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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