UHECRThe most energetic universe

Shigeru Yoshida

Department of Physics

Chiba University

Overview

The basics of UHECR – Ultra-High Energy Cosmic Rays

1st population~ E-2.7

Galactic

2nd pop.~E-3.0

Galactic?

3rd populationThe most energetic

E > O(J)

The Cosmic-ray spectrumextended power-law

Acceleration timeto produce such extremely-high energy

cosmic-rays

Fermi diffusive shock acceleration

~ RB/c x bs2

Typically takes million of years!!

The Hillas Diagram

tA < tE ~ D/c

Must be physically large,But very few satisfies the requirements

Very likely Extra-galactic

How the 3rd population (exrtagalactic?)

turns over is still open questionAhlers et al, Astropart.Phys. 34 106 (2010)

2nd population2nd population

3rd EGpopulation 3rd EG

population

1) softning

1) softning = dip

2)cutoff 2)cutoff

Structures 1) and 2) are consequence of propagation in extra-galactic space

The “cross-over at ankle” case The “dip” case

Horizon of Cosmic-ray Universe

Universe becomes opaque tocosmic-rays when energies gets beyond 1019 eV

pg p e+e-

pg (p,n) p’s

CMB photons

Pair creation with CMB g

Calculation of the cross-sectionis doable in the cosmic-ray rest system

Blumenthal, Phys.Rev.D 1 1956 (1970)

Photopion production with CMB

Threshold energy

D resonance

Inelasticity is sizable significant energy loss channel

Note: channel2: yields secondary g-ray

channel3: yields secondary n

Spectral structures

Yoshida and Teshima, Prog.Theo.Phys. 83 833 (1993)

cutoffcutoff

softening

softening

pile-up

Single source spectrum Adding up all sources over the entire space

Diffuse source spectrum

Heavy nuclei would not survive

Photo-disintegration

AN + g A-1N + pEx.

Lorentz factor gL is conserved,but energy spreads into (sub-)nucleons

Fe ends up with p of energy EFe/56

The Detection Methods

Measurement of Extensive Air-showers

SD – surface detector array

FD – air florescence detector

sampling cascade particlesat surface

e+, e-, g, m

“telescope” to image EAS trackvia air fluorescence light detection

AGASA – SD only (operated in 1990’s)

Pierre Auger ObservatorySD+FD (now in operation)

~100km2

~ 3000 km2

SD event profileand the energy estimation

Energy Indicator local particle density

Particle density at distances far away from the shower axis has beenfound to be proportional to energy with only small fluctuations

A fact:

Why?• Air is a great calorimeter. Hadronic interaction length ~ radiation length• particle yield at far distances is determined by superposing of many secondary sub (hadronic and emg) showers in the early stage of shower development

S(600) density at 600 m from core

S(800) density at 800 m from core

S(1000) density at 1 km from core

used by AGASA

used by TA

used by Auger

Direction reconstruction:using timing difference

Event profile seen by FD

Calorimetric Energy MeasurementFluorescence yield

Total number of fluorescence photons observable!

what you wanna know what you measure

The summary of the present observational results

The Energy SpectrumPierre Auger presented at ICRC2011

The Energy SpectrumPierre Auger presented at ICRC2011

The Energy SpectrumTelescope Array presented at ICRC2011

Mass CompositionAuger

TA

Auger : favors transition to heaver nuclei

TA: indicates proton dominated

By

SD

By

FD

Arrival directions: local AGNs?Auger

TA: consistent with both “isotropic” and “local AGNs”

Arrival Directions: local AGNs?

A side trip to the historywhy AGASA’s measurement was

wrong?

9 events (finally 11events in the end)detected beyond 1020 eV

The 1st report on the super-high energy events

The event feature and its reconstruction was OK…

The highest energy event

Exclusion of the signalfrom this detectorwould not change energy estimation

The energy estimation fully relied upon MC was not too bad.

Only <~ 40% off fromthe present FD-based relation

Computing Power Problem #1

Waveform recorded in one of the (special) detectorin the highest energy event

(probably) delayed neutrons

Delayed neutrons can lead to systematic increase of gain in the log-amplifier

We were aware of it, but not practically feasible to run full cascade MCs to estimate the systematics at that time (1990’s)

Computing Power Problem #2Depth @ q= 0

Depth @ q= 60

Computing Power Problem #2Shower Development Correctiondeduced from real data (AGASA)

Shower Development Correctiondeduced from MC (Telescope A.)

Lack of statistics!No such computing poweravailable in early 90’s

(inconclusive) summary of findingsProbably extra-galactic in origin

cutoff feature in the spectrum, no galactic plane enhancement

Proton or heavy nuclei (ex. Fe) ? completely openHowever, Fe cannot reach to earth as Fe in UHE regime

Any clue on sources ?No sizable n or g fluxes – Strongly disfavors “Top Down” scenario

(See Aya’s IceCube talk next)

Energetics: Must account 1044 erg/Mpc3/year

Acceleration: Ltotal > 1045 Z-2 erg/sec (ex. Lemoine 2009)

Most likely either GRB or the most powerful AGN

Must be “Astronomical”

GRB AGNPros: The UHE acceleration could work out

Cons: E UHECR must be ~1053 erg

Pros: The UHE acceleration could work out

Cons: Only 1% of AGN radio loud FR II only ~10-8 /Mpc3

Source DensityOriginal Idea back to Dubovsky, Tinyakov, Tkachev, PRL 85 1154 (2000) Modified by SY (2001)

Luminosity per sourceSource density

More accurate calculation does not change the numbers so much

The present Auger indication r > 10-4 – 10-5 /Mpc3

FR II Radio Loud Galaxy r ~ 10-8 /Mpc3

GRB r ~ 10-4 /Mpc3

Exercise: How GRBs workas an UHECR emitter

Magnetic Field estimated from equipartition

Acceleration time Escape time

Maximum accelerated proton energyNote: optimistic, b~1

Barely OK

Photopion production?

