Search for a light pseudoscalar particle in the decay K_{L};{0}-->pi;{0}pi;{0}X.
We performed a search for a light pseudoscalar particle X in the decay K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma with the E391a detector at KEK. Such a particle with a mass of 214.3 MeV/c;{2} was suggested by the HyperCP experiment. We found no evidence for X and set an upper limit on the product branching ratio for K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma of 2.4x10;{-7} at the 90% confidence level. Upper limits on the branching ratios in the mass region of X from 194.3 to 219.3 MeV/c;{2} are also presented.
Tung
Y C
YC
Department of Physics, National Taiwan University, Taipei, Taiwan.
Hsiung
Y B
YB
Wu
M L
ML
Chen
K F
KF
Ahn
J K
JK
Akune
Y
Y
Baranov
V
V
Comfort
J
J
Doroshenko
M
M
Fujioka
Y
Y
Inagaki
T
T
Ishibashi
S
S
Ishihara
N
N
Ishii
H
H
Iwai
E
E
Iwata
T
T
Kato
I
I
Kobayashi
S
S
Komatsubara
T K
TK
Kurilin
A S
AS
Kuzmin
E
E
Lednev
A
A
Lee
H S
HS
Lee
S Y
SY
Lim
G Y
GY
Ma
J
J
Matsumura
T
T
Moisseenko
A
A
Morii
H
H
Morimoto
T
T
Nakano
T
T
Nanjo
H
H
Nix
J
J
Nomura
T
T
Nomachi
M
M
Ogata
R
R
Okuno
H
H
Omata
K
K
Perdue
G N
GN
Podolsky
S
S
Sakashita
K
K
Sasaki
T
T
Sasao
N
N
Sato
H
H
Sato
T
T
Sekimoto
M
M
Shinkawa
T
T
Sugaya
Y
Y
Sugiyama
A
A
Sumida
T
T
Suzuki
S
S
Tajima
Y
Y
Takita
S
S
Tsamalaidze
Z
Z
Tsukamoto
T
T
Wah
Y
Y
Watanabe
H
H
Yamaga
M
M
Yamanaka
T
T
Yoshida
H Y
HY
Yoshimura
Y
Y
Zheng
Y
Y