Nuclear structure and dynamics at the

limits

Reiner Krückenfor the NuSTAR collaboration

Physik Department E12Technische Universität München

&Maier-Leibnitz-Laboratory

for Nuclear and Particle Physics

RISING to the Challenges

Bill Gelletlyfor the Surrey nuclear physics group

Centre for Nuclear and Radiation PhysicsPhysics Department University of Surrey

UWS -08/05/2008

Nuclear structure and dynamics at the

limits

Introduction

The NuSTAR facility at the Super-FRS

Modification of shell structure

Soft modes, nuclear EOS and neutron skins

Conclusions

Long Standing Questions of Nuclear Structure Physics

• What are the limits for existence of nuclei?– Where are the proton and neutron drip lines situated? – Where does the nuclear chart end?

• How does the nuclear force depend on varying proton-to-neutron ratios?– What is the isospin dependence of the spin-orbit force?– How does shell structure change far away from

stability?

• How to explain collective phenomena from individual motion?– What are the phases, relevant degrees of freedom, and

symmetries of the nuclear many-body system?

• How are complex nuclei built from their basic constituents?– What is the effective nucleon-nucleon interaction?– How does QCD constrain its parameters?

• Which are the nuclei relevant for astrophysical processes and what are their properties?– What is the origin of the heavy elements?

Mean Field Models• DFT• RMF

Shell Modelw/ configuration interaction

Ab initio• GFMC• NCSM• CC

Towards a predictive (and unified) description of nuclei

Realistic interactions• AV18, CD Bonn + 3N• EFT

Effective interactions• Vlow-k, VUCOM, G-matrix (+3N)

Superheavy elementsNuclear Structure at the extremes

New shell gaps through residual interaction

Neutron skins

Shell quenching bydiffuse surface

New shell gaps through residual interaction

harmonic oscillator+ spin-orbit+centrifugal

diffuse surfaceneutron rich+ spin-orbit

Halos

11Li

9Li

2n

Soft collective modes

FAIR: Facility for Antiproton and Ion Research

Primary Beams

• 1012/s; 1.5-2 GeV/u; 238U28+

• Factor 100-1000 over present in intensity

Secondary Beams

• Broad range of radioactive beams

up to 1.5 - 2 GeV/u; • up to factor 10 000 in intensity over present

• Antiprotons

Storage and Cooler Rings

•Radioactive beams

•e- - A and Antiproton-A collider

100 m

UNILAC SIS 18

SIS 100/300

HESR SuperFRS

NESR

CRRESR

GSI todayGSI today

Future FacilityFuture Facility

ESR

SUPERconducting FRagment Separator

Primary Beams

• 1012/s; 1.5-2 GeV/u; 238U28+

• Factor 100-1000

Secondary Beams

• up to factor 10 000

3 x 9.75° SC Dipole Unit

SuperferricMultiplet

Experiments with slowed and stopped beams

Laser spectroscopy (LASPEC)

Decay spectroscopy(DESPEC)

Energy buncher /spectrometer

In-flight spectroscopy (HISPEC)

Precision mass measurements (MATS)

Gas stopping cell

High Energy BranchReactions with Relativistic Radioactive Beams

(R3B)

Reactions in complete kinematics

Ring Branch

Modification of shell structure

- Reduction of Spin-orbit splitting ?

- Role of the tensor interaction ?

Shell modification through softer potential ?

T.R. Werner, J. Dobaczewski, W. Nazarewicz, Z. Phys. A358 (1997) 169

Possible signatures: reduction of spin-orbit splitting in neutron-rich nuclei new shell gaps (e.g. N=70 in 110Zr) increased neutron skin

-3

-1

1

3

5

7

9

11

13

15

96 106 116 126 136 146 156 166 176 186 196

Neutron number N

Sn

[MeV

]

Pb Isotope

Neutron number N

How to find a shell gap: Sn values

Shellclosure

Pairing

Neutron dripline

Pb Isotopes

Neutron separation energies

Q-values from -decay (DESPEC)

Shortest half-lives, production rates << 1 min-1

Laser spectroscopy and precision masses (MATS & LASPEC)

highest precision masses

2-n

eu

tron

sep

ara

tion

en

erg

y

Rb Spins, Moments isotope shifts

D. Lunney et al. Rev. Mod. Phys. 75 (2003) 1021

40 45 50 55 60 65

10

15

20

25

N (Z = 37)

S 2n (

MeV

)

