ESPRI project and nuclear density distributions

Juzo Zenihiro, RIKEN Nishina Center

for the ESPRI collaboration

Baryon density (fm-3)

EOS

(Me

V)

NM : d = 1

SM : d = 0

Slope L

J

Nuclear matter EOS

Infinite Nuclear matter EOS

Symmetry energy

)(2

)()( 32sym

sat OK

L +++= SS

)()()0,(),( 42 ddd O++= SEE

Radius

Density

Proton: p(r)

Neutron: n(r)

Neutron Skin

Finite nucleus

Density:

Asymmetry: d

0

balanceNeutron

Skin thickness

2

If d = 1, S() = EOSNM - EOSSM

?

= J

?

Known!

Symmetry energy experiments for 208Pb, 48Ca(, 132Sn)

Our work : n & Drnpproton elastic scattering204-208Pb, 116-124Sn, 40-48Ca (RCNP)132Sn, 66,70Ni (RIBF, GSI)→ The ESPRI project

PREX-I&II, CREX : rn & Drnpparity-violating electron elastic scattering208Pb(done), 48Ca(planned) (J-Lab)

Dipole polarizability (DP)

: aD (& Drnp)

(p, p’) at 0 degree 208Pb, 120Sn, 90Zr, 48Ca (RCNP)

3

Symmetry energy at 0 208Pb(, 132Sn) : strong correlation by EDFs

48Ca : • Correlation is not so strong.• ab initio methods available

X. Roca-Maza et al., PPNP101, 96 (2018)

G. Hagen et al., Nature Physics 12,186 (2015)

208Pb

208Pb

208Pb

48Ca

132Sn

52,54Cad = 208Pb : 0.21

132Sn : 0.2448Ca : 0.1654Ca : 0.26

ch(r), p(r), n(r)

➢Stable nuclei✓Nuclear charge distribution ch(r)

✓ EM probe (very simple)

✓ For example, rch = 208Pb : 5.5010(9) fm (0.02% accuracy)

✓Proton density distribution p(r) : derived from ch(r)

Neutron density distribution n(r) Hadronic probe (very complicated) (or electroweak probe like PREX at

J-lab)

Suffering from large uncertainties of incomplete knowledge of NNinteraction inside nucleus

→Our work at RCNP

----------------

➢Unstable nucleiLittle information about ch(r), p(r), n(r)!

→ SCRIT for ch(r) : e-RI collision → T. Suda, K. Tsukada

→ESPRI for p(r), n(r) : Our work at RIBF

2015/11/19 HST15 4

electron scattering

proton scattering

How to determine p(r) & n(r) & Drnp

5

+Ze

N+Z

e- e-

p p

e- elastic scattering

p elastic scattering

@ 300 MeV

g

meson )()()( rrqF npnp ++

; Nuclear charge

; Nuclear matter

MottddA

chdd qF

=

2

)(

Based on RIA + an effective NN interaction at around 300 MeV(t-optical model : no structure model assumption)

pnnp rrr −=D

:established in 1980sH.De Vries, et al. ADNDT36,495(1987)

: our work

n(r)

ch(r)

inp

ut

c2 fitting of n(r)

D. P. Murdock and C. J. Horowitz, PRC35, 1442. H. Sakaguchi et al., PRC57, 1749.

Still in puzzle!

p(r) Radius equation:

.4

3

so

2

2

2

nch

2

pch

2

pp

2

Ach rM

rZ

Nrrr ++++=

nuclear charge

point-proton

proton charge

neutron charge

Darwin-Foldycorrection

Spin-orbit correction

0.033 fm2~ -0.116 fm2

(CODATA)0.768(CODATA) vs0.706(mu-X) fm2

.)(

)(22

=

r

r

dr

drrr

ρ

ρ

Correction terms

SO effect on 48Ca : -0.135 = +0.028 + -0.163 fm2 by RMF (FSUGold)

48Ca : sqrt() = sqrt(3.477^2 – 0.77 + (28/20)*0.116 + 0.135) = 3.41 fm

w/o spin-orbit correction = 3.39 fm

However, SO term depends on the single-particle state of the nucleus

? fm2

C.J.Horowitz and J. Piekarewicz, PRC 86, 045503 (2012)

~0.02 fm

~0.01fm > ~0.02fm

Rch and Rp of Ca isotopes

3.35

3.4

3.45

3.5

3.55

3.6

40 42 44 46 48 50 52

Radiu

s (

fm)

Mass no.

r ch

r p

r p w/ SO

r ch of 40

Ca

r p of 40

Ca

Rch

Rp w/o SO

Rp w/ SO

Experiments @RCNP, Osaka Univ.

polarized

proton beam

scattering

chamber

VDCs & plastic

scintillators

GR LAS ⚫ beam : proton Energy : 295 MeVpolarization : 70~80%intensity : 1 ~ 400 nA

⚫ Energy resolution : ~100keV (FWHM)⚫ target : 204,206,208Pb, 116-122Sn, 90-94Zr, 58Ni, 40-48Ca

pre-ESPRI : Extraction of density distributions in nucleiPolarized proton elastic scattering at 300MeV (RCNP, Osaka University)

⇒We have succeeded in extracting neutron density distributions of Sn, Pb isotopes systematically.

