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Nuclear structure investigations in the
future.
J. Jolie, Universität zu Köln
How do complex systems emerge from simple ingredients
Basic ingredients:
two sets of indistinguishable fermions
a complex short range force (Van der Waals typ)
the possibility that one kind of fermions becomes the other kind
+ Binding energy
3fm
The atomic nucleus forms a unique two-component
mesoscopic system, which is hard to manipulate
but genereous in the number of observables it emits.
Once the atomic nucleus is formed effective (in-medium) forces
generate simple collective motions.
shell structure
Cooper pairing
Quantum fluid
Comparison with another mesoscopic system
Atomic nuclei
Quantum dots
Two components
One component
Fixed number of particles
Variable number of particles
No thermal noise
Thermal noise
Difficult to manipulate
Easy to manipulate
Lots of observables
Few observables
3-Dimensional
1- or 2-Dimensional
Fundamental entities
In contrast to other mesoscopic systems the atomic nucleus can be
excited and observed in a very clean way.
Chart of nuclear excitations.
Eexc
Quantal
chaos
Rotation induced
effects
Particle-hole
excitations
Collective
motion
J
Angular momentum (Deformation)
Radioactive Ion Beams (RIBs) add a new axis to this chart. It will allow
the manipulation of one important degree of freedom in atomic nuclei.
Eexc
Coupling with
continuum
Binding
energy
J
Angular momentum (Deformation)
N- Z
N+Z
and also :
dilute nuclear matter
halos
clustering
new decay modes
Topic: Shell structure at largely asymmetric N, Z values
In contrast to other physical systems the
fact that one has a two-component system
induces N and Z dependent shells.
The shell structure will change drastically for
strongly asymmetrical nuclei, due to changing
spin-orbit interaction and coupling with continuum.
Needed: New magic numbers need to be determined,
farest reachable nuclei to be produced,
mass measurements (traps, storage rings)
transfer, knock-out and fragmentation reactions
low-spin spectroscopy (B(E2), moments, Ex)
Important for: Nuclear structure and astrophysics.
Topic: Pairing: bosonification of a fermionic system.
Nuclei can be very well described as an interacting
boson system due to the strong pairing between
like nucleons. What is the role of the proton-neutron
interaction and the other nucleons?
Does a neutron and a proton form a paired state with
T= 1 and T=0?
Does there exist a even-even nuclei with a groundstate with I   0?
Do the beautiful dynamical symmetries and even supersymmetries exist
in presently unknown nuclei.
Needed: Complete low-spin spectroscopy,
Stable and unstable nuclei need to be produced in large quantities,
Gamma spectroscopy and transfer reactions (beta decay@RIBs).
Important for: Nuclear structure and all other kinds of mesoscopic physics.
Topic: quantum phase transitions at finite N, a new way to look at nuclear
structure.
Recently, a new nuclear shape phase diagram was
introduced as well as new critical point symmetries.
How do these phases
evolve away from
stability?
What are the experimental signatures of such phase transitions and
especially of up to now unknown new phases?
Where do triaxial nuclei or nuclear molecules exist away from stability?
Needed: Low-spin spectroscopy.
Exotic nuclei need to be produced in sufficient quantities,
Gamma, c-e spectroscopy and masses,
Important for: Nuclear structure and mesoscopic physics with small N.
Topic: Quantal chaos versus integrable many-body systems
The atomic nucleus forms an unique laboratory to study chaos in
a quantal system due to the abibility to determine a complete set of
excited states.
The interacting boson model and the shell model are ideal realistic
models to study this subject. Moreover it provides examples of nuclei
that do allow the experimental determination of the characteristic
observables.
Needed: Complete spectroscopy at all possible spins.
Exotic and stable nuclei need to be produced in large quantities,
gamma spectroscopy and transfer reactions,
Important for: Nuclear structure and Quantum Mechanics
Challenge: Low spin physicists need high-spin techniques
and high spin physicists need low-spin methods and theoreticians.
First tries are RISING and MINIBALL.
It works! The I and J community can merge.
Challenge: The target is the beam, so we have to develop new instruments.
Miniball Phase 1
Data from REX-ISOLDE
Advanced Gamma-Ray Tracking array (AGATA)
Challenge: We need a sufficient number of RIB and stable beam facilities.
RIB:
Experiments with few data:
frontier physics.
Experiments with more data:
highlighting physical mechanism.
Experiments at stable beam facilities
with very high sensitivity.
Answering new questions (feedback).
Many questions have to be solved:
GANIL
GSI
REX-ISOLDE
MAFF
EURISOL, RIA, RIKEN, etc.
+STABLE BEAMS all are needed!
Challenge: While the next generation of experimental facilities is in
construction and the field is booming with new ideas, the universities are
still reducing the number of faculty positions.
There is an urgent need for:
large scale nuclear shell model, mean field and many-body theorists,
conserted action to reinforce the university based research,
good and hands-on education at stable beam facilities.
Notice: without a strong university support, no students.
Positive note:
Public relation has improved tremendeously.
Several young full professors were appointed on experimental chairs.
Also Atomic Physics revived with the advent of storage rings and
synchrotron radiation.
Conclusion
Nuclear physics is moving quickly, especially due to the development
of:
152Sm
X(5)
New detectors
New concepts
The future looks bright,
but much work has to be done!
New facilities