1. Development of PID method in nuclear emulsion Shinji KINBARA Phys. Dept., Gifu Univ., JAPAN Outline 1. Motivation 2. Experiment at RIKEN (NP1406 RRC-32-02) 3. Method for identification of decay daughter nuclei from double- Λ hypernuclei 3-1. Measurement of track width 4. Result 5. Summary Collaborators Gifu Univ. K.Nakazawa, J.Yoshida, M.K.Soe, A.M.M.Theint, H.Itoh, H.Kobayashi, R. Murai RIKEN H.Ueno, Y.Ichikawa, T. Fujita, A. Takamine, K. Imamura JAEA S.H.Hwang, H.Ekawa, S. Hayakawa 1/11

2. 1. Motivation We expect to detect about one hundred double-  hypernuclei in J-PARC E07 experiment. Ξ- “NAGARA” event (KEK E373)  6 He was formed at point A, and sequential weak decay was observed point B and C.  6 He To understand  -  interaction, it is necessary for unique identification of many double-  hypernuclei. 2/11

3. 1. Motivation If track #2 is known to be triton, the mode A is identified, and the excitation energy of 2.8 MeV is confirmed. If track #3 is identified as He ( 3 He, 4 He or 6 He ) ， the mode A is identified. B. 3/11

4. ■ 8 isotopes ( 1 H, 2 H, 3 H, 3 He, 4 He, 7 Li, 9 Be, 11 B) 2. Experiment at RIKEN (NP1406 RRC-32-02) Microscope images of Ξ-hyperons at 100 μm from stopping points, where double-  hypernuclei were produced. (July.18~21, 2015) ■ Several incident angles ( θ =0°, 25°, 50°, 75°) 70mm 30mm 5mm θ Emulsion stack A particle was exposed to an emulsion stack with several incident angels. Beam We measure track width depending on the angles (θ) along light axis. ■ Reference 1 H for calibration 1 H was exposed horizontally(θ = 90°) to all emulsion stacks to calibrate width depending on development and optical condition. 4/11

5. For the coming J-PARC E07 experiment, we try to recognize 8 isotopes. ( 1 H +, 2 H +, 3 H +, 3 He 2+, 4 He 2+, 7 Li 3+, 9 Be 4+ and 11 B 5+ ) E sum ( 4 He) / E sum ( 3 He) = 1.1 E sum ( 3 H) / E sum ( 1 H) = 1.6 E sum ( 2 H) / E sum ( 1 H) = 1.3 Challenge!! 「宇宙線」小田稔著，裳華房 (1985)p.113 Track width reflect dE/dx. E sum ( 11 B) / E sum ( 1 H) = 17 E sum ( 9 Be) / E sum ( 1 H) = 12 E sum ( 7 Li) / E sum ( 1 H) = 8 E sum ( 4 He) / E sum ( 1 H) = 4 We expect to separate them well!! 3. Method for identification of decay daughter nuclei from double-  hypernuclei We measure track width in the emulsion. -dE/dx [MeV/mg/cm 2 ] Ratio of energy-loss sum to 1 H 0 0.5 1.0 1.5 2.0 2.5 3.0 0 5 10 15 20 Range from stopping point [  m] 10 -1 10 0 10 1 10 2 10 0 10 1 10 2 HHeLiBeBCNO 5/11

6. K.Nakazawa, et al., Ann. Rep. Tandem V.D.G.Lab. Kyoto Univ. 1996-1997 (1998) p.141 Good recognition We separated well 1 H +, 4 He 2+ and 7 Li 3+ in use of 60  m. Pick up edge of track with image processing method. A superimposed image of a track at focal planes. 1996~1997, isotopes of 1 H +, 4 He 2+ and 7 Li 3+ were exposed horizontally to the emulsion at Tandem V.D.G Lab. Kyoto Univ. 3 ． Method for identification of decay daughter nuclei from double-  hypernuclei 6/11

7. 3-1. Measurement of track width F(x) = A*tanh(Gauss(x,μ,  )) is applicable to fitting both tracks. θ=0° (K-beam) 120 100 80 60 40 20 0 0 0.40.81.21.62.02.4 brightness  m] Inflection points θ=90°( Proton) 00.40.8 1.21.62.0 2.4  m] Inflection points 120 100 80 60 40 20 0 ① Raw image ② blurred image To uniform background ②ー① brightness 7/11

8. 4. Result 1 H and 4 He are separated at 60  m in 3 . 4 He and 7 Li are separated at 80  m in 3 . 11 B and 9 Be are separated at 90  m in 3 . ■ ： 11 B ■ ： 4 He ■ ： 9 Be ■ ： 1 H ■ ： 7 Li Range from stopping point [  m] 010 20 30 4050 60708090 100 2.5 2.0 1.5 1.0 0.5 2.5 2.0 1.5 1.0 0.5 Range from stopping point [  m] 010 20 30 4050 60708090 100 Ratio of volume of reference 1 H ■ ： 11 B ■ ： 4 He ■ ： 9 Be ■ ： 1 H ■ ： 7 Li 57MeV 1 H, 4 He 4 He, 7 Li 11 B, 9 Be 8/11

9. K.Nakazawa, et al., Ann. Rep. Tandem V.D.G.Lab. Kyoto Univ. 1996-1997 (1998) p.141 Range from stopping point [  m] 3236404448525660 2.0 1.8 1.6 1.4 1.2 Ratio of volume of reference 1 H 1.0 0.8 4. Result 4 He/ 1 H=1.28±0.08 7 Li/ 1 H=1.58±0.19 4 He/ 1 H=1.21±0.08 7 Li/ 1 H=1.53±0.13 Consistent 9/11 We compared our result with the data of the paper. ■ ： 7 Li ■ ： 4 He ■ ： 1 H At the 60  m,

10. 2.0 1.5 1.0 0.5 6070 8090 100 ■ ： 6 He ■ ： 4 He 6 He ： 1.50±0.15 4 He ： 1.35±0.08 We try to separate 4 He and 6 He by taking a lot of statistics and using long range. Range from stopping point [  m] Ratio of volume of reference 1 H 4. Result We measured track width of 6 He in emulsion and compared 4 He with 6 He. 10/11

11. 5. Summary ■ We develop PID method to identify daughter nucleus decayed from double-  hypernuclei. ■ 8 isotopes were exposed to emulsion stacks with several angles and 1 H was exposed horizontally to all emulsion stacks to calibrate track width. ■ 1 H and 4 He, 4 He and 7 Li, 11 B and 9 Be are separated at range of 60  m, 80  m, 90  m, respectively. ■ We will measure track width depend on angles(θ) along light axis. 11/11

13. Range from stopping point [  m] 010 20 30 4050 60708090 100 2.5 2.0 1.5 1.0 0.5 2.5 2.0 1.5 1.0 0.5 Range from stopping point [  m] 010 20 30 4050 60708090 100 Ratio of volume of reference 1 H ■ ： 11 B ■ ： 9 Be ■ ： 7 Li ■ ： 6 He ■ ： 4 He ■ ： 1 H 4. Result We measured track width of 6 He in emulsion stack which 9 Be was exposed. 10/11

14. 2.0 1.5 1.0 60708090 100 ■ ： 9 Be ■ ： 6 He ■ ： 4 He Range from stopping point [  m] Ratio of volume of reference 1 H