S.Terashima et al.,

Phys. Rev. C 77,

024317 (2008)

J.Zenihiro et al.,

Phys. Rev. C 82,

044611 (2010)

Sn

Pb

d/d, Ay n(r) Drnp

RIA

+

Medium

Effect

by c2 fitting

Drn/rn < 0.5%

9H. Sakaguchi and J. Zenihiro, PPNP 97, 1 (2017)

40,48Ca

10

experimental data

p

n

p(r), n(r)

2019/1/23

Proton elastic scattering of Unstable nucleiThe ESPRI project at RIKEN RIBF

11

ESPRI project

【nuclear chart】

: doubly magic nuclei process from 208Pb

208Pb@RCNP

132Sn@RIBF

12

66,70Ni@GSI

9,10,11,16C@HIMAC, RIBF

Extension of proton elastic scattering method to unstable nuclei

ESPRI detector setup

ESPRI devices

13

θlab = 66° - 80°, Ep=20-120 MeV, ΔΩ〜10 msr/deg.q=1-2.2 fm-1, ΔEx = 400-500 keV

Recoil drift chamber 436x436 mm2 (x-y-x’-y’-x’-y)

Plastic scintillator 440x440 mm2 x 2 mmt

NaI(Tl) calorimeter 431.8x45.72 mm2 x 50.8 mmt

Recoil Proton Spectrometer (RPS)

RIBF

2019/1/23 14

ESPRI setup

SRC

BigRIPS

ESPRI detectors: p-elastic scattering from RI beams

15

1 mmt

φ30 mm

2019/1/23

beam detectors for HI RI beams

recoil particle spectrometer (RPS)

solid hydrogen target (SHT)

RIs

1

2

3

gas-Xe scintillator large thin SHT good DE resolution (400keV())

beamXe(99.999%)＋PMT

good radiation hardness and E and T resolutions

[deg]

Pro

ton

en

ergy

by

NaI

[ch

]P

roto

n t

of

[ch

]

908580757065

Clear elastic event

Recoil proton angle

1mmt solid hydrogen target

ESPRI detector setup

132Sn：flag ship nucleus

• 132Sn (p, p) at 200 MeV/u in FY2016 !!

2019/1/23 16→ Next : 132Sn(p,p) at 300 MeV/u (FY2019).

17

+Ze

N+Z

e- e-

p p

Electron scattering

Proton scattering

@ 300 MeV

g

meson

)()()(

)()(

rqFqF

rqF

pp

p

ch

A

ch

A

ch

)()( rqF npnp ++

)(),( rr np

; Nuclear charge

; Nuclear matter

MottddA

chdd qF

=

2

)(

pnnp rrr −=D

: well established in 1980s

: our work

For stable nuclei

Simultaneous extraction from two-energy p-elastic data

18

N+Z

p p

Proton scattering

@200MeV

Proton scattering

@ 300 MeV

meson

)(),( rr np pnnp rrr −=D

For unstable nuclei

N+Z

p p

meson )()()()(200200 rrqFtqFt npnpnppp ++

)()()()( 300300 rrqFtqFt npnpnppp ++

Simultaneous extraction from two-energy p-elastic data

Why two energies? 200 & 300 MeV/u

19

p-A @300 → ESPRI → n(r) + p(r)

e-A → SCRIT → ch(r)→ n(r), p(r)

Idea: energy dependences of pp & pn interaction

p-A @300 → ESPRI → an(r) + bp(r)

p-A @200→ ESPRI → cn(r) + dp(r)

101

102

103

10 100 1000

pppnnp

Elab. [MeV]

Cro

ss s

ecti

on

[m

b]

200 300 400

→ Demonstration of the new method with Zr data

Simultaneous extraction from two-energy p-elastic data

20

Fitting results for 90Zr @ 200 & 300 MeV

Simultaneous search of Neutron & Proton

From 300 & 200 MeV data

rn rp Drnp

4.300(17) 4.210(20) 0.090(26)

Extracted densities of 90Zr

(all in fm)(4.20 from e-90Zr)

Future : new ESPRI device w/ storage Ring

• Towards Rare-RIs (54Ca, 78Ni, 100Sn, etc.)• typically, more than 105 cps RI beam is necessary.

• upgrade of the accelerator → 10 times

1. post-ESPRI device : high precision• larger solid angle

2. Recycling w/ storage Ring: high efficiency• →Wakasugi-san

21

2nd SSD1st SSD

SHT

post-ESPRI project

• keep RPS performance• DEx < 500keV

• large solid angle• become compact (1/5 of RPS)

• 8 times solid angle

• design• SHT→10cm→SSD→10cm→SSD+Calorimeters

• elastic scattering

• knock-out reaction

2019/1/23 22

Si tracker + GAGG ballby RIKEN+TUD (planned)

~ 50cm

RI beam recycling w/ storage ring

• How to realize reaction measurements w/ Rare RIs (1 cps)

•→ beam recycling technique!!

2019/1/23 23

RI beam more than 99% RIs areabandoned.

~1mg/cm2

reactionparticle

if 1MHz recycling is realized,gain is 106!!

→ effective intensity : 1 Mcpsw/ 1cps production rate RIs

→ ring can work mass separator : pure RI beam

post ESPRI device

coolerreaccelearation