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The Large-scale Anisotropy of Cosmic Rays Observed with the Partial LHAASO-KM2A Array
Wei Gao, Shandong University
for the LHAASO Collaboration
36th ICRC, July 24th - Aug 1st, 2019 Madison, WI, U.S.A.
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Content
• Introduction
•LHAASO
•Preliminary results
•Summary & Outlook
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Introduction
Cosmic ray anisotropy observation:
--- Northern hemisphere: Tibet-Asγ, ARGO-YBJ, Milagro, HAWC, PAO
--- Southern hemisphere: IceCube & IceTop
Bartoli et al. 2015
Tail-inLoss-cone
[email protected] TeVTibet@5 TeV
IceCube@13 TeV
Tail-inLoss-cone
Multi-TeV
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M. Amenomori et al. 2017
Tibet-ASγ
Anisotropy VS Energy ARGO-YBJ
Bartoli et al. 2018 Aartsen et al. 2016
13 TeV 24 TeV
38 TeV 71 TeV
240 TeV130 TeV
580 TeV
1.6 PeV 5.4 PeV
1.4 PeV
IceCube&IceTop
IceTop
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Anisotropy VS Energy
Energy range of LHAASO
Phase shift
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LHAASO (Large High Altitude Air Shower Observatory)
4410 m a.s.l.@Daocheng, Sichuan, China Kilometer Array (KM2A):5195 Electromagnetic particle Detectors (EDs) 1171 Muon Detectors (MDs)1.3 km2 area
Water Cherenkov Detector Array (WCDA):3 water ponds3120 detectors78,000m2 area
Wide Field Cherenkov Telescope Array (WFCTA):18 wide-field-of-view Cherenkov/fluorescence telescopes
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Detector deployment
The progress is going smoothly:
--- 2018.02 --- 33 EDs started operation (this work)
--- 2019.04 --- 71 EDs and 10 MDs of KM2A, 1st water pool of WCDA in operation
--- 2019.07 --- 960 EDs and 230 MDs of KM2A, 2 telescopes of WFCTA, deployed
……
LHAASO detector deployment will be completed by the end of 2020.
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Data
Collected by 33 EDs (6600 m2)
Trigger: at least 5 EDs are fired
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Event rate is about 42 Hz
Dataset for this work:
--- 2018: 02~12
--- 𝜃 < 50°
--- No. of hits after noise filter (𝑛𝑓𝑖𝑙𝑡𝐸) ≥ 5
Total events: 7.2 × 108
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Simulation
Corsika7.6400: Fluka & EPOS
Gassier model 2013
G4KM2A for 33 EDs
Components H, He, CNO, MgAlSi, Fe
Zenith angle 0°~70°
Total events 3.98 × 109
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𝐸 = 104.562 GeV ≈ 36.5 TeV
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Energy estimation
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3 intervals according to 𝑛𝑓𝑖𝑙𝑡𝐸
--- 5-9: about 23.7 TeV
--- 10-19: about 46.3 TeV
--- ≥20 : about 119.2 TeV
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Preliminary resultsSignificance 36.5 TeV
36.5 TeV
36.5 TeV
Intensity
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Tail-in: 10.5 σ
Loss-cone: 11.4 σ
Tail-in Loss-cone
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Anisotropy VS Energy
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𝟒. 𝟎𝟏 × 𝟏𝟎𝟖
𝟐. 𝟒𝟐 × 𝟏𝟎𝟖
𝟕. 𝟓𝟎 × 𝟏𝟎𝟕
intensity significance
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Anisotropy VS Energy
𝑬(𝐓𝐞𝐕)
𝒂𝒎𝒑 ± 𝝈𝒔𝒕𝒂𝒕 ± 𝝈𝒔𝒚𝒔(× 𝟏𝟎−𝟒)
𝝓(°)
23 9.0 ±0.7 ±1.2 20.8
46 6.1 ±0.9 ±2.6 48.3
119 2.4 ±1.6 ±5.9 11.4
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Anisotropy VS Energy
Phase VS EnergyAmplitude VS Energy
This work is generally consistent with others.
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Summary & Outlook
CR anisotropy is observed by a partial array of LHAASO-KM2A
--- ”Tail-in” and “loss-cone” are observed with significances of 10.5 σ and 11.4 σ respectively.
--- The evolution with energy is consistent with others.
The construction of LHAASO is going on smoothly and the total array will be in operation at the beginning of 2021.
More precise studies for anisotropy will be done.
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Thanks for your attention!
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