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,

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

Nuclear Resonance Fluorescence


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

Determination of Parities in NRF


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)



polarization plane (E-vector)

E1 transition

M1 transition

incident photon beam



experimental asymmetry

N. Pietralla et al., Phys. Rev. Lett. 88 012502 (2002)

E1 transition

M1 transition

Physics


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 20Ne suggested [1] to be one of best cases to study PV

http://irfu.cea.fr/Sphn/Parity/

[1]

A.I

. T

itov

et a

l., J

. P

hys.

G:

Nuc

l. P

art.

Phy

s. 3

2 10

97 (

2006

)

The 20Ne Case: Parity Mixing of Yrast Levels

T<=0

1-

1+

11270 (5)

11262.3(19)

20Ne0+

20F, T< = 1

1- 1+

3+ 4+

5+

2+

(p3/21)(d5/2

3)

gs

T=1isobaric analogs

(d5/21)(d5/2

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

. T

itov

et a

l., J

. P

hys.

G:

Nuc

l. P

art.

Phy

s. 3

2 10

97 (

2006

)


feasibility of measurment of PV effect on 20Ne?

Measurement on 20Ne


target: natural neon gas (90.48% 20Ne) with 2400 psi

28Si 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)

20Ne – Spectra and Preliminary Results


20Ne doublett: strong M1 and weak E1 excitation

energy difference from analysis of peak centroids in both measurements

28Si: 1+

28Si: 1+28Si: 1-

20Ne

20Ne

vertical

horizontal

before:

now (preliminary):

1+

1-

1-

1+

Summary


Documents

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,