Nuclear Theory·nucl-th

Monday·June 11, 2018

8 papers—6 primary·2 cross-listed

01
Energy Spectrum of Neutron-Rich Helium Isotopes: Complex Made Simple
K. Fossez · J. Rotureau · W. Nazarewicz
We demonstrate that the intricate energy spectrum of neutron-rich helium isotopes can be straightforwardly described by taking advantage of the low-energy properties of neutron-neutron interaction and the scale separation that is present in diluted dripline systems. By using arguments based on the halo effective field theory, we carry out a parameter reduction of the complex-energy configuration interaction framework in the $s p d$ space, including resonant and scattering states. By adjusting only one parameter, the strength of the spin-singlet central neutron-neutron interaction, we reproduce experimental energies and widths of $^{5 - 8}$ He within tens of keV precision. We predict a parity inversion of narrow resonances in $^{9}$ He and show that the ground state of $^{10}$ He is an $s$ -wave-dominated threshold configuration that could decay through two-neutron emission.
nucl-thPRC(2018)·35 citations
02
'Running' under tight constraints in pionless effective field theory
Jun-Jun Lü🇨🇳 · Ji-Feng Yang🇨🇳
The contents of renormalization group invariance and equations under tight constraints are explored and demonstrated with closed-form on-shell $T$ matrices of pionless effective field theory for nuclear forces right within the effective field theory philosophy. The 'running' couplings under such tight constraints are presented in $^{1} S_{0}$ and uncoupled $P$ channels up to truncation order $O (Q^{4})$ . Some linear relations are exposed and in turn employed in the pursuit of nonperturbative 'running' solutions which serves as an alternative choice without resorting to special prescription and additional operations or treatments. The utility of such 'running' behaviors inherent in the closed-form $T$ -matrices of pionless effective field theory is remarked and a number of important issues related to effective field theory constructed with various truncations are interpreted or discussed from the underlying theory perspective.
nucl-thhep-phIJMPE(2021)·1 citation
03
Heavy-ion double-charge-exchange and its relation to neutrinoless double-beta decay
E. Santopinto🇮🇹 · H. García-Tecocoatzi🇮🇹 · R.I. Magaña-Vsevolodovna🇮🇹 · J. Ferretti🇨🇳
We introduce the formalism to describe heavy-ion Double-Charge-Exchange (DCE) processes in the eikonal approximation. We focus on the low-momentum-transfer limit -- corresponding to the differential cross section at $θ = 0^{\circ}$ -- and, for the first time, we show that it is possible to factorize the DCE cross-section in terms of reaction and nuclear parts. Whereas in the $θ \neq = 0^{\circ}$ case the nuclear part is a convolution of the beam and target nuclear matrix elements (NMEs), for $θ = 0^{\circ}$ we demonstrate - for the first time- that the transition matrix elements can be written as the sum of Double-Gamow-Teller (DGT) and Double Fermi (DF) type parts, and that they can both be further factorized in terms of target and projectile NMEs. By making use of the Interacting Boson Model (IBM) formalism, we also show that the DGT and total parts of the neutrinoless double-beta decay NMEs are in linear correlation with DCE-DGT NMEs. This confirms the hypothesis of a linear correlation between them, as introduced in [Phys.\ Rev.\ Lett.\ {\bf 120}, 142502 (2018)]. The possibility of a Two-Step Factorization (TSF) of the very forward differential DCE-cross-section and the emergence of DGT and DF types for the DCE nuclear matrix elements, combined with a linear correlation between DCE-DGT and 0 $ν β β$ NMEs, opens the possibility of placing an upper limit on neutrinoless double-beta decay NMEs in terms of the DCE experimental data at $θ = 0^{\circ}$ .
nucl-thPRC(2018)·78 citations
04
Ab initio calculation of nuclear structure corrections in muonic atoms
Chen Ji🇨🇳 · Sonia Bacca🇩🇪 · Nir Barnea🇮🇱 · Oscar Javier Hernandez🇩🇪 · Nir Nevo-Dinur🇨🇦
The measurement of the Lamb shift in muonic hydrogen and the subsequent emergence of the proton-radius puzzle have motivated an experimental campaign devoted to measuring the Lamb shift in other light muonic atoms, such as muonic deuterium and helium. For these systems it has been shown that two-photon exchange nuclear structure corrections are the largest source of uncertainty and consequently the bottleneck for exploiting the experimental precision to extract the nuclear charge radius. Utilizing techniques and methods developed to study electromagnetic reactions in light nuclei, recent calculations of nuclear structure corrections to the muonic Lamb shift have reached unprecedented precision, reducing the uncertainty with respect to previous estimates by a factor of 5 in certain cases. These results will be useful for shedding light on the nature of the proton-radius puzzle and other open questions pertaining to it. Here, we review and update calculations for muonic deuterium and tritium atoms, and for muonic helium-3 and helium-4 ions. We present a thorough derivation of the formalism and discuss the results in relation to other approaches where available. We also describe how to assess theoretical uncertainties, for which the language of chiral effective field theory furnishes a systematic approach that could be further exploited in the future.
nucl-thphysics.atom-phJ.Phys.G(2018)·51 citations
05
Comment on "Measurement of the $Q^{2}$ Dependence of the Deuteron Spin Structure Function $g_{1}$ and its Moments at Low $Q^{2}$ with CLAS"
