Status of TPC experiment ---- Online & Offline M. Niiyama H. Fujimura D.S. Ahn W.C. Chang

From cosmic ray test, 1 track resolution is um in pad plane w/ magnet um in drift direction w/o magnet. If we apply magnetic field, residual in drift direction shifts layer by layer. Possible reason are - circle fitting is not suitable for our solenoid magnet. -> runge kutta is needed - E x B effect disturbs drift property of electrons in TPC. Bx at z=350mm is 0.5T -> simulation of drift property is needed. Results from cosmic ray test

Bx at z=350mm

E // B  Cycloid Motion E&M Calculation

Install & Geometry cm 40.7cm 20cm 32.4cm Collimator Shieldtarget TPC  solenoid Pb Top view Dipole magnet 37.5 cm

dipole magnet Downstream scintillators Side scintillators Ｓｈｉ ｅｌｄ Ｃｏｌｌｉ ｍａｔｏｒ Ｕｐｖ ｅｔｏ ＥＸＰ．ＨＵＴＣＨ （ February ） February run

dipole magnet Downstream scintillators Side scintillators Ｓｈｉ ｅｌｄ Ｃｏｌｌｉ ｍａｔｏｒ Ｕｐｖ ｅｔｏ ＥＸＰ．ＨＵＴＣＨ（Ｍ ａｒｃｈ） Ｓｔａｒｔ ｃ ｏｕｎｔｅｒ ＴＯＦ Ｗ ａｌｌ Ｖｅｔｏ ＠ ＴＯＦ March run

Trigger condition Run in Feb, to know performance of TPC tag x (up-veto) x (8scinti M>=2) x (TPC side scinti M>=1) 95Hz at 400kHz tagger Run in Mar, Particle ID by spectrometer calibration of TPC. gamma-> pi+ pi- p, trigger is similar as K0 exp. - tag x (ATG) x (TOF M>=2) x (veto after TOF) x (TPC side scinti M>=1)

Eye scanning

At least one particle comes from target holder Reject if two tracks overlap each other Scanning criteria

Analysis dE is measured by pad rows By correction by dip angle between pad plane and track was applied. Truncated mean was used to suppress Landau distribution. - for each track, to get truncated mean, - cut the Landau tail of the distribution - keep 60% of the sample, which have the most lowest amplitude - get the mean value of the remaining distribution  truncated mean Circle fitting in pad plane, line fitting in arclength z plane dE/dx value of given tracks Cut condition ; chi2 for pad plane and arclength z plane

Momentum/charge ( dE/dx Truncated mean)*cos(lambda) Calibration of gain is not finished. Runge-Kutta tracking is not yet used. Just circle fitting for p_t determination proton Pions or electrons 1000 events eyescan

DAQ and Offline Analysis

1200-channel FADC Modules (10 bits, 40 MHz, pedestal-subtraction) for TPC

DAQ Speed  Goal: 100 Hz. In total 3 SUN SPARC (collector) to read out data in parallel.  Feb run:15Hz. # of words read = word, for 1 IRQ( = 4events), 1 module Unstable pedestal: drifting with temperatures. (Air- condition is desirable.)  March Run: 20Hz On-board width-cut for discrete pulses (<4 time bins). Tag*\bar{up}*ATG*\bar{e+e-}*(TOF M>=1) * (TPC side M>=2) # of words = 3000, 1 IRQ( = 4events) for 1 module  Where is the bottle neck of DAQ speed? Reduce the number of sampling to 600. Reduce the CLOCK from 40 MHz to 20 MHz. Look for the other possible source in collector or builder.

Determination of Particle Trajectory

TPC analyzer 1 Pad 1 pulse1 Pulse2 ………. ADC TDC ADC TDC Pad 2 pulse1 Pulse2 ………. ADC TDC ADC TDC If overlap in time direction was found in adjacent pad they are include in a cluster. Pad 3 pulse1 Pulse2 ………. ADC TDC ADC TDC Continue in all pads in layer while overlap is found In one layer Pad # Time

TPC analyzer 2 In one layer Cluster Hit x, y, z coordinate ADC To reduce # of hits to be searched by find track. Select hits of enough large ADC. BoneHit x, y, z coordinate ADC TrackFinder Under construction

TrackFinder  Track pattern recognition: Segment the acceptance into sub-volumes in (r,,z). Nose-finding algorithm: pick up hits on the most outer layer and search the nearest hit in the neighboring sub-volume inwards. Construct track-candidates: after conformal mapping, make the cut on the chi2 values of a straight line fit.  Track Parameters for RK fitting: Assuming uniform B field. Circle fitting on the transverse plane: (x0,y0) and (Px0,Py0) Slope of arclength vs z: (z0) and Pz0.  Runge-Kutta Fit with real B field map.

TPC Analyzer  Input file: MC ntuples or real data.  Output ntuples: hits information and track parameters.  Test with MC ntuples.  Test with real data.

Conclusion  TPC has started operation in this Feb.  We are taking data now with triggers from both tracks in TPC and spectrometer.  Struggling with large data size and slow DAQ speed. Need to improve it significantly.  Need to demonstrate the ability of track- finding and PID.  We need helps from other LEPS members for data-taking and offline analysis.