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There are three principal process for producing
diffuse gamma rays in the galaxy. First, cosmic ray
nucleon interactions give rise to gamma rays primarily
through the decay of π0 mesons.
Second, cosmic ray electrons produce gamma rays through
bremsstrahlung. Third, cosmic ray electrons also interact
with the interstellar starlight, optical and infrared
photons and the blackbody radiation through the inverce
Compton scattering to produce gamma rays.
The higher matter density in the galactic plane
expect the dominant radiation.
At 〜MeV to 〜GeV energies, the predicted energy spectrum
of the galactic gamma radiation are compared with
observations and consistent with the data. Both the
COS-B data (≧ 70 MeV) and the EGRET data (≧ 100 MeV)
show the diffuse but rather sharp ridge of gamma ray
intensity along the galactic plane in addition to some
clear point sources, also.
The diffuse galactic gamma ray spectrum above 〜GeV
energies is usually assumed to be dominated bye the
decay of π0s resulting from
cosmic ray - matter interactions.
However, the flattening of the diffuse gamma ray spectrum
above ,1 GeV observed recently bye the EGRET
indicates the possibility of an extra component
which may be important at higher energies.
In this paper,we examined the diffuse gamma ray radiation from the
galactic plane in the energy region around 10 TeV by using
the air shower data obtained by the Tibet ASfl array at
Yangbajing in Tibet in the period from June 1990 through Octorber
1993. However, any significant excess was not found from
the galactic plane ( 20°≦ 1 ≦ 110°,｜b｜≦ 5°).
Then, the upper limit of the diffuse gamma ray intensity
was obtained to be about
2.9 × 10 cm s
at 10 TeV region with 90 % confidence level.
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