Probing the relative momentum of two-nucleon system in 6 He and 6 Li - PowerPoint PPT Presentation

Toshimi Suda Research Center for Electron-Photon Science Tohoku University N. T. Khai (INST), A. Yoshida (RIKEN), I. Tanihata(RCNP) HST 15 @ Osaka, JAPAN Probing the relative momentum of two-nucleon system in 6 He and 6 Li

W. Horiuchi and Y. Suzuki Two-nucleon system 6 He and 6 Li Phys. Rev. C76 (2007) 024311. HST 15 @ Osaka, JAPAN 31 S 0 13 S 1 + n n p n α α 6 He 6 Li

TAGX spect.: large accept. p 2) 3 He(γ,pp)n spectator 1) 3 He(γ,np)p spectator p p n p n Photoabsorption by “np” and “pp” p p n p p n p p n p p n γ+ 3 He -> ppn HST 15 @ Osaka, JAPAN 150 γ +’np’ 100 Total Cross Section ( μ b) p sp p sp p sp 50 0 γ +’pp’ 3 2 n sp n sp n sp 1 0 100 200 300 400 500 E γ (MeV) TAGX collaboration Pn ~ 0 MeV/c PRL 73(94)404, PRL 74(95)1034, PRC49(94)R597

TAGX at INS, Tokyo ( ~1999) HST 15 @ Osaka, JAPAN 1.2 GeV electron synchrotron at INS, UT Photon tagger – E γ = 100 - 1000 MeV ( Δ E γ =±5MeV) – N γ = 1x10 6 /sec TAGX spectrometer – large acceptance ~ 3.2 st – neutron detection capability TAGX

Two-nucleon knockout @ JLAB longitudinal : charge transverse : current HST 15 @ Osaka, JAPAN 12 C(e,e’pp)/ 12 C(e,e’p) virtual photons

W. Horiuchi and Y. Suzuki Two-nucleon system 6 He and 6 Li Phys. Rev. C76 (2007) 024311. HST 15 @ Osaka, JAPAN 13 S 1 + 13 D 1 31 S 0 n n p n α α 6 He 6 Li

“deuteron” in 6 Li HST 15 @ Osaka, JAPAN 6 Li(e,e’d) α @ NIKHEF under quasi-elastic e-d kinematics e’ P m d 6 σ q 2 = K σ ed ( q ) φ ( p m ) d dp e dp d α -P m free deuteron R. Ent et al., NPA578(’94)93.

pd elastic scattering HST 15 @ Osaka, JAPAN Backward scattering One Nucleon Exchange (ONE) process p+d elastic scattering at E d =140 MeV PWIA 100 exchange mechanism p d d σ d p d Ω ∝ | ρ ( k ) | 2 d σ /d Ω (mb/sr) 10 k = 1 2 p pd relative momentum 1 between p and d 0 50 100 150 scattering angle in CM A. P. Kobushkin, J. Phys. G 12 (1986) 487 K. Sekiguchi et al., S. Ishikawa, private communication PRC 65,034003,2002

Probing rel. mom. of 2 N in 6 He and 6 Li HST 15 @ Osaka, JAPAN p +”2 N” at backward for 6 He and 6 Li 70 MeV n n p n p α α 6 He 6 Li p p n p p p p n n n n n 13 S 1 13 S 1 31 S 0 13 S 1 p + “d” -> p + d p + “nn” -> n + d

Probed relative momentum HST 15 @ Osaka, JAPAN 10 -5 10 -6 6 He 6He 6 Li 6Li 10 -7 ρ (p) (MeV/c) -3 10 -8 10 -9 10 -10 10 -11 10 -12 70 MeV 10 -13 0 100 200 300 400 500 600 p (MeV/c)

Kinematics of p + d scattering HST 15 @ Osaka, JAPAN p E p E d = 70 MeV/u p p θ p n θ d p E d n 100 40 θ d (CM) = 0° 80 30 60 120 θ p (deg) 60 n [deg] d [deg] 20 40 θ 120 60 θ 10 20 180 180 0 0 0 0 50 100 150 200 0 50 100 150 Ep (MeV) En [MeV] Ed [MeV]

Kinematics of p + ” 2 N” scattering HST 15 @ Osaka, JAPAN Assuming “Quasi-free” p+”d” scattering p p p n α p α n E 6Li = 70 MeV/u 150 ≤ θ p( CM) ≤ 180° 150 ≤ θ p( CM) ≤ 180°

