1. 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 Education A,Kobe Univ. B Satoru Ogawa, Mitsuhiro Kimura, Hiroshi Shibuya, Koichi Kodama A, Toshio Hara B

2. 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.

3. Motivation ECC （ multilayer of emulsion and lead plate ） ＋ magnetic field this 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.

4. thickness of spacer : 15mm total chamber length : 30mm nonmagnet ic screw emulsion film beam TAC (plastic base) ： 200  m emulsion ： 44  m It’s new emulsion which has same crystal size → automatic coating ･ large scale of production ･ regular thickness small amount of substance acrylic plate 200  m orpolystyrene 40  m support vinyl chloride plate (air gap at central part) Compact emulsion spectrometer(structure) acrylic plate “OPERA film” (emulsion: AgBr crystal)

5. B 248mm depth 244mm N ｄ FeB compact permanent magnet magnetic field １ Tesla (1.057[T] at the center) 1.0T 0 -100 100 Z[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

6. Me A stack has total length of 30mm. reference beam in each stack 2.0GeV/c  + [no magnet]3000/cm 2 stack # support beam momentum （  ± ） and density length of stack stack1 acrylic plate 200  m 0.5 、 2.0GeV/c [4 beams] : 1000/cm 2 for each beam 30mm stack2 acrylic plate 200  m 1.0GeV/c [2 beams] : 1000/cm 2 for each beam 30mm Dec. 7, 2005 KEK-PS T1 line Beam Exposure

7. s = 0.3 B L 2 /(8p[GeV/c]) L L/2 S L = 0.03[m] in this study d d = 2s sagitta s versus stack length L L(mm)30 s(  m) 39.8 d(  m) 79.6 1.0GeV/c L(mm)30 s(  m) 79.6 d(  m) 159.1 L(mm ) 30 s(  m) 19.9 d(  m) 39.8 0.5GeV/c 2.0GeV/c B = 1.057[T] sagitta Alignment among three plates is performed with reference beam.

8. L[mm] 30 s[  m] 39.8 Expected sagitta s     ref. mean: -37.6[  m]mean: 38.1[  m] Sagitta 1.0GeV/c   (stack2) Scan area = 2 cm x 2 cm Preliminary results

9. L[mm] 30 s[  m] 79.6 Expected sagitta s mean: - 78.9  m mean: 79.0  m Sagitta 0.5GeV/c   (stack1) preliminary

10. L[mm] 30 s[  m] 19.9 Expected sagitta s mean: - 19.7  m mean: 19.6  m Sagitta 2.0GeV/c   (stack1) preliminary

11. 0.5GeV  + 0.5GeV   1.0GeV  + 1.0GeV  - 2.0GeV  - 2.0GeV  + More than 5  charge determination has been achieved for 0.5, 1.0, 2.0 GeV/c  ±. superposition of 0.5, 1.0, and 2.0GeV/c  ± preliminary

12. 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.

13. ● 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

15. Outlook The relative error (that is, ) is expected to be : pp p pp p ss s + ～ 0.14 0.029p [GeV/c] In the case of p = 10GeV/c, ～ 0.32. pp p Therefore, probability of the charge mis-identification for a lepton with p = 10GeV/c would be around 0.2%.