Nuclear Theory·nucl-th

Tuesday·October 8, 2019

16 papers—9 primary·7 cross-listed

01
Effects of nuclear symmetry energy and equation of state on neutron star properties
Fan Ji · Jinniu Hu · Shishao Bao · Hong Shen
We study the effects of nuclear symmetry energy on the mass-radius relation and tidal deformability of neutron stars, considering the self-consistency of the equation of state (EOS). We first construct a set of unified EOSs based on relativistic mean-field models with different density dependence of the symmetry energy. For the description of pasta phases appearing in the inner crust of neutron stars, we perform a self-consistent Thomas-Fermi calculation using the same nuclear interaction as that for the uniform matter in the core. To examine possible effects from the self-consistency of the EOS on neutron-star properties, we separately investigate the impacts of crust and core segments. By matching the same core EOS to different crust EOSs, it is found that neutron-star radii are significantly affected by the crust segment. On the other hand, the neutron-star radii are also strongly dependent on the core EOS. However, the correlation between the radius and the symmetry energy slope of the core EOS is opposite to that of the crust EOS. It is likely that the nuclear model with a small slope parameter is favored by recent astrophysical observations.
nucl-thastro-ph.HEastro-ph.SRPRC(2019)·39 citations
02
Diphoton elastic scattering in UPC at smaller $W_{γ γ}$
Antoni Szczurek🇵🇱
We present a study of photon-photon scattering for $W_{γ γ} < 5$ GeV. We extend earlier calculations of this cross section for $W_{γ γ} >$ 5 GeV into the low mass range where photoproduction of the pseudoscalar mesons $η$ (548), $η^{^{'}} (958)$ and other mesonic resonances contribute to the two-photon final states. We consider the dominant background of the two photon final state which arises from $γ γ$ decays of photoproduced $π^{0} π^{0}$ -pairs. We discuss how to reduce the background by imposing cuts on different kinematical variables. We present results for ALICE and LHCb kinematics.
nucl-thhep-phFrascati Phys.Ser.(2019)·0 citations
03
Structure of single- $Λ$ hypernuclei with chiral hyperon-nucleon potentials
Johann Haidenbauer🇩🇪 · Isaac Vidana🇮🇹
The structure of single- $Λ$ hypernuclei is studied using the chiral hyperon-nucleon potentials derived at leading order (LO) and next-to-leading order (NLO) by the Jülich--Bonn--Munich group. Results for the separation energies of $Λ$ single-particle states for various hypernuclei from $_{Λ}^{5}$ He to $_{Λ}^{209}$ Pb are presented for the LO interaction and the 2013 (NLO13) and 2019 (NLO19) versions of the NLO potentials. It is found that the results based on the LO potential show a clear tendency for overbinding while those for the NLO13 interaction underbind most of the considered hypernuclei. A qualitatively good agreement with the data is obtained for the NLO19 interaction over a fairly large range of mass number values when considering the uncertainty due to the regulator dependence. A small spin-orbit splitting of the $p$ -, $d$ -, $f$ -, and $g$ -wave states is predicted by all interactions, in line with the rather small values observed in pertinent experiments.
nucl-thEPJA(2020)·21 citations
04
Do charged pions condense in a magnetic field with rotation?
Hao-Lei Chen🇨🇳 · Xu-Guang Huang🇨🇳 · Kazuya Mameda🇨🇳
We revisit the condensation scenario of charged pions in external magnetic field and rotation, which was first considered by Y. Liu and I. Zahed. Based on the Ginzburg-Landau analysis of the Nambu--Jona-Lasinio model, we find that the charged-pion condensation takes place only when both a strong coupling constant and negatively large baryon chemical potential are applied. Besides, our numerical calculation shows that the chiral restoration induced by the interplay between magnetic field and rotation (i.e., the rotational magnetic inhibition) interrupts the formation of the charged-pion condensate. This suggests that the analysis of such condensation requires a careful treatment of the inner structure of pions, which was not taken into account before. We also discuss the underlying physical mechanism of our finding and the indication of charged-rho condensation.
nucl-thhep-phJHEP(2024)·41 citations
05
Rotation induced charged pion condensation in a strong magnetic field: A Nambu--Jona-Lasino model study
Gaoqing Cao🇨🇳 · Lianyi He🇨🇳
