Sep. 1, 2007 JPARC TREK Collaboration meeting at Saskatchewan. Tracking(1) K p 2 decay-in-flight BG simulation. K. Horie Osaka University. Simple estimation of K p 2 BG fraction.
Fraction of Kp2 decay-in-flight in the target is BR(Kp2)/BR(Km3) * decay probability ~ * (1.- exp (target radius / bgct) ) ~1.
momentum of Kp2 p+ 205MeV/c; b= 0.84
bgct ~ 100cm
target radius ~ 10cm
1- exp(-10/100) ~ 0.1
The number of Kp2 decay-in-flight in the target is comparable to the number of Km3 events
MC simulation (GEANT3) for Kp2 BG rejection (1) fiber size
(2) target thickness
(3) Kp2 BG fraction
Last meeting at KEK
Source of Kp2 BG(1)scatter in the spectrometer(2)dif in the spectrometer can be rejected by installing C0.
(3)dif before C0
… to be rejected by target fiber.
Maximum energy deposit in 1 fiber (MeV)
Energy deposit in each fiber (MeV)
2 different type of ADC or amplifier are needed.
total energy deposit (MeV)
number of hit fiber
LFiber size and spatial resolution of K+ stopping position
rdiff =true – measured
open : method 1 (using 1 fiber info.)
closed: method 2 (using 2 fibers info.)K+ stopping position was obtained to be 0.07cm in RMS.
K+ stop. pos. (hit-fit) (cm)
0.12 cm in RMS
0.07 cm in RMS
Kp2 BG could be rejected by target diff. cut.
The number of Kp2 decay-in-flight in the target is comparable to the number of Kmu3 events