“PeV γ-ray in relevance toν, CR and particle physics”:
Can we peep into γ-ray PeV region through “cosmic cascade” ?
by T. Kifune, a talk in ICRR, Oct 3, 2014•

Many related ? talks in this meeting“CTA Key Science Projects”

井上 進（東大宇宙線研 & MPI)•
“Recent Fermi-LAT resultstoof Active
Galactic Nuclei” PeV田中康之（広島大学） rays ?
Necessaryobservegamma••「活動銀河「ジェットを”持たない”銀河からの高エネルギーガンマ線放射」 林田 将明（東大宇宙線研）
風からのガンマ線と超高エネルギー宇宙線」
井上 進（東大宇宙線研 & MPI）••

「最高エネルギー宇宙線による極限宇宙観測」
野中 敏幸（東大宇宙線研）“Current status and future prospects for ultrahigh-energy cosmic raysfrom a theoretical point of view”
高見 一（KEK）••“Recent results from IceCube”「低光度活動銀河核からの高エネルギーニュートリノ放射」••「宇宙近赤外線放射観測の現状」
津村耕司（東北大学）“Can gamma-ray observations probe the cosmic infrared background radiation?” 井上芳幸 (ISAS)

石原 安野 （千葉大学）
木村 成生（大阪大学）

ClosedAbsorption
lengthDistance tovarious objects

For
extragalactic
γ-raysof PeVenergy

From Jim Hinton
2010

“PeV γ-ray in relevance to ν, CR and particle physics”:

Can we peep into γ-ray PeV region
through “cosmic cascade” ?

by T. Kifune, a talk in ICRR, Oct 3, 2014

1. PeV ガンマ線の検出
Try to “observe”
PeV γ raysfrom TeV region
2. 展望
Prospect for
UHE CR and universe
3. 究極の物理
basic concept

PeV γ-ray astronomy ?
Gamma rays from pion decay ハドロン起源ガンマ線 ?

Implication of IceCube event ?
Origin of cosmic rays 宇宙線の起源 ？

the viewpoint of Planck scale, “LIV” ?
Elementary particle and Universe 「素粒子的宇宙像」 ?

Outline of the talkextended halo around AGN ?

intrinsic 1ry γ-ray emitted from AGN
γ + ε  e+ e-,ip + ε  p(n) + π,ii

Ice Cubeν evente+εe+γ

TeV Gammarays

Cosmiccascade ?

PeV Gamma rays

Emission ofPeV γ-rays

Can we look into PeV γ-ray region
from TeV ?

π  γ, νΘint ≈ (me/E)・N0.5
Θmag ≈ (RLarmor/λ)・N0.5
N ≈ λ/distanceλ : absorption length

modification of γ-ray spectrum

2ry γ-ray emitted in
extragalactic spaceby extragalactic CRs

PeV peaked neutrino ?
constraint, restriction, informationiii

PeV energy region, and LIV, QG

Contents Free, Association Thoughts (空想、迷想、連想…..の放談 )関連論文(i)

Cosmiccascade?

“Search forextended emission
around AGN ….”“Pair halo”,“Magnetically– HESS AA
Broadened562,A145(2014), Cascade”
arXiv1401.2915 γ + ε  e+ e-,“Role of line of sight CR
Int. of distant blazars ….
to TeV γ and HE ν”

Cascade process of“CR interaction
In extragalacticspace”

Essey et al.
ApJ 731, 51 (2011)arXiv 1303.0300(2013)
p + ε  p(n) + ππ  γ, νe+εe+γiiiii

PeV νLIV, QG“First observation of PeV-energy
neutrinos with IceCube”
arXiv 1304.5356 (2014)“Cosmic neutrino pevatrons:
A brand new pathway to astronomy,astrophysics, and particle physics”
Journal of High Energy
Astrophysics 1–2 (2014) 1–30

“The CTA Sensitivity to Lorentz-Violating Effects on the Gamma-Ray Horizon”
arXiv:1401.8178v2
by M.Fairbairn, A.Nilsson, J.Ellis, J.Hinton, R.Whited“Detection method and observation data of high energy gamma rays
under the influence of QG”
T. Kifune, ApJ 787, 4 (2014)“Tests of Lorentz Invariance Violation with Gamma Rays to probe
Quantum Gravity” ,….. G.Sinnis,…..arXiv:1305.0264

Ice Cubeneutrino

PeV peaked neutrino ?

