Today's Progress 1. Aug. 2006

PA-PB/T0-PA TOF analysis for (pi^-, 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. Then, now we examine the 4He(pi^-, 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 - TOFpi - TOFsec,

for the 4He(pi^-, pi^+/-) / 4He(pi^-, 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.

Results

First, 4He(pi^-, p) results are presented. Since Delta E range is large on PA, the large-energy-effect on the PAtiming should be seen here, if something exist.

A comparison of the correlations between proton 1/beta (horizontal) determined by PAPB system and deltaT(T0->PA) (vertical) after(left) and before (right) the accurate calculation of TOFsec.

The enlarged view of the correlation between proton 1/beta (horizontal) determined by PAPB system and deltaT(T0->PA) after the accurate calculation of TOFsec. A weak negative correlation is seen. The y-averaged histgram is overlayed with red lines.

The resulting correlation is moderate, although non-negligible 1/beta dependence still remains. Since 1/beta is strongly dependent on the delta E on PA, it may be attributed to the deviation of the slewing correction function from the realistic one at high-energy-deposit. This problem is treated AFTER T0-PA TOF is studied with (K^-, p) with huge statistics up to 1,000,000 proton events. Even if it really exist also on (K^-, p), the maximum error value caused by this effect is at most 100 psec on the PAPB TOF. The correlation between delta E on PA and delta T(T0->PA) is shown below.

The correlation between sqrt(phL*phR) of PA(horizontal) and deltaT(T0->PA) after the accurate calculation of TOFsec. A weak negative correlation is seen again. The y-averaged histgram is overlayed with red lines.

It is interesting to compare the width of deltaT(T0->PA) between (pi^-, pi^+-/mu^+-(e^+-)) and (pi^-, p). For the comparison, relatively fast non-proton-particles are selected to avoid possible uncertainty by the deceleration inside the target system.

delta T(T0->PA) from 4He(pi^-, p) on the various 1/beta range.

delta T(T0->PA) from 4He(pi^-, p) on the various 1/beta range, with DCA<3.0 (mm) (black) and >3.0 (mm) (red) selections. Top-left: 1.6<1/beta<2.2, Top-right: 2.2<1/beta<3.0, Bottom-left: 3.0<1/beta<4.0, Bottom-right: 4.0<1/beta .

Correlation between total energy detected on PB/NT and PAPB 1/beta. The presence of pi/mu is clearly seen, while almost no electron component is seen.

delta T(T0->PA) from 4He(pi^-, pi/mu) on the various 1/beta range.

4He(in-flight pi^-, p) spectrum

Here, 4He(in-flight pi^-, p) momentum spectrum from E549 run 292 is presented. 29124 protons are energy-loss-corrected for 30362 protons identified (95.92 % correction efficiency).