cosmic-ray energy spectrum around the knee j.huang institute of high energy physics, chinese academy...

Cosmic-ray energy spectrum around the knee

J.Huang

Institute of high energy physics,

Chinese Academy of Sciences China, Beijing 100049.

The 2nd HERD international workshop( 1-4 December 2013 , IHEP)

Contents

•Global and fine structures seen in cosmic-ray energy spectrum

•Chemical composition of CRs

•Interaction model dependence in AS exp.

•Possible interpretation on the knee

•Enhancement of electron spectrum at several hundred GeV

•SummaryJ.Huang (The 2nd HERD international workshop)

AS array at high altitude (4300m a.s.l.)Tibet-III array:50000m2 with 789 scint. YAC array: 500m2 with 124 scint. MD array: 5000m2 with 5 pools of water Cherenkov muon D.s .Measure:energy spectrum around the kneeand chemical composition using sensitivity of air showers to the primary nuclei through detection of high energy AS core.

Tibet ASgamma experiment(50 TeV - 1017 eV)

PbIron

Scint.

Box

7 r.l.

YAC

Merit of high altitude

The 2nd HERD international workshop

Tibet-III: Energy and direction of air shower

Cosmic ray(P,He,Fe…)

Particle density & spread

Separation of particles

Tibet YAC 　 array(Yangbajing Air shower Core arary)

J.Huang (The 2nd HERD international workshop)

KASCADE experiment 40000 m2 1015-1017 eV

Measure electron and muon size at Karlsruhe, Germany(near sea level).Energy spectra of 5 primary mass groupsare obtained from two dimensional Ne-Nμ spectrumby unfolding method (P,He,CNO,Si,Fe).

All particle spectrum.Knee at 4 PeVdJ/dE E∝ -γ γ=2.653.1

The results agree wellbetween Tibet and KASCADE.


7

Model

Knee　Position　(PeV)

Index　of　spectrum

QGS.+HD

4.0± 0.1 R1=　-2.67±　0.01

R2=　-3.10±　0.01

QGS.+PD

3.8± 0.1 R1=　-2.65±　0.01

R2=　-3.08±　0.01

SIB.+HD

4.0± 0.1 R1=　-2.67±　0.01

R2=　-3.12±　0.01

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All-particle spectrum measured by Tibet ASgamma from 1014 ~1017eV (ApJ 678, 1165-1179 (2008))


　　 Tibet 　　　　　　　　　　　　 KASCADE 　　　　　　　　 HEGRA

CASA/MIA 　　　　　　　　 BASJE 　　　　　　　　　　　 AkenoDICE

Energy spectrum around the knee measured by many experiments

J. Huang (ISVHECRI2012, Berlin, Germany)

Normalized spectrum


10

A sharp knee is clearly seen (ApJ 678, 1165-1179 (2008)) (ApJ 678, 1165-1179 (2008))

6/ 31

What is the origin of the sharp knee?There were many models: nearby source, new interaction threshold, etc.In the following, I would introduce our two analyses for the origin of the sharp knee.


What is the origin of the sharp knee?

•Cannot be explained by propagation effect (diffusion during long confinement time in the galaxy)•Additional component?

Astrophysical scenario : nearby source

Particle physics scenario : beyond STD model•Acceleration mechanism?

High acceleration efficiency in diffusive shock acceleration (DSA) leads hard source spectrum at

the acceleration limit due to nonlinear effect.


　Malkov, E. & Drury, L.O.C. 2001, Rep. Prog. Phys. 64, 429 Ptuskin, V.S., & Zirakashvili, V.N., 2006, Adv. Space Res., 37, 1898

][][ exp)(1),( 0 EE

EjE ss

Nonlinear effect in DSA process

Assume source spectrum as

Ref . (M.Shibata, J.Huang et al. ) ApJ,716,1076–1083 (2010)


Composition measurement

Sensitivities to the primary chemical composition used in AS exp. are:

•Ne-Nμ correlation -- μrich showers are induced by heavy primary (traditional method)•Detection of high energy core selects AS induced by light elements (P,He) -- Tibet•Xmax -- fluorescence technique at VHE

Model dependence comes from and .

inel )( Fxf


KASCADE QGSJET01


KASCADE SIBYLL

KASCADE P,He,CNOcompared with direct observations


KASCADE Si, Fecompared with direct observations


Proton and Helium by TibetQGSJET

SIBYLL

All All

All All

P

P

He

He

P+He spectrum


Model dependence

P

HeP

He

All All

All All

Tibet 〜 30%

KASCADE 〜 twice

Tibet concludes :“Knee is dominated by nuclei heavier than helium.

KASCADE :QGSJET analysis : helium dominanceSIBYLL analysis : CNO dominance

L3+C muon spectrum compared to MC model

Interaction model dependence in Tibet ASgamma experiment (Some preliminary results from YAC1 data samples)

30 TeV 90 TeV

260 TeV 1800 TeV

1) The shape of the distributions of sumNb are consistent between the YAC-I data and simulation data in all four cases, indicating that form *10TeV to 1800 TeV, the particle production spectrum of QGSJET2 and SIBYLL2.1 may correctly reflect the reality within our experimental systematic uncertainty of a level about 10%.


30 TeV

1800 TeV260 TeV

90 TeV

Comparison of event absolute intensities between Expt. and MC


LHCf experiment

(P+He) “ knee”: 400TeV

Primary (P+He) spectra obtained by (YAC1+Tibet-III)

The interaction model dependence is less than 25% in absolute intensity, and the composition model dependence is less than 10% in absolute intensity.

