Hyperon-Nucleon Scattering Experiments

1. Hyperon-Nucleon Scattering Experiments Kozi Nakai (KEK) Summary of the 30-years efforts for the VLSdetermination since 1978. ΣN

2. Experimental Studies of Hyperon -Nucleon Interaction ◆ Hypernuclear experiments High-resolution spectroscopy Hyper-gammaray Spectroscopy Good theoretical leadership ◆ Hyperon-nucleon scattering experiments Triggerable tracking detector Active target 3D image reconstruction

3. 1978 Heidelberg-Saclay Coll. at CERN ΛN interaction （Central force） Hypernuclear Exp. （L-S force） 0 u L d s ∞ ∞ u ∞ ∞ N d u Gluon and quark combined exchange Historical Background: Physics Motivation Confirmed later by KEK and BNL Experiments. 1979 Pirner 1982 Pirner and Povh 1988 Yazaki Quark cluster model

4. 1978 at CERN Heidelberg-Saclay Coll. Search for Σhypernuclei with in-flight method B.Povh, Th.Walcher, S. Paul, ‥‥ 1986 at KEK Heidelberg-Tokyo Coll. T.Yamazaki, R.Hayano, K.Tanaka, ‥‥ Σhypernuclear experiment with the stopped-K method. 1998 at KEK Tokyo group Σhypernuclei are produced only limitted case 1998 at KEK TSU group SCITIC development for the hyperon-scattering experiments 2002 Osaka PANIC 30 y Large asymmetry in the Σ+P scattering experiments 2006 Mainz HYP-2006

5. 3“Φx3” NAI 60Co Can you see the scintillation light ? SCITIC SCIntillation Track Image Camera

6. p+ + p → K+ + S+(Production) • S+ + p → S+ + p (Scattering) • p+ + n → K+ + L (Production) • L + p → L + p (Scattering) Candlin et al, Nucl. Phys B226(1983)1 p+ K+ Candlin et al, Nucl. Phys B226(1983)1 Haba et al, Nucl. Phys. B299(1988)627

7. PANIC 2002 θK Polarization (R/L)asymmetry θKLab θKLab

8. p+ + p → K+ + S+(Production) • S+ + p → S+ + p (Scattering) • p+ + n → K+ + L (Production) • L + p → L + p (Scattering)

9. SCITIC ( SCI ntillation T rack I mage C amera) ( E452 ) IIT (Image Intensifier Tube) Any target material Adjustable magnification Triggerable Detector

10. Production p Scattering + S + S SCITIC0 p Scattering L Production L Beam SCITIC2 SCITIC1

11. E452 Data Analysis Raw Data (On-line Mass Trigger) Kinematical Cut (Spectrometer) z-vertex invariant mass Computer (Spectrometer analysis) ( Image Correction (Distortion) ) Scanning Categorize image (S, Sp, L, Lp) Pointing Vector of each track Human (Image analysis) Kinematical Cut Free (H) Quasi Free (C) Geometrical cut (Ambiguity of 3-D image) Computer (Image analysis) Polarization Left-Right Asymmetry 1,700,000 (Σp events) 26,485 13,817 7,621 81

12. Scanning (Event categorization) OTHER Image Data D D D D Σ D D K K K K Σ Σ p p π π π π SIG SIG-P LAM LAM-P Pointing (Vector of each track) 5 6 6 7 3 3 D 3 5 3 6 D D D 5 4 4 Σ 4 D 5 D K K K K Σ Σ p 2 2 4 2 2 p 7 8 π π π π 1 1 1 1 SIG SIG-P LAM LAM-P

14. Beam SCITIC2 SCITIC1

15. Marked point in pointing process Projected track on third SCITIC image chi Select 3D pattern having minimum square

16. Results Polarization + S p LR Asymmetry + S

17. Analyzing Power LpScattering S+pScattering Kyoto Model fss2 PL=900MeV/c PS=900MeV/c FSS Kyoto Model fss2 FSS q_LCM (degree) Analyzing Power q_SCM (degree) Analyzing Power 15 – 45 -0.08±0.30 67evnets 81evnets 25 – 50 0.75±0.32 45 – 75 -0.18±0.31 50 – 75 0.96±0.20 75 – 105 -0.14±0.19 75 – 100 0.42±0.23 105 – 135 0.00±0.35 100 – 125 0.00±0.27 125 - 150 -0.75±0.45

20. uds ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ Χ No s-quark vs. u,d-quark interaction Gluon and quark combined exchange Λ-spin behaves like a spectator