Isoto

pe sh

ifts

0.0

0.5

1.0

1.5

<r 2> (fm

2)

time

4 particles with different m/q

Schottky Mass Spectrometry

Y. Litvinov

Schottky Mass Spectrometry

Sin(1)

Sin(2)

Sin(3)

Sin(4)

1234time

Fast Fourier Transform

Y. Litvinov

Schottky Frequency in Storage Ring (ILIMA)

ILIMA mass measurements

mass surveys

N=82

Probing shell closures: Decay Spectroscopy (DESPEC)

A. Jungclaus et al., PRL 99, 132501 (2007)A. Jungclaus et al., PRL 99, 132501 (2007)

no shell quenching information on excited

states needed !!

-decay Q-value: 130Cd less bound Quenching of N=82 shell

I. Dillmann, PRL91 (2003) 162503

1h11/2 neutrons

1h11/2 protons

1g7/2 protons

11/2-

7/2+

Reduced spin-orbit or tensor force?

T. Otsuka et al., PRL 97 (2006) 162501

T. Otsuka et al., PRL 95 (2005) 232502

j<

j>

j’>

j’<

protons

neutrons

RIBbeams

J.P. Schiffer et al., PRL 92 (2004)

Z=51 Sb isotopes

Single-particle structure from direct reactions

Cross sections:- exclusive for excited states

via gamma-decay ( AGATA) spectroscopic factors

Knock-out reaction - Peripheral collision- Possible with few particles/s

P. Maierbeck et al., GSI-FRS + MINIBALL

L=3L=1

P||

(HISPEC, R3B)

Momentum distribution:- L of knocked-out particle

GXPF1A

56Ti

f 5/2

p 1/2p 3/2

xx

L=1

A. Gade

Soft modes, nuclear EOS and neutron skins

Giant resonances

Radioactive beams allow study of isospin dependence

probe bulk properties of nuclei in-medium modification of NN

interaction symmetry energy compressibility

New soft modes

Dipole Excitations of Neutron-Rich Nuclei- Symmetry Energy, Neutron Skin, and Neutron Stars -

neutron skin core vibration

LAND

collaboration A. Klimkiewicz, PRL subm. P. Adrich, PRL 95 (2005)

124Sn

132Sn

Photoabsorption

Coulomb excitation

130Sn

P. Ring et al.

δrRn-Rp

excitation of the neutron skin

Properties of Neutron Stars

Neutron-skin thickness

Dipole Excitations of Neutron-Rich Nuclei- Symmetry Energy, Neutron Skin, and Neutron Stars -

Neutron skins

M. Bender, et al.RMP 75 (2003)

Alternative access to asymmetry parameter

• established methods for charge radii • neutron radii difficult to measure

Electron Ion Collider (ELISe)

to FLAIR

fromRESR

• charge densities from (e,e) scattering• collective modes via (e,e’) scattering • single-particle structure from (e,e’N) reactions

The EXL experiment

Electroncooler

RIB‘s from the Super-FRS

Inelastic scattering Isoscalar Giant Monopole resonance

isospin dependence of incompressibilityElastic proton scattering Matter distribution

Neutron skins from Antiprotons

A A-1

p

H. Lenske, P. KienlePLB647 (2007) 82

P. Kienle, NIM B 214 (2004) 193

Antiproton Ion Collider (AIC)

M. Wada, Y.Yamazaki

• annihilation cross-section at high energies proportional to mean square radius

• count surviving A-1 nuclei

Proton and neutron radii in the same experiment

EXOpbar

• antprotons on atomic orbits

• annihilation on tail of density distribution

Halo or Skin ?

Neutron skins Deeply bound pionic states

In medium modificationof pion decay constant

Pion-Nucleus Optical potential related to neutron skin

In medium modification of quark condensate

205Pb

Kolomeitsev et al. PRL90 (2003) 092501

The aims of NUSTAR @ FAIR

• Nuclear Structure Physics:– Isospin dependence of effective nuclear interaction

– Modification of shell structure far off stability

– New effects near the driplines (halos, skins, soft modes, …)

– Relevant symmetries, structural evolution, role of phase transitions

• Nuclear Astrophysics Studies:– Understand the origin of the heavy elements K.H. Langanke

• Nuclear Reaction studies– Investigate reaction dynamics for RIB production, spallation, ADS– Dynamics in systems with weakly bound nucleons (halos, correlations,

continuum)

Towards a unified description of nuclear structure and dynamics