Today's Progress 7. Aug. 2006 (updated every moment)

PA-PB/T0-PA TOF analysis for (K^-, X) (2)

Until now,

1. Run-by-run tune of T0/PA/PB timing,

2. Systematic proton ID criteria on PB/NT system, and

3. vertex->PA TOF calculation code from PAPB TOF

are investigated and developed, and (pi^-, X) reaction is successfully studied. Then, now we examine the 4He(K^-, X) prompt timing analysis, which has been once examined (see, here), but remained as an advanced subject.

Formalization

Here, we investigate the time residual,

DeltaT(T0->PA) = Tpa - Tt0 - TOFkstop - TOFsec,

for the 4He(K^-, pi^+/-) / 4He(K^-, p) reactions. Note that Tpa/Tt0/Tpb run-by-run time walk/relative offsets had been already eliminated here. For the former reaction, TOFsec is just simply calculated with the PAPB-detected velocity and flight distance without any correction, while energy loss correction is applied and TOFsec is re-calculated for the latter.

(K^-, p) results

Arm-by-arm plot of deltaT(T0->PA) for all / stopK by T0 energy+vertexz / .NOT.(stopK by T0 energy+vertexz) with black / red / green colors, respectively. Small amount of stopped K events, several % by the event fraction, are found in the .NOT.(stopK by T0 energy+vertexz) events. It should be noted that in-flight reaction is strongly suppressed when proton events are selected on PA/PB/NT.
Correlation between deltaT(T0->PA) and 1/beta for stop K events for Rarm. Weak dependence on the 1/beta exists, which is consistent to (pi^-, X) result.

(K^-, pi/mu) results