Measurement of Cosmic rays with LHAASO at 10PeV~100PeV

1. Institute of High Energy Physics, CAS Measurement of Cosmic rays with LHAASO at 10PeV~100PeV Lingling Ma IHEP China 4th Workshop on Air Shower Detection at High Altitude

2. Outline • The motivation: • The multi-parameters measurement at the energy range 10PeV~100PeV • Introduction and the re-arrangement of WFCTA • The study of the properties of LHAASO detectors • Summary

3. Motivations • At low energy end: • connect the direct measurement (50 TeV) • get the energy scale of the detectors • At high energy end: • Connect the UHCRs measurement (>100 PeV) • Transfer the energy scale to detectors • The energy range is about 5 magnitude, it’s hard to cover by one type detectors • Three phases are required • ~50 TeV ~10 PeV, 10 PeV ~100 PeV, 100 PeV ~ 1000 PeV • Overlapped

4. The multi-parameters measurement • KM2A: • Geometry reconstruction • µ-content • WFCTA: • Energy reconstruction • Xmax, Hillas parameters • Tunka-like: • Energy recontruction • lateral distributions of Cherenkov light

5. Wide Field Cherenkov Telescope Array • Field of view:14º×16º • Pix size: 0.5º, PMT array: 32×32 • Door : 2.3 m×2.3 m • Optics: spherical mirror • Mirror size: 2.3 m×2.3 m • Curvature of the mirror: 5500 mm • Focus: 2720 mm: • to achieve the best consistent of light spot size

6. Re-arrangement of WFCTA • To get more effective aperture • Two site • To reduce the night sky background • Filter • To improve the optics quality • A diaphragm at the door • To select data with Rp more than 60m

7. Study of the properties of LHAASO detectors KM2A • ED：distance :15m，size: 1m*1m*2cm， 0.5cm lead plate • MD：distance:30m，size:6m*6m*2cm，2.8m dirt overburden • Trigger ：hit time window 600ns，Ntrig>=20 • Corsika • Zenith: 25~45 degree • Azimuth:0~360 degree • Composition: P, Fe • Hadronic model: QJSJetII and Fluka • Thin: 5.E-6 • Telescope array: • N_telescope:13*13 • D_telescope: 80m • Scattered range: -800, 800 (m) • WFCTA • Spherical mirrors • Curvature: 5500mm • Focus: 2720mm • Reflectivity: 80% • transparency: 90%

8. study of the properties of LHAASO detectors • Geometry reconstruction offered by KM2A • The ability to separate compositions • Energy reconstruction offered by WFCTA or Tunka detectors • Aperture of the WFCTA detectors

9. Core reconstruction offered by KM2A If only inner core events are considered , the core resolution is about 3m

10. Arriving directions reconstructions offered by KM2A Only events with inner core are condidered

11. Parameters to separate compositions from WFCTA Blue proton Red iron Dist: distance between image center to the arriving directions of the shower Dist: is Rp depended

12. parameters to separate compositions from KM2A The ratio of muons and and electrons Core positions independ

13. Energy reconstruction offered by WFCTA and Tunka-like detectors WFCTA’s results Tunka –like detectors The energy is the function of image size and RP. Showers’ energy can be estimated from the table By fitting the lateral distribution of Cherenkov light The Density of Cherenkov photon at 175m from core Just count the number of Cherenkov photons on the detector with a 4m×4m area

14. Energy resolution and bias

15. Effective Aperture The effective aperture with RP less than 300m No. of events observed per year with pure proton composition

16. Summary • A brief introduction of WFCTA detectors design • The properties of the detectors have been studied • resolution of core position reconstruction: 3m • resolution of arriving direction reconstruction: 0.5º • resolution of primary energy reconstruction: 15%~25% • effective aperture is about: • 3500m2Sr@100PeV ,300 events/year

17. THANKS