During TAx4 construction, data collection with the TA detectors and the data analyses continued. Here shows the recent TA results as part of TAx4 (as of May 31, 2020)
Energy spectrum (Back to top)
- TA energy spectrum PoS(ICRC2019)298（11 years of TA SD data)
- TA: E>〜1018eV
- Ankle at 1018.69±0.01eV
- Suppression at 1019.81±0.03eV (Statistical significance 8.4σ)
- Declination dependence of energy spectrum PoS(ICRC2019)298 (11 years of TA SD data)
- Suppression at 1019.64±0.04eV (-16.0°< Decl.δ<24.8°); 1019.84±0.02eV (24.8°<Decl. δ<90°)
- Local significance of the difference of the above energies is 4.7σ The chance probability that local significances above 4.7&sigma occur is 4.7σ。
Mass composition (Back to top)
- TA mass composition Astrophys. J., 858:76 (2018)（8.5 years of hybrid data)
- Study of shower maximum depth (Xmax): Xmax average; Xmax width; comparison between distributions of data Xmax and 1-element composition model (p-value); Xmax average versus Xmax width
- TA mass composition PoS(ICRC2019)280 (10 years of hybrid data)
- Comparison of Xmax distributions between TA data and 4-element composition model (hadron interaction model = QGSJET II-04)
- best fit: proton:57%, helium:18%, nitrogen:17%, iron:8% (1018.2eV < E < 1019.1eV)
- TA mass composition Physical Review D 99, 022002 (2019)（9 years of TA SD data)
- Average atomic mass <ln A> = 2.0±0.1(stat.)±0.44(syst.) (E > 1018eV)
- The result is qualitatively consistent with atomic mass obtained from Xmax measured with hybrid data
Anisotropy (Back to top)
- Correlation of energies and arrival directions of ultra-high-energy cosmic rays with supergalactic structure PoS(ICRC2019)343（seven and 10 years of TA SD data)
- The following are expected for cosmic-ray deflection by universe regular and random magnetic fields:
- Cosmi-ray arrival directions are closer to the sources and cluster around the same directions as cosmic-ray energies are larger (deflection is smaller)
- Cosmic-ray arrival directions are more deflected from the cosmic-ray sources and their arrival directions are spread wider as cosmic-ray energies are smaller (deflection is larger)
- Using this feature, from cosmic-ray energies and arrival directions, we found the correlation of cosmic-ray sources with supergalactic plane with global significance of about 4σ.
- TA hotspot PoS(ICRC2019)310 (11 years of TA SD data)
- 168 events (E>57EeV)
- Maximum pretrial significance is 5.1σ (in the case of oversampling using circles with 25°-radius)
- The chance probability that significances greater than the above pretrial significance appear is 2.5×10-3 (2.9σ)
- TA hot/cold spot Astrophys J. 862:91 (2018) (7 years of TA SD data)
- For energies greater than 1019.2eV, we found maximum local significance (6.17σ) of energy spectrum anisotropy at (Right Ascension of 9hour 16 min, Declination of 45°) (a circle with a radius of 28.43°)
- Comparing energy spectra inside and outside the circle, we found deficit and excess below and above 1019.75eV, respectively.
- The chance probability of obtaining the local maximum siginificance greater than the above local significance is 9×10-5 (3.74σglobal)
- Point source search (10 years of TA SD data) in TA Anisotropy Summary (UHECR2018) EPJ Web of Conf. 210, 01004 (2019)
- Two doublets with energies greater than 100EeV (Δθ<√2°) in the TA field of view
- The chance probability that More than two doublets appear is .3×10-3 (2.8σ)
Search for ultra-high-energy photons and neutrinos (Back to top)
- Ultra-high-energy photon search
- Diffuse photon flux limit Astropart. Phys. 110 (2019) 8-14 (9 years of TA SD data)
- Diffuse photon search was performed for energies greater than 1018eV、1018.5eV、1019eV、1019.5eV、1020eV, but no significant evidence was found.
- Ultra-high-energy photon point source search MNRAS 492, 3984-3993, 2019 (9 years of TA SD data)
- Point source search was performed for energies greater than 1018eV、1018.5eV、1019eV、1019.5eV、1020eV, no significant evidence was found.
- First result for energies greater than 1018.5eV
- Ultra-high-energy neutrino search