Nuclear Theory·nucl-th

Wednesday·July 6, 2022

9 papers—5 primary·4 cross-listed

01
Cluster folding analysis for the 6,7Li and 20Ne + 24Mg nuclear systems
Sh. Hamada
The experimentally available angular distributions (ADs) for 6,7Li and 20Ne ions elastically scattered from a 24Mg target are reanalyzed using various nuclear potentials based on phenomenological and microscopic approaches. The ADs for the 6Li + 24Mg system at energies Elab = 20, 88, and 240 MeV are considered, as are the ADs for the 7Li + 24Mg system at Elab = 20, 34, and 88 MeV, and the ADs for the 20Ne + 24Mg systems at Elab = 50, 60, 80, 90, and 100 MeV. Special emphasis is placed on the (d + {\alpha}) and (t + {\alpha}) cluster structures of 6Li and 7Li weakly bound projectiles, which appear at relatively low energies of 1.4737 and 2.468 MeV, respectively. Furthermore, the 20Ne stable nucleus is a candidate to reveal the {\alpha} + 16O cluster structure at an energy of 4.73 MeV. These systems are analyzed within the framework of the cluster folding model by taking into consideration the aforementioned cluster nature of the (6Li, 7Li, and 20Ne) projectiles. The adopted approaches fairly reproduced the experimental ADs.
nucl-th0 citations
02
Covariant Density Functional Theory with Localized Exchange Terms
Qiang Zhao · Zhengxue Ren · Pengwei Zhao · Jie Meng
A new density-dependent point-coupling covariant density functional PCF-PK1 is proposed, where the exchange terms of the four-fermion terms are local and are taken into account with the Fierz transformation. The coupling constants of the PCF-PK1 functional are determined by empirical saturation properties and ab initio equation of state and proton-neutron Dirac mass splittings for nuclear matter as well as the ground-state properties of selected spherical nuclei. The success of the PCF-PK1 is illustrated with properties of the infinite nuclear matter and finite nuclei including the ground-state properties and the Gamow-Teller resonances. In particular, the PCFPK1 eliminates the spurious shell closures at Z = 58 and Z = 92, which exist commonly in many covariant density functionals without exchange terms. Moreover, the Gamow-Teller resonances are nicely reproduced without any adjustable parameters, and this demonstrates that a self-consistent description for the Gamow-Teller resonances can be achieved with the localized exchange terms in the PCF-PK1. ?
nucl-thnucl-exPRC(2022)·26 citations
03
Nuclear incompressibility and sound speed in uniform matter and finite nuclei
Guilherme Grams🇫🇷 · Rahul Somasundaram🇫🇷 · Jerome Margueron🇫🇷 · Elias Khan🇫🇷
We have extended the compressible liquid-drop model (CLDM) with a density-dependent surface term (eCLDM), which allows for a unified description of both the nuclear ground state energies and the incompressibility modulus in finite nuclei $K_{A}$ . We analyse the role of the nuclear empirical parameters, e.g., $K_{s a t}$ , $Q_{s a t}$ , $L_{sy m}$ and $K_{sy m}$ , which contribute to the bulk properties, as well as the role of the finite size contributions. For the bulk properties, the density and isospin dependencies of the nuclear incompressibility in infinite matter are characterized by introducing new empirical parameters, and two new constraints for the value of $K_{sy m}$ are suggested. For finite nuclei, we employ a Bayesian approach coupled to a Markov-Chain Monte-Carlo (MCMC) exploration of the parameter space to confront the model predictions of $K_{A}$ in Zr, Sn and Pb isotopes to the experimental data. We show that $Q_{s a t} \approx - 950 \pm 200$ ~MeV describes the experimental measurements of $K_{A}$ in these isotopes. This value is different from the ones deduced from phenomenological nuclear energy density functionals, suggesting a possible explanation of their difficulty to accurately describe Zr, Sn and Pb data all together. In addition we explore the impact of a fictitious measurement of the Giant Monopole Resonance energy in $^{132}$ Sn. We show that this measurement, provided it is accurate enough, will allow to better determine $K_{sy m}$ and $K_{τ}$ . Finally we explore the properties of the sound speed around saturation density and show the important role of finite size terms in finite nuclei since they reduce the sound speed to approximately half compared to nuclear matter.
nucl-thPRC(2022)·23 citations
04
Final state interactions in semi-inclusive neutrino-nucleus scattering: Application to T2K and MINER $ν$ A experiments
J.M. Franco-Patino🇪🇸 · R. González-Jiménez🇮🇹 · S. Dolan🇨🇭 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · J.M. Udias🇮🇹
We present a complete comparison of semi-inclusive $ν_{μ}$ - $^{12}$ C cross-section measurements by T2K and MINER $ν$ A collaborations with the predictions from the SuSAv2-MEC model implemented in the neutrino-nucleus event generator GENIE and an unfactorized approach based on the relativistic distorted wave impulse approximation (RDWIA). Results, that include cross sections as function of the final muon and proton kinematics and correlations between both, show that the agreement with data obtained by the RDWIA approach, that accounts for final-state interactions, matches or improves GENIE-SuSAv2 predictions for very forward angles where scaling violations are relevant.
nucl-thhep-phPRD(2022)·41 citations
05
Solving the matrix exponential function for the groups SU(3), SU(4) and Sp(2)
Norbert Kaiser
