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Many-body Nuclear Structure, Few-Nucleon Systems and Hadron Structure: next 5 years

Many-body Nuclear Structure, Few-Nucleon Systems and Hadron Structure: next 5 years. TUNL Faculty: M.W. Ahmed, H. Karwowski and H.R. Weller; and C.R. Howell, W. Tornow and A. Young. Research Objectives (5-year program): 1. Many-body nuclear structure

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Many-body Nuclear Structure, Few-Nucleon Systems and Hadron Structure: next 5 years

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  1. Many-body Nuclear Structure, Few-Nucleon Systems and Hadron Structure: next 5 years • TUNL Faculty: • M.W. Ahmed, H. Karwowski and H.R. Weller; and • C.R. Howell, W. Tornow and A. Young • Research Objectives (5-year program): • 1. Many-body nuclear structure • Studies of collective excitations at HIGS using nuclear resonance fluorescence • Fission studies with neutrons (tandem lab) and g-rays at HIGS • Nuclear reactions important for astrophysics , e.g., (g, n) at HIGS • (3He, n) cross-section measurements to check wavefunctions used in QRPA calcs. of 0nbb decay in the tandem lab • 2. Advance descriptions of low-energy few-nuclear phenomena in terms of QCD using either models with effective degrees of freedom or Lattice calculations, • few-nucleon measurements with neutron beams in the tandem lab • few-nucleon measurements with g-ray beams at HIgS • Double polarized photodisintegration of the deuteron • Nucleon polarizabilities with polarized beam Compton scattering at HIGS: • Independent measurements of electric and magnetic polarizabilities of proton and neutron • Spin polarizabilities of the proton and neutron

  2. Nuclear Resonance Fluorescence (NRF) Studies at HIgS a) Understanding the Pygmy Dipole Resonance Numerous nuclei investigated. b) Supporting 0nbb NME Calculations Dipole response of nuclei in the A=40 -150 mass range: If models can’t describe the measured dipole response correctly, you can’t trust their 0nbb NME predictions. Done 76Ge, 76Se, 136Xe, 136Ba, 130Te and propose to continue in the future: 130Xe is missing, for example. c) Extending the reach of NRF studies by g-g coincidences: g3 setup Just starting. d) Extending the science reach by g-n coincidences: g2-n setup Proposing for future.

  3. Study of Nuclear Dipole Response to Electromagnetic Radiation M1 E1 Xλ ? E1 n p Cross Section p,n P, n n Sn 1 10 20 5 Ex ()‏ (,Xn)‏ • Giant Dipole Resonance: Ex ~ 10 - 20 MeV, B(E1) ~ 5 - 10 W.u. • Orbital “Scissors” mode: Ex ~ 3 MeV, B(M1) ~ 3 N2 • Two Phonon Excitation: Ex ~ 4 MeV, B(E1) ~ 10-3 W.u. • Pygmy Dipole Resonance

  4. Example of a Pygmy Resonance Study Nuclear Resonance Fluorescence E1 strength concentration at 5 – 7 MeV Fragmented strength Strength seems to scale with N/Z Collective effect

  5. Need data to untangle deformation effects from isospin dependences

  6. g3 Setup and Collaboration The new epoch in photon-induced reaction studies: g2 g1 g3 The coincidence setup g3 4 HPGe 60%: very high energy resolution (8 keV) @ 5 MeV, low efficiency 4 LaBr 3”x 3” : good energy resolution (80 keV) @ 5 MeV, ~5 times higher efficiency than HPGe

  7. Enhanced sensitivity via coincidence measurements

  8. Nuclear Astrophysics Studies at HIgS: (g,n) Reactions a) Did (g,n) measurement [86Kr(g,n)85Kr] to investigate the branching point nucleus 85Kr , s-process nucleosynthesis, continue in future: 87Rb(g,n)86Rb to study the branching point nucleus 86Rb. b) Did (g,n) measurement on 26Mg to obtain level information relevant to 22Ne(a,n)25Mg neutron source reaction. c) In the future concentrate on neutron energy measurements (via TOF) rather than only on neutron detection without any energy info. d) Do g’-n coincidence measurements in A(g,g’n)B reactions using instead of the g3 setup the g2n setup by replacing some of the g-ray detectors by neutron detectors.

  9. u e– e– u  W– W– d d u d u e– e– u d u p p  W– W– d d u u d d n n A-2 Search for 0nbb decay <mbb> = 17.5 meV pnQRPA calculations From April 2014 NSAC report on 0nbb npQRPA calculations can accommodate large model space but are based on simplifying assumptions about the structure of the ground-state of the initial and final nuclei. They assume that the nucleons are arranged in the ground states are in configurations consistent with the BCS approximation. (Operate with pair of creation and annihilation operators) J. Suhonen and O. Civitarese, Nucl. Phys. A 847 (2010) 207.

  10. Concerns about BCS approximation Relevant Orbits for 0nbb decay:A = 76, 82 Not included in npQRPA calc., but could exist in nature. Examples of Excitations due to pair vibrations S.J. Freeman and J.P. Shiffer, J. Phys. G: Nucl. Part. Phys. 39, 124004 (2012).