•616 days = 5.3 x 107 sec Area = 10 m2 = 105 cm2, ST = 5 x 1012 cm2s

•flux is about 2 x 10-13 cm-2s-1 = 102 eV cm-2s-1 at 1015eV

There may be a high-energy cutoffof neutrino events in IceCube data.
In particular, IceCube does notobserve the Standard Model
Glashow-resonance events
expected at 6.3 PeV.

First of all, if the neutrino flux is indeed aFermi-shock flux falling as an unbroken E−2
ν power-law spectrum(Fermi,1949) would
lead to about 8–9 events above 1PeV,
which thus far are not observed:
From “Review Cosmic neutrino
pevatrons: A brand new pathway toastronomy, astrophysics, and particle
physics”
Glashow resonanceICE Cube Neutrino ?
“Point source” emission from blazar

extragalactic diffuse γ-ray

1-10 eV cm-2 s-1
10-100 eV cm-2 s-1sr-1

PeV peaked neutrino

A peaked neutrino spectrum accompanies secondary
gamma rays produced in line-of-sight interactions of cosmic
rays emitted by Blazars (Essey and Kusenko,2010;
Esseyetal.,2010,2011b). The lowest position of the peak is
at1PeV. Assuming that a distribution of AGN with respect
to maximal proton energy Ep,max is a decreasing
function of Ep,max, a decreasing function of Ep,max

The proton injection spectrum has a spectral index
α=2.6 and maximum energy Ep,max = 3×1017eV.
Also shown are the predicted gammaray (lower curves
Below 10TeV) and cosmic ray (upper curve) fluxes.

There may be a high-energy cutoff of neutrino events in IceCube data. In particular, IceCube
does not observe the Standard Model Glashow-resonance events expected at 6.3 PeV.
From “End of the cosmic neutrino energy spectrum”
arXiv:1404.0622v2 Anchordoqui et al. （... Learned, ... Pakvasa, )PeV peaked
neutrino ?

ニュートリノがとり得るエネルギーに最大値が存在する！？

This new phenomenon at the Planck scale may take several forms.
Some possibilities are(i) Gravity becomes strong for the neutrinos at the Planck scale, either preventing the formation of theneutrino wave packet or presenting a strong cross section for neutrino scattering o gravity/geometry, withsignificant loss of neutrino energy.
(ii) Space-time manifests itself as foam at the Planck scale, either preventing the formation of the neutrino
wave packet or presenting a strong neutrino-foam scattering cross-section with significant loss of neutrinoenergy. These continued foam interactions are reminiscent of the quantum Zeno effect.
(iii) Lorentz Invariance is violated (LIV) at the Planck scale. A simple manifestation of LIV, broken rotational
symmetry, results if space dimensions are latticized at the Planck scale, as often discussed over the pastdecades; in the the scale present context, the manifestation of LIV is the apparent maximum neutrino energy.
(iv) The neutrino may even transit from our brane into extra space dimension(s) having size natural togravity, the Planck length.

