Expectation on Observation of Cosmic Ray Energy Spectrum

Expectation on Observation of Cosmic Ray Energy Spectrum from 10 Pe. V to 100 Pe. V with LHAASO Experiment L. L. Ma for LHAASO collaboration Beijing China

Outline • • Difficulties in cosmic ray detection LHAASO introduction LHAASO science in cosmic ray measurement Performance Study of LHAASO detectors – Composition separation – Energy resolution – Effective aperture and event rate • Summary

Difficulties in cosmic ray detection • Energy > 100 Te. V Air shower measurement – EAS array – Cherenkov telescope or Array – Fluorescence telescope • Calibration of primary energy estimate uncertain. • Composition measurement diffcult • Model dependent

4400 m above see level Dao. Cheng Si. Chuan Water Cherenkov detector Array (WCDA) 78, 000 m 2 Wide Field View Cherenkov telescope Array (WFCTA) 18 Telescopes Geometry reconstruction Core information Energy meaurements Hillas Large High Altitude Air Shower Observatory Geometry reconstruction ， Muon content 1 KM 2 Array (KM 2 A) 5195 scintillator detectors every 15 m 1171 muon detectors every 30 m

LHAASO science in cosmic ray measurement � Measure individual cosmic ray spectra from 10 Te. V to Ee. V ◦ Multi-parameters, Multi-stages Ø 10 Te. V-100 Te. V Ø 100 Te. V-10 Pe. V Ø 10 Pe. V-100 Pe. V Ø 100 Pe. V-2 Ee. V Ø Energy Scale Ø WCDA, WFCTA Proceedings 206 Ø Knees for H, He, … Ø WCDA, WFCTA, KM 2 A Ø knee of Fe Ø WFCTA, KM 2 A Ø 2 nd knee & composition changing Ø Transition from galactic to extra-galactic Ø WFCTA, KM 2 A

KM 2 Array (KM 2 A) 2. 8 m 1. 2 m ED MD Effective area 1 m 2 36 m 2 Spacing 15 m 30 m NO. of detectors 5195 1171 Time resolution 2 ns 10 ns Muon number Core reconstruction : 5 m Direction reconstruction: 0. 3°

Wide Field view Cherenkov Telescope Array (WFCTA) � Reflectors: ◦ 25 spherical mirrors ◦ Side length： 300 mm ◦ curvature： 5800 mm � Cameras ◦ ◦ 32 x 32 Si. PMs 16 degree X 14 degree Pixel diameter: 25. 4 mm Focal length: 2870 mm • Hillas Parameters • Xmax • Energy reconstruction

Performance Study of LHAASO detectors � Shower generation ◦ ◦ ◦ CORSIKA V 74005 Energy range: 10 Pe. V ~100 Pe. V Compositions: Proton, helium, CNO, Mg. Al. Si, iron hadronic model: QGSJETII 04+FLUKA Layout of detectors � Pointing direction of WFCTA � ◦ 45°in zenith ◦ 0~360°in azimuth Air depth with zenith 45° Air depth of LHAASO

Composition separation Obtained from KM 2 A Log 10(Ne/Nmuon) Blue: iron Red: proton Obtained from WFCTA Distance: the angular distance between image center to the arriving directions

KM 2 A Blue: iron Red: proton WFCTA Purity in selecting iron: 84% Purity in selecting iron and Mg. Al. Si: 94%

Energy reconstruction � � The reconstructed energy is a function total Npe recorded by WFCTA and Rp Energy resolution ◦ <20% (Rp<100 m) ◦ <25%(Rp<200 m) ◦ ~30%(Rp<300 m) Rp<100 m Rp<200 m Rp<300 m

Effective aperture and event rate 15% duty cycle All particle 50 m<Rp<250 m 50 m<Rp<230 m 50 m<Rp<200 m 15% duty cycle 100 irons Iron

Summary � With multiple detectors LHAASO can measure individual spectra of cosmic rays by multiparameters ◦ KM 2 A and WFCTA can be used in the 10 Pe. V to 100 Pe. V energy range � 25 % energy resolution can be achieved � 100 gold iron events can be obtained with 87% purity and at 100 Pe. V

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