Transcript Document

Nuclear structure and dynamics
(The theory activities within INFN – in brief !)
Seminar at NuPECC Meeting
LNS, March 12th, 2010
G. Colò
What, where and who ?
Milano
Few-body and nuclear matter:
Pisa, Trento, Padova, Catania
Shell model: Napoli
Mean field and beyond:
Milano, Napoli, Lecce, Firenze
Algebraic models: Padova
Trento
Padova
Torino
Pisa
Firenze
Lecce
Napoli
Reactions:
Catania, Padova, Milano, Pisa
Electroweak interactions:
Torino, Lecce
Neutron stars, astrophysics:
Catania, Milano, Pisa
Catania
FTE = 55
(individuals ~ 70)
• Collaborations with many Universities
institutes spread around the world
and
research
• Strong link with experimental activities (proposals, joint
papers, PAC participation) in Italy, Europe, USA, Japan …
• Activity oriented towards training of young scientists
One example: Asia Link
Programme # CN/AsiaLink 008 (94791)
Key question : the NN effective force
The effective force is related to a method !
QCD (χPT)
Fit to observables
free or bare NN interaction
ab-initio approaches
(variational, Montecarlo …)
Shell model
effective NN interaction
relativistic models
non-relativistic models
Skyrme, Gogny
free or bare NN interaction
Tests of the bare NN interaction in bound or scattering states of
few nucleon systems are performed in Pisa, Trento and
Padova.
The modern few-body techniques are either “exact” or “close
to”.
3-body: Variational methods, Hyperspherical harmonics
expansion, Fadeev equations
The Trento group has proposed a method to treat the manybody problem exactly also in the continuum, namely the
Lorentz Integral Transform (LIT) method.
Electron RL(E,q) vs E in 4He
Pisa : accurate calculations of
scattering observables, of M1
transitions including exchange
currents, and PV components
in the NN potential
H. Witała et al., PRC 73, 044004
Nd spin-transfer coefficients
extracted from elastic data at
22.7 MeV
Chiral potentials: blue=NLO,
red=NNLO including 3-body
Going to next order: sometimes
better and sometimes worse ??
Napoli : shell-model studies of exotic nuclei
Use of modern Vlow-k
Intensive exploration
of the region around
132Sn.
L. Coraggio et al., PRC 80, 044320.
3-body force ?
Energy density functional (EDF) methods
E   Hˆ    Hˆ eff   Eˆ 
ˆ 1-body density matrix
 Slater determinant  
• The unknown exact energy is set equal (ansatz !) to a much
simpler expectation value on a Slater determinant. If Heff is well
designed, the resulting energy can fit experiment at best
• Linear response theory can be applied → self-consistent
description of nuclear collective motion
Milano: accurate calibration of
the functional using exp. data
for the collective response
Coll. with LNS: functionals
derived from Brückner-HF
The largest uncertainities
concern the ISOVECTOR,
or SYMMETRY part of the
energy functional which is
very POORLY constrained.
usual (stable) nuclei
neutron-rich (unstable) nuclei
Dipole response
PDR
GDR
It has been shown that
the GDR can constrain
the symmetry energy at
density around 0.1 fm-3
while the PDR can
constrain the derivative
of the symmetry energy.
L. Trippa et al., PRC 77, 061304(R),
A. Carbone et al., PRC in press
LNS : focus on REACTION mechanisms and constraints
extracted from observables. Big expertise in transport models,
applied from intermediate (≈εF) up to relativistic energies.
Time evolution of the one-body distribution function
Vlasov
Boltzmann
f ( r , p, t )
Langevin

f (r , p )  h( f ), f (r , p )  K ( f )  K (r , p, t )
t
Courtesy:
B. Tsang
Vlasov Boltzmann
Analysis of the isospin content of the
fragments, or of other observables (cf.
double rations) ↔ Symmetry energy
Langevin
Nuclear and Coulomb inelastic excitations
Microscopic double folding
Role of nuclear and Coulomb potentials in
the excitation of PDR and GDR
Matching of structure and reaction theories
Courtesy: E. Lanza
Reactions with (very) exotic nuclei like breakup
Advanced quantum models by Pisa and Padova groups
Fusion reactions
Two-particle transfer reactions as a probe of nuclear pairing
Other approaches : more emphasis on the
MB technique rather than on VNN
Catania : many-body correlations, extended linear response
calculations. How reliable is it the HF-RPA level ?
Padova : algebraic approach to nuclei displaying critical
symmetries. Can we pick up the interesting cases without resorting to
heavy numerics ?
Milano : nuclear field theory approach to properties of singleparticle, collective states and pairing beyond mean-field.
Relevance of coupling of particles and vibrations at highest orders.
Lecce : FHNC calculations extended to medium-heavy
systems. Is the effective tensor force quenched ?
The physics of compact
stellar objects is of course
interesting in itself. In the
present context, we stress the
opportunity to test the nuclear
models in a wide range of
densities and extreme isospin
asymmetry.
Properties of the crust, role of the EOS to
determine mass vs. radius, role of e-capture in
supernova collapse, transition to deconfined
phase…
Pairing properties of neutron
matter are still an open
question !
Other national funding
MIUR-PRIN 2008
Many-body theory of nuclear systems and implications
on the physics of neutron stars
Universities involved:
Milano
Trieste
Roma
Catania
• In summary, the different groups involved in theoretical
nuclear structure and nuclear reaction physics cover, with
their study, a large variety of approaches and methods.
• In some cases, there is a clear contiguity/continuity with
hadron physics. Just one example: role of hyperons in nuclei
and neutron stars.
nucleon
} incl.
hyperons
P. Finelli et al.
H.-J. Schulze et al,
PRC73 (2006) 058801
• In other cases, some of the sophisticated many-body
techniques introduced by the nuclear theorists are applied to
other systems as well: typically, molecules and clusters or
trapped atomic gases.
A bottom line…
• The interest of the theory community in nuclear structure
and nuclear dynamics has a longstanding tradition, and
several schools have developed – with high expertise in
specific techniques, as well as strong interactions with
experimentalists.
• The level of the various groups is quite high, as testified by
the number of publications in high-quality journals and
invited talks at conferences.
• There is still significant fragmentation in the activities;
however, synergies are increasing (directly or indirectly).
New requests for computing
So far, calculations have been based on local, existing
computer resources.
A few of the mentioned groups have recently made a
single request to the CSN4-INFN for new local units:
• 6- or 8-core
• 32 GB RAM
• 2 TB HD
(6 units).