report of the ntpc test experiment in 2007sep and others yohei nakatsugawa
TRANSCRIPT
NTPC test experiment in 2007Sep
●beam time: 2007Sep 20 – Oct 04
●test experiment with almost full setup ・ NTPC ・ LEPS spectrometer ・ new LH2 target ・ new drift chamber ・ trigger scintillators ・ magnetic Field 2Tesla
Inner Scintillators
・ 6 counters (1 for each sector)
・ one-side read out
・ fiber light guide
・ bad time resolution ~800ps RF separation using tagger
will be reported by Yamamura-kun
1
2
3
4
5
6
Outer Scintillators
・ 12 counters ( 2 for each sector)
・ Both sides are read out.( 24 PMT’s)・ time resolution = ~180ps
Forward Scintillators
・ temporary use ( Top & bottom ones wereused for 1st TPC exp.The other one is from ring cyclotron. )
will be replaced by 4 new ones (designed by Kon-kun)
Trigger Condition
● “Sector” trigger ・ inner ( OR of opposite 4 outers ) e.g. Sector2 trigger = (inner 2) (outer 2 3 4 5 )
123
45
6
1
2
34
5
6
7
8
910
11
12
charged particle on Sector2
1
2
3
4
5
6
●At least one “Sector” hit should be required. = more than one charged particle in TPC
・ outer = upstream PMT downstream PMT
Problem & Final Trigger
solenoid
TPC
● magnetic field of solenoid no signal from upstream PMT’s ! (even though PMT’s were covered by iron shields)
We could not use coincidence triggers of outer scintillators . Only signal from downstream PMT’s were used as trigger signal of outer.
●tagger rate was very low ~60kcps inner OR trigger ( (inner 1 2 3 4 5 6 ) AC ~40cps DAQ acceptable rate We used inner OR as main trigger. (minimum bias)
Angle of Upstream PMT
solenoid
no signalsignal
●Best PMT angle was searched during no beam time in November.
●Highest signal was obtained at vertical.
●Additional light guides have been made.
“Circle” Event
●low energy electron?●inner OR trigger contains too many “circle” events. hadron-like events (events with clean track) … ~10% “Sector” trigger strongly suppress “circle” events. hadron-like events … 80~90%
“Sector” hits should be required to reduce trigger rate.
Analysis
●analyzer for newTPC ( NTPCana ) is under construction.●TPCana modified for newTPC●main difference … geometry 1st TPC : concentric circle layers , r-φcoordinate newTPC : 6 sectors , x-y coordinate in local sector
φ
rx
y
Analysis
●tracking strategy ・ find hits and determine coordinates of hit positions in local sector
・ transform from local sector to global system
・ find track candidates in global system
・ Runge-Kutta tracking in global system and calculate residual in local sector
Analysis
●ExB effect on drift electrons ・ ExB correction already applied to hit position
・ residual of helix fitting was improved. 310 μm 270μm ( no cut of drift length, track angle )
・ Map of magnetic field was made with RADIA by Yamamura-kun. (Original code of RADIA was made by Ishikawa-san for 1st TPC experiment.)
Analysis
●To Do ・ y coordinate determination using wire ADC ( x : center of gravity of ADC value of pad y : center of gravity of ADC value of wire) identification of wire pulse which corresponds to pad hit
・ dip angle dependence of pad gain Correction of ADC value of pad is needed. dE/dx resolution
y1
y2
y3
y4
y5
x=p3
x3x2x1
y
cosmic ray data
|θ|<5° 5°<|θ|<10° 10°<|θ|<15°15°<|θ|<20°20°<|θ|<25°25°<|θ|<30°
z
padplane
θ CR
peakpad ADC
~150mmCFRP cap
VTZ
●vertex distribution of 2 track event●Clear shape of LH2 target and CFRP cap can be seen.
Physics Motivation
● Θ+ photoproduction accompanied by K* meson with deep UV laser (Eg ~ 3GeV)
● TPC can detect decay particles with large acceptance. invariant mass of Θ+ Θ+ K0 + p ππ
● There are some theoretical calculation which suggest decay asymmetry K* from neutron target is sensitive to parity of Θ+.