investigation of parity quantum numbers with laser compton back-scattered photons eli-np: the way...
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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
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
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)
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
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
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 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
)
March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead
feasibility of measurment of PV effect on 20Ne?
Measurement on 20Ne
March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead
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
March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead
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
March 11th, 2011 | Christopher Romig | Technische Universität Darmstadt | AG Pietralla | ELI-NP: The Way Ahead