Nuclear Theory·nucl-th

Wednesday·May 12, 2021

11 papers—4 primary·7 cross-listed

01
[Submitted on 10 May 2021]
Incoherent approximation for neutron up-scattering cross sections and its corrections for slow neutrons and low crystal temperatures
Stefan Döge🇩🇪 · Chen-Yu Liu🇺🇸 · Albert Young🇺🇸 · Christoph Morkel🇩🇪
The incoherent approximation (IA) is often used for calculating the one-phonon inelastic neutron scattering cross section for arbitrary solids. It is valid for thermal neutrons but for slow neutrons it requires a correction, which is significant for isotopes that are strong coherent scatterers. In this article, we present the extension of the Placzek--Van Hove corrections for slow neutrons in the limit of low temperatures using the example of solid \emph{ortho}-deuterium (sD $_{2}$ ). Our approach yields realistic one-phonon up-scattering cross sections for sD $_{2}$ and shows the IA to be a factor of 2 to 5 too high for ultracold neutron (UCN) up-scattering in sD $_{2}$ . Our calculations are compared with previously published Monte Carlo calculations of the one-phonon cross section based on the dynamic structure function $S (q, ω)$ of polycrystalline \emph{ortho}-deuterium and are found to be consistent with them. Furthermore, we provide the means for easily replicable calculations of the one-phonon up-scattering cross sections of solid \emph{ortho}-deuterium for slow neutrons. These should from now on be used in calculations and simulations of UCN scattering in sD $_{2}$ .
Comments:
6 pages, 1 figure, 1 table
Subjects:
Nuclear Theory (nucl-th); cond-mat.other (cond-mat.other)
arXiv:
2105.04624 [pdf]
PRC(2021)·4 citations
02
[Submitted on 10 May 2021]
Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817
Bao-An Li🇺🇸 · Bao-Jun Cai🇨🇳 · Wen-Jie Xie🇨🇳 · Nai-Bo Zhang🇨🇳
New observational data of neutron stars since GW170817 have helped improve our knowledge about nuclear symmetry energy especially at high densities. We have learned particularly: (1) The slope parameter $L$ of nuclear symmetry energy at saturation density $ρ_{0}$ of nuclear matter from 24 new analyses is about $L \approx 57.7 \pm 19$ MeV at 68\% confidence level consistent with its fiducial value, (2) The curvature $K_{sym}$ from 16 new analyses is about $K_{sym} \approx - 107 \pm 88$ MeV, (3) The magnitude of nuclear symmetry energy at $2 ρ_{0}$ , i.e. $E_{sym} (2 ρ_{0}) \approx 51 \pm 13$ MeV at 68\% confidence level, has been extracted from 9 new analyses of neutron star observables consistent with results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories, (4) while the available data from canonical neutron stars do not provide tight constraints on nuclear symmetry energy at densities above about $2 ρ_{0}$ , the lower radius boundary $R_{2.01} = 12.2$ km from NICER's very recent observation of PSR J0740+6620 of mass $2.08 \pm 0.07$ $M_{⊙}$ and radius $R = 12.2 - 16.3$ km at 68\% confidence level sets a tight lower limit for nuclear symmetry energy at densities above $2 ρ_{0}$ , (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars indicate that the phase transition shift appreciably both the $L$ and $K_{sym}$ to higher values but with larger uncertaintie , (6) The high-density behavior of nuclear symmetry energy affects significantly the minimum frequency necessary to rotationally support GW190814's secondary component of mass (2.50-2.67) $M_{⊙}$ as the fastest and most massive pulsar discovered so far.
Comments:
Published version with added discussions and references
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2105.04629 [pdf]
Universe(2021)·229 citations
03
[Submitted on 11 May 2021]
Model investigations of the correlation between the mean transverse momentum and anisotropic flow in shape-engineered events
Niseem Magdy🇺🇸 · Roy A. Lacey🇺🇸
The correlation between the event mean-transverse momentum $[p_{T}]$ , and the anisotropic flow magnitude $v_{n}$ , $ρ (v_{n}^{2}, [p_{T}])$ , has been argued to be sensitive to the initial conditions in heavy-ion collisions. We use simulated events generated with the AMPT and EPOS models for Au+Au at $s_{N N}$ = 200 GeV, to investigate the model dependence and the response and sensitivity of the $ρ (v_{2}^{2}, [p_{T}])$ correlator to collision-system size and shape, and the viscosity of the matter produced in the collisions. We find good qualitative agreement between the correlators for the string melting version of the AMPT model and the EPOS model. The model investigations for shape-engineered events as well as events with different viscosity ( $η / s$ ), indicate that $ρ (v_{2}^{2}, [p_{T}])$ is sensitive to the initial-state geometry of the collision system but is insensitive to sizable changes in $η / s$ for the medium produced in the collisions. These findings suggest that precise differential measurements of $ρ (v_{2}^{2}, [p_{T}])$ as a function of system size, shape, and beam-energy could provide more stringent constraints to discern between initial-state models and hence, more reliable extractions of $η / s$ .
