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New physics and astrophysical neutrinos in IceCubeseminar/pdf_2015... · V ~ 1 km3. Energy...
Transcript of New physics and astrophysical neutrinos in IceCubeseminar/pdf_2015... · V ~ 1 km3. Energy...
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New physics and astrophysical neutrinos in IceCube
Atsushi Watanabe (Maskawa Institute, Kyoto Sangyo University)
November 10th, 2015, @Particle Physics Theory Group, Osaka University
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Outline
We review recent results on IceCube and discuss the Lμ – Lτ gauge symmetry as an example of new physics probable by IceCube
● Introduction ・ Motivation ・ IceCube, High-energy astrophysical neutrinos ・ Typical picture on the source ● Recent results on IceCube ・Intensity, spectrum, directions, flavor composition, etc. ● From particle physics point of view ・Absorption lines in the spectrum (Lμ – Lτ gauge symmetry)
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Introduction
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Motivation
Neutrinos from natural sources have played important roles in the history of particle physics ● Solar neutrinos ● Atmospheric neutrinos We are really hungry for:Experimental inputs ⇒ Can we take advantage of the high-energy ones recently observed by IceCube? (Though we don’t know almost anything about the sources…)
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1930 Pauli’s proposal for the spectrum of the electron from beta decay 1934 Named ``neutrino” (Fermi) 1959 First detection(Reines, Cowan) 1962 Discovery of νμ(Lederman, Schwartz, Steinberger) 1970 Proposal of the solar neutrino problem(Davis) 1987 Supernova neutrinos(Kamiokande, IMB) 1998 Atmospheric neutrino oscillation(Super-Kamiokande) 2002 Solar neutrino oscillation(HomeStake, Gallex, SK, SNO) 2004 Reactor neutrino oscillation(KamLAND) 2010 Check of νμ→ ντ oscillation(OPERA) 2011 Hint of θ13(T2K,MINOS, Double Chooz) 2012 Determination of θ13(Daya Bay, RENO) 2013 High-energy neutrinos(IceCube)
A brief history of neutrino
20XX Discovery of ・・・in astrophysical neutrinos (IceCube, …)
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IceCube observatory
“A gigantic neutrino detector made of the Antarctic ice” 2005: Construction start 2011: Construction complete
V ~ 1 km3 Energy threshold ~100GeV By now neutrino events up to 2PeV have been observed → The first discovery of the high energy neutrinos of extratrrestrial origin
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IceCube observatory
Shower Track
Two types of the “main” event
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IceCube observatory
Track Shower
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・Atmospheric ν ~E-3.6 ・Astrophysical ν ~E-2 ・Cosmogenic ν (GZK neutrinos)
[Halzen, 2007]
Neutrino Sky
PeV
1000 PeV
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● Up to PeV (Knee) → -2.6 ● Below 2nd Knee → Galactic, SNe remnants ● Above 100 PeV → Extra Galactic ● Above 1019 eV → cut by GZK effect
E2 Φ ~ 10-8 GeV cm-2 s-1 sr-1
PeV 1000 PeV
High energy cosmic rays [PDG, 2014]
Active Galactic Nuclei(AGN) Gamma Ray Burst (GRB)
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A typical picture
pγ→Δ+ → π0 p pγ→Δ+→ π+ n pp→π±
AGN, etc.
pγ→Δ+ → π0 p pγ→Δ+ → π+ n (γ:CMB)
p
p
p
p
ν
ν
p
High energy cosmic rays ⇔ High energy neutrinos
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Flavor transitions
arXiv:1412.5106
Incoherent propagation
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Astrophysics
● Muon-dumped: 0:1:0 ⇒ (0.26, 0.36, 0.38)
● Neutron: 1:0:0 ⇒ (0.55, 0.26, 0.19)
● Charm: 1:1:0 ⇒ (0.40, 0.31, 0.29)
● Pion: 1:2:0 ⇒ (0.35, 0.33, 0.32)
With the best fit oscillation parameters [Gonzalez-Garcia, Maltoni, Schwetz, 2014]
IceCube, arXiv:1502.03376
Deviation from 1:1:1
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Recent results on IceCube
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● June 2012 Report on the 2 events (~1 PeV)@Neutrino2012 ● May 2013 28 events @IC Particle Astrophy. Symposium ● Nov. 2013 28 events paper, 1311.5238 (Science 342 (2013) 1242856) ● April 2014 Mena, Palomares-Ruiz, Vincent, 1404.0017 「Flavor composition」 ● May 2014 36 events paper, 1405.5303 「3 years data, 5.7σ」 ● Dec. 2014 AW, 1412.8264 「Spectrum and flavor composition」 ● Feb. 2015 Mena, Palomares-Ruiz, Vincent, 1502.02649 「Spectrum, flavor composition etc. 」 ● Feb. 2015 Flavor composition, 1502.03376 ● July 2015 Up-going muon, 1507.04005 「3.7σ」 Combined analyses 1507.03991 「spectrum etc.」
A chronology
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● arXiv:1405.5303 988 days data 36 events ⇒ ATM is rejected at 5.7σ ● γbest = -2.3
Starting events(3 years) The neutrino events whose vertices are fully contained in the fiducial volume
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● No significant clustering (Isotropic) ● 36 events in 30 TeV - 2 PeV ( 8 tracks, 28 showers) Background is 8.4 ± 4.2 (Cosmic lay muons) 5.0-12.5 (Atmospheric neutrinos) ⇒ Paucity of tracks?
