National Institute of Radiological Science (NIRS)

S. Suzuki, A. Kitagawa, M. Fukuda, S. Sato

Reaction cross sections of 14B and 8Heon proton target for the separation

of proton and neutron density distributions

M. Tanaka, Osaka Univ., Japan

Osaka Univ.M. Fukuda, K. Matsuta, M. Mihara,

Y. Morita, Y. Kamisho, J. Oono,R. Kanbe, S. Yamaoka, K. Watanabe Tokyo Univ. Sci.

D. Nisimura, S. Kinno, Y. Taguchi

Niigata Univ.M. Takechi, T. Ohtsubo, T. Izumikawa,

A. Honma, D. Murooka

Saitama Univ.T. Suzuki, T. Yamaguchi, J. Kouno,

S. Yamaki, S. Matsunaga

σpn ＞ σpp(nn)

Nucleon-nucleon total cross section σNN ( ＊ )

σR on proton target

p-n asymmetry

Proton target(Largest p-n asymmetry)

σNN has high sensitivity to the surface structure of nucleus

at Intermediate energy region.

＊ (http://pdg.lbl.gov/2010/hadronic-xsections/hadron.html)

Sensitive to the composition of surface

〜 3 timesProtonProton

NeutronProton1s1/2

1p3/2

1p1/2

2s1/2

1d5/2

NeutronProton1s1/2

1p3/2

1p1/2

2s1/2

1d5/2

Neutron rich nucleus 14B

14B

Magnetic moment [1]

Q moment [2]

1n removal reaction [3,4]

(14B→13B+n)

These data point out large contribution of 2s1/2 orbit.

[1] H. Okuno et al., Phys. Lett. B354, 41 (1995).[2] H. Izumi et al., Phys. Lett. B366, 51 (1996).[3] D. Bazin et al., Phys. Rev. C57, 2156 (1998).[4] V. Guimaraes et al., Phys. Rev. C61, 064609 (2000). [5] G. Audi and A. H. Wapstra, Nucl. Phys. A 565 (1993).

S1n= 0.970(21)MeV [5]

so small

Halo nucleus

Neutron rich nucleus 8He

[*] ] I. Tanihata, et al., Phys. Lett. B 160 (1985) 380-384. [**] A.A. Korsheninnikov, et al.,Nuclear Phys. A 617 (1997) 45-56.

Structure ?

σI at high energy [*](790MeV/nucleon)Elastic Scattering [**]

Large neutron radius

Nucleon density distribution of 8He

[**]

Purpose of this study

Measurement of the σR for 8He and 14B ① on nucleus targets

② on proton targets at intermediate energies

Obtaining the information of proton and neutron density distributions respectively

from σR on nucleus and proton targets.

Set upHIMAC in Chiba (Japan)

SB2 Course14B 　 130, 110, 85, 60MeV/nucleonPrimary beam 　 18O, 15N 　 160AMeVF0 Target Be 　 3.0, 0.55g/cm2

8He 　 125, 110, 80, 65MeV/nucleonPrimary beam 　 11B 　 160AMeVF0 Target Be 　 3.7, 9.2g/cm2

Production Target(F0)

BeamDegrader

Slit

D1

D2

F1PL

Slit

Go to F3 focal plane

ΔECsI(Tl)F1PL F3PL

TOFΔE

Reaction Target

VETOSi NaI(Tl)

PPAC

E

Bρ − TOF − ΔEΔE − E

At F3 Focal Plane

Upstream

Measurement of σR

Transmission methodReaction target: Be, C, Al, CH2

Proton=(CH2 − C)/2

Glauber calculation

Nucleon-Nucleon total cross section ( ＊ )

Density distributionof projectile nucleus.

(Model density)

Density distributionof target nucleus

＊ (http://pdg.lbl.gov/2010/hadronic-xsections/hadron.html)

Nucleon-nucleon total cross section σNN ( ＊ )

withModified Optical Limit approximation.