The well known analytical formula for $S U (2)$ matrices $U = exp (i τ \cdot φ) = cos ∣ φ ∣ + i τ \cdot φ^sin ∣ φ ∣$ \\ is extended to the $S U (3)$ group with eight real parameters. The resulting analytical formula involves the sum over three real roots of a cubic equation, corresponding to the so-called irreducible case, where one has to employ the trisection of an angle. When going to the special unitary group $S U (4)$ with 15 real prameters, the analytical formula involves the sum over four real roots of a quartic equation. The associated cubic resolvent equation with three positive roots belongs again to the irreducible case. Furthermore, by imposing the pertinent condition on $S U (4)$ matrices one can also treat the symplectic group $S p (2)$ with ten real parameters. Since there the roots occur as two pairs of opposite sign, this simplifies the analytical formula for $S p (2)$ matrices considerably. An outlook to the situation with analytical formulas for $S U (5)$ , $S U (6)$ and $S p (3)$ is also given.
nucl-thEPJA(2022)·6 citations
06
Strong-field magnetohydrodynamics for neutron stars
Shreya Vardhan · Sašo Grozdanov · Samuel Leutheusser · Hong Liu
We present a formulation of magnetohydrodynamics which can be used to describe the evolution of strong magnetic fields in neutron star interiors. Our approach is based on viewing magnetohydrodynamics as a theory with a one-form global symmetry and developing an effective field theory for the hydrodynamic modes associated with this symmetry. In the regime where the local velocity and temperature variations can be neglected, we derive the most general constitutive relation consistent with symmetry constraints for the electric field in the presence of a strong magnetic field. This constitutive relation not only reproduces the phenomena of Ohmic decay, ambipolar diffusion, and Hall drift derived in a phenomenological model by Goldreich and Reisenegger, but also reveals new terms in the evolution of the magnetic field which cannot easily be seen from such microscopic models. This formulation gives predictions for novel diffusion behaviors of small perturbations around a constant background magnetic field, and for the two-point correlation functions among various components of the electric and magnetic fields.
↳ astro-ph.HEhep-phhep-thnucl-th+1PRResearch(2024)·19 citations
07
Reevaluation of heavy-fermion-induced electron EDM at three loops
Yohei Ema🇺🇸 · Ting Gao🇺🇸 · Maxim Pospelov🇺🇸
Motivated by improved limits on electric dipole moments (EDMs), we revisit the three-loop light-by-light mechanism that transmits $C P$ violation from a heavy fermion to a light one. Applying it to the electron EDM induced by EDMs of heavier flavors, we find additional contributions at the order $m_{e} / m_{μ}$ or $m_{e} / m_{τ}$ that were missing before and that make the result 1.4 times larger. Consequently we improve bounds on the tau EDM, and update indirect limits on the muon EDM as well as charm and bottom quark color EDMs.
↳ hep-phhep-exnucl-thPLB(2022)·17 citations
08
Preparations for Quantum Simulations of Quantum Chromodynamics in 1+1 Dimensions: (I) Axial Gauge
Roland C. Farrell🇺🇸 · Ivan A. Chernyshev🇺🇸 · Sarah J. M. Powell🇨🇦 · Nikita A. Zemlevskiy🇺🇸 · Marc Illa🇺🇸 · Martin J. Savage🇺🇸
Tools necessary for quantum simulations of $1 + 1$ dimensional quantum chromodynamics are developed. When formulated in axial gauge and with two flavors of quarks, this system requires 12 qubits per spatial site with the gauge fields included via non-local interactions. Classical computations and D-Wave's quantum annealer Advantage are used to determine the hadronic spectrum, enabling a decomposition of the masses and a study of quark entanglement. Color edge states confined within a screening length of the end of the lattice are found. IBM's 7-qubit quantum computers, ibmq_jakarta and ibm_perth, are used to compute dynamics from the trivial vacuum in one-flavor QCD with one spatial site. More generally, the Hamiltonian and quantum circuits for time evolution of $1 + 1$ dimensional $S U (N_{c})$ gauge theory with $N_{f}$ flavors of quarks are developed, and the resource requirements for large-scale quantum simulations are estimated.
↳ quant-phhep-lathep-phnucl-thPRD(2023)·166 citations
09
The Anomalous Magnetic Moment of the Muon: Beyond the Standard Model via Chiral Enhancement
Andreas Crivellin🇨🇭 · Martin Hoferichter🇨🇭
The anomalous magnetic moment of the muon displays a $4.2 σ$ tension with the Standard-Model prediction, if $e^{+} e^{-} \to hadrons$ data are used for hadronic vacuum polarization. In these proceedings we review possible explanations of this anomaly in terms of heavy new particles. As the necessary effect is of the order of the electroweak Standard-Model contribution, viable explanations with TeV-scale physics must involve an enhancement factor; in particular, one can obtain the chirality flip of the dipole operator via a sizable coupling to the Higgs doublet instead of the small muon Yukawa coupling. Such Standard-Model extensions then also predict effects in Higgs and $Z$ -boson decays to muons, with details depending on the $S U (2)_{L} \times U (1)_{Y}$ representations of the new particles. We first review the general case of chirally enhanced new physics, before discussing in more detail the concrete example of leptoquark models.
↳ hep-phhep-exnucl-thNuovo Cim.C(2022)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE