign of m31

2 .

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HE neutrino detection

• Oscillating probability after a very long travel: P( →, x) = ∑|Um|2|Um|2 + m m’∑ Re(UmUm’Um’Um) cos(m2 x/2p) + m m’∑ Im(UmUm’Um’Um) sin(m2 x/2p)

P =∑|Um|2|Um|2

• The ranges in elements estimated from PMNS at 3s CL:

0.48-0.64 0.12-0.34 0.11-0.35 P =0.33-0.53 0.30-0.41 0.33-0.47

Averaged out !

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Astronomical neutrinos

e

e

Kashti & Waxman 2005

• Flavor ratio: ( e : )

• Pion source: (1:2:0) The four leptons share equally the energy of the pion. (1:1:1) at telescope

• • Muon damped source: (0:1:0)

muon decay is suppressed due to EM energy loss.(1:1.8:1.8) at telescope

• Review on atmospheric neutrinos:

Re) = 2 at low energy (E < 1GeV)

R(e) -> higher and higher at high energy

Atmospheric neutrinos

e

e

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HE Neutrino Detection

• Ice Cube: A km3-scale neutrino telescope to detect high energy, 0.1TeV < E < 10PeV.

• 1 Gton effective detector mass, 4800 optical modules.

15 m

O(km) long muon tracks

ντ

τ ντ

kmkm33

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Initial flux identification

• Assumptions:

[1] Telescopes distinguish the muon-damped source from the pion source.

[2] Telescopes distinguish three flavors of neutrinos near O(1015)eV, t(e) : t() : t() .

[*] Independent are three of the following four fluxes:

*t(e) from pion source * t(e) from muon-damped source* t() from pion source * t() from muon-damped source

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Flux sensitivity to

mixing angles

The flux of e :

• Linear and sensitive to 23

• No degeneracy with the complementary angle, cf. 1-P

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Degeneracy in probability• Probabilities and fluxes can be 8-folded degenerate at most from different s

ets of (13, 23) and NH or IH.

• P is considered together to get rid of factors of ambiguities: uncertainties or degeneracies

• (a,b,c,d) for 23 < /4(e,f,g,h) for 23 > /4

• (a,b,e,f) for NH(c,d,g,h) for IH

The JHF-Kamioka neutrino project

hep-ex/0106019

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Composition of a mixed beamType of source?• In reality, neither pure pion

source nor pure muon-damped source is detected.

Difficulties come from• No idea for the compositio

n in the initial flux depending on the physical condition at astronomical bursts.

• Neutrino parameters themselves bear ambiguities, broad uncertainties and degeneracies.

source damped

chosen

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Breaking degeneracy (1)

• The m2 is hidden in flux measurements at telescopes.• The determination of 13 is likely to indicate whether NH or IH.• If 13 >0.03, its value will be found in a few years by Double Chooz, Day

a Bay, or RENO. IceCube starts running in 2013.

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Breaking degeneracy (2)• In oscillation, 1-P is most sensitive to 23, but is degenerate

by a value of 23 and /2- 23,, the complementary angle.• The fluxes at telescope are sensitive to 23, without giving

rise to the degeneracy.

The existence of source-blind fluxes:

The same magnitude of flux is obtained by

a pair of initial flux from pion source and a value of 23 and

a pair of initial flux from muon-

damped source and /2-23.

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Concluding Remarks

• The settlement of degeneracy problems by the telescope requires somewhat of improvement in precision of other experiments ahead, whose accomplishment is likely possible before 2013, the year of telescope working.

• The composition of astronomical HE neutrino beams requires better precision for mixing parameters.

• The determination of the neutrino parameters in different types of experiments complementary to each other.– Long-base line neutrino oscillation– Reactor neutrino oscillation– Neutrino telescope with high energy sources.