Discussion on Low-energy nuclear structure and reactions Workshop on Future directions in the physics of nuclei at low energies May 21 st -23 rd 2014, ECT*, Trento, Italy

Discussion I.Topics to be discussed  Organization/strategy of the field in Europe  Physics (theory and experiment)  Any other you feel strong about II.Points to jumpstart the discussion  Key points raised by the 3 theory + 2 experimental speakers (have them as back-up slides here)  Points to be raised by conveners in this brief intro  Any point you wish to raise III.Objectives  Come up with a list of important points for the future (to be further elaborated and discussed) Rule of thumb: If we take 20mns per topic we can cover about 11 of them…

General perspectives from theoretical viewpoint I.Justification/interest/visibility/organization of the field II.General goals of nuclear structure and reaction theory III.Going towards very neutron-rich nuclei (and other extremes) IV.Scale- and scheme-dependence of analysis and interpretations V.Take true advantage of massively parallel computing

General perspectives I.Justification/interest/visibility/organization of the field 1)Justification and visibility need healthy balance  First and foremost for, and by, the field itself: always (re)phrase key questions  Interdisciplinary features further strengthen the field: new ideas? 2)Add “new” degree of freedom to our system, e.g. should it be the strangeness/hyper-nuclei era? 3)New thinking come from extremes BUT true understanding come from systematics 4)Never trust experiment/theory without uncertainty quantification

General perspectives II.General goals of nuclear structure and reaction theory 1)What do we want to achieve with QCD-based approaches? 2)From few- to many-body physics with controlled approximations from consistent ANF  Emergence of magic numbers, collective and individual excitations at the same energy scale?  Limits of nuclear stability as a function of I, A, J, E, T, S?  Phenomena: superfluidity, exotic collective excitations, one-nucleon dynamics, halos… 3)Precise/systematic/controlled account of rich phenomenology at play in stable and unstable systems 4)Uncertainty quantification and error propagation 5)Unified view of structure and reactions 6)…

General perspectives III. Going towards very neutron-rich nuclei (and other extremes) 1)Is there any innovative production mechanism on the table? 2)Predictive theories with as large a reach as possible  E.g. innovative ab-initio many-body methods + ab-initio-rooted EDF and CI  Era of theoretical uncertainty evaluation (not easy)

General perspectives IV. Scale- and scheme-dependence of analysis and interpretations 1)Always split true observables from scale-dependent interpretation-related ingredients  E.g. wf, correlations, ANF component, spectroscopic factors, s.p. shell structure…  Needs to be fully integrated in our “mental algorithm”  Needs to be seriously communicated in theoretical modeling and “extraction” 2)Reaction theory needed to revisit various factorization schemes as a function of scale

General perspectives V. Take true advantage of massively parallel computing 1)Arena for collaboration between nuclear theorists, applied mathematicians, computer scientists 2)How to promote? E.g. SciDAC-DOE in the US 3)What is feasible within the next five years? Fifteen years?

Points from Elias I.Wishes from theory 1)Converging mass predictions for exotic nuclei 2)Deep understanding of clusterisation in nuclei 3)Unification of structure and reaction: accurate reaction models based on TD-EDF 4)Determination of EoS quantities: L, K sym, K inf II. Wishes from experiment 1)Measurement of soft and exotic modes in exotic (deformed) nuclei 2)Neutron skin (direct measurement) 3)GMR in extended isotopic chains including exotic nuclei 4)Clusterisation signals in the ground state of light nuclei ?

Points from Jacek I.Need for theoretical uncertainty estimate and propagation 1)The family of Skyrme EDF parametrizations reflect large intrinsic error bars 2)Fitting procedure strongly impact performance 3)Need to quantify and propagate (statistical) uncertainties in fit II. Improve on performance of current EDF parametrizations 1)One should be impressed by performance achieved by current EDF calculations 2)However current, i.e. Skyrme, Gogny, relativisitic families of EDF parameterizations are insufficient 3)Need to change paradigm to reach spectroscopic quality  New analytical form(s) with enriched physics based on a systematic approach  More professional fitting strategies including uncertainty evaluation and propagation  Both points must benefit from emerging ab-initio many-body theories

Points from Javier I.Wishes from theory 1)Precise and extensive enough ab-initio calculations of light- and medium-mass nuclei to test ANF  NCSM, SCGF, CC, IMSRG 2)Calculations based on  -EFT ANF that cover the nuclear chart  CI, EDF 3)Uncertainties associated with input ANF and many-body method must be systematically assessed 4)Exploit high-performance computing  Improved ANF based on  -EFT (and lattice-QCD?) II. Wishes from experiment Push towards the neutron drip-line and beyond, e.g. light unbound nuclei