New physics and astrophysical neutrinos in IceCube Atsushi Watanabe (Maskawa Institute, Kyoto Sangyo University) November 10 th, 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 )
A brief history of neutrino 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 ν μ (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 ν μ ν τ oscillation(opera) 2011 Hint of θ 13 (T2K,MINOS, Double Chooz) 2012 Determination of θ 13 (Daya Bay, RENO) 2013 High-energy neutrinos(icecube) 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 km 3 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 Two types of the main event Shower Track
IceCube observatory Shower Track
Neutrino Sky Atmospheric ν ~E -3.6 Astrophysical ν ~E -2 Cosmogenic ν (GZK neutrinos) [Halzen, 2007] PeV 1000 PeV
High energy cosmic rays [PDG, 2014] Up to PeV (Knee) -2.6 Below 2 nd Knee Galactic, SNe remnants Above 100 PeV Extra Galactic Above 10 19 ev cut by GZK effect E 2 Φ ~ 10-8 GeV cm -2 s -1 sr -1 PeV 1000 PeV Active Galactic Nuclei(AGN) Gamma Ray Burst (GRB)
A typical picture p p pγ Δ + π 0 p pγ Δ + π + n pp π ± ν p p pγ Δ + π 0 p pγ Δ + π + n (γ:cmb) ν AGN, etc. p High energy cosmic rays High energy neutrinos
Flavor transitions Incoherent propagation arxiv:1412.5106
Deviation from 1:1:1 Astrophysics Pion: 1:2:0 (0.35, 0.33, 0.32) With the best fit oscillation parameters [Gonzalez-Garcia, Maltoni, Schwetz, 2014] 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) IceCube, arxiv:1502.03376
Recent results on IceCube
A chronology 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.
Starting events(3 years) The neutrino events whose vertices are fully contained in the fiducial volume arxiv:1405.5303 988 days data 36 events ATM is rejected at 5.7σ γ best = -2.3
Starting events(3 years) No significant clustering (Isotropic) Northern Up-going But see Neronov, Semikoz, arxiv:1509.03522 for an argument 36 events in 30 TeV - 2 PeV ( 8 tracks, 28 showers) Southern down-going Background is 8.4 ± 4.2 (Cosmic lay muons) 5.0-12.5 (Atmospheric neutrinos) Paucity of tracks?
Flavor composition 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
Spectrum and flavor composition AW, arxiv:1412.8264 Fitting the energy distribution with four parameters Seeking the min of χ 2 function
Spectrum and flavor composition Fixed case is the best fit point (1 : 0.1 : 0) Inner : 68% Outer:95% CL region 1:1:1 is tangent to 76% surface
Spectrum and flavor composition The best fit of γ is 2.7 Χ 2 min as a function of γ n α :free n e =n μ =n τ n α :free n e =n μ =n τ The quality of the energy distribution fit is not much different between Flavored and Democratic
Spectrum and flavor composition Fixed case 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 IceCube Collaboration, arxiv:1502.03376 974 days data 129 showers, 8 tracks (starting events) 1:1:1 γ best is 2.6 Best fit ratio is 0 : 0.2 : 0.8 1:1:1 exclusion < 68% Tau is dominant
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 This analysis (best fit) 3-flavor model γ : same as the single case Previous analysis (best fit) 0:1:0 (muon dump) 55% 1:2:0 (pion) 27% 1:0:0 (neutron) 0.014% (3.6σ)
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 Line two body decay [1] Line + soft component [2] Long-lived particle X [4] 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;.
Neutrino mass, dark matter Neutrino mass 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
On the scale of new physics 10 19 GeV String GUT Energy scale 100 GeV
U(1) Lμ Lτ gauge symmetry 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 Bell, Volkas,2000; Joshipura, Mohanty, 2004; Bandyopadhyay, Dighe, Joshipura, 2007; Samanda, 2011; Heeck, Rodejohann,2011
U(1) Lμ Lτ gauge symmetry Muon g-2 can be addressed Ma, Roy, Roy,2002; Baek, Deshpande, He, Ko, 2001; Neutrino trident production Altmannshofer, Gori, Pospelov, Yavin, 2014
U(1) Lμ Lτ gauge symmetry It relates physics of IceCube Araki, Kaneko, Konishi, Ota, Sato, Shimomura, 2014 High energy neutrino CνB Interaction length The resonance energy is about
Z Earth ν ν(cνb) Source objects
U(1) Lμ Lτ gauge symmetry 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)
Regeneration and flavor composition DiFranzo, Hooper, arxiv:1507.0301 z=1 source
Regeneration and flavor composition DiFranzo, Hooper, 2015 T < mν the resonance window is narrow mν < T CνB momenta become Important, the resonance window get broadened
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
g-mz map Borexino CCFR BBN 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
Source distributions DiFranzo, Hooper, arxiv:1507.0301 Araki, Kaneko, Konishi, Ota, Sato, Shimomura, arxiv: 1508.0747 Normal ordering, Mz = 11 MeV