1. Investigation of Parity Quantum Numbers with Laser Compton Back-Scattered Photons ELI-NP: The Way Ahead – 10-12 March, 2011 C. Romig, J. Beller, J. Isaak, N. Pietralla, D. Savran, M. Scheck, K. Sonnabend, J. Wagner, M. Zweidinger Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany H.R. Weller, M. Ahmed, E. Kwan, R. Raut, G. Rusev, S.C. Stave, A. Tonchev, W. Tornow Departement of Physics, Duke University, Durham, NC, USA D. Deleanu, D.M. Filipescu, T. Glodariu, N.-V. Zamfir National Institute for Physics and Nuclear Engineering „Horia Hulubei“, Bucharest-Magurele, Romania March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead

2. Nuclear Resonance Fluorescence March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  Nuclear Resonance Fluorescence (NRF): excitation of nuclear level by resonant absorption of real photon and subsequent decay by reemission of a photon  low momentum transfer  spin selective to dipole excited states  observables: level energy, spin quantum number, parity quantum number, branching ratios, and transition strengths  important tool for investigation of nuclear structure at low energies

3. Determination of Parities in NRF March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  determination of parity quantum numbers requires polarization measurements  measurement of polarization in exit channel difficult because of low analyzing power ( <10%)  using polarized photons in entrance channel is preferable:  analyzing power is ≈ 100% (energy-independent)  parity information obtained by relatively simple intensity measurements M. Buessing et al., Phys. Rev. C 78 041602(R) (2008)

4. Determination of Parities in NRF March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead polarization plane (E-vector) E1 transition M1 transition incident photon beam

5. Determination of Parities in NRF March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  experimental asymmetry N. Pietralla et al., Phys. Rev. Lett. 88 012502 (2002) E1 transition M1 transition

6. Physics March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  Electric Dipole response:  Pygmy Dipole Resonance  Two-Phonon State  Magnetic Dipole response:  Scissors Mode  Spin-Flip Excitations  parity violation (PV) effect postulated in 1956 and experimentally verified in 1957 by Wu et al.  various theoretical and experimental attempts but impact of weak interaction on nuclear structure not well tested, yet  1 + /1 - doublet in 20 Ne suggested [1] to be one of best cases to study PV http://irfu.cea.fr/Sphn/Parity/ [1] A.I. Titov et al., J. Phys. G: Nucl. Part. Phys. 32 1097 (2006)

7. The 20 Ne Case: Parity Mixing of Yrast Levels T < =0 1-1- 1+1+ 11270 (5) 11262.3(19) 20 Ne 0+0+ 20 F, T < = 1 1-1- 1+1+ 3+3+ 4+4+ 5+5+ 2+2+  (p 3/2 1 ) (d 5/2 3 ) gs T=1 isobaric analogs  (d 5/2 1 ) (d 5/2 3 )  doublet is isobaric analog of simple shell model states  effect of PV is expected to be very small  high nuclear enhancement factor [1]:  overlapping wavefunctions  small energy splitting (large uncertainty) [1] A.I. Titov et al., J. Phys. G: Nucl. Part. Phys. 32 1097 (2006) March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  feasibility of measurment of PV effect on 20 Ne?

8. Measurement on 20 Ne March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  target: natural neon gas (90.48% 20 Ne) with 2400 psi  28 Si target for energy calibration and determination of analyzing power  container: aluminum core wrapped in carbon fiber T.C. Li et al., Phys. Rev. C 73 054306 (2006)  beam energy: 11.26 MeV (ΔE ≈ 350 keV)  4 h with circular polarized photons (isotropic emission -> reference point)  20 h with linear polarized photons (separation of 1 + and 1 - state)

9. 20 Ne – Spectra and Preliminary Results March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead  20 Ne doublett: strong M1 and weak E1 excitation  energy difference from analysis of peak centroids in both measurements 28 Si: 1 + 28 Si: 1 - 20 Ne vertical horizontal  before:  now (preliminary): 1+1+ 1-1- 1-1- 1+1+

10. Summary March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead