Measurement of the K0 charge radius and a CP-violating asymmetry and a search for CP-violating E1 direct photon emission in the rare decay KL--> pi+ pi- e+ e-.
Using the complete KTeV data set of 5,241 candidate K(L)--> pi(+) pi(-) e(+) e(-) decays (including an estimated background of 204 +/- 14 events), we have measured the coupling g(CR)= 0.163 +/- 0.0149(stat) +/- 0.023(syst) of the CP conserving charge radius process and from it determined a K(0) charge radius of <r(2)(K(0))> = [-0.077 +/- 0.007(stat) +/- 0.011(syst)]fm(2). We have determined a first experimental upper limit of 0.04 (90% C.L.) /g(e1)/ / /g(M1)/ of the couplings for the E1 and M1 direct photon emission processes. We also report the measurement of /g(M1)/ including a vector form factor /g(M1)/(1 + (a(1)/a(2))/((M(2)(p)-(M(2)(k))= 2M(K)E(gamma*)), where vector /g(M1)/= 1.11+/- 0.12(stat) +/- 0.08(syst) and a(1)/a(2) = [-0.744 +/- 0.027(stat) +/- 0.032(syst)] GeV(2)/c(2). Finally, a CP-violating asymmetry of [13.6 +/- 1.4(stat) +/- 1.5(syst)]% in the CP and T odd angle phi between the decay planes of the e(+) e(-) and pi(+) pi(-) pairs in the K(L) center of mass is reported.
Abouzaid
E
E
The Enrico Fermi Institute, The University of Chicago, Illinois 60637, USA.
Arenton
M
M
Barker
A R
AR
Bellantoni
L
L
Bellavance
A
A
Blucher
E
E
Bock
G J
GJ
Cheu
E
E
Coleman
R
R
Corcoran
M D
MD
Corti
G
G
Cox
B
B
Erwin
A R
AR
Escobar
C O
CO
Glazov
A
A
Golossanov
A
A
Gomes
R A
RA
Gouffon
P
P
Hanagaki
K
K
Hsiung
Y B
YB
Huang
H
H
Jensen
D A
DA
Kessler
R
R
Kotera
K
K
Ledovskoy
A
A
McBride
P L
PL
Monnier
E
E
Nelson
K S
KS
Nguyen
H
H
Niclasen
R
R
Ping
H
H
Qi
X R
XR
Ramberg
E J
EJ
Ray
R E
RE
Ronquest
M
M
Santos
E
E
Shields
J
J
Slater
W
W
Smith
D
D
Solomey
N
N
Swallow
E C
EC
Toale
P A
PA
Tschirhart
R
R
Velissaris
C
C
Wah
Y W
YW
Wang
J
J
White
H B
HB
Whitmore
J
J
Wilking
M
M
Winstein
B
B
Winston
R
R
Worchester
E T
ET
Worchester
M
M
Yamanaka
T
T
Zimmerman
E D
ED
Zukanovich
R F
RF