Northern Up-going
Southern down-going
Starting events(3 years)
But see Neronov, Semikoz, arXiv:1509.03522 for an argument
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Mena, Palomares-Ruiz, Vincent, arXiv:1404.0017/1411.2998
● 2 bin analysis; 28 shower events and 8 track events in 30 TeV - 2 PeV range ● The best fit is 1:0:0 ● For E-2 spectrum, 1:1:1 is disfavored at 92%CL
Flavor composition
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AW, arXiv:1412.8264
Fitting the energy distribution with four parameters
Seeking the min of “χ2 function”
Spectrum and flavor composition
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★ is the best fit point (1 : 0.1 : 0) Inner : 68% Outer:95% CL region
1:1:1 is tangent to 76% surface
Fixed
Spectrum and flavor composition
case
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Χ2min as a function of γ
The best fit of γ is 2.7
nα:free ne=nμ =nτ
nα:free
ne=nμ =nτ
The quality of the energy distribution fit is not much different between Flavored and Democratic
Spectrum and flavor composition
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★ is the best fit (still 1 : 0.1 : 0) 1:1:1 is tangent to 38% surface ⇒ with the miss ID of the track events, it goes down to12%
Spectrum and flavor composition
Fixed case
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IceCube Collaboration, arXiv:1502.03376
974 days data 129 showers, 8 tracks (starting events)
1:1:1 → γbest is 2.6 Best fit ratio is 0 : 0.2 : 0.8 1:1:1 exclusion < 68% Tau is dominant
Spectrum and flavor composition
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Up-going muon IceCube Collaboration, arXiv:1507.04005
● 659.5 days (May 2010 – May 2012) ● ATM only is disfavored at 3.7σ ● Consistent with the starting event
● No point source so far
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Combined analysis IceCube Collaboration, arXiv:1507.03991
A “global fit” of the up-going muon and the starting event data
● Non-flavored, single power low ● 2.0 is disfavored at 3.8σ ● High-energy cut does not help much, it’s still disfavored (2.1σ w.r.t free γ)
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Combined analysis
● 3-flavor model ● γ : same as the single case ● 0:1:0 (muon dump) 55% 1:2:0 (pion) 27% 1:0:0 (neutron) 0.014% (3.6σ)
Previous analysis (best fit)
This analysis (best fit)
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Combined analysis
● Northern sky ● Southern sky But significance is low (1.1 σ)
● Consistent with 3-flavor model, Muon dump > pion > neutron
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From the particle physics point of view
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Dark matter, long-lived particles
An incomplete list; [1]Feldstein, Kusenko, Matsumoto, Yanagida, 2013; [2]Esmaili, Serpico, 2013; Higaki, Kitano, Sato, 2014; [3]Bhattacharya, Gandhi, Gupta, 2014;[4] Ema, Jinno, Moroi, 2014; [5]Fong, Minakata, Panes, Funchal, 2014; [6]Dudas, Mambrini, Olive, 2014; ….
● Line ⇒ two body decay [1] ● Line + soft component [2] ● Long-lived particle X [4] …
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Dark matter
・ Right-handed neutrinos ・ Triplet Higgs ….etc.
・ Particle dark matter (stable, neutral, non-baryonic)
Gauge-singlet fields
The known gauge group of the standard model should not be the final one
Neutrino mass
Neutrino mass, dark matter
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On the scale of new physics
GUT
String
Energy scale
100 GeV
1019 GeV
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U(1) Lμ – Lτ gauge symmetry
Bell, Volkas,2000; Joshipura, Mohanty, 2004; Bandyopadhyay, Dighe, Joshipura, 2007; Samanda, 2011; Heeck, Rodejohann,2011
Right-handed neutrinos
● The new gauge field does not coupled to the electrons ● It naturally explains large μ-τ mixing ● One can build models at the renormalizable level ● The new gauge boson can be lighter than the EW scale
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U(1) Lμ – Lτ gauge symmetry
Muon g-2 can be addressed Ma, Roy, Roy,2002; Baek, Deshpande, He, Ko, 2001; ・・・
Altmannshofer, Gori, Pospelov, Yavin, 2014
Neutrino trident production
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It relates physics of IceCube Araki, Kaneko, Konishi, Ota, Sato, Shimomura, 2014
CνB High energy neutrino
The resonance energy is about
U(1) Lμ – Lτ gauge symmetry
Interaction length
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Source objects
ν
Earth
ν(CνB)
Z’
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Araki, Kaneko, Konishi, Ota, Sato, Shimomura, arXiv:1409.4180; arXiv: 1508.0747
The parameter region interesting for Icecube has an overlap with the region favored by the muon g-2 anomaly Other constraints ● CCFR (neutrino trident) ● Borexino (νe → νe) ● BBN (# of relativistic dof)
U(1) Lμ – Lτ gauge symmetry
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Regeneration and flavor composition DiFranzo, Hooper, arXiv:1507.0301 z=1 source
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Regeneration and flavor composition
T < mν → the resonance window is narrow
mν < T → CνB momenta become Important, the resonance window get broadened
DiFranzo, Hooper, 2015
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Regeneration and flavor composition DiFranzo, Hooper, 2015
●Inverted case ● T < mν → same as the Normal ● mν < T → drastically changed
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Energy distribution of the events
work in progress
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CCFR
Borexino
BBN
g-Mz’ map
work in progress
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Summary and outlook
● The observation of the high-energy neutrino so far get along with typical astrophysical scenarios ・ ~E^(-2.5) (-2.0 is disfavored) ・Isotropic diffuse flux ● What are the sources ? ● Tau flavor (double bang), neutrino/antineutrino fraction would be the key information to go farther ● The relation to particle physics is also interesting
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DiFranzo, Hooper, arXiv:1507.0301
Araki, Kaneko, Konishi, Ota, Sato, Shimomura, arXiv: 1508.0747
Source distributions
Normal ordering, Mz’ = 11 MeV