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

HST 15 @ Osaka, JAPAN

Probing the relative momentum

• f two-nucleon system in 6He and 6Li

Toshimi Suda Research Center for Electron-Photon Science Tohoku University

• N. T. Khai (INST), A. Yoshida (RIKEN), I. Tanihata(RCNP)

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Two-nucleon system 6He and 6Li

31S0 13S1 +

6He 6Li

• W. Horiuchi and Y. Suzuki
• Phys. Rev. C76 (2007) 024311.

n n α p n α

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TAGX collaboration PRL 73(94)404, PRL 74(95)1034, PRC49(94)R597 100 200 300 400 500

Eγ (MeV)

1 2 3 50 100 150 γ+’np’ γ+’pp’

Total Cross Section (μb)

Photoabsorption by “np” and “pp”

γ+3He -> ppn TAGX spect.: large accept. 2) 3He(γ,pp)nspectator

psp psp nsp nsp

1) 3He(γ,np)pspectator

Pn ~ 0 MeV/c

p p n p p n p p n p p n p p n p p n

psp nsp

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Photon tagger –Eγ = 100 - 1000 MeV (ΔEγ=±5MeV) –Nγ = 1x106 /sec TAGX spectrometer – large acceptance ~ 3.2 st – neutron detection capability TAGX at INS, Tokyo ( ~1999) 1.2 GeV electron synchrotron at INS, UT TAGX

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12C(e,e’pp)/12C(e,e’p)

Two-nucleon knockout @ JLAB

virtual photons longitudinal : charge transverse : current

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Two-nucleon system 6He and 6Li

31S0 13S1 +13 D1

6He 6Li

• W. Horiuchi and Y. Suzuki
• Phys. Rev. C76 (2007) 024311.

n n α p n α

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“deuteron” in 6Li

free deuteron

d6σ dpedpd = Kσ ed (q)φ(pm)

2

• R. Ent et al.,

NPA578(’94)93. d Pm α

• Pm

e’ q 6Li(e,e’d)α @ NIKHEF under quasi-elastic e-d kinematics

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pd elastic scattering

1 10 100 50 100 150

dσ/dΩ (mb/sr) scattering angle in CM

p+d elastic scattering at E

d=140 MeV

p d d p

exchange mechanism

• K. Sekiguchi et al.,

PRC 65,034003,2002

One Nucleon Exchange (ONE) process Backward scattering

dσ dΩ ∝ |ρ(k)|2 k = 1 2ppd

• A. P. Kobushkin, J. Phys. G 12 (1986) 487

relative momentum between p and d

PWIA

• S. Ishikawa, private communication

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p+”2N” at backward for 6He and 6Li

p + “d” -> p + d p + “nn” -> n + d

70 MeV

6He 6Li

n n α p n α p

13S1 13S1

p n p p p n n

31S0 13S1

n p p n n

Probing rel. mom. of 2N in 6He and 6Li

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Probed relative momentum

10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5

100 200 300 400 500 600 6He 6Li

ρ(p) (MeV/c)-3 p (MeV/c)

6He 6Li

70 MeV

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Kinematics of p+d scattering

10 20 30 40 50 100 150

θ

d [deg]

Ed [MeV]

20 40 60 80 100 50 100 150 200

θ

n [deg]

En [MeV]

Ep (MeV) θp (deg)

θd(CM) = 0° 60 120 180 60 120 180

p p n p p n

θd θp Ep Ed

Ed = 70 MeV/u

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Kinematics of p+”2N” scattering

p n α p p p n α

Assuming “Quasi-free” p+”d” scattering

E6Li = 70 MeV/u

150 ≤ θp(CM) ≤ 180° 150 ≤ θp(CM) ≤ 180°

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Kinematics of ONE process

Backward p+”2N” scattering events in the inverse kinematics

p n α p p p n α

θp ≤ 20° Ep ~ 130 MeV 6Li: p+”pn” -> p+d spectator (~70 MeV/u) θd ≤ 30° Ed ~ 10-30 MeV

n α p p n α n n

θn ≤ 20° En ~ 130 MeV spectator (~70 MeV/u) θd ≤ 30° Ed ~ 10-30 MeV 6He: p+”nn” -> n+d

