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{\Large \bf
Experimental Particle Physics Group
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Professor            &:& Atsuto Suzuki, Akira Yamaguchi and Hitoshi Yamamoto\\
Associate Professor  &:& Junpei Shirai, Fumihiko Suekane, Kunio Inoue \\
& &and Tomoki Hayashino\\
Assistant Professor &:& Tadashi Nagamine, Takuya Hasegawa and Masayuki Koga\\
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(http://www.awa.tohoku.ac.jp/)
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\noindent
{\bf Non-Accelerator Experiments}
\bigskip

   Exploring the ultimate structure of matter, the fundamental principles of
nature and the birth, evolution and death of the universe is an inevitable
practice, which is imposed on the human beings. In order to study these
subjects, experimental approaches in particle physics tend to pioneer the
two different research fields with the opposite side energy. One is the
ultra-high energy side, which is realized by high-energy particle
accelerators. The other is the ultra-low energy side, where large volume and
high sensitive particle detectors are equipped in a deep underground. In
particular large volume underground detectors give opportunities
for exploring the most important unsolved subjects on particle physics,
astrophysics and cosmology.

The KamLAND project of Tohoku University was launched in 1997 with
main objectives of (1) measurement of the neutrino masses and mixings through a search for neutrino oscillations of antineutrinos from faraway nuclear power reactors, (2) observation of $^7$Be and $^8$B solar neutrinos in order to understand an evolution of main sequence stars, 
(3) the first observation of geoneutrinos, and (4) study of relic and burst neutrinos from supernova explosions.

The construction was finished in the year 2001 and the data taking started
from January 2002.  The striking first results, "evidence of reactor anti-neutrino disappearance," has been announced in the end of 2002. It solves the long-standing (more than 30 years) solar neutrino problem. The data also indicated an excess of geo-neutrino events. KamLAND will pin-points neutrino oscillation parameters and starts a new field of "Neutrino Geophysics" in coming years. And "Neutrino Astrophysics" with an observation of low energy solar neutrinos will be accomplished by on-going big efforts.

\medskip
  Quasar/galaxy surveys to search for large scale structures of the
  universe such
as the great wall, voids, super clusters at high red shifts are
  proceeding with Subaru telescope and Kiso Schmidt telescope.

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\noindent
{\bf Accelerator-based Experiment}
\bigskip

   Collisions of accelerated particles such as electrons and positrons make
it possible to produce heavy particles such as B mesons and Z$^0$ bosons in the
cleanest state. Observation of their production and decay is quite important
to understand basic properties of elementary particles.

   The BELLE experiment at KEK is an e$^+$e$^-$ colliding experiment to 
study CP violation (asymmetry of the matter and anti-matter) in B
particle, which is expected to be large in the standard model with 
Kobayashi-Masukawa scheme.
The Tohoku group has joined the project and constructed 
resistive plate counters as a detector of K$_{\rm L}$. 
The beam collisions in the accelerator KEKB, and data taking with the
BELLE detector started in June 1999.
The results from the BELLE experiment have led to new discoveries of CP 
violation in B meson decays. 




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