Speaker
Dr
Suguru Shimizu
(Osaka University)
Description
As a precision frontier experiment at J-PARC, we proposed a
search for
time reversal invariance violation by measuring the transverse muon
polarization (Pt) in the $K^+ \rightarrow \pi^0 \mu^+ \nu$ (Kmu3)
decay
which constitutes a T-odd observable. This observable is one of
the few
test of T-invariance and the corresponding CP violation in
non-neutral
meson sector and is sensitive to direct CP violation. At J-PARC,
we aim
to improve the precision of the measurement by a factor of 20
comparing
with the best result from our own KEK-PS E246 experiment, and reach a
limit of $\Delta$Pt$\sim10^{-4}$.
The final state interaction contributions in the SM descriptions are
significantly smaller than the sensitivity of this experiment. On the
other hand, several exotic models inspired by Multi-Higgs mechanism
etc. predict sizable Pt values within the sensitivity attainable to
us. Thus, this experiment is likely to find new source of CP
violation,
if any of these models are viable. Since it will certainly
constrain the
parameter space of the candidate models, the sensitivity of this
experiment is comparable or superior to that of the proposed new
neutron
EDM experiment and other rare decay processes. The physics
potential in
terms of discovery of new physics along with the power to
constrain the
exotic model is shown to be competitive with other experiments being
planned or prepared.
It is pointed out that the improved sensitivity will be achieved
thanks
to the new J-PARC facility beam quantities, namely, the newly
designed
low-momentum $K^+$ beam line. The experiments will use a stopped
$K^+$
beam in conjunction with the upgraded E246 setup. Major changes
of the
detector system are 1) improved charged particle tracking by
incorporating the sate-of-art GEM detectors, 2) new readout of the
CsI(Tl) calorimeter with APD, 3) introducing active polarimeter
for the
e+ measurement from muon, and 4) a new magnet to hold the muon spin
polarization. This arrangement with increased $K^+$ beam
intensity and a
runtime of $10^7$ seconds will improve the E246 result by a factor of
20, bringing the discovery potential to $\Delta$Pt$\sim10^{-4}$
in our
quest for new physics.
Primary author
Dr
Suguru Shimizu
(Osaka University)
Co-authors
Dr
B. Surrow
(Massachusetts Institute of Technology)
Dr
C. Djalali
(University of South Carolina)
Prof.
C. Rangacharyulu
(University Saskatchewan)
Dr
D. Hasell
(Massachusetts Institute of Technology)
Dr
E. W. Anderson
(Iowa State University)
Dr
F. Simon
(Massachusetts Institute of Technology)
Prof.
G.Y. Lim
(KEK)
Prof.
Hirohiko Shimizu
(KEK)
Dr
Hirohito Yamazaki
(Tohoku University)
Dr
J. Doornbos
(TRIUMF)
Dr
J. Kelsey
(Massachusetts Institute of Technology)
Prof.
Jun Imazato
(KEK)
Dr
K. Dow
(Massachusetts Institute of Technology)
Dr
K. Paton
(University Saskatchewan)
Dr
Keito Horie
(Osaka University)
Prof.
M. Hashinoff
(University of British Columbia)
Dr
M. Kohl
(Massachusetts Institute of Technology)
Dr
M. Plesko
(Massachusetts Institute of Technology)
Prof.
P. Depommier
(Universite de Montreal)
Dr
R. E. Pywell
(University Saskatchewan)
Prof.
R. Milner
(Massachusetts Institute of Technology)
Dr
S. Steadman
(Massachusetts Institute of Technology)
Dr
S. Strauch
(University of South Carolina)
Prof.
Shin'ya Sawada
(KEK)
Dr
Youichi Igarashi
(KEK)