“PeV gamma ray ……
From Kifune ApJ 787, 4 (2014)
Quantum Gravity, LIV ? ” E2 = p2 + m2 + pn+2/Mn , M ≈ Planck mass
10TeV-PeV gamma ray の：“Planck scale での LIV”を仮定すると、実は1. 放出機構： 通常の conventional な理解は、 正しくないのではないか？
Emission mechanism Inverse Compton^

2. 吸収・伝播の効果： 地球に、 到達できるのではないか？
Propagation/absorption effect
3. 検出方法： 通常の方法では、正しく効率よく検出できないのではないか？
Detection mechanism/efficiency「観測データ」、その「常識的解釈」は信用できるか？

Critical energy E*, ε*• Obsrvation data tell us the truth ?
n=11 E* = (Mme2)1/3 ≈ 1013 eV,
ε* = (me4/M)1/3 ≈ 10-2 eV• Are we seeing the true image of the Universe?
• Can we get “smoking gun” evidence ?

n=21

E* =(Mme)1/2 ≈ 1017 eV,
ε* =(me3/M)1/2 ≈ 10-4 eV

Propagation of γ-rays :γ-rayflux

absorbed by CMB, EBL
causing “cosmic cascade”

a bump, deformation ofenergy spectrum in TeV region

spatiallyextended
halo

Cascade of electron and γ-ray reaction
Gamma rays
we observe

PeV ガンマ線を「覗き見る」

Absorption by 2.7K MWB

TeVFlux of PeV γ-ray
as large as the PeV ν of the IceCube events

PeV

Case 1

1ry

AGN of HESS analysis for “Halo”

if LIV effect of n=1 is true,
1ry (HESS): partly diminished,
2ry (Essey etal.)  0

1ES 1101-232, 1ES0229+200, PKS 2155-304 obs time 63-165 hrs, flux, Γ= 3.1, 2.6 and 3.4

These AGN are in the preferable redshift range andhave emission extending into the multi-TeV energy,
thus making them ideal candidates of this study.
Extreme blazar
Case 22ry

AGN of Essey et al. (Kalashev et al.) for “CR cascade”
from PeV neutrino event

1ES 1101-232, 1ES0229+200, 1ES 0347-121; EBL model, Lp

PeV peaked γ

We have chosen three most distant blazars observed in the TeV energy range,
which show no variability.
We fit the spectra with secondary gamma rays producedby cosmic-ray interactions along the line of sight. .

The observed high-energy gamma-ray signals from distant blazars may
be dominated by secondary gamma rays produced along the line of sightby the interactions of cosmic-ray protons with background photons.

AGN

E2 φ eV cm-2 s-1(sr-1)

pEBL

Cascade processabsorbed

Case 2 : Essey et al. papercascade from 2ry γ-rays only in PeV regio

AGN

1ry spectrum“bump”

1012

Case 1 : HESS paper on “halo aroundAGN”
1ry + cascade γ-rays

1015

E (eV)

1018

Extendedhaloaround AGN– HESSAA(2014),
arXiv
1401.2915

Both extended pair halo (PH) and magnetically broadenedcascade (MBC) emission from regions surrounding a blazar.

1ES 1101-232, 1ES 0229+200 and PKS 2155-304

Spatially extended
halonot detectedenergy spectrum

Essey et al.
ApJ 731,51(2011)
Role of Line ofsight CR int. ….
from AGN

The total flux” = “EBL intensity” x Lp
1ES 1101-232, 1ES0229+200, and 1ES 0347-121

high EBL

low EBLThe data show some preference for high EBL, although it is not significant .
(this is in contrast with the limit set on EBL under the assumptionthat all the observed gamma rays are primary).

How the cascade process modifies γ-ray spectrum ?
A part of the observed flux issecondary γ-rays, product of cascade process.
A “bump”
due to cascade
appears
below 1 TeV
Injection
spectrum

Injection(intrinsic)
Spectrumto be changed ?

Contribution
From cascade

本来の (intrinsic) ガンマ線スペクトル？

after absorption

two models comparedfor 1ES0229+200

Observed spectrum of TeV γ-rays
can be fitted bya F(TeV-PeV) + (1-a) G(PeV) where 0 < a < 1
Injection spectrum F (TeV-PeV)

HESS analysis

Cosmic cascade of γ-rays
Emitted/radiated from AGN

γ –ray energy
TeVPeV

Same observation data in TeV region
Essey et al. analysis

Injection spectrum

G (PeV)

TeV γ
TeV

PeV γPeV

Cascade of proton
reactions emitted/
escaped from AGN

Conclusion /discussion from HESS paper on the halo
• HESS and Fermi data shows no indication of such (extended halo) emission.

