Transcript Document

Les jeunots en physique nucléaire de basse énergie
Some remarks on current theoretical activities:
France vs the rest of the world
Thomas Duguet (SPhN)
Theory of Nuclei
• Goals
•Comprehensive and unified description of all nuclei
•Low-energy reaction and structure properties
•From basic interactions between protons and neutrons
•Understand different states of nuclear matter in astrophysics environments
• Difficulties
•Self-bound, two-component quantum many-fermions system
•Complicated interaction from low-energy regime of QCD
•Tensor and spin-orbit components
•Unnaturally large scattering lengths (2-body virtual and bound states)
•NNN unavoidable
•Repulsive core and strong tensor at short distances?
•Properties of finite and bulk nucleonic matter
•Deuteron to SHE nuclei to neutron stars and nuclear (strange) matter
•Need to extrapolate to unknown regions
• Some trivial facts
•No “one size fits all” theory for nuclei
•All theoretical approaches need to be linked
•Theoretical activity strongly linked to experiment…
Selection of advances in the recent years
• Ab-initio (NCSM&GFMC) methods allowed for interaction tests
•Consistent proof of the role of NNN interaction in light nuclei
• Nuclear interactions: c-EFT provides missing links
•Explains hierarchy NN > NNN > NNNN + 2N-3N, N, ,… consistency
•Chiral symmetry breaking of QCD encoded => constrains N interaction
• Renormalization Group provides gentle NN (“Vlowk”) + NNN
•Use relevant degrees of freedom/energy scales for low energy nuclear physics
•Many-body problem becomes (mostly) perturbative (HUGE practical implications)
• Quantitative microscopic nuclear structure
•CI calculations into the fp shell ; sSD608 = 140 keV!
•LACM: shape coexistence and fission
•Transfermiums as a window on SHE nuclei
•First EDF mass tables (SR) and systematics of correlations (MR) in heavy nuclei
•Multipole strength S(El)/b-decay from fully self-consistent (deformed!) QRPA
•Shell evolution towards drip-lines ; role of tensor force raised
• Integration of structure and reaction for light nuclei
•Multistep reactions calculations using coupled discretized continuum channels
•GSM, CSM and SMEC to incorporate (many-body) continuum in CI
•Use of nuclear inputs into reaction models ; e.g. JLM optical model
• Astrophysics
•Use of consistent nuclear inputs for NS, r-process calculations, supernovae
Selection of challenges for the coming years
• Bridge between hadrons and nuclei
•e.g., lattice QCD with smaller pion masses; match cPT with lattice results
• NNN interaction
•Test NNN (NNNN) from c-EFT at N3LO through NCSM calculations of light nuclei
•Role in medium mass nuclei through CC and spectroscopy through CI and EDF
• Interplay of phenomenological and non-empirical EDF
•Constructed from low-momentum interactions/c-EFT and benchmarked against CC
•Predictability (theoretical error bars) and accuracy (new (re)fitting protocols)
•Strong focus on spectroscopy
•Coherent formulation of SR and MR EDF methods from first principle
• Superfluidity
•Nature of pairing correlations in finite nuclei
•Pairing in asymmetric systems ; e.g. neutron-proton pairing, polarized cold atoms
• Shell position/evolution in stable/neutron rich nuclei
•Role of tensor, NNN, spin-orbit (matter diffusivity), other?
• LACM: coexistence, fusion and fission
•Quantitative methods including both diabatic and adiabatic effects
• Integration of structure and reaction
•Advance GSM/CCSD (interaction) and apply to complex open light nuclei
•Extend TDHF(B) (excitations and reactions) ; e.g. neutron skin for heavy ion fusion
•Microscopic optical potentials and level densities (inputs from EDF/CI)
• Astrophysics
•Quantal calc. of NS (inner) crust: compos., clusters shape, pairing prop.,
transport…
Some useful experimental data (not exhaustive!!)
• Fission
•Barriers and life-time
•Mass and kinetic energy distributions of fragments
•Evaporated neutrons and g’s
• Systematic data into the “next major shell” (few mass units)
•Mass differences ; e.g. shell evolution and pairing
•First 2+, B(E2) and Qs; e.g. deformation and shell evolution
•Single-particle energies and spectroscopic factors ; i.e. shell evolution
•Pair transfer ; e.g. quantitative information on pairing?
•Data at large deformations (low and high J)
•Beta-decay and charge-exchange reactions ; e.g. pin down theories for weak rates
• Transfermiums
•Rotational bands ; i.e. pairing and shell positioning
•K-isomers ; i.e. pairing and shell positioning
• Neutron radii
•Parity violation from e- scattering (208Pb) at JLAB ; i.e. Rn-Rp <=> asym(rsat)/P(rsat/2)
•Same in more (neutron-rich) nuclei might be of interest
• Neutron star observations
•Thermal X-ray emission for cooling
•Example 2
Young « french » theorists’ activities by methods/subjects
STRUCTURE
REACTION
Heavy / Light Heavy / Light
ASTRO
NS / n
Symmetry
Model stand.
TOTAL
(TD)EDF
11,75 / -
2/-
1,5 / -
0,25
15,5
CI
0,5 / 2
-/-
-/1
-
3,5
GSM
- / 0,5
- / 0,5
-/-
-
1
Opt. Pot.
-/-
1/-
-/-
-
1
CChannel
-/-
-/1
-/-
-
1
GFMC
-/-
-/-
-/-
-
-
NCSM
-/-
-/-
-/-
-
-
CCluster
-/-
-/-
-/-
-
-
SCGF
-/-
-/-
-/-
-
-
NN/NNN
-/-
-/-
-/-
-
-
TOTAL
12,25 / 3
3 / 1,5
1,5 / 0,5
0,25
22
Are we well positioned for the next 10/15 years?
• Community extremely biased towards EDF methods
•Chance to propose a coherent effort
•Promising future as experimental facilities move to medium-mass exotic nuclei
•Cultural advantage but US and Japan now put strong emphasis on EDF ; e.g. UNEDF
• Our expertise suggest to
•Push MREDF methods ; e.g. QRPA, GCM/Projection-like methods
•Develop further and systematize the use of Time-Dependent EDF methods
•Push cross-fertilization between EDF and CI ; e.g. ESNT workshop on April 7-10
• Such a bias carries the danger to miss the big picture
•E.g., somewhat true about ab-initio methods and nuclear interactions in the
80/90’s
•Could be detrimental as overlap/benchmarks are envisioned ; e.g. with CC
• Might need to recruit a few theorists with different expertise
•Interplay between structure and reaction ; e.g. GSM
•“Hard core” reaction theory ; e.g. issue with extracting spectroscopic factors
•Promising ab-initio method for medium mass nuclei: Coupled Cluster
Geography
• Strong on-going theoretical collaborations
•GANIL-IPNO
•CENBG-GANIL-IPNL-SPhN
•GANIL-SPhN
• Future
•Projects will naturally follow historical collaborations
•But new ones will hopefully arise…