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p+”2N”@backward exp. at RIPS

TOF 12C (92 AMeV) 9Be target 6

H e a n d

6

L i b e a m 7 A M e V

Slow-d HE-n, p α

p-target

5o ≤ θd ≤ 30o 5o ≤ θn, p ≤ 20o θα ≤ 4o

RIPS

1) primary beam : 12C ( 92 MeV/u) 2)

6Li, 6He as secondary beams

E = 70 MeV/u N ~ 104 /s : 6LI 105 /s : 6He

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Detector Setup

SHT (Solid Hydrogen Target) t = 3mm SDD (Strip Deuteron detector) “onion-shaped” plastics 5 ≤ θd ≤ 30° CV (charged particle Veto) TPW (Thick Plastic Wall) (10 + 10 cmt) Active Collimators 10 mmφ, 75 % transmission AD (Alpha Detector) MWPC+plastics

6

L i ,

6

H e p (n) d α

He bag 120 ≤ θCM ≤ 180°

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low-energy deuteron detector

TOF - E Two-layer “onion-shaped” stip detectors (2nd layer for high-E particle veto)

slow-d

Strip detectors: 2 arrays

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α detectors

α

Layers

MWPC + Range conter (ΔE-E) thee thick plastics (3rd for veto) θα ≤ 4°

6Li fragmentation ( p+n+α）

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High-E proton (neutron) detector

B F HE-p, n

Plastic wall: 2 thick layers CV

p : ΔE-E and TOF n : TOF (flight path = 75, 85 cm)

neutron detection eff. : 6Li fragmentation ( p+n+α）

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Eα-Ep(n) correlation

ΔE by TOF

ONE

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α α α α

ONE process Two-step process

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

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Cross section ratio of ONE for 6Li and 6He

ONE = YONE Ntarget · Nbeam · ✏det(·✏n)

R = σONE(6He) σONE(6Li)

= 0.045 ± 0.007± 0.010 stat. sys.

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13S1 13S1

! 1 2 + ! 1 → ! 1 2, ! 3 2 → ! 1 2 + ! 1 ! 1 2 + 0 → ! 1 2 → ! 1 2 + 0

Spin Isospin

J=1 T=0 J=1 T=0

p+’d’->p+d

31S0 13S1

! 1 2 + 0 → ! 1 2 → ! 1 2 + ! 1 ! 1 2 + ! 1 → ! 1 2, ! 3 2 → ! 1 2 + 0

Spin Isospin

J=1 T=0 J=0 T=1

p+’nn’->n+d

σONE(p+'nn'→ nd) σONE(p+' pn'→ pd) = |< spin ⋅ isospin >|2 ρnn(p)

[ ]

2

|< spin ⋅ isospin >|2 ρpn(p)

[ ]

2

= < nd ˆ O | p(nn) >|2 < pd ˆ O | pd >|2 ρnn(p)

[ ]

2

ρpn(p)

[ ]

2 = 0.4444 ρnn(p)

[ ]

2

ρpn(p)

[ ]

2

ˆ O = V(σ1⋅σ2)(τ1⋅ τ2)

2) Radial wave functions is assumed to be identical 1)

Cross section ratio of ONE for 6Li and 6He

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10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5

100 200 300 400 500 600 6He 6Li

ρ(p) (MeV/c)-3 p (MeV/c)

6He 6Li

Ratio of ρ2N for 6Li and 6He

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Summary

1. p+2N backward scattering events at Ep = 70 MeV p+6Li -> p + d + α p+6He -> n + d + α

• 2. ONE (One Nucleon Exchange) events observed

in the reaction p+6Li -> p + d + α

R = σONE(6He) σONE(6Li)

• 4. Theoretical calculations for p+6Li (6He) -> p(n)+d+α reaction

= 0.045 ± 0.007± 0.010

stat. sys.

• 3. Ratio of the ONE process