Cosmicray energy spectrum around the knee J Huang

Cosmic-ray energy spectrum around the knee J. Huang Institute of high energy physics, Chinese Academy of Sciences China, Beijing 100049. The 2 nd 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 Ge. V • Summary J. Huang (The 2 nd HERD international workshop)

Merit of high altitude Tibet ASgamma experiment (50 Te. V - 1017 e. V) AS array at high altitude (4300 m a. s. l. ) l. Tibet-III array: 50000 m 2 with 789 scint. l. YAC array: 500 m 2 with 124 scint. l. MD array: 5000 m 2 with 5 pools of water Cherenkov muon D. s. Measure: energy spectrum around the knee and chemical composition using sensitivity of air showers to the primary nuclei through YAC detection of high energy AS core. Pb 7 r. l. Iron Scint. Box The 2 nd HERD international workshop

Tibet YAC　array (Yangbajing Air shower Core arary) Cosmic ray(P, He, Fe…) Particle density & spread Separation of particles Tibet-III: Energy and direction of air shower J. Huang (The 2 nd HERD international workshop)

KASCADE experiment 40000 m 2 1015 -1017 e. V Measure electron and muon size at Karlsruhe, Germany (near sea level). Energy spectra of 5 primary mass groups are obtained from two dimensional Ne-Nμ spectrum by unfolding method (P, He, CNO, Si, Fe).

All particle spectrum. The results agree well between Tibet and KASCADE. J. Huang (The 2 nd HERD international workshop) Knee at 4 Pe. V d. J/d. E∝E-γ γ=2. 65 3. 1

All-particle spectrum measured by Tibet ASgamma from 1014 ~1017 e. V (Ap. J 678, 1165 -1179 (2008)) J. Huang (The 2 nd HERD international workshop) Model Knee Position (Pe. V) Index of spectrum QGS. + HD 4. 0± 0. 1 R 1= -2. 67± 0. 01 QGS. + PD 3. 8± 0. 1 SIB. + HD 4. 0± 0. 1 R 2= -3. 10± 0. 01 R 1= -2. 65± 0. 01 R 2= -3. 08± 0. 01 R 1= -2. 67± 0. 01 R 2= -3. 12± 0. 01 7 5/ 31

Energy spectrum around the knee measured by many experiments 　　Tibet　　　　　　KASCADE　　　　HEGRA CASA/MIA　　　　BASJE　　　　　　Akeno DICE J. Huang (ISVHECRI 2012, Berlin, Germany)

Normalized spectrum J. Huang (The 2 nd HERD international workshop)

A sharp knee is clearly seen (Ap. J 678, 1165 -1179 (2008)) 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. J. Huang (The 2 nd HERD international workshop) 10 6/ 31

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. J. Huang (The 2 nd HERD international workshop)

Nonlinear effect in DSA process Malkov, E. & Drury, L. O. C. 2001, Rep. Prog. Phys. 64, 429 Ptuskin, V. S. , & Zirakashvili, V. N. , 2006, Adv. Space Res. , 37, 1898 Assume source spectrum as Ref. (M. Shibata, J. Huang et al. ) Ap. J, 716, 1076– 1083 (2010) J. Huang (The 2 nd HERD international workshop)

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 J. Huang (The 2 nd HERD international workshop) and .

KASCADE QGSJET 01 J. Huang (The 2 nd HERD international workshop)

KASCADE SIBYLL

KASCADE P, He, CNO compared with direct observations J. Huang (The 2 nd HERD international workshop)

KASCADE Si, Fe compared with direct observations J. Huang (The 2 nd HERD international workshop)

Proton and Helium by Tibet QGSJET All P He SIBYLL All P All He

P+He spectrum J. Huang (The 2 nd HERD international workshop)

Model dependence P Tibet concludes : Tibet〜 30% “Knee is dominated by nuclei heavier than helium. All He KASCADE : KASCADE〜twice QGSJET analysis : helium dominance SIBYLL analysis : CNO dominance All P He All

L 3+C muon spectrum compared to MC model

Interaction model dependence in Tibet ASgamma experiment (Some preliminary results from YAC 1 data samples) l 1) The shape of the distributions of sum. Nb are consistent 30 Te. V 90 Te. V between the YAC-I data and simulation data in all four cases, indicating that form *10 Te. V to 1800 Te. V, the particle production spectrum of QGSJET 2 and SIBYLL 2. 1 may correctly reflect the reality within our experimental systematic uncertainty of a level about 10%. 260 Te. V J. Huang (The 2 nd HERD international workshop) 1800 Te. V

