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Fission barrier of uranium including Λ hyperon. F. Minato A , S. Chiba A , K. Hagino B. A. Japan Atomic Energy Agency B. Tohoku Univ. Nucl.Phys.A831, 150 (2009). Nucl . Phys. A856, 55 (2011) . Table of Contents. 1 . Λ impurity effects 2. Motivation

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slide1

Fission barrier of uranium including Λ hyperon

F. MinatoA, S. ChibaA, K. HaginoB

A. Japan Atomic Energy Agency

B. Tohoku Univ.

Nucl.Phys.A831,150 (2009)

Nucl. Phys. A856, 55 (2011)

slide2

Table of Contents

1.Λ impurity effects

2.Motivation

3.fission barrier & density distribution

4.Summary

slide3

Λ Impurity effect

  • Shrinkage
  • Level
  • cluster model
  • experiment

p

Rcore-(np)

density distribution

α

n

Rcore-(np)

T. Motoba et al., Prog. Theor. Phys. 70, (1983) 189.

E. Hiyama et al., Phys. Rev. C59, (1999) 2351.

H. Tamura et al., NPA754, 58(2005)

6Li

slide4

Λ Impurity effect

  • RPA with degree of freedom of Λ

Dipole motion of 18ΛΛO

peak at E= 12.8 MeV

Λ [1p(1s)-1] 80 %

n&p [1d5/2(1p3/2)-1] 20%

FM&KH, Physical Review C 85, 024316 (2012)

slide5

Motivation

  • What is impurity effect like in Λ hyper-actinide?
  • 1) production of Λ in nuclei
  • 2) decay of Λ in nuclei
  • K-+ 238U  239ΛU + π- + 178 MeV
  • Λ + N  N + N + 190 MeV

Λlife-time~10-10sec

  • High energy is released in production & decay of Λ

⇒ promote Fission & destruction of Fission Product

Fragment distribution

after Λ weak decay in 13853I

 change of “final” fission yield

slide6

Fission of Hyper-uranium

  • Experiment
  • Theory

T.A.Armstrong, J.P.Bocquet, G.Ericsson, et al.

Phys. Rev. C 47, 1957 (1993).

H.J. Krappe and V.V. Pashkevich, Phys. Rev. C 53,1025 (1996).

heavy fragment

light fragment

F.F. Karpeshin, C.G. Koutroulos, M.E. Grypeos,

Nucl. Phys. A595, 209 (1995).

H.J. Krappe and V.V. Pashkevich, Phys. Rev. C 47, 1970 (1993).

Λ-attachment probability

Fission barrier of Hypernuclei ??

slide7

r

Skyrme-Hartree-Fock

z

1. reflection asymmetry

2. quadrupole constraint

NNinteraction:

SkM* parameter set

Skyrme-type interaction for ΛN & ΛΛinteraction

9 parameters: t0Λ, x0Λ, t1Λ, t2Λ, t3Λ, λ0, λ1, λ2, λ3

◆ΛN interaction

M. Rayet, Nucl. Phys. A367 (1981) 381

◆ΛΛinteraction

Lanskoy PRC58, 3351(1998)

slide8

Skyrme-Hartree-Fock

ΛN:

1. B.E. of 5ΛHeand 209ΛPb

2. m*Λ/mΛ =0.8 in nuclear matter

3. energy difference between0+ and 1+ of4ΛHe

4. W0Λ=0

Y. Yamamoto, H. Bando, and J. Zofka, Prog. Theor. Phys. 80, (1988) 757.

YBZ4 set: t0Λ=-315.3, t1Λ=23.14, t2Λ=-23.14, t3Λ=2000, x0Λ=-0.109

ΛΛ :

Λ bond energy ΔBΛΛ=BΛΛ-2BΛ

ΔBΛΛ(13BΛΛ) = 4.8 or 0.6 MeV

λ2=λ3= 0

cf. FM & SC Nucl. Phys. A856, 55 (2011)

range of “equivalent”

single gaussian potential

Lanskoy PRC58, 3351(1998)

slide9

Result

Fission barrier height

single-Λ 239ΛU

double-Λ 240ΛΛU

0.61-0.63↑

0.27↑

0.53

0.91-1.03

x 2

slide10

Why Increase of Bf?

Λ Energy

Core Energy

238U

239ΛU

0.5

0.25

Energy of Λ particle increases due to transfer to fragment with smaller mass

Change of Core Energy

SMALL

slide11

Density distribution of 239ΛU

ground state

outer barrier

Q2=200 barn

Λ particle moves to heavier fragment

slide12

Density distribution of 240ΛΛU

FM & SC Nucl. Phys. A856, 55 (2011)

ground state

Q2=200 barn

CORE

Λ(SΛΛ1)

range μ=0.61fm

Λ(SΛΛ3)

range μ=1.61fm

slide13

SUMMARY

Calculate Fission Barrier height & density distribution of 239ΛU, 240ΛΛU

with Skyrme-Hartree-Fock approach

◆Fission barrier height

Barrier height is increased

InnerBf : 0.27 MeV↑

OuterBf : 0.50 MeV↑

InnerBf : 0.61~0.63 MeV↑

OuterBf : 0.91~1.03 MeV↑

◆Density distribution

Λ particle(s) move to heavier fragment

in adiabatic approximation