(K - ,K + ) 反応を 用いた Ξ ハイパー核分光実験に おける バックグラウンド の 評価

1. 日本物理学会2015年秋季大会 2015/9/25 - 28 (K-,K+) 反応を用いたΞハイパー核分光実験におけるバックグラウンドの評価 金築俊輔、市川裕大A、江川弘行、後神利志、永江知文 京大理, 原研A

2. Contents • hypernuclear spectroscopy at J-PARC (E05 exp.) • Expected counting rate • Rate study with SKS • Experimental setup • Analysis • Results • Comparison with simulation • A few comments on Pilot E05 experiment • Summary

3. J-PARC E05 experiment S-2S construction is almost done K+ Goal: Determine the ΞN interaction by measuring Ξ- hypernuclear missing mass with a higher energy resolution. Experiment Item 2.4 m K- 2.4 m

4. Expected background particles in S-2S SIMULATION B.G. which originate from a target ( Geant4 + JAM ) A few 10 counts of charged particles due to other origins. SIMULATION Safety factor of 5  p and π+ backgrounds Counts/(106 K- beams)

5. Background rate study with SKS(2015/5/7 @J-PARC K1.8 Beam Line) K+ Purpose Investigation of an origin of background particles.  Trigger rate in S-2S !! SKS Experimental setup: Same as J-PARC E13 exp. Beam Time: 1 hour in total • 9.6 g/cm2 CH2 target: min • Empty target: 12 min Iron block SAC Hyperball-J K1.8 beam line K- CH2 15 cm 10 cm 4 cm 5 cm Beam direction 12cm A Photograph of Polyethylene Target E13 setup @K1.8 beam line

6. Trigger condition K+ LC SKS Iron block TOF: TOF detector BH2: Beam Hodoscope SAC1 K1.8 beam line K- K- = 190 / spill π- = 160 / spill

7. Analysis Flow Chart Tracking 2 (TR2) TOF SKS Tracking () × ○ Drift Chambers TR1 Mass square × p and π+ from target ○ TR2 Drift Chambers ○ × × ○ Tracking 1 (TR1) Target ③ ④ ② ① BH2 Particles from no target Trigger:

8. Results (Rate Study with SKS) Trigger: ① K-Decay ② K- beams hit on Yoke  γ ③ Charge exchange in the target   Charged particles ④ Charge exchange in the target   γ

9. Results (Rate Study with SKS) Our simulation is able to reproduce the data for SKS !!  The rate estimation in S-2S would not be far from reality. Trigger: ① K-Decay ② K- beams hit on Yoke  γ ③ Charge exchange in the target   Charged particles ④ Charge exchange in the target   γ

10. Pilot E05 experiment with SKS • p(K-,K+) cross section at forward angle • Mechanism of production • Optimization of incident K- momentum • hypernuclear spectroscopy • N interaction Pilot E05 experiment (2015/10/26 – 11/11) Reduced by >70%

11. Summary Performed a rate study with SKS for the (K-,K+) experiment at J-PARC K1.8 Beam Line on 2015/5/7 Counting rates in data are consistent with our simulation • Origins of background particles are well understood • Rate estimation in S-2S would not be far from reality • Pilot E05 experiment will be carried out in this autumn

12. Thank you for your attention 金築 　　市川 江川 永江 後神 2015/9/18 @K1.8 Counting Room

13. Backup

14. DAQ Efficiency

15. Data summary

17. Results ① K+ Decay, inelastic p, inelastic e+ ② K- beams hit on Yoke  γ ③ Charge exchange in the target   Charged particles ④ Charge exchange in the target   γ

18. TOF distribution

19. Count Rate (Results 1)

20. Count Rate (Results 2)

21. Beam profile

22. TOF vs. TOF-segment

23. TOF vs. TOF-dE DATA

24. Mass square vs. TOF-segment

25. Gamma SIMULATION

29. Geant4 Simulation for S-2S

30. Particle distribution at 3 cm before WC

31. Solid angle of S-2S (Geant4) Target distance from Q1 entrance: 600 mm Magnet power of 2500 A カット条件:  fabs(x[8])<569.0 && fabs(y[8])<290. && // TOF selection mom[8]>1000.0 && Q1Trig && Q2Trig && // Pass through Q1 and Q2 VDTrig && // Hit virtual detectors WCTrig && // WC selection vdPID[8]==2 // Require K+

32. Momentum vs. theta at target

33. S-2S solid angle for different scaling factors on the dipole magnetic field

34. 金築君の熱川の資料よりBackground estimation in S-2S

35. Backgrounds 2. Decay of beam K－ • K－  π－π－π＋(B.R. 5.6%) K－@1.8 GeV/c: βγcτ 〜13.5 m 1. Various products off targets • Reaction rate: ～10% 3 m “D1Hit event” 3. Reactions on the D1 yoke • K－ + Fe  many particles 2014.9.26 研究会「ストレンジネスを含む原子核の最近の展開」

36. Backgrounds not from the Target • Decay of beam K－&Reactions on the D1yoke Geant4 simulation Beam K− =106 Only neutrons can reach the counters at the exit Most charged particles stop inside of the D1 a few tens of π＋ from K− decay Particles passing through the magnets 2014.9.26 研究会「ストレンジネスを含む原子核の最近の展開」

37. Reactions in target S-2S: θ＜18° 1.2~1.4 GeV/c K－p  Ξ－K＋ K－p Ξ*－ K＋ K+ • Background estimation • JAM v1.210 : Jet AA Microscopic transport model Out of Acceptance! K－p p K－ K－pp πK K－n p π－K－ Decay of hyperons p K－ 12C K－p  Λπ＋π－ K－p Σ－π＋ π+ • “Compilation of Cross-Sections : K± induced reactions”, CERN-Library(1983) Y. Nara et.al., Phys. Rev. C61 (2000) 024901 2014.9.26 研究会「ストレンジネスを含む原子核の最近の展開」

38. Background Distributions JAM simulation 106K－@1.8GeV/c 3 g/cm2, 12C target +DetectorCut Λ Σ－ 2014.9.26 研究会「ストレンジネスを含む原子核の最近の展開」

39. Elementary Production

40. Cross section at forward angle

41. Cross section at forward angle Maximum yield at ~ 1.8 GeV/c ?

42. Total cross section as a function of Data were taken from V.Flaminioet al., CERN-HERA 83-02 (1983)

43. One of predictions R.Shyam, NPA914, 79-84 (2013)

44. The differential cross sections G. Burgun et al., NPB8, 447 (1968) P.M. Dauber et al., PR179, 1262 (1969)

45. Data with higher statistic G. Burgun et al., NPB8, 447 (1968) P.M. Dauber et al., PR179, 1262 (1969) Better constraint at forward angle A few 10% error  < a few % error

46. Data with higher statistic G. Burgun et al., NPB8, 447 (1968) P.M. Dauber et al., PR179, 1262 (1969) Better constraint at forward angle A few 10% error  < a few % error