In this case, n emission expected.

GRB nMost likely PeV n if emitted

Constraint on energy from the D-resonance condition

Ep ~ O(100 PeV) En ~ O(10PeV) for kg ~ 100 keV

Even if p colliding g can be much higher (ex. k g ~ O(eV)),

Synchroton cooling suppresses En < 1018 eV = EeV

Possible Scenarios(all of them is debatable)GRBs

Must release vast energy in hadronic form more than we observed with keV-MeV g-rays, but a good acceleration site

Never be able to ID GRBs by UHECRs themselves, because they are DELAYED due to the magnetic field

Prompt n detection is a key, but null detection by IceCubestarted strongly to constrain this scenario….

Flare of Radio-loud AGNs ( FR II type radio galaxies)Consistent with no-obvious correlations with AGNs

Only rarely occurs not well fit with the Auger obs. Solution: let the magnetic field play more role

Example: the CenA, or M87 model

It essentially implies Our LOCAL universe can be differentfrom the rest of the universe

UHE n searchprovides a clue!

Propagation in EGMF

Sigl, Lemoine, Biermann, Astropart.Phys. 1999Delay time [yr]

Ene

rgy

[EeV

]

0.3 mG pancake

E-1/3

E-1

(bohm diffusion)

E-2

(rectilinear)

Why GZK cosmogenic n ?

(Our Galaxy) (Super Cluster)

Distant, younger universe

Non-Observable Space by g and Cosmic Nuclei Accessible

volume

~10-6

of

observable

universe

GZ

K

cuto

ff g g ++ g g2.7K 2.7K ee++ ++ ee--

γ ・陽子から見た

宇宙の死角

銀河直径１0万光年 超銀河団直径

se

Xp K

'

7.2

nnm

pg

+®+®+®

±

±

±

SDSS

GZ

K

cuto

ff g g ++ g g2.7K 2.7K ee++ ++ ee-- g g ++ g g2.7K 2.7K ee++ ++ ee--

銀河直径１0万光年 超銀河団直径

se

Xp K

'

7.2

nnm

pg

+®+®+®

±

±

±

SDSS

1PeV

1EeV

1ZeV

n = early history of cosmic radiation!

pme decay chain

(EHE) Photons in EBL

EM cascades lead tothe diffuse g-ray BGin the GeV range

URB

CMB

IR/O

Transparent

GeVEHEdE

dNE

dE

dNE 22

Energy Conservation

“GZK” n = history of UHECR radiationYoshida and Teshima, Prog.Theo.Phys. 83 833 (1993)

r ~ (1+z)m

m=2

m=4

Emax =1021 eV

Emax =1022 eV

In < 1 EeV source evolution

In > 10 EeV Emax

Kotera, Allard, Olinto JCAP 10 013 (2010)

IceCube collaboration (Corres. A. Ishihara) PRD 83 092003 (2011)

In @ 1EeV is robust againstEmax and UHECR transition model

Emax dependence

Transition model dependence

IceCubeEnergyRange

Identify UHECR sources by measurement of cosmological evolution

Kotera, Allard, Olinto JCAP 10 013 (2010)

Evolution Curve GZK n

n @O(1EeV)= early history of cosmic radiation!

IceCubeEnergyRange

GZK cosmogenic n flux estimates:model-independent analytical

approach

n yield with EGEN=En(1+zn) from UHECR proton

emitted from sources at z>zn. zn; redshift when generates n

Adding up contribution from sources at z

Emission rate per comoving volume

~(1+z)m

Semi-analytically computable when

1. neglect IR/O background – n is generated only by pgCMB

2. photo-pion production only via D-resonance 3. simplify the pg collision kinematics as a single pion production4. approximate UHECR energy attenuation length as a constant above 1020 eV

Usable as GZK n version of Waxman-Bahcall Formula

Comparison with the “full-blown” MC

IceCubeEnergyRange

Analytical formula

Numerical/MC

Remarkable agreementaround En~ 1EeV

departure at En<100PeVdue to the far-IR contribution and -D resonance approximation

departure at En>5EeVdue to Emax, E-a dependence

Provides reasonable estimatesIn the IceCube energy rangewithin uncertainty of ~factor of two

consistent with• uncertain far-IR roles• uncertain UHECR flux• accuracy of the approx.

Constraints on UHECR source evolution

At present --- a half IceCube 2008-2009 runIceCube collaboration PRD 83 092003 (2011)

AGNFR II

r ~ (1+z)m

0<z<zmax

Already disfavors AGN radio-loud jet as UHECR emitter

Constraints on UHECR source evolution

In 3 years --- full IceCube 5 year run

AGNFR II

r ~ (1+z)m

0<z<zmax

Completely rule out AGN radio-loud jet as UHECR emitter

IF null detection…

Constraints on UHECR source evolution

In 3 years --- full IceCube 5 year run

Disfavors GRB/normal galaxies as UHECR emitter

IF null detection…

r ~ (1+z)m

0<z<1

r ~ const. 1<z<zmax

SFR

GRB

UHECR composition hypothesis(proton dominated)

now in question!