1. Physics with Medium Energy (>100 MeV) Gamma-Rays Blaine Norum University of Virginia 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays Blaine Norum, Univ of Virginia

2. Outline: Range: ~100 MeV ≤ Eγ ≤ ~ 500 MeV  Nucleonic/pionic degrees of freedom  Focus on Threshold pion prodution Radiative pion production Other 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 2

3.  Quark masses are direct consequence of Chiral Symmetry Breaking  Must be accounted for in the Higgs mechanism  Constrains the Lattice QCD calculations Quantitative determination of (m d – m u ) as the source of isospin symmetry violation in QCD Origin of isospin symmetry violation in QCD

4. π-β Detector 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 4

5. π-β Detector 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 5

6. π-β Detector 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 6 240 pure CsI crystal calorimeter 3π sr coverage 2 thin walled wire chambers

7. π-β Detector 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 7 9 different shapes yields soccer ball coverage

8. π-β Detector 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 8 US PI – Dinko Pocanic, UVA π-β Experiment completed at PSI Detector available for attractive experimental program - electronics included

9. Recall: Induced Neutron Polarization 10/16/15 FACET II Science Workshop Physics with Low Energy (<100 MeV) Gamma Rays 9 Unitary cusp at E np = 9 MeV suggests new channel?

10. New Channel? 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 10

11. Search at LEGS 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 11

12. LEGS results – OOPS! 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 12

13. LEGS results – OOPS! 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 13 What do we know? 1)Energy spectrum suggests H.O. states 2)Pions // gamma polarization  electric 3)Pions // gamma polarization  S=1 4)Narrow  doesn’t couple to NN, Pauli blocked

14. Supporting Evidence 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 14 Huisman et al.

15. Supporting Evidence 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 15 Khrykin et al. Sequential decay?

16. Experiment at FACET-II 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 16 Open questions: Repeatable? The γ’ threshold set at 10 MeV – too high Are γ’ energies consistent with sequential decay? Do γ’ multiplicities yield reasonable cross section ratios? Could we look for ? The π-β detector (plus neutron wall) for π + case would be excellent.

17. Potential Impact - Somewhat Speculative 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 17 Big question – is the deuteron the only 2- nucleon, or 6-quark, system?

18. Big Bang Nucleosynthesis- principal reaction chains 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 18 Problems: 1) too much deuterium (solved by introducing Dark Matter) 2) too little lithium-7 Carlos BertulaniCarlos Bertulani - http://www.worldscientific.com/ worldscibooks/10.1142/8573 http://www.worldscientific.com/ worldscibooks/10.1142/8573

19. Big Bang plus Minutes 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 19

20. Big Bang plus Minutes 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 20

21. Big Bang plus Minutes 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 21

22. Neutron Stars 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 22 Biggest nucleus? Neutron star “… the description of these ultracompact objects remains one of the biggest challenges facing nuclear and particle physics today.” CERN Courier, April 2013

23. Neutron Stars - Speculative 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 23 Mysteries: Exact composition Origins Magnetic field – 10 8 T (compare to 25 T at National Magnet Lab) To zero-th order, a neutron star is a cold, essentially neutral Fermi gas. If two neutrons form a bosonic (nn) * that lasts long enough for their Fermionic states to be occupied then their decay could be suppressed and they, with S=1, could contribute to generating a magnetic field (I told you it was speculative).

24. Two Nucleons at Nuclear Energies 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 24

25. Two Nucleons at Nuclear Energies 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 25 Nucleon momentum distributions: Three-body force: Not a sum of two-body forces Both can be more easily understood in terms of a 6- q entity 1-body 2-body

26. Additional Reactions 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 26

27. Additional Detectors 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 27 JLAB Proton Polarimeter

28. Additional Detectors 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 28 Vrije University Range Telescope

29. Conclusions and Acknowledgements 10/16/15 FACET II Science Workshop Physics with Medium Energy (>100 MeV) Gamma Rays 29 I barely touched on what is possible. Questions range from very fundamental nucleon physics to basic nuclear structure questions. Acknowledgements: Mohammad Ahmed Brad Sawatzky Rob Pywell Don Crabb Henry Weller