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Resonant Neutrino Self-Interaction
with U(1)Lμ-Lτ Model
AYUKI KAMADA (UC Riverside) in collaboration with Hai-bo Yu (UCR)
@第28回宇宙ニュートリノ研究会
“Dip” in IceCube
Good fit w/ ϕ(Ε)∝E-2
Missing events
at subPeV M. Aartsen et al. 2014
Possible InterpretationSources w/ ϕ(Ε)∝E-2
• Astrophysical (GRB, SNR)• Cosmogenic (pp, pγ…)• New Physics (DM decay, annihilation)
Origins w/ dip• Statistical fluctuation
-a few events expected (2σ consistent)• New Physics (neutrino interactions)
This talk
How does neutrino self-interaction work?
𝛎p~PeV
𝛎
k~10-4 eV
𝛎
𝛎
p’~p/2
k’~p/2
High energy neutrino
cosmic neutrinobackground (C𝜈Β)
High energy neutrino deposits their energy in cosmic neutrino background
Exclusive for subPeVOnly subPeV neutrinos interact effectively
achieved by Breit-Wigner Resonance
cosθ: injection angleTypically m𝜈 ~ 0.1 eV
>> k~10-4 eV~10 MeV
𝜈𝜈 -> Z’ -> 𝜈𝜈
mZ0 =p2m⌫p
m2Z0 = 2p(
pk2 +m2
⌫ � k cos ✓)
10 MeV mediator implied!!
Well-motivated model
Gauging (muon number - tau number) 𝜈μ(+1), 𝜈τ(-1)… anti-particles(opposite sign)
couple with Z’-boson (mZ’~10MeV!!)
Advantages• Anomaly-free (well-defined theory)• natural explanation of maximal mixing
for atmospheric neutrino θ23~π/4• No experimental difficulty
unlike U(1)Le-Lμ, U(1)Le-Lτ
(e.g. beam-dump experiment)
U(1)Lμ-Lτ
Muon g-2
aμ=(g-2)/2~0.001
Measured muon anomalous magnetic moment (g-2) deviates from standard model prediction
𝛥aμ(exp)=aμ(exp) - aμ(SM)=(42.6±16.5)×10-10
Z’-boson exchange contribution
�a
Z0
µ =g
0 2
8⇡2
Z 1
0dx
2m2µx
2(1� x)
x
2m
2µ + (1� x)m2
Z0
Gauge coupling of g’~10-4 can fill the gap!!
Optical depth
e⌧s(z) = 18⇣(3)T 3⌫,0(1 + z)3
1
H(z)m2Z0
�Z0
mZ0
' 1
✓g0
2.5⇥ 10�5
◆2
C𝜈Β number density
Streaming Length
Cross section
Gauge coupling of g’~10-4 is also sufficient to explain dip in IceCube!!
T. Araki et al. 2014
𝛎Β
𝛎Β
Is this brilliant story true?𝛎e
𝛎Β
𝛎μ
𝛎τ
𝛎e 𝛎Β
𝛎
𝛎
𝛎
𝛎
𝜈e’s can reach us without losing energy flavored (<->flavor-blind)
Neutrino oscillation I𝛎e
Starting with
IceCube
w/o oscillation𝛎Β
𝛎Β 𝛎e
Source 𝛎e
𝛎e 𝛎μ
𝛎τ
Neutrinos change their flavors during
oscillations
(c) IceCube
(c) NASA
Neutrino oscillation II𝛎e
Starting with
IceCube
w/ oscillation𝛎Β
𝛎Β 𝛎e
Source 𝛎e
𝛎μ
𝛎τ
𝛎Β
𝛎Β
Even starting with 𝜈e’s, only a part of 𝜈’s can reach us
(c) NASA
(c) IceCube
Neutrino oscillation IV
P '
2
40.30 0.13 0.120.13 0.06 0.050.12 0.05 0.04
3
5
+e�e⌧s(zs)/2
2
40.07 �0.05 �0.03�0.05 0.03 0.02�0.03 0.02 0.01
3
5
+e�e⌧s(zs)
2
40.18 0.15 0.120.15 0.29 0.310.12 0.31 0.35
3
5
Starting with
Probability matrix𝛎e 𝛎μ 𝛎τ End up with
𝛎e
𝛎μ
𝛎τ
Predictions and Prospectspp interaction(�⌫e ,�⌫µ ,�⌫⌧ ) ' (1, 2, 0)
@ IceCube (1/3 survived)(0.56, 0.25, 0.22)
z=zs z=0 Accumulated date can
distinguishflavored modelfrom
flavor-blindmodel
Cosmological/Astrophysical Aspects
Cosmology of 10 MeV Z’-boson I
inverse decay pair creation
decay pair annihilationTwo relevant processes
Dominant @ high-T @ low-TTcrit ' 100GeV ⇥
✓10�4
g0
◆⇥
⇣ mZ0
10MeV
⌘
Cosmic history w/ Z’
T~10 MeV T~0.1 MeVT~1 MeV
e 𝜈 𝛾
𝜈
e 𝛾 𝛾
BBNe-e+ annihilation𝜈’s decoupling
Ζ᾽
Ζ᾽
μ/π’s decay
Important question: When is Z’ decays?
Decoupling of Z’ III
T~10 MeV T~0.1 MeVT~1 MeV
e 𝜈 𝛾
𝜈
e 𝛾
BBNe-e+ annihilation𝜈’s decoupling
Ζ᾽
Ζ᾽
μ/π’s decay
Z’ decays in-between
heated 𝜈’s change the expansion ratespoil success of SM in BBN
𝛾
mZ’> 6.3 MeV
Core Collapse SNCore
Produced 𝜈’s can not escape from proto-neutron star
Neutrino sphere
Random walk
R = λ√N
T~8 MeVR~15 km
mean free path # of collisions
N=t/λλ~4 mt~10s
It takes
until escape
λ
𝛎
SN1987AThis 10s determines the duration of neutrino cooling
M. Nakahata 2007
Core Collapse SN w/ Z’Core
Same story for 𝝂e, but not for 𝝂μ 𝝂τ
Neutrino sphere
𝝂e
T~8 MeVR~15 km
inverse decay
decay𝛎e𝛎μ
Diffusion time w/ Z’
Diffusion time t~105s >> 10s (SN1987A)Mean free path λ~0.01cm
For g’~10-4 (good for Muon g-2, IceCube dip)
Notion• More detailed study needed to conclude…• Some additional cooling mechanism of core
(e.g. axion, hidden photons)
Only 𝝂e’s contribute to SN cooling
Prediction
𝛎e𝛎μ
SN
Super Kamiokande
𝛎τOnly 𝝂e’s are emitted from SN
Important hint ofthis scenario
(c) NASA
Summary
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