Kinematics of ONE process HST 15 @ Osaka, JAPAN Backward p+”2N” scattering events in the inverse kinematics 6 Li: p+”pn” -> p+d θ p ≤ 20° p E p ~ 130 MeV p p n α spectator (~70 MeV/u) p α n θ d ≤ 30° E d ~ 10-30 MeV 6 He: p+”nn” -> n+d θ n ≤ 20° n E n ~ 130 MeV n p n α spectator (~70 MeV/u) p α n θ d ≤ 30° E d ~ 10-30 MeV

p+”2N”@backward exp. at RIPS HST 15 @ Osaka, JAPAN 5 o ≤ θ d ≤ 30 o m θ α ≤ 4 o TOF a Slow-d e p-target b α i L 6 d n a V e e H M 6 A 0 7 1) primary beam : 12 C ( 92 MeV/u) HE-n, p 5 o ≤ θ n, p ≤ 20 o RIPS 2) 6 Li, 6 He as secondary beams E = 70 MeV/u N ~ 10 4 /s : 6 LI 10 5 /s : 6 He 9 Be target 12 C (92 AMeV)

Detector Setup HST 15 @ Osaka, JAPAN 120 ≤ θ CM ≤ 180° TPW (Thick Plastic Wall) (10 + 10 cmt) AD (Alpha Detector) MWPC+plastics CV (charged particle Veto) α p (n) SHT (Solid Hydrogen Target) t = 3mm d 6 L i , 6 H e SDD (Strip Deuteron detector) Active Collimators “onion-shaped” plastics 10 mm φ , 75 % transmission 5 ≤ θ d ≤ 30° He bag

low-energy deuteron detector HST 15 @ Osaka, JAPAN Two-layer “onion-shaped” stip detectors (2nd layer for high-E particle veto) TOF - E slow-d Strip detectors: 2 arrays

α detectors HST 15 @ Osaka, JAPAN MWPC + Range conter ( Δ E-E) thee thick plastics (3rd for veto) θα ≤ 4° 6 Li fragmentation ( p+n+ α ） Layers α

High-E proton (neutron) detector HST 15 @ Osaka, JAPAN p : Δ E-E and TOF n : TOF (flight path = 75, 85 cm) Plastic wall: 2 thick layers B F HE-p, n CV neutron detection e ff . : 6 Li fragmentation ( p+n+ α ）

E α -E p(n) correlation HST 15 @ Osaka, JAPAN Δ E by TOF ONE

HST 15 @ Osaka, JAPAN ONE process α α Two-step process α α

p + 6 Li -> p + d + α events HST 15 @ Osaka, JAPAN consistent with ONE for 6 Li events Events for 6 He are smaller than expected. detailed analysis is not possible

Cross section ratio of ONE for 6 Li and 6 He HST 15 @ Osaka, JAPAN Y ONE � ONE = N target · N beam · ✏ det ( · ✏ n ) R = σ ONE ( 6 He ) = 0.045 ± 0.007± 0.010 σ ONE ( 6 Li ) stat. sys.

Cross section ratio of ONE for 6 Li and 6 He HST 15 @ Osaka, JAPAN σ ONE ( p + ' pn ' → pd ) = | < spin ⋅ isospin > | 2 ρ nn ( p ) 2 [ ] σ ONE ( p + ' nn ' → nd ) ˆ 1) O = V ( σ 1 ⋅ σ 2)( τ 1 ⋅ τ 2) | < spin ⋅ isospin > | 2 ρ pn ( p ) 2 [ ] 2) Radial wave functions is assumed to be identical = < nd ˆ 2 2 O | p ( nn ) > | 2 [ ] [ ] ρ nn ( p ) 2 = 0.4444 ρ nn ( p ) < pd ˆ 2 O | pd > | 2 [ ] [ ] ρ pn ( p ) ρ pn ( p ) p+’d’->p+d ! ! ! ! ! ! 1 1 3 1 Spin 1 → 2, 1 2 + 2 → 2 + ! ! ! 13 S 1 13 S 1 1 1 1 2 + 0 → 2 + 0 2 → J=1 J=1 Isospin T=0 T=0 ! ! ! p+’nn’->n+d ! 1 1 1 Spin 2 + 0 → 1 2 → 2 + ! ! ! ! ! 1 1 3 1 1 → 2, 2 + 0 2 + 2 → 31 S 0 13 S 1 Isospin J=0 J=1 T=1 T=0

Ratio of ρ 2N for 6 Li and 6 He HST 15 @ Osaka, JAPAN 10 -5 10 -6 6 He 6He 6 Li 6Li 10 -7 ρ (p) (MeV/c) -3 10 -8 10 -9 10 -10 10 -11 10 -12 10 -13 0 100 200 300 400 500 600 p (MeV/c)

Summary HST 15 @ Osaka, JAPAN 1. p+2N backward scattering events at Ep = 70 MeV p+ 6 Li -> p + d + α p+ 6 He -> n + d + α 2. ONE (One Nucleon Exchange) events observed in the reaction p+ 6 Li -> p + d + α 3. Ratio of the ONE process R = σ ONE ( 6 He ) = 0.045 ± 0.007± 0.010 σ ONE ( 6 Li ) stat. sys. 4. Theoretical calculations for p+ 6 Li ( 6 He) -> p(n)+d+ α reaction