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

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

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

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

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

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

Study of the properties of LHAASO detectors KM2A WFCTA Spherical mirrors Curvature: 5500mm Focus: 2720mm Reflectivity: 80% transparency: 90% 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) 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

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

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

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

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

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

Energy reconstruction offered by WFCTA and Tunka-like detectors The energy is the function of image size and RP. Showers’ energy can be estimated from the table WFCTA’s results Tunka –like detectors 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

Energy resolution and bias

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

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: 3500m events/year

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