new physics and astrophysical neutrinos in icecubeseminar/pdf_2015... · v ~ 1 km3. energy...

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