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The detection of 8 extremely high-energy (EHE) cosmic rays
with energies above 1020eV in recent ten years gives question
about their origin and the acceleration mechanism if it is.
It is dramatically confirmed that the cosmic-ray spectrum does not end
with well known GZK cutoff.
But, it is undeniable fact that there is not seen any decisive optical
counterpart, neither Galactic nor extragalactic exotic object,
at the arrival directions of EHE cosmic rays exceeding 1020eV.
Such an EHE cosmic ray, even as a charged particle, keeps almost
straight trajectory in the Galactic magnetic field.
And, EHE particles, even though gamma rays or protons,
can not arrive from the space beyond 60 Mpc (200 million light years)
through the collision with cosmic microwave background photons.
This work is exploratory analysis whether TeV gamma rays come
significantly or not from the arrival directions of
these EHE cosmic rays, expecting to find a clue to solve this mystery.
We analyzed directions of 8 EHE cosmic-ray events observed by AGASA and
Fly's Eye experiments. No clearly significant excess is seen in
directions of these EHE cosmicrays.
An upper limit was given for the flux of TeV gamma rays from
3C147 lying near the highest energy (3×1020 eV)
the Fly's Eye event as 8.0×10-13cm-2s-1.
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