Vadim Lensky🇩🇪 · Franziska Hagelstein🇨🇭 · Astrid Hiller Blin🇩🇪 · Vladimir Pascalutsa🇩🇪
We argue that the recently published CLAS results on the deuteron spin polarizability $γ_{0}$ [Adhikari {\it et al.}, Phys.\ Rev.\ Lett.\ {\bf 120}, 062501 (2018)], as well as their comparisons with chiral perturbation theory ( $χ$ PT), are misleading. In reality, the deuteron polarizability is larger by 4 orders of magnitude, as demonstrated here by a novel calculation in pionless EFT. The CLAS paper, on the other hand, presents only a tiny correction to it, based on a partial evaluation of a sum rule for $γ_{0}$ . The sum rule is assumed to have the same form as for the nucleon; we argue it does not. Moreover, their "test of $χ$ PT" tacitly involves assumptions which, as we demonstrate, may not be valid at the claimed accuracy.
nucl-thhep-phnucl-ex4 citations
06
Extended Skyrme interactions for transport model simulations of heavy-ion collisions
Rui Wang🇨🇳 · Lie-Wen Chen🇨🇳 · Ying Zhou🇨🇳
Based on an extended Skyrme interaction that includes the terms in relative momenta up to sixth order, corresponding to the so-called Skyrme pseudopotential up to next-to-next-to-next-to leading order (N3LO), we derive the expressions of Hamiltonian density and single nucleon potential under general non-equilibrium conditions which can be applied in transport model simulations of heavy-ion collisions induced by neutron-rich nuclei. While the conventional Skyrme interactions, which include the terms in relative momenta up to second order, predict an incorrect behavior as a function of energy for nucleon optical potential in nuclear matter, the present extended N3LO Skyrme interaction can give a nice description for the empirical nucleon optical potential. We also construct three interaction sets with different high-density behaviors of the symmetry energy, by fitting both the empirical nucleon optical potential up to energy of $1$ GeV and the empirical properties of isospin asymmetric nuclear matter. These extended N3LO Skyrme interactions will be useful in transport model simulations of heavy-ion collisions induced by neutron-rich nuclei at intermediate and high energies, and they can also be useful in nuclear structure studies within the mean-field model.
nucl-thastro-ph.SRhep-phnucl-exPRC(2018)·31 citations
07
Thermomagnetic properties and Bjorken expansion of hot QCD matter in a strong magnetic field
Shubhalaxmi Rath🇮🇳 · Binoy Krishna Patra🇮🇳
In this work we have studied the effects of an external strong magnetic field on the thermodynamic and magnetic properties of a hot QCD matter and then explored these effects on the subsequent hydrodynamic expansion of the said matter once produced in the ultrarelativistic heavy ion collisions. For that purpose, we have computed the quark and gluon self-energies up to one loop in the strong magnetic field, using the HTL approximation with two hard scales - temperature and magnetic field, which in turn compute the effective propagators for quarks and gluons, respectively. Hence the quark and gluon contributions to the free energy are obtained from the respective propagators and finally derive the equation of state (EOS) by calculating the pressure and energy density. We have found that the speed of sound is enhanced due to the presence of strong magnetic field and this effect will be later exploited in the hydrodynamics. Thereafter the magnetic properties are studied from the free energy of the matter, where the magnetization is found to increase linearly with the magnetic field, thus hints the paramagnetic behavior. The temperature dependence of the magnetization is also studied, where the magnetization is found to increase slowly with the temperature. Finally, to see how a strong magnetic field could affect the hydrodynamic evolution, we have revisited the Bjorken boost-invariant picture with our paramagnetic EOS as an input in the equation of motion for the energy-momentum conservation. We have noticed that the energy density evolves faster than in the absence of strong magnetic field, i.e. cooling becomes faster, which could have implications on the heavy-ion phenomenology. As mentioned earlier, this observation can be understood by the enhancement of the speed of sound.
↳ hep-thcond-mat.stat-mechhep-phnucl-thEPJA(2019)·26 citations
08
Factorization of the soft gluon divergence from the dipole picture deep inelastic scattering cross sections at next-to-leading order
B. Ducloué🇫🇷 · H. Hänninen🇫🇮 · T. Lappi🇫🇮 · Y. Zhu🇩🇪
We use a factorization scheme analogous to one proposed for single inclusive forward hadron production to factorize the soft gluon divergence present in the deep inelastic scattering cross sections in the dipole picture at next-to-leading order (NLO). We show numerically that in this carefully constructed scheme it is possible to obtain meaningful results for the DIS cross sections at NLO, and so we are able to quantitatively study the recently derived NLO corrections to the DIS cross sections. We find that the NLO corrections can be significant and sensitive to the details of the factorization scheme used for the resummation of the large logarithms into the BK evolution equation. In the case of an approximative factorization scheme we observe a problematic behavior of the DIS cross sections similar to what has been seen with analogously factorized single inclusive cross sections.
↳ hep-phnucl-thPoS(2018)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE