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ESPRI project and nuclear density distributions
Juzo Zenihiro, RIKEN Nishina Center
for the ESPRI collaboration
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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!
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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
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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
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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!
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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
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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
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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
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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)
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40,48Ca
10
experimental data
p
n
p(r), n(r)
2019/1/23
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Proton elastic scattering of Unstable nucleiThe ESPRI project at RIKEN RIBF
11
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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
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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
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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
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[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).
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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
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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
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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
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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)
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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
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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
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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