Comments:
8 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2105.04879 [pdf]
PLB(2021)·12 citations
04
[Submitted on 11 May 2021]
Pauli energy contribution to nucleus-nucleus interaction
A.S. Umar🇺🇸 · C. Simenel🇦🇺 · K. Godbey🇺🇸
Background: The Pauli exclusion principle plays a crucial role as a building block of many-body quantal systems comprised of fermions. It also induces a "Pauli repulsion" in the interaction between di-nuclear systems. It has been shown in [Phys. Rev. C 95, 031601 (2017)] that the Pauli repulsion widens the nucleus-nucleus potential barrier, thus hindering sub-barrier fusion. Purpose: To investigate the proton and neutron contributions to the Pauli repulsion, both in the bare potential neglecting shape polarization and transfer between the reactants, as well as in the dynamical potential obtained by accounting for such dynamical rearrangements. Methods: As the basis of our study we utilize the Pauli kinetic energy (PKE) obtained by studying the nuclear localization function (NLF). Recently this approach has been generalized to incorporate all of the dynamical and time-odd terms present in the nuclear energy density functional. This approach is employed in the DCFHF and DC-TDHF methods. Results: The PKE spatial distribution shows that a repulsion occurs in the neck between the nuclei when they first touch. Inside the barrier, neutrons can contribute significantly more to the Pauli repulsion in neutron-rich systems. Dynamical effects tend to lower the Pauli repulsion near the barrier. Proton and neutron dynamical contributions to the PKE significantly differ inside the barrier for asymmetric collisions, which is interpreted as an effect of multinucleon transfer. Conclusions: The PKE is shown to make a significant contribution to nuclear interaction potentials. Protons and neutrons can play very different roles in both the bare potential and in the dynamical rearrangement. Further microscopic studies are required to better understand the role of transfer and to investigate the effect of pairing and deformation.
Comments:
11 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.05245 [pdf]
PRC(2021)·21 citations
05
[Submitted on 7 May 2021] (cross-list from cond-mat.quant-gas)
The van der Waals interaction as the starting point for an effective field theory
Daniel Odell🇺🇸 · Arnoldas Deltuva🇱🇹 · Lucas Platter🇺🇸
We consider the system of three $^{4}$ He atoms to assess whether a pure van der Waals potential can be used as a starting point for an effective field theory to describe three-body processes in ultracold atomic systems. Using a long-range van der Waals interaction in combination with short-distance two-body counterterms, we analyze the dependence of two- and three-body observables on the short-distance regulator that is required due to the singular nature of the van der Waals interaction. We benchmark our approach with results obtained with the realistic $^{4}$ He- $^{4}$ He LM2M2 interaction and find good agreement. We furthermore show that in this effective field theory approach no three-body force is required at leading order and that universal van der Waals physics leads to a universal correlation between three-body observables in the absence of an Efimov three-body parameter.
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2105.03442 [pdf]
PRA(2021)·7 citations
06
[Submitted on 10 May 2021] (cross-list from hep-ph)
Improved Standard-Model prediction for $π^{0} \to e^{+} e^{-}$
Martin Hoferichter🇨🇭 · Bai-Long Hoid🇨🇭 · Bastian Kubis🇩🇪 · Jan Lüdtke🇩🇪
We present an improved Standard-Model (SM) prediction for the dilepton decay of the neutral pion. The loop amplitude is determined by the pion transition form factor for $π^{0} \to γ^{*} γ^{*}$ , for which we employ a dispersive representation that incorporates both space-like and time-like data as well as short-distance constraints. The resulting SM branching fraction, $BR [π^{0} \to e^{+} e^{-}] = 6.25 (3) \times 1 0^{- 8}$ , sharpens constraints on physics beyond the SM, including pseudoscalar and axial-vector mediators.