• Upper bound on past 5 years activity; time variability for the primary gamma ray and no variability for the secondary.
• Some constraint on high energy electrons in extragalactic space and extragalactic magnetic field.

Conclusion of Essey et al. paper•

The surprisingly low attenuation of high-energy gamma rays; secondary gamma rays produced in interactions ofcosmic-ray protons with background photons in the intergalactic space.
•We have obtained excellent fits to observed spectra of several distant blazars.
•
At low energies the spectra are harder than predicted by theoretical models (Malkov & Drury 2001; Stecker et al. 2007).
•Secondary gamma rays expected to show no temporal variability. a strong discriminant between 1ry and 2ry gamma
rays.
•predictions for secondary neutrino signals from blazars at about 1–10eV cm−2 s−1, depending on source and model
parameters.
•predictions for neutrinos, besides the spectral shape. (1), there should be no temporal variability observed forneutrinos. (2), the luminosity of sources should vary with distance as 1/d, as opposed to the usual 1/d2 scaling law.
more distant sources observable, as compared to predictions for primary neutrinos. (3), the flavor structure of theobserved signal should differ from primary neutrino models.
•A new powerful method to probe the radiation and magnetic field contents of intergalactic space, as well as AGNproperties.
Implication of EBL and CR acceleration model•
The overall flux depends on the EBL multiplied by the unknown and poorly constrained Lp. …At present, the data show
some preference for high EBL, although it is not significant . (this is in contrast with the limit set on EBL under theassumption that all the observed gamma rays are primary).

ここまでを まとめると……

HESS paper: 1, 2 …. Essey et al. paper: 3, 4
1. No extended halo : some constraint on extragalactic mag. Field
2. Upper bound on past 5 years activity; time variability
3. dependence on IR-FIR EBL intensity, distance“The total flux” = “EBL intensity” x Lp (in the case of Essey et al.)
4. “γ-ray flux 1-10 eV cm-2 s-1 = 10-12-10-11 erg cm-2 s-1 from the AGNs”
can be explained as consistent with IceCube ν
0. The two models explain the same observational data :Interpretation of observed data is ambigousa F(TeV- PeV) + (1-a) G(PeV), “intrinsic” spectrum ?
Gの形も任意！

Questions from the viewpoints of this talk
A. Can we peep into PeV γ-ray sky?
PeV を覗き見ることができるか？
B. Some information about LIV effect in PeV region ?
“cosmic cascade model” は LIV effect 否定,
i.e. No absorption due to 2.7K MWB の clear evidenceとなりえるのか ?

B.

Yes/No Emax ?, G(PeV)?

A. maximum energy

and “shape” of γ-rays
radiated by “galaxy”

Too ambigous, situation is too complicated,
not as simple as to examine/claim just “no LIV”.

(1) “intrinsic” γ-ray spectrum from extragalactic sources ?
observed spectrum ≄ “intrinsic spectrum” from AGN(2) Are we required to detect ν signal, PeV γ-ray signal from AGNs,
in order to correctly understand AGN, Origin of CRs, …….. ?

