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Institute of Modern Physics, Chinese Academy of Sciences Direct Breakup Reaction of 8B，J.S.Wang S.L.Jin et al

DIRECT BREAKUP RECTIONS OF 8B AT FERMI ENERGY

Jian-Song Wang, Shi-Lun Jin et al.,

Institute of Modern Physics，

Chinese Academy of Sciences


Outline

•Scientific Background and Motivation

•Experiment of 8B Breakup Reaction

•Results and Discussion

•Summary and Outlook

2016/9/12 2International Nuclear Physics Conference 2016


Background

2016/9/12 3

Nuclear

Force

First principal

Theory

(QCD

Ab initio)

Elastic

scattering

Knockout

reaction

Coulomb

excitation

Direct

breakup

……

Decay

(γ,β,α,n,p…)

Phenomenologic

al Theory

The precise and accurate experimental data is the benchmarkInternational Nuclear Physics Conference 2016


New Phenomena

4

Exotic Structure

Exotic Decay Mode

New Collective Motion

Shell Evolution

HIRFL-RIBLL1CSR-RIBLL2

Phys.Rep.389,1-59

Rep.prog.Phys.71,046301

2016/9/12 International Nuclear Physics Conference 2016


Light Halo Nuclei

5

8B: Sp= 136.4 keV 10, T1/2=770 ms 3

found in 1950 at Berkley linear accelerator [Phys. Rev. 80 (1950) 519]



S17(0) factor

• Coulomb dissociation

T. Motobayashi et al., PRL73(1994)2680，B. Davids et al., PRL81(1998)2019,

N. Iwasa et al., PRL83(1999)2910, B. Davids et al., PRL86(2001)2750,

F. Schumann et al., PRL90(2003)232501.

• 7Be(d,n)8B

Weiping Liu et al., PRL77（1996）611.

• 7Be(p,γ)8B

F. Hammache et al., PRL86(2001)3985, R. Junghans et al., PRL88(2002)041101,

L.T. Baby et al., PRL90(2003)022501,.

2016/9/12 International Nuclear Physics Conference 2016 6


Neutrino Spectrum

• 8B β decay α spectrum, C. E. Ortiz et al., PRL85(2000)2909，

W.T.Winter et al., PRL91(2003)252501,

T. Roger et al., PRL108(2012)162502



Reaction Cross Section

• I. Tanihata et al., PLB206(1988) ，J. S. Al-Khalili and J. A. Tostevin, PRL76(1996)3903

the intrinsic few-body structure of these projectiles and the adiabatic nature of the projectile-target interaction are considered

• R.E. Warner et al., PRC52(1995)R1166

rms radius=2.72fm

• F. Negoita et al., PRC54(1996)1787

rms radius=2.55fm


pygmy proton halo/proton skin

Proton halo


Reaction Cross Section（cont’d）



Quadruple Moment

• T. Minamisono et al.,PRL69(1992)2058 :

• Q(8B) =68.3 ±2. 1 mb,


Cohen-Kurath shell model calculation

Partly from core

deformation,

PLB315,24


Longitudinal Momentum of 7Be


△r△p～h

1995 GSI 8B(1471AMeV) 81±6MeV/c ZPA,350,283

1999 GSI 8B(1440AMeV) 91±5MeV/c PLB,452,1

2002 GSI 8B(936AMeV) 95±5MeV/c PLB,529,317Be fragment Measured by Magnet Spectrometer

1996 GANIL 8B(40AMeV) 93±7MeV/c PRC,54,17877Be fragment Measured by Si telescope


MSU 8B(41AMeV) 81± 7MeV/c PRL77 (1996) 5020

Using 0 degree telescope

Theoretical Calculation: 160MeV/c

( transparent limit of the Serber model)

Conclusion:

1, Reaction mechanisms influence the 7Be momentum

distributions

2, they do not directly reflect the Valence proton momentum

wave function

Longitudinal Momentum of 7Be(cont’d)



Angular distribution of 7Be

• 2000 Notre Dame, PRL84, 1862 @27.75MeV


The comparison with theory illustrates the importance of the inclusion of the exotic

proton halo structure of 8B in accounting for the data.


Is Coulomb Rainbow Peak Enhanced for 8B?


Y.Y.Yang, J.S.Wang et al., PRC87(2013)044613

Sp=5606.85keV Sp=136.4keV


Is Coulomb Rainbow Peak Enhanced for 8B?


