No. 55 (00167)

Family name : Yamaga
Given name : Mitsuhiro
Affiliation : High Energy Accelerator Research Organization
Abbreviation : KEK
E-mail address : yamaga@post.kek.jp
Title : The Klong reconstruction for the Belle experiment at KEK
        B-factory
Authors : Mitsuhiro Yamaga
Abstract : 
The primary goal of the Belle experiment at the KEK B-factory is to 
study the origin of the CP-violation with the B-meson decays.
B0->J/psi+Klong decay is one of the most important and promising mode
for the measurement of the CP-violation parameter, sin2phi1.

In order to measure this decay mode with high efficiency, the Klong and
muon detector (KLM) is instrumented in the Belle detector.  It consists
of the alternating structure of 14- or 15-layers of the active detectors
of thin resistive-plate chamber and the absorptive iron plates.  The KLM
then acts as a hadron-shower detector for the Klong detection.  The
electromagnetic calorimeter (ECL) is also used in conjunction with the
KLM to improve the detection efficiency of the Klong.  The Klong
detection-efficiency strongly depends on its momentum, and is typically
over 50% at the momentum range over 1.5 GeV/c where most of the Klong
from the B0->J/psi+Klong decay belongs to.

We will present the reconstruction algorithm and its performance for the
Klong detection with the KLM and ECL. The latest physics result with the
Klong will also be presented.