われわれは どう対処すべきか？ How to diminish ambiguity ?
● to examine spectra of γ-rays from galaxies of various distances :CTA observation at ∼100 TeV ? ---- F-N-Ellis-Hinton-W paper

LIV effect exists

No LIV effect

Cutoff energy:(i) High (ii) low

Cutoff energy:(i) High (ii) low

E2 φ eV cm-2 s-1 (sr-1)

Intrinsic spectrum + absorption by EBL

Cutoff :(i) High

Cutoff :(i) High(ii) low(ii) low

intrinsic
cutoff

TeVPeV

TeVPeVE2 φ eV cm-2 s-1 (sr-1)

z ≈ 0.1 :distantAGN

LIV effect exists

No LIV effect

Cutoff energy:(i) High (ii) low

Cutoff energy:(i) High (ii) low

Bump as a result ofCascade process
Cutoff :(i) High

Cutoff :(i) HighHESS case.
(ii) low(ii) low

intrinsic
cutoff
No 1ry TeV γ-rays
in case of Essey et al.

TeVEssey et al.

PeV
Cascade due toabsorption by IR,EBLTeV

PeV
Cascade due to
2.7K MWB

Schematic explanation of cascade effect ( the effect might be a bit exaggerated)From Jim Hinton
2010

2.7K
photon10-3-10-4eV

We have shown in this paper that CTA potentially has very
competitive sensitivity to Lorentz violation, namely to MLV 11019 GeV and MLV 2 1011 or more. The most promising of
the sources we have studied is Markarian 501. As shown inTable 1, assuming a power-law spectrum with noexponential cut-off, we estimate a 5- sensitivity to MLV 1 =4:51020 GeV after 50 hours of observations, assuming acontinuing power-law emission flux. Under the sameassumptions, in the case of a quadratic modification of thephoton dispersion relationone could detect photons if MLV 2= 5:9 1012 GeV for n = 2.

IR, FIR
photon10-0-10-2eV

“The CTA Sensitivity to Lorentz-Violating Effects on the Gamma-Ray Horizon”
M.Fairbairn, A.Nilsson, J.Ellis, J.Hinton, R.Whited. arXiv:1401.8178v2,J. Cosmology Astroparticle Physdistance that leads tojust absorption,

Mrk 501 to testify LIV effectno cascadedue to EBR (IR, FIR) photon● Mrk 501 z=0.034 137Mpc
5.8x10-12 (E/1TeV)-2.72 cm-2s-1TeV-1

50 hrs observation,
3-5 sigma result claimed● Mrk 421 z=0.03 125Mpc
Cutoff of energy spectrum
at 1.4 TeV
1.6x10-9 (E/0.2TeV)-2.2 exp(-E/1.4TeV)cm-2s-1TeV-1
To fall too steeply above 1TeV for a useful flux ti be exoected at 100TeV● M87 z=0.0044 18Mpc; too near

7.1x10-12 (E/0.3TeV)-2.21 cm-2s-1TeV-1

z ≈ 0.03 : Mrk 501
LIV effect exists No absorption

No LIV effectby 2.7K MWB

E2 φ eV cm-2 s-1 (sr-1)

Clear enough to distinguish these ?

Bump as a result ofCascade process

Absorption
by EBL of IR
intrinsic cutoff

TeV

PeV

TeV

PeV

…some other fundamental physics mechanism,,,,(e.g. axion-like particles)….We would also
like to emphasize that different modifications of fundamental physics, such as energy
non-conservation, might conspire to diminish or even eliminate the effect discussed here.
Despite these caveats, we think that our analysis opens up a physics area of great
potential interest for CTA. and ….. (conclusion---Fairbairn, Nilsson, Ellis, Hinton and White)

Gamma-rays from local group galaxies:
TeV gamma-ray detected M87(16Mpc), Cen A(5Mpc), M82 (3.6Mpc),
NGC253(3Mpc):

arXiv 1012.1951

Local group galaxies :No Cascade process
Due to absorption
By EBL of IR photon

No LIV effect

LIV effect exists

E2 φ eV cm-2 s-1(sr-1)

The effect is simpler,
Easier to check ….

intrinsic cutoff

TeVPeV

TeV

Just a Bump
as a result of Cascade process
due to absorption by 2.7K MWBPeVLocal galaxies

