1. Measurement of high energy cosmic rays by the new Tibet hybrid experiment
J. Huang for the Tibet ASγCollaboration a a Institute of high energy physics, Chinese Academy of Sciences China, Beijing a
CRI 1269, Jul 17 from 16:30 to 18:30, ICRC2017, BEXCO, BUSAN, KOREA

2. Contents Knee of the spectrum.
New hybrid experiment (YAC-II+Tibet-III+MD).
Test of hadronic interaction models and compositions models.
Expected primary P, He and iron spectra by YAC-II
Summary
J. Huang (ICRC2017, KOREA )

3. Knee of the spectrum KASCADE Tibet-EC Proton Helium
J. Huang (ICRC2017, KOREA )

4. Knee of the spectrum
Proton
Helium
YAC-II
KASCADE
Tibet-EC
The YAC-II aims to observe the energy spectrum of proton ,
helium, iron whose energy range will overlap with direct
　　 observations at lower energies such as CREAM, ATIC
　　 and TRACER, and Tibet-EC experiment at higher energies.
J. Huang (ICRC2017, KOREA )

5. New hybrid experiment (YAC-II+Tibet-III+MD)
This hybrid experiment consists of low threshold Air shower core array (YAC-II) and Air Shower array ( Tibet-III ) and Muon Detector ( MD ) . Pb
7 r.l.
Scint.
Iron
YAC-II aims to measure the primary energy spectrum of 4 mass groups of Proton, Helium, iron and 4<A<56, at 50 TeV – 1016 eV range covering the knee. MD AS
YAC2
Tibet-III (50000 m2) : Primary energy and incident direction.
YAC-II ( 500 m2 ): High energy AS core within several x 10m from the axis.
Tibet-MD ( 4500 m2 ) : Number of muon.
J. Huang (ICRC2017, KOREA ) 5

6. - Full M.C. Simulation - Hadronic interaction model
CORSIKA (Ver )
– EPOS -LHC–
– QGSJETII-04–
– SIBYLL 2.1 –
　　 = Air Shower simulation =
CORSIKA (EPOS –LHC, QGSJETII-04,
SIBYLL2.1)
( 1 ) Primary energy: E0 >1 TeV
( 2 ) All secondary particles are traced until their energies become 1 MeV in the atmosphere.
( 3 ) Observation Site : Yangbajing (606 g/cm2 )
　　 = Detector simulation =
Geant 4 ( Ver. 9.5)
Simulated air-shower events are reconstructed with the same detector configuration and structure as the Tibet-III YAC and Muon detector array.
Primary composition model
　Helium poor model [1]
　Helium rich model [1]
Gaisser’s fit model [1]
see [1] J. Huang et al. Astropart. Phy 66 (2015) 18
J. Huang (ICRC2017, KOREA )
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7. Primary cosmic-ray composition models
( see the paper: J. Huang et al. Astropart. Phy. 66 (2015) 18 )
J. Huang (ICRC2017, KOREA )

8. Tests of hadronic interaction models by ( YAC-I + Tibet-III )
J. Huang (ICRC2017, KOREA )

9. Prototype experiment (YAC-I+Tibet-III) ( data taking started from 2009
Total : 16 YAC detectors
Effective area: 10 m2
J. Huang (ICRC2017, KOREA )
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10. Tests of hadronic interaction models and composition models (Some preliminary results from YAC-I data samples) ( primary energy: 100TeV -1PeV )
J. Huang (ICRC2017, KOREA )

11. preliminary preliminary
Comparison of event absolute intensities between Expt. and MC
preliminary
preliminary
Expt.data
Fig. 1: Intergral burst-size spectra (SumNb)
Fig. 2 : The intensity ratios of (SumNb) to that obtained by the Expt. Data.
The red dash line (Ratio =1) is Expt.data.

12. Comparison of event mean lateral spreads (<NbR>) between Expt
Comparison of event mean lateral spreads (<NbR>) between Expt. and MC
preliminary
Fig. 3. Mean lateral spread of AS-cores
J. Huang (ICRC2017, KOREA )

13. (YAC-II +Tibet-III+MD) is well running now ( data taking started from 2014. 2)Pb
50cm
80cm
Total : 124 YAC detectors
Cover area: ~ 500 m2
J. Huang (ICRC2017, KOREA )
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14. measure the P,He and iron component at the knee
Sensitivity of (YAC-II+Tibet-III+MD) to
measure the P,He and iron component at the knee
Other like Iron like
Purity – 83.5%
Efficiency – 65.3%
J. Huang (ICRC2017, KOREA )

15. Expected results by (YAC-II+Tibet-III +MD)
MC simulation shows that (YAC-II+Tibet-III +MD) is powerful enough to obtain proton, helium, iron and 4<A<56 spectra of primary CRs in the range of
50 TeV eV with an energy resolution better than 12% at 1015 eV.
Expected primary P, He spectra
Expected primary Iron spectra
Iron 15
J. Huang (ICRC2017, KOREA ) 15

16. Summary
YAC-I shows the ability and sensitivity in checking the hadronic interaction models. Based on the “He-poor” primary model, we estimate that the difference of EPOS-LHC, QGSJETII-04, SIBYLL2.1 is within 10 % in our concerned energy region. High core events are very sensitive to the light components in CRs and the core parameters of sum Nb, Nb_top, <R> and <Nb*R> are very useful to separate the light components from all the observed events using a ANN technique.
The flux of high energy core events are sensitive to the light components, since the interaction model seems to depend strongly on the production of high energy core events, we can obtain the energy spectrum of light components in primary CRs with sufficient accuracy as discussed in the YAC-I experiment.
Simultaneous observation of core events with YAC and MD array may allow us to obtain the spectrum of each of primary components separately. Actually, the full MC simulation shows that the (YAC-II+Tibet-III +MD) array is powerful enough to obtain the energy spectra of proton, helium, medium nuclei and iron spectra of primary CRs in the range of 50 TeV -10 PeV with sufficient accuracy. It is estimated that the energy resolution of primary particles of
1 PeV is better than 12%。

17. Thank you for your attention !!

18. Core event selection Selected Events QGSJET+HD 216942 SIBYLL+HD 304785
Event selection condition for AS core event was studied by MC and following criteria were adopted to reject non core events whose shower axis is far from the YAC array.
Nb>200, Nhit≧4, Nbtop ≧1500, Ne>80000
| AS axis by LDF – burst center| < 5 m
Statistics of core events in MC simulation and experiment
Live Time is days.
Selected Events
QGSJET+HD
216942
SIBYLL+HD
304785
QGSJET+NLA
80861
SIBYLL+NLA
64331
YAC1
5035
Event selection condition for AS core event was studied by MC and following criteria were adopted to
reject non core events whose shower axis is far from the YAC array.
Nb>200, Nhit≧4, Nbtop ≧1600, Ne>80000
| AS axis by LDF – burst center| < 5 m
Statistics of core events in MC simulation and experiment are shown in this Table.
J. Huang (ISVHECRI2012, Berlin, Germany)