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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
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)
Introduction
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…)
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, …)
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
IceCube observatory
Shower Track
Two types of the “main” event
IceCube observatory
Track Shower
・Atmospheric ν ~E-3.6 ・Astrophysical ν ~E-2 ・Cosmogenic ν (GZK neutrinos)
[Halzen, 2007]
Neutrino Sky
PeV
1000 PeV
● 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)
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
Flavor transitions
arXiv:1412.5106
Incoherent propagation
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
Recent results on IceCube
● 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
● 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
● 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
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
AW, arXiv:1412.8264
Fitting the energy distribution with four parameters
Seeking the min of “χ2 function”
Spectrum and flavor composition
★ 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
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
★ 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
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
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
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)
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)
Combined analysis
● Northern sky ● Southern sky But significance is low (1.1 σ)
● Consistent with 3-flavor model, Muon dump > pion > neutron
From the particle physics point of view
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] …
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
On the scale of new physics
GUT
String
Energy scale
100 GeV
1019 GeV
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
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
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
Source objects
ν
Earth
ν(CνB)
Z’
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
Regeneration and flavor composition DiFranzo, Hooper, arXiv:1507.0301 z=1 source
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
Regeneration and flavor composition DiFranzo, Hooper, 2015
●Inverted case ● T < mν → same as the Normal ● mν < T → drastically changed
Energy distribution of the events
work in progress
CCFR
Borexino
BBN
g-Mz’ map
work in progress
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
DiFranzo, Hooper, arXiv:1507.0301
Araki, Kaneko, Konishi, Ota, Sato, Shimomura, arXiv: 1508.0747
Source distributions
Normal ordering, Mz’ = 11 MeV