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

Recent results from the Tibet air shower experiment Masato TAKITA (ICRR, Univ. of Tokyo) For the Tibet AS g Collaboration September 12, 2019 @TAUP2019, Toyama International Conference Center, Toyama, Japan 1

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Outline • Tibet AS g 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 3

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

Tibet Air Shower Array  Site: Tibet (90.522 o E, 30.102 o N) 4,300 m a.s.l. Present Performance 0.5 m 2 x 597  # of detectors  Effective area ~65,700 m 2  Angular resolution ~0.5 ° @10TeV ~0.2 ° @100TeV ~40%@10TeV g  Energy resolution ~20%@100TeV g → Observation of secondary (mainly e +/- ,γ) in AS Primary energy : 2 nd particle densities Primary direction : 2 nd relative timings 5

’ Underground Water Cherenkov Muon detectors ✓ 2.4m underground (~515g/cm 2 ~19 X 0 ) ✓ 4 pools, 16 units / pool ✓ 7.35m × 7.35m × 1.5m deep (water) ✓ 20”ΦPMT (HAMAMATSU R3600) ✓ Concrete pools + white Tyvek sheets m m g e Soil & Rocks 2.6m ~3400m 2 1.0m 20 inch Air 0.9m PMT Water 1.5m 7.3m Cherenkov lights Reinforced concrete Waterproof & reflective materials Basic idea: T. K. Sako et al., Astropart. Phys. 32, 177 (2009) Measurement of # of m in AS → g ／CR discrimination DATA: February, 2014 - May, 2017 Live time: 719 days 6

’ Muons in Air Shower Simulated by COSMOS ground Electron ・ Positron ・ Muon 200TeV Gamma-ray induced AS ground Electron ・ Positron ・ Muon 200TeV Proton induced AS 7

’ Amenomori et al., PRL (2019) E ( Sr ) vs. N m Plot # of muons log( S N m ) by MD → Optimization of cut Gamma: MC sample （ Crab orbit & Crab Flux) CR ： DATA(excluding Crab and Galctic plane) 10TeV 100TeV S N m =0 AS size log( Sr ) by AS # of muons log( S N m ) by MD S N m =0 Sampling AS size( Sr ) AS size log( Sr ) by AS After N m cut,~99.9% CR rejection & ~90% g efficiency @100 TeV 8

’ Gamma-like Event from the Crab lateral distribution S 50 fitting with NKG function ➡️ E rec ( S 50 , q ) Sr (from AS array) : 3256 SNm (MD) : 2.3 zenith angle : 29.8 ° circle size ∝ log(# of detected particles) +46 E rec : 251 TeV - 43 circle color ∝ relative timing [ns] S50 improves E resolutions (10 - 1000 TeV) → ~40%@10 TeV , ~20%@100 TeV Amenomori et al., PRL (2019) 9

’ Amenomori et al., PRL (2019) Muon Distribution # of muons log( S N m ) by MD in Crab Direction >100 TeV from the Crab S N m =0 AS size log( Sr ) by AS # of muons log( S N m ) by MD CR BG g MC Observed # of muons R m = S N m =0 # of muons at the cut value AS size log( Sr ) by AS Amenomori et al., PRL 10 Supplemental Material (2019)

’ Gamma-ray Emission from Crab Data vs MC >10TeV 24 g rays against 5.5 CR BGs >100TeV First Detection of Sub-PeV g (5.6s) Amenomori et al., PRL 11 Supplemental Material (2019)

’ Energy spectrum of the Crab The highest energy g ~ 450 TeV Amenomori et al., PRL (2019) Thick curve： the expected fmux by the inverse Compton model normalized to HEGRA data Aharonian+, ApJ, 614, 897 (2004) 12

’ Comparison with HAWC (3.3 s >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) 13

’ SNR G106.3+2.7 E > 10 TeV ✓ Tibet emission centroid coincident with molecular cloud indicated by CO emission contours ※ consistent with VERITAS ✓ spectrum under analysis T. K. Sako ICRC2019 #778 14

𝜹 𝝉 𝜾 𝟐 × × ”Φ ฀ 𝟏 ° 𝟏 ° 𝟔 × × 𝒆 𝒆 𝑶 𝒕 𝒆 ’ 𝜽 𝒆 Geminga 𝑶 𝒕 𝒆 𝑶 𝒄𝒉 𝒆 𝟗 ° ×± 𝟗 ° ± E > 10 TeV Th the Smoothed by nu 3-deg radius circle ev dis the fr Gem the on was 𝝉 𝟑 𝟒 ° s ✓ Very extended source → Consistent with HAWC ✓ Spectrum under analysis Katayose ICRC2019 #770 15

’ MGRO J1908+06 E > 10 TeV Pulsar contribution ✓ Flux below 10 TeV is consistent with VERITAS ✓ Spectrum under analysis D. Chen ICRC2019 #648 16

γ γ ific 90.522˚E, 30.102˚N, 4300 m a.s.l.) (2) Angular Resolution ~ 0.9˚ (> 3 TeV) d flo nfig γ μ ’ Pulsar Analysis (>10TeV) α ± δ ± ν − first ν ̇ − ν ̈ − Geminga pulsar PSR J1907+0602 Crab pulsar α ± (b) δ ± (b) (b) Tibet Tibet Crab Pulsar ν − Geminga J1907+0602 Tibet first ν ̇ − × − 200 130 110 ν ̈ − 180 120 100 Counts (>10 TeV) 160 110 90 Counts Counts α ± 100 80 140 Background δ ± ν − 90 70 120 first ν ̇ − − × − Background ν ̈ − × − Preliminary 80 60 Preliminary Preliminary Background 100 70 50 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Pulsar Phase Pulsar Phase Pulsar Phase MAGIC, Ref. [5] d s defin e n Fermi-LAT, Ref. [2] Fermi-LAT, Ref. [3] ✓ No significant pulsed signals are found ay flu ific ✓ Under analysis around 100 TeV 133–6 Hibino ICRC2019 #695 17

’ Summary • Multi-purpose experiment – Gamma-ray astronomy from TeV to sub-PeV → Crab: First detection of g rays > 100 TeV observed (5.6 s) 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 18