Comments:
9 pages, 3 figures; journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2105.04563 [pdf]
PRL(2022)·41 citations
07
[Submitted on 10 May 2021] (cross-list from hep-ph)
European Spallation Source: a future for Coherent Neutrino Nucleus Scattering
Ivan Esteban🇺🇸
The European Spallation Source (ESS), currently finishing its construction, will soon provide the most intense neutron beams for multi-disciplinary science. At the same time, it will also produce a high-intensity neutrino flux with an energy suitable for precision measurements of Coherent Elastic Neutrino-Nucleus Scattering. We describe some physics prospects, within and beyond the Standard Model, of employing innovative detector technologies to take the most out of this large flux. We show that, compared to current measurements, the ESS will provide a much more precise understanding of neutrino and nuclear properties.
Comments:
Contribution to the 2021 EW session of the 55th Rencontres de Moriond
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2105.04669 [pdf]
3 citations
08
[Submitted on 11 May 2021] (cross-list from hep-ph)
Model independent analysis of coupled-channel scattering: a deep learning approach
Denny Lane B. Sombillo🇵🇭 · Yoichi Ikeda🇯🇵 · Toru Sato🇯🇵 · Atsushi Hosaka🇯🇵
We develop a robust method to extract the pole configuration of a given partial-wave amplitude. In our approach, a deep neural network is constructed where the statistical errors of the experimental data are taken into account. The teaching dataset is constructed using a generic S-matrix parametrization, ensuring that all the poles produced are independent of each other. The inclusion of statistical error results into a noisy classification dataset which we should solve using the curriculum method. As an application, we use the elastic $π N$ amplitude in the $I (J^{P}) = 1/2 (1/ 2^{-})$ sector where $1 0^{6}$ amplitudes are produced by combining points in each error bar of the experimental data. We fed the amplitudes to the trained deep neural network and find that the enhancements in the $π N$ amplitude are caused by one pole in each nearby unphysical sheet and at most two poles in the distant sheet. Finally, we show that the extracted pole configurations are independent of the way points in each error bar are drawn and combined, demonstrating the statistical robustness of our method.
Comments:
11 pages, 6 figures, 5 tables, companion paper to arXiv:2104.14182
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2105.04898 [pdf]
PRD(2021)·28 citations
09
[Submitted on 11 May 2021] (cross-list from hep-ph)
Influence of chiral asymmetry on phase structure of the two-color quark matter
T. G. Khunjua🇬🇪 · K. G. Klimenko🇷🇺 · R. N. Zhokhov🇷🇺
In this paper the influence of chiral chemical potential $μ_{5}$ on the phenomenon of diquark condensation and phase structure of dense quark matter altogether is contemplated in the framework of effective two-color and two-flavor Nambu--Jona-Lasinio model. We show that the duality relations, found $μ_{5} = 0$ , are also valid for any value of $μ_{5} \neq = 0$ . Hence the dualities seem to be a real fundamental feature of the phase diagram of two color quark matter, and besides they are a very powerful tool of studying the phase structure. In terms of dualities and the influence on the phase diagram chiral imbalance $μ_{5}$ stands alone from other chemical potentials. Two regimes in the phase diagram could be discerned, the first one, rather small or moderate values of chemical potentials $μ_{B}$ , $μ_{I}$ and $μ_{I 5}$ , where the picture is rather concise and elegant: each of the above phenomena is in one-to-one correspondence with some chemical potential ( $μ_{I 5}$ induces chiral symmetry breaking, $μ_{I}$ propels charged pion condensation and $μ_{B}$ leads to diquark condensation). In this regime chiral chemical potential $μ_{5}$ does not break this correspondence, it has a property of being universal catalyzer, i.e. it {\it catalyzes/enhances} all the phenomena on equal footing. The feature of chiral imbalance $μ_{5}$ to catalyze chiral symmetry breaking phenomenon was known before but its catalytic properties appeared to be more universal and it can catalyze also diquark and charged pion condensation. These happen due to the dual properties. In the second regime, when several chemical potentials reach rather large values, one could observe a rather complicated and rich phase structure, and $μ_{5}$ can be a factor that not so much catalyzes as {\it triggers} rather peculiar phases. For example, it can lead to the formation of diquark condensation at zero baryon chemical potential.
