eport of the NTPC Test Experime in 2007Sep and Others Yohei Nakatsugawa
Jan 14, 2016
Report of the NTPC Test Experimentin 2007Sep and Others
Yohei Nakatsugawa
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
Set up
Fwdsolenoid
dipole
TPC
inner
outer
new
DC
ACtargetγ
※not scaled
New Liquid Target System
● will be reported by Maeda-san
New Drift Chamber
●will be reported by Sawada-san
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)
Set up
Set up
Set up
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.
Event Display
x
yy
z
“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.
VTZ of gas target
●LH2 shape disappeared CFRP remained
VTX & VTY
vtx vty
dE/dx vs momentumdE
/dx
momentum * charge[GeV]
Beam Time in 2008
● NTPC experiment 2008.Jan.25 -- Feb.25 Apr. 5 -- Apr.24 May.12 -- Aug.1
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+.