Historical Perspective and Future Prospects for Nuclear Interactions APS 2017 April Meeting, January 28-31, 2017, Washington, DC Historical Perspective and Future Prospects for Nuclear Interactions R. Machleidt University of Idaho CNS Summer School

Outline The Past The Present The Future Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

The Past Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

History of Nuclear Forces: Phase I Chadwick (1932): Neutron Heisenberg (1932): First Phenomenology (Isospin) 1930’s Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt CNS Summer School

Heisenberg and his contribution of 1932 Niels Bohr Pauli Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Zeitschrift fuer Physik 77, 1 (1932) On the Structure of Atomic Nuclei. I. …. … Chadwick … … suggests the assumption that atomic nuclei are built from protons and neutrons without electrons … Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Zeitschrift fuer Physik 77, 1 (1932), cont’d … the force … between proton and neutron … ….. in analogy to the H2+-ion --- an exchange of negative charge will take place, … This exchange can be visualized by electrons which do not have spin and follow the rules of Bose Statistics … Precursor of the idea of Boson Exchange! Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

History, Phase I cont’ d 1930’s Chadwick (1932): Neutron Heisenberg (1932): First Phenomenology (Isospin) Yukawa (1935): Meson Hypothesis 1930’s Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

S. Tomonaga, H. Yukawa, and S. Sakata in the 1950s. Yukawa and his idea Yukawa Tomonaga Sakata S. Tomonaga, H. Yukawa, and S. Sakata in the 1950s. Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

H. Yukawa, Proc. Phys. Math. Soc. Japan 17, 48 (1935). From: H. Yukawa, Proc. Phys. Math. Soc. Japan 17, 48 (1935). Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

History, Phase I cont’d 1930’s 1950’s 1940’s Chadwick (1932): Neutron Heisenberg (1932): First Phenomenology (Isospin) Yukawa (1935): Meson Hypothesis 1930’s Discovery of the pion in cosmic ray (1947) and in the Berkeley Cyclotron Lab (1948). Nobelprize awarded to Yukawa (1949). 1940’s Taketani, Nakamura, Sasaki (1951): 3 ranges. One-Pion-Exchange (OPE): o.k. Multi-pion exchanges: Problems! Taketani, Machida, Onuma (1952); Brueckner, Watson (1953). Quote by Goldberger (1960) 1950’s “Pion Theories” Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Midwestern Conference on Theoretical Physics, Purdue University, 1960 “There are few problems in nuclear theoretical physics which have attracted more attention than that of trying to determine the fundamental interaction between two nucleons. It is also true that scarcely ever has the world of physics owed so little to so many … … It is hard to believe that many of the authors are talking about the same problem or, in fact, that they know what the problem is.” M. L. Goldberger Midwestern Conference on Theoretical Physics, Purdue University, 1960 Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

History, Phase I (The “Pion Theories”) Chadwick (1932): Neutron Heisenberg (1932): First Phenomenology (Isospin) Yukawa (1935): Meson Hypothesis 1950’s Taketani, Nakamura, Sasaki (1951): 3 ranges. One-Pion-Exchange (OPE): o.k. Multi-pion exchanges: Problems! Taketani, Machida, Onuma (1952); Brueckner, Watson (1953). Quotes by Bethe (1953) and Goldberger (1960) “Pion Theories” Discovery of the pion in cosmic ray (1947) and in the Berkeley Cyclotron Lab (1948). Nobelprize awarded to Yukawa (1949). 1940’s Phase I results in a disaster Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Phase II: The meson theories Many pions = multi-pion resonances: One-Boson-Exchange Model 1960’s Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Phase II: The meson theories Many pions = multi-pion resonances: One-Boson-Exchange Model 1960’s Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Phase II: The meson theories Many pions = multi-pion resonances: One-Boson-Exchange Model 1960’s Refined Meson Theories Sophisticated models for two-pion exchange: Paris Potential (Lacombe et al., PRC 21, 861 (1980)) Bonn potential (Machleidt et al., Phys. Rep. 149, 1 (1987)) 1970’s 1980’s Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

The exponential tail of Phase II Nijmegen: We need more precision!!! “A χ²/dat of ≈ 2 is not good enough, it has to be 1.0” 1990’s 1993: The high-precision Nijmegen phase shift analysis 1994-2001: High-precision NN potentials: Nijmegen I, II, ’93, Reid93 (Stoks et al. 1994) Argonne V18 (Wiringa et al, 1995) CD-Bonn (Machleidt et al. 1996, 2001) Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Gell-Mann and Zweig (1963): 3 quarks! Many pions = multi-pion resonances: One-Boson-Exchange Model 1960’s Gell-Mann Zweig Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt 18 18

