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

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

Breakup Reaction of 8B

Jiansong Wang, Shilun Jin

Institute of Modern Physics，Chinese Academy of Sciences

The 9th Japan-China Joint Nuclear Physics Symposium ， OSAKA

05/03/23 1


Outline

Scientific Background and Motivation Experiment of 8B Breakup Reaction Results and Discussion Summary and Outlook

05/03/23 The 9th Japan-China Joint Nuclear Physics Symposium ， OSAKA

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Background


Nuclear Force

First principal Theory(QCD

Ab initio)

Elastic scattering

Knockout reaction

Coulomb excitation

Direct breakup

……

Decay (γ,β,α,n,p…)

Phenomenological Theory

The precise and accurate experimental data is the benchmark

3


New Phenomena


Exotic Structure

Exotic Decay Mode

New Collective Motion

Shell Evolution

HIRFL-RIBLL1

CSR-RIBLL2Phys.Rep.389,1-59

Rep.prog.Phys.71,046301

4


Light Halo Nuclei

8B: Sp= 136.4 keV 10, T1/2=770 ms 3 found in 1950 at Berkley linear accelerator [Phys. Rev. 80 (1950) 519]


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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,.


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


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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

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Reaction Cross Section （ cont’d）


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Quadruple Moment

T. Minamisono et al.,PRL69(1992)2058 : Q(8B) =68.3 ±2. 1 mb,


Cohen-Kurath shell model calculation

10

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

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MSU 8B(41AMeV) 81± 7MeV/c PRL77 (1996) 5020Using 0 degree telescope

Theoretical Calculation: 160MeV/c ( transparent limit of the Serber model)

Conclusion: 1, Reaction mechanisms influence the 7Be momentum

distributions2, they do not directly reflect the Valence proton momentum

wave function

Longitudinal Momentum of 7Be(cont’d)


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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.

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The Coulomb Rainbow Peak is Enhanced for 8B?


The different structure between proton and neutron halo

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

PRL105(2010)022701

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Primary Beam: 12C 80MeV/uProduction Target ： Be 4171umC1 Degrader: Al 1112umSlits ： C1 ±10mm, C2 ±6mmReaction Target ： C 45mg/cm2

Secondary Beam: 9C 41 MeV/u 8B 36 MeV/u 7Be 30MeV/u 6Li 23 MeV/u

Radioactive Ion Beam Line in Lanzhou (RIBLL1)

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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

16


Data analysis


Energy Calibration1 DSSD

2 CsI

△ E(Calibrated)-E (Channel)

2

2 20 1 3 2

2

, , ln E a AZL E A Z a a E a AZa AZ

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Energy Calibration for CsI


particle Energy Energy Energy Energy Energy

p 14.81 29.89 50.426Li 89.31 104.8

2126.69 193.54 151.4

7Be 135.92 159.41

192.51 293.51 229.89

8B 185.36 271.71

262.31 399.36 316.06

9C 236.72 277.46

334.79 509.17 399.41

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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

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Protons in the CsI Crystals


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Selecting the reaction events(cont’d)


9C

8B

7Be

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Identifying the reaction mechanism


Present work [email protected]/u PRC91,054617

MSU [email protected] PRL 102,232501

Width by fitting:Diff: 92±7MeV/cStrip:124±17MeV/c

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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 overlaps and spectroscopic factors were taken from PRL102,232501

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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. Tostevin24


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

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Summary and Outlook

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

Longitudinal momentum distributions for both stripping and diffraction mechanisms have been obtained by a coincidence technique for the first time.

The present experimental data show a marginal difference of the longitudinal momentum distributions between stripping and diffraction.

Further studies of 8B are needed both experimentally and theoretically.


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


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Thanks for your attention !

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

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