1. status of experiment trigger conditon rate@500kHz,CH2 (empty)
TPC meeting 2004Jun04
status of experiment
Another 2 scinti. has been installed to cover forward acceptance,
called as forward left & right.
The vertical gap between forward up & down was increased.
The coverage is 6 ~7 layers hit. Re-alignment on 20th June.
The magnetic shield for AC PMTs was moved off from
tracking area. → caused gain drop. We need to study the
position dependence again. This is very time consuming.
Study while beam-line tuning (not user time) is desirable.
trigger conditon
(empty)
Tag*UpVeto*ACVeto*TPC≥1*SC*TOF≥2
1 Hz
Tag*UpVeto*ACVeo*(TPC+SC*TOF)≥3
42Hz (3Hz)
Tag*UpVeto*ACVeto*(TPC+SC*TOF)≥2
91Hz (14.2Hz)
Pre-scale 2charge trigger by factor of 3. Totally 47Hz request
35Hz tagger. The arrival of new laser tube is
delaying.

2. Beam time schedule In June and July, we have 102 shifts.
We spent most of time to trigger study.
But still AC doesn’t have enough efficiency (98%) and Imai-san is proposing to install small veto counter, 20mmФ at AC.
CH2, C and Cu target will be used and share # of triggers
by 2 : 1 : 1 .
The most important thing is to estimate # of Λ(1405) from real data
As detection of Λ is easer than Σ. We will look for , assuming same production cross-section as Λ(1405)
Detection of Λ is urgent.
From September, 2.9GeV beam will be available. We may need to think about it.

3. re-solve RF in LEPSana Targ SC Miss-ID of RF TOF between target &
SC causes miss-ID of RF
Miss-ID of RF

4. procedure Solve mass of particle by TOF between SC and TOF.
Select fastest particle if ntrk>1. Get beta.
At TrackVertex.F call findRfAgain.c
giving beta and path-length from target and SC as
arguments.
Find RF again after correction of TOF from target to
SC. And correct TOF from target to TOF-wall
Re-calculate mass in TrackVertex.F
New ntuple variables
dTTarST (dTTarget2STA)
slengSTA (path-length from SC to TOF)
(uncorrected TOF, RF, mass will be included)

5. After RF correction There still exist miss-ID bands.
Further study necessary.
sleng – slengSTA (mm)
dTTarg2STA (nS)
TOF (nS), ntrk=1

6. Runge Kutta tracking Uchida-san made nice frame-work for the study
based on the analyzer of En’yo-san’s Ф experiment.
Niiyama is improving it.
In current version residual is calculated when a track cross the pad layer. Tracking get stacked when 2 hits found in one layer. → Tracking based on arcLength
Improve the formula to calculate residual
Field map
Linear approximation to calcurate
residual is not good for low pt
particles. circle approx.
Runge-Kutta step
measured point
pad layer

7. display runge-kutta trackingXY XZ YZ
White : measured
Black : traced point by RK

8. Residuals assuming uniform field
residual Z
layer 6
residual X
layer 6
residual Z
layer 10 mm mm