  11. Cross-section measurements for two-proton drop off reaction on nuclei used in 0nbb searches Faculty: A.E. Champagne, C.R. Howell, W. Tornow and A. Young Thesis Students: Dustin Combs and David Ticehurst Facility: tandem lab Objective: Measure cross sections for the (3He, n) reaction for particle transfers to the 0+ ground state and 0+ excited states of the residual nucleus. The ratio of the relative strengths for leaving the residual nucleus in an excited 0+ state relative to that for leaving the nucleus in the ground state provides a test of assumptions about the wavefunctions used in QRPA calculations of the nuclear matrix elements for 0nbb.

  12. Setup for (3He, n) cross-section measurements Top view of experimental setup 12C(a, n)15Oex 12C(a, n)15Ogs 16O(a, n)19Negs 13-m flight path for n tof measurements Liquid scintillators Ea = 20 MeV fp = 3 m • Status: • Development of a-particle beam pulsing system completed • Test runs with pulsed 4He beam using (a, n) reactions demonstrate that signal-to-background ratio is adequate to proceed with (3He, n) measurements • Installation of 3He gas recirculation/recovery system on the helium ion source is underway Beam defining apertures lined with lead

  13. Planned Cross-section Measurements

  14. Studies of Few-nucleon systems and Hadron Structure Over arching goal: Develop theoretically consistent descriptions of strongly interacting matter from quark-gluon dof to collective motion phenomena From 2007 Nuclear Science LRP PQCD Hybrids (quarks and gluonic combinations) Lattice QCD Effective Field Theories (EFTs) Meson-exchange interactions ab initio 3N and 4N calculations Region where TUNL groups contribute Few-nucleon Many-body Quantum Monte Carlo techniques Quasi-particle Random Phase Approximation Configuration Models (e.g., Shell Model) Density Functional Theory

  15. Discrepancy with nn QFS in nd breakupfrom: H. Witała and W. Glöckle, Phys. Rev. C 83, 034004 (2011) Univ. Bonn, En=26 MeV Ep=0 CD Bonn pot. ann = -18.8 fm l = 1.18 CD Bonn pot. reff = 2.79 fm A. Siepe et al., Phys. Rev. C 65, 034010 (2002). Calculations: CD-Bonn NN potential Witała: Must increase the nn 1S0 strength to fit data CIAE, En=25 MeV Consequence: shallow nn 1S0 bound state l = 1.18 Remeasure nn-QFS Search for di-neutron bound state via g+ 3H -> n + n +p X.C. Ruan et al., Phys. Rev. C 75, 057001 (2007). Calculations: CD-Bonn NN potential Two-pronged approach

  16. R&D for nnQFS measurement in nd breakup Faculty: C.R. Howell and W. Tornow Thesis Student: Ron Malone Facility: Tandem Lab Experiment setup Neutron source: 2H(d, n) absolute luminosity determined in situ via nd elastic scattering Locus for nd breakup CD2 nd elastic n2 n1 12Cel 12Cinel Signal-to-background ratio acceptable will move on to first Phase of measurements

  17. 2.5.1 Photodisintegration of the triton Faculty: M.W. Ahmed,C.R. Howell and W. Tornow Thesis Students: Forrest Friesen and Zhonglin Han Facility: HIgS Experimental Setup nn FSI 80 cm ~210 Ci of tritium gas in 7 cells • Status: • Tritium gas target design underway • Detector R&D underway (silicon strip detectors and wire chambers)

  18. Chiral Expansion of the Nuclear Forces

  19. Neutron-Deuteron Ay(q) Calculations : H. Witała et al. Chiral NN potential of Epelbaum et al. AV18, CD Bonn Nijm1, Nijm2 NLO 2NF Tornow et al. 1983 AV18, CD Bonn Nijm1, Nijm2 & TM99 3NF N2LO 2NF N3LO 2NF N3LO 2NF N3LO 2NF & N3LO 3NF contact terms and 2p exchange N3LO 2NF N3LO 2NF & N3LO 3NF plus (2p - 1p)-exchange N3LO 2NF & N2LO 3NF N3LO 2NF & N3LO 3NF plus ring

  20. 4N Systems p-3He Ay(q), T=1 n-3He Ay(q), T=0,1 Esterlineet al. Proposal: Obtain n-3H Ay(q) data (T=1) at En=2.26 MeV and En=5.54 MeV to check on isospin dependence (p-3H is also T=0,1). TUNL Ec.m.-EB3N

  21. Electric and Magnetic Polarizabilities of the nucleons 2014 TAC Visit

  22. The Status of Nucleon EM Polarizabilities EFT Extractions – HWG, JAMcG, DRP, GF HWG, JAMcG, DRP, GF, PPNP, 67 (2012) 841-897 JAMcG, DRP, HWG, EJP, A 49 (2013) 12 PDG - 2013 2014 TAC Visit

  23. Setup for EM measurements at HIGS The HINDA Array • Cryo-Cooler • Cooling Power: 1.5 W @ 4.2 K • Base T = 3.5 K • L = 20 cm, V = 0.24 Lit • D/H/cm2 = 1024

  24. HIGS Cryogenic Target ( TUNL + GWU Joint Effort) 2014 TAC Visit

  25. GDH sum rule on the deuteron: 2H(g, n)

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