Recent results from the Tibet air shower experiment Masato TAKITA - - PowerPoint PPT Presentation

Masato TAKITA (ICRR, Univ. of Tokyo) For the Tibet ASg Collaboration

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Recent results from the Tibet air shower experiment

September 12, 2019 @TAUP2019, Toyama International Conference Center, Toyama, Japan

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Outline

• Tibet ASg Experiment (Multi-purpose)
• Gamma-ray observation

Skipped in this talk are:

• Sun shadow observation to probe solar MFs
• Cosmic-ray anisotropy measurement
• Chemical composition study around Knee
• Hadronic interaction tests using air shower

data

• Summary

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Received April 4, 2019, accepted June 13, published July 29, 2019 in PRL

Tibet Air Shower Array

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 Site: Tibet (90.522oE, 30.102oN) 4,300 m a.s.l. Present Performance  # of detectors 0.5 m2 x 597  Effective area ~65,700 m2  Angular resolution ~0.5°@10TeV ~0.2°@100TeV  Energy resolution ~40%@10TeV g ~20%@100TeV g →Observation of secondary (mainly e+/-,γ) in AS Primary energy : 2nd particle densities Primary direction : 2nd relative timings

Underground Water Cherenkov Muon detectors

Measurement of # of m in AS → g／CR discrimination DATA: February, 2014 - May, 2017 Live time: 719 days

~3400m2

✓ 2.4m underground (~515g/cm2 ~19X0) ✓ 4 pools, 16 units / pool ✓ 7.35m×7.35m×1.5m deep (water) ✓ 20”ΦPMT (HAMAMATSU R3600) ✓ Concrete pools + white Tyvek sheets

Soil & Rocks 2.6m Waterproof & reflective materials Reinforced concrete

e g m

1.0m

PMT

7.3m

Water 1.5m Cherenkov lights

20 inch

Air 0.9m

Basic idea: T. K. Sako et al., Astropart. Phys. 32, 177 (2009)

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m

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Muons in Air Shower

200TeV Gamma-ray induced AS 200TeV Proton induced AS

Electron・Positron・Muon ground ground Electron・Positron・Muon

Simulated by COSMOS

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E (Sr) vs. Nm Plot

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100TeV 10TeV

AS size log(Sr) by AS # of muons log(SNm) by MD

Sampling AS size(Sr)

After Nm cut,~99.9% CR rejection & ~90% g efficiency @100 TeV SNm=0 SNm=0

→Optimization of cut

Gamma: MC sample（Crab orbit & Crab Flux) CR：DATA(excluding Crab and Galctic plane)

AS size log(Sr) by AS # of muons log(SNm) by MD

Amenomori et al., PRL (2019)

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Sr (from AS array) : 3256 SNm (MD) : 2.3 zenith angle : 29.8° Erec : 251 TeV

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Gamma-like Event from the Crab

circle size ∝ log(# of detected particles) circle color ∝ relative timing [ns] fitting with NKG function ➡️ Erec (S50, q) lateral distribution S50

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Amenomori et al., PRL (2019)

S50 improves E resolutions (10 - 1000 TeV) → ~40%@10 TeV , ~20%@100 TeV

Muon Distribution in Crab Direction

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AS size log(Sr) by AS # of muons log(SNm) by MD

SNm=0 SNm=0

AS size log(Sr) by AS # of muons log(SNm) by MD

Observed # of muons # of muons at the cut value

Rm =

>100 TeV from the Crab CR BG g MC Amenomori et al., PRL (2019) Amenomori et al., PRL Supplemental Material (2019) ’

>10TeV >100TeV Data vs MC

Gamma-ray Emission from Crab

First Detection of Sub-PeV g (5.6s)

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Amenomori et al., PRL Supplemental Material (2019) ’

24 g rays against 5.5 CR BGs

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Energy spectrum of the Crab

Thick curve： the expected fmux by the inverse Compton model normalized to HEGRA data Aharonian+, ApJ, 614, 897 (2004)

Amenomori et al., PRL (2019)

The highest energy g ~450 TeV

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Comparison with HAWC (3.3s>100 TeV)

Abeysekara et al. ApJ 881:134 (pp1-13), Received May 28, 2019, accepted July 3,2019, published August 20 or 21, 2019

Thick curve： the expected flux by the inverse Compton model normalized to HEGRA data Aharonian+, ApJ, 614, 897 (2004)

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SNR G106.3+2.7

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• T. K. Sako ICRC2019 #778

✓ Tibet emission centroid coincident with molecular cloud indicated by CO emission contours ※consistent with VERITAS ✓ spectrum under analysis

E > 10 TeV

Geminga

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𝟏 ° 𝟔 𝟏 ° × ×

𝜹

𝝉

𝜾𝟐

s Th the nu ev dis the fr Gem the

• n

was 𝝉 𝟑 𝟒° 𝒆 𝒆 𝑶𝒕 𝒆 𝜽 𝒆 𝑶𝒕 𝒆 𝑶𝒄𝒉 𝒆 ± 𝟗°×± 𝟗°

฀

× × ”Φ

E > 10 TeV

Smoothed by 3-deg radius circle

✓ Very extended source → Consistent with HAWC ✓ Spectrum under analysis

Katayose ICRC2019 #770 ’

MGRO J1908+06

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E > 10 TeV

✓ Flux below 10 TeV is consistent with VERITAS ✓ Spectrum under analysis

Pulsar contribution

• D. Chen ICRC2019 #648

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Pulsar Analysis (>10TeV)

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γ

γ ific

d s defin e n μ

α ± δ ± ν − first ν ̇ − − × − ν ̈ − × − α ± δ ± ν − first ν ̇ − ν ̈ − α ± δ ± ν − first ν ̇ − × − ν ̈ −

90.522˚E, 30.102˚N, 4300 m a.s.l.) (2) Angular Resolution ~ 0.9˚ (> 3 TeV) d flo γ nfig 133–6

Fermi-LAT, Ref. [3] Fermi-LAT, Ref. [2]

ay flu ific

Tibet

Tibet

(b) (b) (b)

Tibet

Preliminary Preliminary Preliminary

MAGIC, Ref. [5]

✓ No significant pulsed signals are found ✓ Under analysis around 100 TeV Crab pulsar Geminga pulsar PSR J1907+0602

Hibino ICRC2019 #695 ’

Summary

• Multi-purpose experiment

– Gamma-ray astronomy from TeV to sub-PeV → Crab: First detection of g rays > 100 TeV observed (5.6s) Highest energy photon ever observed: 450 TeV Opened a new energy window in astronomy, ie, sub-PeV gamma ray astronomy! Other interesting sources under study! Skipped in this talk are: – Sun shadow observation to probe solar MFs – Cosmic-ray anisotropy measurement – Chemical composition study around Knee – Hadronic interaction tests using air shower data

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