The different structure between proton and neutron halo

PRL105(2010)022701


Radioactive Ion Beam Line in Lanzhou (RIBLL1)


Primary Beam: 12C 80MeV/u

Production Target：Be 4171um

C1 Degrader: Al 1112um

Slits：C1 ±10mm, C2 ±6mm

Reaction Target：C 45mg/cm2

Secondary Beam:9C 41 MeV/u8B 36 MeV/u7Be 30MeV/u6Li 23 MeV/u


Experimental Setup


PPAC：50×50 1mm space Resolution，Charge distribution Readout

DSSD：thickness，1000um 40×40 strip width 1mm

CsI Array：8 ×8 Forward size 21×21mm2 Length 50mm Readout by PMT, FWHM ～7% for α @ 5.8MeV



Selecting the reaction events

Selecting the event

with two fragments

(7Be + p) which

could be from the

following 2 reaction

channels

8B-7Be+p

9C-7Be+p+p


Selecting the reaction events


9C

8B

7Be


Identifying the reaction mechanism


Present work [email protected]/u

PRC91,054617MSU [email protected] D.Bazin et al., PRL 102,232501

Width by fitting:

Diff: 92±7MeV/c

Strip:124±17MeV/c


Theoretical Calculations-Stripping


Calculation done by Prof. J. A. Tostevin

The stripping momentum distributions were

calculated using the eikonal approximation formalism

(PRC70, 034609) and the eikonal phase shifts and S-

matrices of the following potentials (denoted KDe)

The complex 7Be-target optical potential was

calculated using the double-folding method of

PRC74,064604, assuming Gaussian 7Be and 12C densities

of rms radii 2.31and 2.32 fm. The proton-target potential

was calculated from the Koning and Delaroche global

parameterization (NPA713, 231)

In addition, due to the relatively low beam energy,

calculations were repeated using the improved

description of the proton-target S-matrix (denoted KDp).

The 8B(g.s.) to 7Be final state radial overlapsand spectroscopic factors were taken fromPRL102,232501


Theoretical Calculations-Diffraction


The diffraction mechanism differential cross sections were calculated using a CDCC

(Coupled Discretized Continuum Channels) breakup model space as PRL102,232501,

and the resulting momentum distributions constructed by integration over the solid angles

covered by the current detection system, as is discussed in Phys. Rev. C 66, 024607.

Calculation done by Prof. J. A. Tostevin


A summary of width calculated in different model


The experimental data show the width of longitudinal momentum distribution for

stripping breakup is obviously wider than diffraction breakup.

85±4 8B@41AMeV PRL77(1996)5020


Summary and Outlook

• The longitudinal momentum distributions of 7Be have beenmeasured for the breakup of 8B at 36 MeV/u at RIBLL1.

• Longitudinal momentum distributions for both stripping anddiffraction mechanisms have been obtained by a coincidencetechnique.

• The present experimental data show a marginal difference of thelongitudinal momentum distributions between stripping anddiffraction.

• Further studies of 8B are needed both experimentally andtheoretically.



Collaborators

IMP: Y. Y. Yang(杨彦云)，P. Ma(马朋)，M. R. Huang(黄美容)，J. B. Ma(马军兵)，F.Fu(付芬)，Q. Wang(王琦)，M. Wang(王猛)，Z. Y. Sun (孙志宇)，Z.G.Hu(胡正国)，R. F.Chen(陈若富)，X. Y. Zhang(张雪荧)，X. H. Yuan(袁小华)，X. L. Tu (涂小林)，Z. G. Xu(徐治国)，K. Yue(岳珂)，J. D. Chen(陈金达)，B. Tang(唐彬)，Y. D. Zang(臧永东)，D. P.Wu(武大鹏)，Q. Hu(胡强)，Z. Bai(白真)，Y. J. Zhou(周远杰)，W. H. Ma(马维虎)，J.Chen(陈杰)，Y. H. Zhang(张玉虎)，H. S. Xu(徐瑚珊) and G. Q. Xiao(肖国青)

Nanjing Univ.：Z. Z. Ren(任中洲)，C. Xu(许昌)，D. D. Ni(倪冬冬)

CIAE：C. J. Lin(林承键)，X. X. Xu(徐新星)

Surrey Univ.: J. A. Tostevin

Grateful to George Bertsch, Carlos Bertulani, and Henning Esbensen for informative discussions




Thanks for your attention !

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