Study of compact emulsion spectrometer

for identification of neutrino/anti-neutrino

interaction

061209 OPERA emulsion workshop @ Nagoya Univ.

Chika Fukushima 　 Toho University

Toho Univ. ,Aichi Univ. of EducationA,Kobe Univ.B

Satoru Ogawa, Mitsuhiro Kimura, Hiroshi Shibuya,Koichi KodamaA, Toshio HaraB

Introduction

Only emulsion detector achieved identification of interaction by detection.

+ magnet: to distinguish anti-neutrino() interaction

+ New technique → emulsion : large-scale production by automatic coating data taking : high speed automated track selector

ECC(Emulsion Cloud Chamber) : multilayer detector of emulsion and metal plate(lead etc.)

Emulsion detector(ECC) can identify neutrino/anti-neutrino interaction.

Motivation

ECC （ multilayer of emulsion and lead plate ）　＋　　 magnetic fieldthis detector has large amount of material

★ bending of magnet must be dominated scattering.★ short flight length before electromagnetic shower

Compact emulsion spectrometer less amount of substance Can this detector be charge identification

after production charged lepton immediately?If that can be, how thickness do we need ?

Such a detector should become important in future neutrino experiments.

thickness of spacer : 15mm

total chamber length : 30mm

nonmagnetic

screw

emulsion film

beam

TAC (plastic base) ： 200memulsion ： 44m

It’s new emulsion which has same crystal

size → automatic coating　 ･ large scale of

production　　 ･ regular thickness

　 small amount of substance

acrylic plate 200m

or polystyrene 40m

support

vinyl chloride plate(air gap at central part)

Compact emulsion spectrometer(structure)

acrylic plate

“OPERA film” (emulsion: AgBr crystal)

B

248mm

248m

m

depth 244mm

N ｄ FeB compact permanent magnetmagnetic field １ Tesla (1.057[T] at the center)

1.0T

0-100 100Z[mm]

distribution of magnetic field along the beam direction

Good point using permanent magnet is:☆ compact （ no need space ）☆ no electric power is needed

0%

-1%

1%

2%

-2%

relative error

distribution of magnetic field in middle of magnet(z=0)

１ Tesla permanent

magnet

Me

A stack has total length of 30mm.

reference beam in each stack2.0GeV/c +[no magnet]3000/cm2

stack # support beam momentum （ ± ） and densitylength of stack

stack1acrylic plate 200m

0.5 、 2.0GeV/c [4 beams] : 　

1000/cm2 for each beam

30mm

stack2acrylic plate 200m

1.0GeV/c [2 beams] :

1000/cm2 for each beam

30mm

Dec. 7, 2005 KEK-PS T1 line

Beam Exposure

s = 0.3 B L2/(8p[GeV/c])

L

L/2 L/2

S

L = 0.03[m] in this study

d

d = 2s

sagitta s versus stack length L

L(mm) 30s(m) 39.8d(m) 79.6

1.0GeV/c

L(mm) 30s(m) 79.6d(m) 159.1

L(mm)

30

s(m) 19.9

d(m) 39.8

0.5GeV/c

2.0GeV/c

B = 1.057[T]

sagittaAlignment among three plates is performed with reference beam.

L[mm] 30

s[m] 39.8

Expected sagitta s

ref.

ref.mean: -37.6[m]mean: 38.1[m]

Sagitta 1.0GeV/c (stack2)

Scan area = 2 cm x 2 cm

Preliminary results

L[mm] 30

s[m] 79.6

Expected sagitta s

mean: -78.9m

mean: 79.0m

Sagitta 0.5GeV/c (stack1) preliminary

L[mm] 30

s[m] 19.9

Expected sagitta s

mean: -19.7m

mean: 19.6m

Sagitta 2.0GeV/c (stack1) preliminary

0.5GeV +0.5GeV 1.0GeV +1.0GeV -

2.0GeV -

2.0GeV +

More than 5 charge determination has been achievedfor 0.5, 1.0, 2.0 GeV/c ±.

superposition of 0.5, 1.0, and 2.0GeV/c ±

preliminary

Relation between sagitta and momentum(1/p) preliminary

Horizontal axis is inverse of ± momentum.

and vertical axis sagitta for each inverse momentum.

I’m preparing a paper.

Momentum resolution is about 14% on average,

mostly due to a multiple scattering.

● Slim spectrometer :3-layer low density structure ,30mm thick ,with permanent magnet of 1 Tesla.

● Slim spectrometer was exposed to 0.5, 1.0, and 2.0GeV/c ±

at KEK-PS T1 line. • The average of momentum resolution was found to be about 14%, mostly due to multiple scattering.

conclusions

OutlookThe relative error (that is, ) is

expected to be :pp

pp

ss

+～ 0.14 0.029p [GeV/c]

In the case of p = 10GeV/c, ～ 0.32. pp

Therefore, probability of the charge mis-identification

for a lepton with p = 10GeV/c would bearound 0.2%.