Comments:
typos corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2105.04952 [pdf]
PRD(2022)·22 citations
10
[Submitted on 11 May 2021] (cross-list from astro-ph.HE)
Multimessenger constraints for ultra-dense matter
Eemeli Annala🇫🇮 · Tyler Gorda🇩🇪 · Evangelia Katerini🇬🇷 · Aleksi Kurkela🇳🇴 · Joonas Nättilä🇺🇸 · Vasileios Paschalidis🇺🇸 · Aleksi Vuorinen🇫🇮
Recent rapid progress in neutron-star (NS) observations offers great potential to constrain the properties of strongly interacting matter under the most extreme conditions. In order to fully exploit the current observational inputs and to study the impact of future observations of NS masses, radii, and tidal deformabilities, we analyze a large ensemble of randomly generated viable NS-matter equations of state (EoSs) and the corresponding rotating stellar structures. We discuss the compatibility and impact of various hypotheses and measurements on the EoS, including those involving the merger product of the gravitational-wave (GW) event GW170817, the binary merger components in GW190814, and radius measurements of the pulsar PSR J0740+6620. We obtain an upper limit for the dimensionless spin of a rigidly rotating NS, $∣ χ ∣ < 0.81$ , an upper limit for the compactness of a NS, $GM / (R c^{2}) < 0.33$ , and find that the conservative hypothesis that the remnant in GW170817 ultimately collapsed to a black hole strongly constrains the EoS and the maximal mass of NSs, implying $M_{TOV} < 2.53 M_{⊙}$ (or $M_{TOV} < 2.19 M_{⊙}$ if we assume that a hypermassive NS was created). Additionally, we derive a novel lower limit for the tidal deformability as a function of NS mass and provide fitting formulae that can be used to set priors for parameter estimation and to discern whether neutron stars or other compact objects are involved in future low-mass GW events. Finally, we find that the recent NICER results for the radius of the massive NS PSR J0740+6620 place strong constraints for the behavior of the EoS, and that the indicated radius values $R (2 M_{⊙}) ≳ 11$ km are compatible with moderate speeds of sound in NS matter and thus with the existence of quark matter cores in massive NSs.
Comments:
25 pages, 2 appendices, 15 figures, 1 table. Differences from v2: Central energy densities added to all ep figures; additional figures added; additional fitting formulas added; additional references added; additional discussions added; baryon masses added to table; appendix on EOS construction added. Version published in PRX
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2105.05132 [pdf]
PRX(2022)·199 citations
11
[Submitted on 11 May 2021] (cross-list from astro-ph.HE)
r-Process Radioisotopes from Near-Earth Supernovae and Kilonovae
Xilu Wang · Adam M. Clark · John Ellis · Adrienne F. Ertel · Brian D. Fields · Zhenghai Liu · Jesse A. Miller · Rebecca Surman
The astrophysical sites where r-process elements are synthesized remain mysterious: it is clear that neutron star mergers (kilonovae (KNe)) contribute, and some classes of core-collapse supernovae (SNe) are also likely sources of at least the lighter r-process species. The discovery of 60Fe on the Earth and Moon implies that one or more astrophysical explosions have occurred near the Earth within the last few million years, probably SNe. Intriguingly, 244Pu has now been detected, mostly overlapping with 60Fe pulse. However, the 244Pu flux may extend to before 12 Myr ago, pointing to a different origin. Motivated by these observations and difficulties for r-process nucleosynthesis in SN models, we propose that ejecta from a KN enriched the giant molecular cloud that gave rise to the Local Bubble, where the Sun resides. Accelerator mass spectrometry (AMS) measurements of 244Pu and searches for other live isotopes could probe the origins of the r-process and the history of the solar neighborhood, including triggers for mass extinctions, e.g., that at the end of the Devonian epoch, motivating the calculations of the abundances of live r-process radioisotopes produced in SNe and KNe that we present here. Given the presence of 244Pu, other r-process species such as 93Zr, 107Pd, 129I, 135Cs, 182Hf, 236U, 237Np and 247Cm should be present. Their abundances and well-resolved time histories could distinguish between the SN and KN scenarios, and we discuss prospects for their detection in deep-ocean deposits and the lunar regolith. We show that AMS 129I measurements in Fe-Mn crusts already constrain a possible nearby KN scenario.
Comments:
45 pages, 14 figures, 11 tables, v2 matches version to appear in ApJ
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); physics.geo-ph (physics.geo-ph)
arXiv:
2105.05178 [pdf]
ApJ(2021)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE