Electromagenetic Probes of Nuclei

Event Date:
2018-09-06T14:00:00
2018-09-06T15:00:00
Event Location:
TRIUMF Auditorium
Speaker:
Mirko Miorelli (TRIUMF)
Related Upcoming Events:
TRIUMF Talks
Event Information:

Electromagnetic probes represent a fundamental tool to study nuclear structure and dynamics. The perturbative nature of the electromagnetic interaction allows for a clean connection between calculated nuclear structure properties and measured cross sections. Ab initio methods
have long represented the gold standard for calculations of nuclear structure observables in light nuclei. Thanks to recent developments in the scientific community, ab initio calculations have finally reached the medium- and heavy-mass region of the nuclear chart. However, the challenges modern nuclear structure calculations face are multiple, ranging from the construction of nuclear forces from chiral effective field theory and the solution of the highly correlated quantum many-body problem, to a quantitative description of observables with solid treatment of uncertainties.

I will address some of these challenges, using the ab initio coupled-cluster (CC) theory formulation of the Lorentz integral transform (LIT) method and show how we can combine the CC and LIT methods for the computation of electromagnetic inelastic reactions into the continuum [1,2]. I will show that the bound-state-like equation characterizing the LIT method can be reformulated based on extensions of the coupled-cluster equation-of-motion (EOM) method, and will discuss strategies for viable numerical solutions. I will then focus on the calculation of the electric dipole polarizability (EDP), which quantifies the low-energy behaviour of the dipole strength and is related to critical observables such as the radii of the proton and neutron distributions. Using a variety of chiral interactions, and singles and doubles excitations, I will show results for  4He, 16,22O and 40Ca [1,2,3]. Exploiting correlations between EDP and the charge radius, I will show results for the neutron-skin radius and the polarizability for the double-magic 48Ca [4], the latter recently measured by the Osaka-Darmstadt collaboration [5]. Finally, I will show our last study regarding the impact of triples excitations (and thus the uncertainty of the CC truncations) on the dipole strength in 4He, 16O and 48Ca [6]. In particular, the addition of new correlations allows us to improve the precision of our 48Ca calculations and reconcile the recently reported discrepancy between coupled-cluster results based on these interactions and the experimentally determined EDP from proton inelastic scattering in 48Ca.

[1] S. Bacca et al., Phys. Rev. C 90, 064619 (2014)
[2] M. Miorelli et al., Phys. Rev. C 94, 034317 (2016)
[3] M. Miorelli et al., EPJ Web of Conferences 113, 04007 (2016)
[4] G. Hagen et al., Nature Physics 12, 186190 (2016)
[5] J. Birkhan et al., Phys. Rev. Lett. 118, 252501 (2017)
[6] M. Miorelli et al., Phys. Rev. C 98, 014324 (2018)
 

Add to Calendar 2018-09-06T14:00:00 2018-09-06T15:00:00 Electromagenetic Probes of Nuclei Event Information: Electromagnetic probes represent a fundamental tool to study nuclear structure and dynamics. The perturbative nature of the electromagnetic interaction allows for a clean connection between calculated nuclear structure properties and measured cross sections. Ab initio methods have long represented the gold standard for calculations of nuclear structure observables in light nuclei. Thanks to recent developments in the scientific community, ab initio calculations have finally reached the medium- and heavy-mass region of the nuclear chart. However, the challenges modern nuclear structure calculations face are multiple, ranging from the construction of nuclear forces from chiral effective field theory and the solution of the highly correlated quantum many-body problem, to a quantitative description of observables with solid treatment of uncertainties. I will address some of these challenges, using the ab initio coupled-cluster (CC) theory formulation of the Lorentz integral transform (LIT) method and show how we can combine the CC and LIT methods for the computation of electromagnetic inelastic reactions into the continuum [1,2]. I will show that the bound-state-like equation characterizing the LIT method can be reformulated based on extensions of the coupled-cluster equation-of-motion (EOM) method, and will discuss strategies for viable numerical solutions. I will then focus on the calculation of the electric dipole polarizability (EDP), which quantifies the low-energy behaviour of the dipole strength and is related to critical observables such as the radii of the proton and neutron distributions. Using a variety of chiral interactions, and singles and doubles excitations, I will show results for  4He, 16,22O and 40Ca [1,2,3]. Exploiting correlations between EDP and the charge radius, I will show results for the neutron-skin radius and the polarizability for the double-magic 48Ca [4], the latter recently measured by the Osaka-Darmstadt collaboration [5]. Finally, I will show our last study regarding the impact of triples excitations (and thus the uncertainty of the CC truncations) on the dipole strength in 4He, 16O and 48Ca [6]. In particular, the addition of new correlations allows us to improve the precision of our 48Ca calculations and reconcile the recently reported discrepancy between coupled-cluster results based on these interactions and the experimentally determined EDP from proton inelastic scattering in 48Ca. [1] S. Bacca et al., Phys. Rev. C 90, 064619 (2014) [2] M. Miorelli et al., Phys. Rev. C 94, 034317 (2016) [3] M. Miorelli et al., EPJ Web of Conferences 113, 04007 (2016) [4] G. Hagen et al., Nature Physics 12, 186190 (2016) [5] J. Birkhan et al., Phys. Rev. Lett. 118, 252501 (2017) [6] M. Miorelli et al., Phys. Rev. C 98, 014324 (2018)   Event Location: TRIUMF Auditorium