A. Abramowski et al. 2012 ApJ 757 158

NGC 253
Γ=2.14

Γ=2.24
Γ=2.34

Γ=2.3, ….. 2.1

Cosmic cascadestudied as a function of distance

γ-ray flux as high as ICECube ν
1-10 eV cm-2 s-1(1) AGN of z = 0.1 - 0.2 :1-10 eV cm-2 s-1 = 10-12-10-11 erg cm-2 s-1
z = 0.117, 0.14, and 0.186, IR EBL contributes to cascade effectdip & bump : γ-ray spectrum largely deformed(2) Mrk 501 z = 0.03 1-10 eV cm-2 s-1(Mrk 421: cut off, M87: too near)a “dip”, but no “bump”

absorption due to EBL(3) Nearby active/local group galaxies
0.1-10 eV cm-2 s-1

a “bump”, no “dip”

cascade effect due to 2.7K MWB

flux : dependence on distance, d-1 or d-2 ?
Emax: cutoff energy ?
correlation with jet, time-variability

extragalactic diffuse gamma ray

多面的な視点を加えて

to observe direction of ν signal, PeV γ-ray signal ?

Hopefullydiminishuncertainties

P + ε → p + pion

LIV effect on radiation mechanism

LIV effect may change the estimation of“CR proton (intergalactic space) + EBL photonπ production

Fn= 1 or 3 for n=1 or 2, respectively
a = K/E0 , where K is pion energy••

Left-hand side > 1st term of right-hand side:
ε E0 > mpmπ ≈ 1017 (eV)2Left-hand side > 2nd term of right-hand side
E0 < (ε M)1/2 ≈ 1014 ε1/2 eV, that is, ε > 10-28 E02 eV• suppression by LIV crosses at E0 = 1015 eV and ε < 100 eV,
LIV effect of “photo-pion production” can bring about“PeV peaked neutrino” ?

Photo-pion production

p + ε → p/n + π0/+→ γ or νn=11
E* = (Mmpmπ)1/3 ≈ 1015eV,
ε* = (mp2mπ2/M)1/3 ≈ 102eV
n=21(M2mpmπ)1/4 ≈ 3x1018eV,
ε* = (mp3mπ3/M2)1/4 ≈ 1 eVdiffuse emission
from GRB, …….

PeV peakedneutrino / gamma-ray?
Intense photons ofshort wavelengths

Summaryandremarks

Necessary to directly detect PeV γ-rays ?
a tough road not paved as TeV γ-ray astronomy

UHE CRs

PeV νDetection
sensitivity

覗き見 ？

γ-ray astronomy?
?

Planckenergyenergy“Cosmic Probes of Fundamental Physics”： Community Planning Study: Snowmass 2013
Conveners: J.J. Beatty, A.E. Nelson, A. Olinto, G. Sinnis et al. : 29.5 Tough Questions
PeV region そして Planck scale のenergy region を、如何なる具体的方法で、窺い知るか？
• What are the roles of cosmic-ray, gamma-ray, and neutrino experiments for particle physics?

• What future experiments are needed in these areas andwhy?
How to conquer Uncertainties,• Are there areas in which these can have a unique impact? 不定要素を、いかに総合的に理解し克服できるか？
(dark matter, axions, primordial black holes, Q-balls, Lorentz invariance violation,intergalactic magnetic fields, particle interactions at high energies, neutrino mass hierarchy, etc.)

Thoughts: coming up from what T.C. Weekes said some years ago
in a chat about 20 years ago,

“No energy thresholdfor astrophysical observation”
presented at the beginning of his talk , about 10 years ago,

(I heard from Trumper,)
Total energy of all the X-rays detected by ROSAT satellite
is just equal to one TeV photon”
109 x 1 keV = 1TeV
X-ray astronomy  TeV γ1010 x 1 EeV = 1028eV
UHE sky  Plank scaleA commentby a messenger
from the future:「どらえもん」

You are misunderstanding !
To choose a way is not always to selecta safe, paved one, easy to walk along !