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 rate@500kHz,CH2 (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 accept @420k tagger. The arrival of new laser tube is delaying.

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.

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

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)

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

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

display runge-kutta tracking XY XZ YZ White : measured Black : traced point by RK

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