1. 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

2. Outline The Past The Present The Future
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R. Machleidt

3. The Past
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R. Machleidt

4. History of Nuclear Forces: Phase I
Chadwick (1932): Neutron
Heisenberg (1932): First Phenomenology (Isospin)
1930’s
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R. Machleidt
CNS Summer School

5. Heisenberg and his contribution of 1932
Niels Bohr
Pauli
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R. Machleidt

6. 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 …
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R. Machleidt

7. 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!
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R. Machleidt

8. History, Phase I cont’ d 1930’s Chadwick (1932): Neutron
Heisenberg (1932): First Phenomenology (Isospin)
Yukawa (1935): Meson Hypothesis
1930’s
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R. Machleidt

9. 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.
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R. Machleidt

10. H. Yukawa, Proc. Phys. Math. Soc. Japan 17, 48 (1935).
From:
H. Yukawa, Proc. Phys. Math. Soc. Japan 17, 48 (1935).
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R. Machleidt

11. 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”
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12. 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
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13. 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
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R. Machleidt

14. Phase II: The meson theories
Many pions = multi-pion resonances:
One-Boson-Exchange Model
1960’s
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15. Phase II: The meson theories
Many pions = multi-pion resonances:
One-Boson-Exchange Model
1960’s
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R. Machleidt

16. 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
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17. 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
: 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)
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18. Gell-Mann and Zweig (1963):
3 quarks!
Many pions = multi-pion resonances:
One-Boson-Exchange Model
1960’s
Gell-Mann
Zweig
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19. Gell-Mann and Zweig (1963):
3 quarks!
Many pions = multi-pion resonances:
One-Boson-Exchange Model
1960’s
QCD
Gell-Mann
Zweig
1970’s
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20. 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 –
???
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R. Machleidt

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

22. 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
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23. 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)
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24. Future of NN Interaction APS APR17, 01/30/2017
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25. Status
A.D. 2000
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26. Chiral nuclear forces PKU-CUSTIPEN, August 2, 2015
Status
A.D. 2010
R. Machleidt
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Chiral nuclear forces PKU-CUSTIPEN, August 2, 2015
R. Machleidt

27. 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?
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R. Machleidt

28. Revisit the lower orders
Because of the problems just pointed out, improvement of current nuclear forces is called for.
How?
Revisit the lower orders
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R. Machleidt

29. Status
A.D. 2000
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30. 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
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R. Machleidt

31. 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

32. 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

33. Future of NN Interaction APS APR17, 01/30/2017
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34. Future of NN Interaction APS APR17, 01/30/2017
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35. Converged
at N4LO
From Entem, Kaiser, Machleidt, Nosyk, PRC 92, (2015)
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36. How about the 3NF? Thus, the chiral 2NF is under control.
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37. Future of NN Interaction APS APR17, 01/30/2017
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38. Future of NN Interaction APS APR17, 01/30/2017
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39. Future of NN Interaction APS APR17, 01/30/2017
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40. Future of NN Interaction APS APR17, 01/30/2017
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41. 1-loop graphs: 5 topologies
2PE PE-1PE Ring Contact-1PE Contact-2PE
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42. 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 PE-1PE Ring Contact-1PE Contact-2PE
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R. Machleidt

43. 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.
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R. Machleidt

44. The Future
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45. When will the Future start?
Find out by extrapolating the Past and Present.
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R. Machleidt

46. ? 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

47. 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!
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R. Machleidt

48. The End
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R. Machleidt