Nuclear Theory·nucl-th

Friday·May 26, 2017

6 papers—2 primary·4 cross-listed

01
Tetrahedral $4 α$ and $^{12} C + α$ cluster structures in $^{16}$ O
Yoshiko Kanada-En'yo🇯🇵
We have investigated structures of the ground and excited states of $^{16} O$ with the method of variation after spin-parity projection in the antisymmetrized molecular dynamics model combined with the generator coordinate method of $^{12} C + α$ cluster. The calculation reasonably reproduces the experimental energy spectra, $E 2$ , $E 3$ , $E 4$ , $I S 1$ transitions, and $α$ -decay properties. The formation of 4 $α$ clusters has been confirmed from nucleon degrees of freedom in the AMD model without assuming existence of any clusters. They form "tetrahedral" $4 α$ - and $^{12} C + α$ -cluster structures. The $^{12} C + α$ structure constructs the $K^{π} = 0^{+}$ band consisting of the $0_{2}^{+}$ , $2_{1}^{+}$ , and $4_{1}^{+}$ states and the $K^{π} = 0^{-}$ band of the $1_{2}^{-}$ , $3_{2}^{-}$ , and $5_{1}^{-}$ states. The $0_{1}^{+}$ , $3_{1}^{-}$ , and $4_{2}^{+}$ states are assigned to the ground band constructed from the tetrahedral 4 $α$ structure. The $0_{1}^{+}$ and $3_{1}^{-}$ are approximately interpreted as $T_{d}$ band members with the ideal tetrahedral configuration. The ground state $4 α$ correlation plays an important role in enhancement of the $E 3$ transition strength to the $3_{1}^{-}$ . The $4_{2}^{+}$ state is not the ideal $T_{d}$ member but constructed from a distorted tetrahedral $4 α$ structure. Moreover, significant state mixing of the tetrahedral $4 α$ and $^{12} C + α$ cluster structures occurs between $4_{1}^{+}$ and $4_{2}^{+}$ states, indicating that the $T_{d}$ configuration of $4 α$ is rather fragile at $J^{π} = 4^{+}$ .
nucl-thPRC(2017)·21 citations
02
Experimental status of the nuclear spin scissors mode
E.B. Balbutsev🇷🇺 · I.V. Molodtsova🇷🇺 · P. Schuck🇫🇷
With the Wigner Function Moments (WFM) method the scissors mode of the actinides and rare earth nuclei are investigated. The unexplained experimental fact that in $^{232}$ Th a double hump structure is found finds a natural explanation within WFM. It is predicted that the lower peak corresponds to an isovector spin scissors mode whereas the higher lying states corresponds to the conventional isovector orbital scissors mode. The experimental situation is scrutinized in this respect concerning practically all results of $M 1$ excitations.
nucl-thPRC(2018)·24 citations
03
Is Renormalization in QCD Necessary at High Energy Colliders ?
Gouranga C. Nayak🇺🇸
In this paper by using the path integral formulation of the background field method of QCD in the presence of SU(3) pure gauge background field we simultaneously prove the renormalization of ultra violet (UV) divergences and the factorization of infrared (IR) and collinear divergences in QCD at all orders in coupling constant. We prove that although perturbative QCD is renormalizable but due to confinement in QCD it is not necessary to renormalize QCD to study hadrons production at high energy colliders. This is consistent with the fact that the partons are not directly experimentally observed but the hadrons are directly experimentally observed.
↳ hep-phnucl-th19 citations
04
A QFT-induced phase in neutrino flavour oscillations
Dharam Vir Ahluwalia🇮🇳 · Cheng-Yang Lee🇮🇳
In the extended Standard Model of particle physics, each neutrino mass eigenstate is predicted to have a tiny but non vanishing magnetic moment induced by quantum field theoretic corrections. These QFT-induced magnetic momenta depend linearly on masses of the underlying mass eigenstates with a proportionality constant $3 e G_{F} / (82 π^{2})$ . As a consequence when neutrinos are embedded in an environment containing magnetic fields the flavour oscillations get a contribution from the induced relative phases.
↳ hep-phnucl-thEPL(2017)·3 citations
05
Optimization of self-interstitial clusters in 3C-SiC with Genetic Algorithm
Hyunseok Ko · Amy Kaczmarowski · Izabela Szlufarska · Dane Morgan
Under irradiation, SiC develops damage commonly referred to as black spot defects, which are speculated to be self-interstitial atom clusters. To understand the evolution of these defect clusters and their impacts (e.g., through radiation induced swelling) on the performance of SiC in nuclear applications, it is important to identify the cluster composition, structure, and shape. In this work the genetic algorithm code StructOpt was utilized to identify groundstate cluster structures in 3C-SiC. The genetic algorithm was used to explore clusters of up to ~30 interstitials of C-only, Si-only, and Si-C mixtures embedded in the SiC lattice. We performed the structure search using Hamiltonians from both density functional theory and empirical potentials. The thermodynamic stability of clusters was investigated in terms of their composition (with a focus on Si-only, C-only, and stoichiometric) and shape (spherical vs. planar), as a function of the cluster size (n). Our results suggest that large Si-only clusters are likely unstable, and clusters are predominantly C-only for n <= 10 and stoichiometric for n > 10. The results imply that there is an evolution of the shape of the most stable clusters, where small clusters are stable in more spherical geometries while larger clusters are stable in more planar configurations. We also provide an estimated energy vs. size relationship, E(n), for use in future analysis.
↳ cond-mat.mtrl-scinucl-thJ.Nucl.Mater.(2017)·0 citations
06
Comment on "Are two nucleons bound in lattice QCD for heavy quark masses? - Sanity check with Lüscher's finite volume formula -"
Silas R. Beane🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸 · Assumpta Parreño🇪🇸 · Martin J. Savage🇺🇸 · Brian C. Tiburzi🇺🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸 · Frank Winter🇺🇸
In this comment, we address a number of erroneous discussions and conclusions presented in a recent preprint by the HALQCD collaboration, arXiv:1703.07210. In particular, we demonstrate that lattice QCD determinations of bound states at quark masses corresponding to a pion mass of $m_{π} = 806$ MeV are robust, and that the phases shifts extracted by the NPLQCD collaboration for these systems pass all of the 'sanity checks' introduced in arXiv:1703.07210.
↳ hep-latnucl-th31 citations

Affiliations

first authorsco-authorsvia INSPIRE

Tetrahedral 4α and 12C+α cluster structures in 16O

Experimental status of the nuclear spin scissors mode

Is Renormalization in QCD Necessary at High Energy Colliders ?

A QFT-induced phase in neutrino flavour oscillations

Optimization of self-interstitial clusters in 3C-SiC with Genetic Algorithm

Comment on "Are two nucleons bound in lattice QCD for heavy quark masses? - Sanity check with Lüscher's finite volume formula -"

Affiliations

Tetrahedral $4 α$ and $^{12} C + α$ cluster structures in $^{16}$ O