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

AS array at high altitude (4300m a.s.l.) Tibet-III array:50000m 2 with 789 scint. YAC array: 500m 2 with 124 scint. MD array: 5000m 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 detection of high energy AS core. Tibet ASgamma experiment (50 TeV eV) Pb Iron Scint. Box 7 r.l. YAC Merit of high altitude The 2 nd 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 2 nd HERD international workshop)

KASCADE experiment m eV 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. Knee at 4 PeV dJ/dE ∝ E -γ γ=2.65  3.1 The results agree well between Tibet and KASCADE. J.Huang (The 2 nd HERD international workshop)

7 ModelKnee Position (PeV) Index of spectrum QGS.+ HD 4.0 ± 0.1R1= ± 0.01 R2= ± 0.01 QGS.+ PD 3.8 ± 0.1R1= ± 0.01 R2= ± 0.01 SIB.+ HD 4.0 ± 0.1R1= ± 0.01 R2= ± / 31 All-particle spectrum measured by Tibet ASgamma from ~10 17 eV (ApJ 678, (2008)) J.Huang (The 2 nd HERD international workshop)

Tibet KASCADE HEGRA CASA/MIA BASJE Akeno DICE Energy spectrum around the knee measured by many experiments J. Huang (ISVHECRI2012, Berlin, Germany)

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

10 (ApJ 678, (2008)) A sharp knee is clearly seen (ApJ 678, (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. J.Huang (The 2 nd HERD international workshop)

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)

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

KASCADE QGSJET01 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 SIBYLL All P P He

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

Model dependence P He P All Tibet 〜 30% KASCADE 〜 twice Tibet concludes : “Knee is dominated by nuclei heavier than helium. KASCADE : QGSJET analysis : helium dominance SIBYLL 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%. J.Huang (The 2 nd HERD international workshop)

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

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 Prelimin ary

Common results between Tibet and KASCADE Knee is located at 4 PeV. (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 200 GeV/n. J.Huang (The 2 nd HERD international workshop)

A.D.Panov et al., Arxiv:astro-ph/ v1 (2006) ATIC >200 GeV/n Hardening of the energy spectrum J.Huang (The 2 nd HERD international workshop)

H.S.Ahn et al., ( CREAM collaboration )ApJ, 714, L89, (2010) CREAM data: P&He spectra are not the same He γ He =2.58±0.02 P γ p = 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/ v1 (2006) ATIC

Spectrum of nuclei by CREAM as a function of energy/particle  Simple extrapolation does not work to fit the knee energy region.  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 Assumptions: E b (p)=300 TeV, Rigidity dependence of break point for nuclei, E b (Z)=Zx300 TeV Δγ=0.4 Need extra component J.Huang (The 2 nd HERD international workshop)

Scenario AScenario B Possible knee scenario Hard src spect? Nearby src? J.Huang (The 2 nd 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 ~1kpc) 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? PeV nuclei + target （ ＊ 10 TeV/n) π 0 γ ＊ 100GeV e ± This may be quite possible scenario. (W.Bednarek and R.J.Protheroe,2002,APh) J.Huang (The 2 nd HERD international workshop)

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. 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 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)

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 - ν Mass: M D.M. =2.5TeV Decay Time: τ D.M. = 2.1x10 26 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 spectrum by 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 and eV. KASCADE-GRANDE claimed second knee at 8x10 16 eV. B : Heavy dominance up to the maximum energy of GCR.