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+.