ρN of 14B, 8He Nucleus target

ρn, ρp of 14B, 8HeProton target

Obtain this information

Derivation of proton and neutron density distributions ρp, ρn

χ2 fitting with the width of ρp as a free parameter.

ρNucleon

ρn is deduced by subtraction.ρn=ρN− ρp

From σR on nucleus target

ρp and ρn of 8He ρp(R) and ρN(R)

σR(E) on proton target

σI @ LBL [*]

σR(E) on nucleus target

[*] I. Tanihata, et al., Phys. Lett. B 160 (1985) 380-384

ρp and ρn of 14B ρp(R) and ρN(R)

σR(E) on proton target Neutron tail

σR(E) on nucleus target

σI @ LBL [*]

[*] I. Tanihata, et al., Phys. Lett. B 206 (1988) 592-596

8He root mean square radii Rproton, Rneutron, Rmatter

[1] I. Tanihata et al., Phys. Lett. B 289, (1992) 261-266.[2] G. D. Alkhazov et al., Nucl. Phys. A. 712, (2002) 269-299[3] M. Puchalski et al., Hyperfine Interact (2010) 196:35-42[4] R. Baldik et al., Phys. of Atomic Nuclei (2010) Vol. 73, No. 1 74-80

14B root mean square radii Rproton, Rneutron, Rmatter

[2] A. Bhagwat et al., Eur. Phys. J. A. 8, 511-520 (2000)[3] H. Takemoto et al. Phys. Rev. C. 63. 034615

Preliminary

Summary• We measured σR for 8He and 14B on nucleus and proton targets at

the HIMAC heavy ion synchrotron facility.

• ρp and ρn were separated successfully through the χ2 fitting procedure with the modified Glauber calculation.

• Rp, Rn, Rmatter were derived from ρp, ρn and ρN.

• As a future prospect, we will finalize the data analysis. And we deduce more accurate ρp, ρn of 8He and 14B, then make a detailed discussion on their structures.

Sub

Energy dependence of σR

on Nucleus target

Nucleon density distribution ρN

Relation between Reaction cross section(σR)and density distribution

It is impossible to clarify a composition of the surface

by means of σR

on p-n symmetric target.

σR

High energy →The inner part of nucleusLow energy →The outer part of nucleus

p-n symmetric target

Measurement of σR

〜Transmission method〜

Incident partices

Reaction target

Detector１

Detector ２

Incident particles

Non-reacted particles

N1in N2

in

Reation target outDetector １ Detector ２

Non-reacted particles

N1out N2

out

Target thickness t

Correction for reactions in the detector.

ρN of 8He

Best FitCore: Z=2, N=4Tail: 2nucleons (1p3/2 orbit)

The core is not a “bare” 6He.(6He is a halo nucleus.)

S2n=2.14MeV

Best Fit is 1p3/2 2nucleon with B.E= 3MeV

Single particle density calculation

Binding Energy

Woods-SaxonCoulombCentrifugal Potential

Calculate SP density with adjustingthe potential depth to reproduce

Binding energy.

Best Fit Results14B 2s1/2 orbit with B.E=0.97MeV(consistent with S1n=0.97MeV)

8He 1p3/2 orbit with B.E=3MeV(inconsistent with S1n=3MeV)

TailNeutron or Proton

Orbit2s1/2 or 1d5/2

TailNeutron or Proton

Orbit2s1/2 or 1d5/2

14B Comparison between Exp. and Calc. value

σR for 8He on nucleus targets

[*] I. Tanihata, et al., Phys. Lett. B 160 (1985) 380-384.

σI @ LBL(Tanihata et al.)

Preliminary

σR for 8He on proton targets

σRH=(σI

CH2−σIC)/2

σR on proton target

Measurement of interaction cross section σI

on C, CH2 targets.

Determined by subtracting the σI

C from σICH2.

CH2 : Polyethylene

σI for 14B, 8He on C, CH2 targets.