Most new interaction models (EPOS-LHC, QGSJETII-04 ) has been used !

Our results agree well with direct experiment

(P+He) “ knee”: 400TeV

Preliminary

Common results between Tibet and KASCADE

•Knee is located at 4 PeV. (γ=2.653.1)

•Steep spectrum of protons at the knee (protons are not the majority).

•Fraction of heavy nuclei increases with increasing energy.


Direct observations

Cosmic ray energy spectrum below the knee has been considered to follow simple power law.

Recently, hardening of the spectrum has been reported by ATIC and CREAM @ 200 GeV/n.


A.D.Panov et al., Arxiv:astro-ph/0612377v1 (2006)

ATIC >200 GeV/n Hardening of the energy spectrum


H.S.Ahn et al., ( CREAM collaboration )ApJ, 714, L89, (2010)

CREAM data: P&He spectra are not the same

He γHe=2.58±0.02

P γp= 2.66 ±0.02

CREAM suggests that:

1) Their fluxes are significantly higher than the extrapolation of a single-power law fit to the low energy spectra.2) Different types of sources or acceleration mechanisms? (e.g., Biermann, P.L. A&A, 271, 649, 1993)

H.S.Ahn et al., ApJ, 714, L93 (2009)

CREAM

Heavy dominance toward the Knee(TeV spectra are harder than spectra < 200 GeV/n)

A.D.Panov et al., Arxiv:astro-ph/0612377v1 (2006)

ATIC

Spectrum of nuclei by CREAM as a function of energy/particle

Simple extrapolation does not work to fitthe knee energy region.

Change of power index is required forall elements again.


Extrapolation of CREAM data using broken power law cannot fit to the sharp knee

Assumptions:Eb(p)=300 TeV,Rigidity dependenceof break pointfor nuclei,Eb(Z)=Zx300 TeVΔγ=0.4

Need extra component


Scenario 　 A Scenario 　B

Possible knee scenario

Hard src spect?

Nearby src?


Primary electrons

High energy electrons cannot travel long distance due to their energy loss proportional to E2.

The energy spectrum can show the contribution of nearby sources (say ~1kpc)

or new physics such as dark matter decay or beyond STD model.

ATIC, Pamela, Fermi-LAT, H.E.S.S.


The ATIC Electron Results Exhibits a “Feature”J.Chang et al, Nature, 456,362,(2008)

Possible candidate local sources would include supernova remnants (SNR), pulsar wind nebulae (PWN) and micro-quasars.


Anomalous positron abundance

O.Adriani et al., Nature, 458,607(2009)

V.Mikhailov et al.ESCR 2010, Turku, 3 August

Fermi-LAT

?

Relation between Fermi e± and extra component

at the knee?

PeV nuclei + target（＊ 10 TeV/n) π0 γ　　　　　　　＊ 100GeV e± This may be quitepossible scenario.

(W.Bednarek and R.J.Protheroe ,2002,APh)


Summary• Knee　is　located　at　4　PeV　exhibiting　

sharp　structure　with　Δγ=0.4±0.1• Disagreement　of　chemical　composition　

between　KASCADE　and　Tibet　is　due　to　strong　interaction　model　dependence　of　Air　Shower　MC　which　is　larger　in　KASCADE　experiment.

• Extrapolation　of　CREAM　data　using　simple　broken　power　law　formula　cannot　fit　to　the　AS　data　at　the　knee.


• Tibet　data　and　ATIC/CREAM　spectra　of　nuclei　suggests　knee　is　dominated　by　heavy　nuclei,　which　can　be　attributed　to　nearby　source　　dominated　by　heavy　element　(Pulsar?)　or　hard　cosmic-ray　source　spectrum.　

• Enhancement　of　electron　spectrum　at　hundreds　GeV　range　might　be　correlated　with　the　structure　of　cosmic-ray　spectrum.　---　possible　contribution　of　nearby　sources?

• Further　study　of　the　chemical　composition　up　to　the　knee　and　beyond　is　necessary　to　solve　the　problem.　　HERD　plan　and　indirect　observations　(Tibet　ASgamma,　KASCADE-G,　LHAASO,　Grapes,　TA-TAIL).

High Energy cosmic-Radiation Detection (HERD)

Expected HERD ( 2 yr) results :

Proton

Helium

C

Iron

(Please see Dr. Xu Ming’s talk)

The New Tibet hybrid experiment (YAC+Tibet-III+MD)The New Tibet hybrid experiment (YAC+Tibet-III+MD)

LHAASO (Large High Altitude Air Shower Observatory)

Thank　you　for　your　attention　!!

M.Ave et al., ApJ, 678, 262 (2008)

TRACER

KASCADE all particle spectrum

Highest energy data

Electron　and　Positron　　from　Dark　Matter　Decay

49

Decay　Mode:　D.M.　->　l+l-νMass:　MD.M.=2.5TeVDecay　Time:　τD.M.　=　2.1x1026　s

Ibarra et al. (2010)

Expected e+/(e-+e+) ratio by a theory and the observed data

Observation　in　the　trans-TeV　

region

　　　　　 Dark　Matter　signal

Expected e-+e+ energy spectrumby CALET observation

July 21, 2010

Discriminating scenario A and B

A : Find candidate of nearby source.B : Does break point show rigidity dependence?

Chemical composition after the knee:A : becomes lighter between 1016 and 1017 eV. KASCADE-GRANDE claimed second knee at 8x1016 eV.B : Heavy dominance up to the maximum energy of GCR.

cosmic-ray energy spectrum around the knee j.huang institute of high energy physics, chinese academy...

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