Comparison of event absolute intensities between Expt. and MC 30 Te. V 260 Te. V J. Huang (The 2 nd HERD international workshop) 90 Te. V 1800 Te. V

LHCf experiment

Primary (P+He) spectra obtained by (YAC 1+Tibet-III) (P+He) “ knee”: 400 Te. V Most new interaction models (EPOS-LHC, QGSJETII-04 ) has been used ! The interaction model dependence is less than 25% in absolute intensity, and the composition model dependence is less than 10% in absolute intensity.

Our results agree well with direct experiment Preliminary (P+He) “ knee”: 400 Te. V

Common results between Tibet and KASCADE • Knee is located at 4 Pe. V. (γ=2. 65 3. 1) • Steep spectrum of protons at the knee (protons are not the majority). • Fraction of heavy nuclei increases with increasing energy. J. Huang (The 2 nd HERD international workshop)

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 Ge. V/n. J. Huang (The 2 nd HERD international workshop)

ATIC >200 Ge. V/n Hardening of the energy spectrum A. D. Panov et al. , Arxiv: astro-ph/0612377 v 1 (2006) J. Huang (The 2 nd HERD international workshop)

CREAM data: P&He spectra are not the same H. S. Ahn et al. , ( CREAM collaboration )Ap. J, 714, L 89, (2010) CREAM suggests that: He γHe=2. 58± 0. 02 P γp= 2. 66 ± 0. 02 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)

Heavy dominance toward the Knee (Te. V spectra are harder than spectra < 200 Ge. V/n) ATIC A. D. Panov et al. , Arxiv: astroph/0612377 v 1 (2006) CREAM H. S. Ahn et al. , Ap. J, 714, L 93 (2009)

Spectrum of nuclei by CREAM as a function of energy/particle u. Simple extrapolation does not work to fit the knee energy region. u Change of power index is required for all elements again. J. Huang (The 2 nd HERD international workshop)

Extrapolation of CREAM data using broken power law cannot fit to the sharp knee Need extra component J. Huang (The 2 nd HERD international workshop) Assumptions: Eb(p)=300 Te. V, Rigidity dependence of break point for nuclei, Eb(Z)=Zx 300 Te. V Δγ=0. 4

Scenario　A Scenario　B Hard src spect? Nearby src? J. Huang (The 2 nd Possible knee scenario HERD international workshop)

Primary electrons High energy electrons cannot travel long distance due to their energy loss proportional to E 2. The energy spectrum can show the contribution of nearby sources (say ~1 kpc) or new physics such as dark matter decay or beyond STD model. ATIC, Pamela, Fermi-LAT, H. E. S. S. J. Huang (The 2 nd HERD international workshop)

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. J. Huang (The 2 nd HERD international workshop)

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? (W. Bednarek and R. J. Protheroe , 2002, APh) ? J. Huang (The 2 nd HERD international workshop) Pe. V nuclei + target （ ＊10 Te. V/n) π0 γ ＊100 Ge. V e± This may be quite possible scenario.

Summary • • • Knee is located at 4 Pe. V 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. J. Huang (The 2 nd HERD international workshop)

• • • 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 Ge. V 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) Proton Helium Expected HERD ( 2 yr) results : C (Please see Dr. Xu Ming’s talk) Iron

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

LHAASO (Large High Altitude Air Shower Observatory)

Thank you for your attention !!

TRACER M. Ave et al. , Ap. J, 678, 262 (2008)

KASCADE all particle spectrum

Highest energy data

Electron and Positron from Dark Matter Decay Mode: D. M. -> l+l-ν Mass: MD. M. =2. 5 Te. V Decay Time: τD. M. = 2. 1 x 1026 s Expected e-+e+ energy spectrum by CALET observation Expected e+/(e-+e+) ratio by a theory and the observed data Observation in the trans-Te. V region 　　　　　Dark Matter signal July 21, 2010 Ibarra et al. (2010) 49

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 e. V. KASCADE-GRANDE claimed second knee at 8 x 1016 e. V. B : Heavy dominance up to the maximum energy of GCR.