1. Neutrino telescopes and possible solutions to ambiguities in neutrinos
Yong Pyong 2008 APCTP Workshop
Neutrino telescopes and possible solutions to ambiguities in neutrinos
Kim Siyeon
Chung-Ang University

2. Contents Degenerate probability of oscillation 3 - 5
Astrophysical neutrinos
High energy neutrino detection
Neutrino ambiguity settlement
Concluding remarks 17
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3. Degenerate probability (1)
Neutrino Oscillation: The transition probability from na to nb
Pab = |< nb | na (t) >| = dab - 4 i<j∑ Re(UaiU*ajU*biUbj) sin2 xij i<j∑ Im(UaiU*ajU*biUbj) sin 2xij xij = (mi2-mj2)L/4E = 1.27 Dm2L/E in unit of (eV2.km/GeV)
Actual measurements:
Ambiguities: uncertainties and degeneracies
∫dEn dF/dEn sCC(En) Pab(En) e(En)
∫dEn dF/dEn sCC(En) e(En)
<Pab>=
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4. Degenerate probability (2)
Ambiguities: Either uncertainty or degeneracy ?
Degeneracy: Too many parameters but not that many experimental data
Physical parameters: me, mm, mt, m1, m2, m3 , q12, q23, q13, d.
Probabilities are degenerate due to: sign(Dm312), sign(q23-p/4), pairs of (q13 , d).
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5. Degenerate probability (3)
Disappearance probability: degenerate under changes q > p/2-q23 Dm231 -> -Dm231 normal hierarchy Inverted hierarchy
Appearance probability: sign(Dm231)sin2q13cosd is degenerate under multiple combinations
Pairs of (q13, d) consist 8-fold degeneracy.
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6. Astronomical neutrinos (1)
UHECR observation !
GRB models : A relativistic jet breaks through the stellar envelope 100TeV (or higher) neutrino sources, c.f., choked jets can produce TeV neutrino burst.
pg -> D+ -> pp+ dominant in GRB, producing HE neutrinos below the threshold. pp -> p+-,K +- dominant in low energy.
Typical energy of neutrinos from pion(20%) decay is 5% of protons.
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7. Astronomical neutrinos (2)
Flavor ratio: ( Fe : Fm : Ft )
Pion source: (1:2:0) ~ (p+ → … → e++nm+nebar+nmbar). The four leptons share equally the energy of the pion. (1:1:1) at telescope
Muon damped source: (0:1:0) from pion decays with muon absorption. dN/dE ~E-2, e.g., from GRB, above O(PeV).
(1:1.8:1.8) at telescope
pmnm
enmne
pm nm
e nmne
Kashti & Waxman 2005
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8. HE neutrino detection (1)
Oscillating probability after a very long travel: P( a →b, x) = ∑|Uam|2|Ubm| m  m’∑ Re(UamUam’Ubm’Ubm) cos(Dm2 x/2p) m  m’∑ Im(UamUam’Ubm’Ubm) sin(Dm2 x/2p)
= dab - 2 m<m’∑ Re(UamUam’Ubm’Ubm)
Neutrino fluxes are normalized s.t. F(ne)+F(nm)+F(nt)=1 Detected fluxes at telescope are F(na)=1/3(Pae+2Pam) for pion source. F(na)=Pam for muon-damped source.
Averaged out !
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9. HE Neutrino Detection (2)
Ice Cube: A km3-scale neutrino telescope to detect high energy, 0.1TeV < En < 10PeV.
1 Gton effective detector mass, 4800 optical modules.
 15 m
O(km) long muon tracks
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10. HE Neutrino Detection (3)
Measurement of neutrino flux:
IceCube will distinguish nm, ne, nt based on the event characteristics:
nm → m produce long muon tracks Good angular resolution, but limited energy resolution
ne → e produce EM showers Good energy resolution, poor angular momentum
nt → t → nt produce ‘double-bang’ events at high energy. One shower when t is produced, another when it decays. ντ τ
km3
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11. Neutrino ambiguity settlement (1) - Hwang and Siyeon arXiv:0711
Neutrino ambiguity settlement (1) - Hwang and Siyeon arXiv: , submitted to PRD
Assumptions: [1] Telescopes distinguish the muon-damped source from the pion source. [2] Telescopes distinguish three flavors of neutrinos near O(1015)eV, independently.
Kashti and Waxman
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12. Neutrino ambiguity settlement (2)
Probabilities and fluxes can be 8-folded degenerate at most from different sets of (q13, q23) and NH or IH.
Physical values are common in all figures.
In principle, the detection at tele- scope can solve all the degeneracy problems.
The JHF-Kamioka neutrino project hep-ex/
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13. Neutrino ambiguity settlement (3)
The Dm2 is hidden in flux measurements at telescopes.
The determination of q13 is likely to direct indication of mass spectrum, NH or IH.
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14. Neutrino ambiguity settlement (4)
In oscillation, 1-Pmm is most sensitive to q23, but is degenerate by a value of q23 and p/2- q23,, the complementary angle.
The fluxes at telescope are sensitive to q23, without giving rise to the degeneracy.
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15. Neutrino ambiguity settlement (5)
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 q23 and a pair of initial flux from muon-damped source and p/2-q23.
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16. Neutrino ambiguity settlement (6)
Safe distinction between different types of initial fluxes require better precisions in mixing angles, which can be obtained at coming stage of LBL and Reactor oscillations.
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17. 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 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.
Neutrino astronomy ! - Direct messenger of astronomical events. (better than protons) - Background-free detection.
KS…
Yong Pyong 2008 APCTP