Gell-Mann and Zweig (1963): 3 quarks! Many pions = multi-pion resonances: One-Boson-Exchange Model 1960’s QCD Gell-Mann Zweig 1970’s Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt 19 19

Phase III: The QCD/EFT period Nuclear physicists discover QCD: Quark cluster models. Weinberg van Kolck Nuclear physicists discover Effective Field Theory (EFT): Weinberg, van Kolck (Texas). Another “pion theory”; but now right: constrained by chiral symmetry 1990 – ??? Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

The Present Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Motivation for the chiral EFT approach (= Phase III approach) QCD at low energy is strong. Quarks and gluons are confined into colorless hadrons. Nuclear forces are residual forces (similar to van der Waals forces) Separation of scales Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Low-momentum expansion: (Q/Λχ)ν with ν bounded from below. Calls for an EFT: soft scale: Q ≈ mπ , hard scale: Λχ ≈ mρ ; pions and nucleons are relevant d.o.f. Low-momentum expansion: (Q/Λχ)ν with ν bounded from below. Most general Lagrangian consistent with all symmetries of low-energy QCD, particularly, chiral symmetry which is spontaneously broken. Weakly interacting Goldstone bosons = pions. π-π and π-N perturbatively NN has bound states: (i) NN potential perturbatively (ii) apply nonpert. in LS equation. (Weinberg) Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Status A.D. 2000 Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Chiral nuclear forces PKU-CUSTIPEN, August 2, 2015 Status A.D. 2010 R. Machleidt Future of NN Interaction APS APR17, 01/30/2017 Chiral nuclear forces PKU-CUSTIPEN, August 2, 2015 R. Machleidt

Evaluate current status Evaluate current status. Anything left to do in the nuclear force business? Current status: 2NFs and 3NFs up to N3LO are applied in nuclear few- and many-body systems. In general, quite a bit of success, but some persistent problems remain. In the few-body sector: Ay puzzle, N-d break-up, … Light nuclei: Spectra not perfect. Intermediate nuclei: Overbinding. Convergence of the chiral expansion in the many-body system? Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Revisit the lower orders Because of the problems just pointed out, improvement of current nuclear forces is called for. How? Revisit the lower orders Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Status A.D. 2000 Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

NNLO/N3LO revisited: NNLO revisited: Piarulli et al., 2015+ Ekstroem et al., 2013+ Carlsson et al., 2016 NNLOopt NNLOsat NNLOsep NNLOsim NNLO/N3LO revisited: Piarulli et al., 2015+ Local potentials. Status A.D. 2000 Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Revisit the lower orders. Move to higher orders. Because of the problems just pointed out, improvement of current nuclear forces is called for. How? Revisit the lower orders. Move to higher orders. Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Chiral nuclear forces PKU-CUSTIPEN, August 2, 2015 Status A.D. 2010 R. Machleidt Future of NN Interaction APS APR17, 01/30/2017 Chiral nuclear forces PKU-CUSTIPEN, August 2, 2015 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Converged at N4LO From Entem, Kaiser, Machleidt, Nosyk, PRC 92, 064001 (2015) Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

How about the 3NF? Thus, the chiral 2NF is under control. Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

1-loop graphs: 5 topologies 2PE 2PE-1PE Ring Contact-1PE Contact-2PE Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

Epelbaum et al., Eur. Phys. J. A51, 26 (2015) All possible 20 isospin-spin-momentum/position structures occur in the 3NF at N4LO! Epelbaum et al., Eur. Phys. J. A51, 26 (2015) 1-loop graphs: 5 topologies 2PE 2PE-1PE Ring Contact-1PE Contact-2PE Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

This was the Present – There is trouble! We are still faced with many unresolved many-body problems. The new NNLO potentials (NNLO_sat, NNLO_sim, …) are an attempt to solve those problems in an unconventional way. They are the beginning of a revolt against the dogmatic view of chiral EFT. The explosion of the 3NFs at N3LO and N4LO make the EFT approach unfeasible for the average many-body researcher. Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

The Future Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

When will the Future start? Find out by extrapolating the Past and Present. Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

? Summarizing History There is a pattern: 30-year Periods Phase I Pion-Theories Phase II Meson-Theories Phase III Chiral EFT (the dogmatic way) Phase IV A more Effective EFT (a more pragmatic way?) Intensity of research/interest In trouble!? ? 1930 1960 1990 2020 time

Conclusions The history of the research on nuclear forces is beautiful, exciting, and diverse. This history has a pattern. If true, the chiral EFT as we understand it now will undergo substantial changes in the near future. But the details of these modifications are not clear at this time. Be prepared and get involved! Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt

The End Future of NN Interaction APS APR17, 01/30/2017 R. Machleidt