We investigate the possibility of charged pion condensation in the presence of parallel rotation and magnetic field within the Nambu--Jona-Lasinio model with quarks as the fundamental degrees of freedom. Previous study based on non-interacting Klein-Gordon theory for pions showed that the charged pions will undergo Bose-Einstein condensation under this circumstance [Y. Liu and I. Zahed, Phys. Rev. Lett. $120$ , 032001 (2018)]. In this work, we take into account the internal quark structures of charged pions self-consistently through quark polarization loops in an interacting theory, i.e., the Nambu--Jona-Lasino model. The stability of the system is explored against the formation of a nonzero expectation value of the composite charged pion field $u ˉ i γ_{5} d$ . We find that two competing effects are induced by the rotation: the isospin enhancement which favors charged pion condensation and the spin breaking which disfavors the condensation. For a strong magnetic field ( $e B \sim 1 GeV$ ) and system size of a few fermi, the isospin enhancement effect is stronger than the spin breaking one, and the charged pion condensation becomes energetically favored beyond a critical angular velocity of a few MeV.
nucl-thhep-phhep-thPRD(2019)·36 citations
06
Pion-induced production of $Λ (1520)$ hyperons on nuclei near threshold
E. Ya. Paryev🇷🇺 · Yu. T. Kiselev🇷🇺
We study the pion-induced inclusive $Λ (1520)$ hyperon production from nuclei near threshold within a nuclear spectral function approach accounting for incoherent primary $π^{-}$ meson--proton $π^{-} p \to K^{0} Λ (1520)$ production processes. We calculate the absolute differential and total cross sections for the production of $Λ (1520)$ hyperons off carbon and tungsten nuclei at laboratory angles of 0 $^{\circ}$ --10 $^{\circ}$ , 10 $^{\circ}$ --45 $^{\circ}$ and 45 $^{\circ}$ --85 $^{\circ}$ by $π^{-}$ mesons with momentum of 1.7 GeV/c as well as their relative (transparency ratio) differential and integral yields from these nuclei within four scenarios for their total in-medium width. We demonstrate that these absolute observables, contrary to the relative ones, reveal some sensitivity to the $Λ (1520)$ in-medium width. Therefore, their measurement in a dedicated experiment at the GSI pion beam facility will allow to shed light on this width.
nucl-thnucl-exNPA(2019)·3 citations
07
Possible lightest $Ξ$ Hypernucleus with Modern $Ξ N$ Interactions
E. Hiyama🇯🇵 · K. Sasaki🇯🇵 · T. Miyamoto🇯🇵 · T. Doi🇯🇵 · T. Hatsuda🇯🇵 · Y. Yamamoto🇯🇵 · Th. A. Rijken🇳🇱
Experimental evidence exists that the $Ξ$ -nucleus interaction is attractive. We search for $N N Ξ$ and $N N N Ξ$ bound systems on the basis of the AV8 $N N$ potential combined with either a phenomenological Nijmegen $Ξ N$ potential or a first principles HAL QCD $Ξ N$ potential. The binding energies of the three-body and four-body systems (below the $d + Ξ$ and $^{3} H$ / $^{3} He + Ξ$ thresholds, respectively) are calculated by a high precision variational approach, the Gaussian Expansion Method. Although the two $Ξ N$ potentials have significantly different isospin ( $T$ ) and spin ( $S$ ) dependence, the $N N N Ξ$ system with quantum numbers $(T = 0, J^{π} = 1^{+}$ ) appears to be bound (one deep for Nijmegen and one shallow for HAL QCD) below the $^{3} H$ / $^{3} He + Ξ$ threshold. Experimental implications for such a state are discussed.
nucl-thhep-lathep-phnucl-exPRL(2020)·61 citations
08
Complications in the interpretation of the charge asymmetry dependent $π$ flow for the chiral magnetic wave
Hao-jie Xu🇨🇳 · Jie Zhao🇺🇸 · Yicheng Feng🇺🇸 · Fuqiang Wang🇨🇳
The charge asymmetry ( $A_{ch}$ ) dependence of the $π^{-}$ and $π^{+}$ elliptic flow difference, $Δ v_{2} (A_{ch})$ , has been regarded as a sensitive observable for the possible chiral magnetic wave (CMW) in relativistic heavy ion collisions. In this work, we first demonstrate that, due to non-flow backgrounds, the flow measurements by the Q-cumulant method using all charged particles as reference introduce a trivial linear term to $Δ v_{2} (A_{ch})$ . The trivial slope can be negative in the triangle flow difference $Δ v_{3} (A_{ch})$ if the non-flow is dominated by back-to-back pairs. After eliminating the trivial term, we find that the non-flow between like-sign pairs gives rise to an additional positive slope to $Δ v_{2} (A_{ch})$ because of the larger dilution effect to $π^{+}$ ( $π^{-}$ ) at positive (negative) $A_{ch}$ . We further find that the competition between different $π$ sources can introduce another non-trivial linear- $A_{ch}$ term due to their different multiplicity fluctuations and anisotropic flows. We then study the effect of neutral cluster (resonance) decays as a mechanism for local charge conservation on the slope parameter of $Δ v_{2} (A_{ch})$ . We find that the slope parameter is sensitive to the kinematics of those neutral clusters. Light resonances give positive slopes while heavy resonances give negative slopes. Local charge conservation from continuum cluster mass distribution can give a positive slope parameter comparable to experimental data. Our studies indicate that many non-CMW physics mechanisms can give rise to a $A_{ch}$ -dependent $Δ v_{2} (A_{ch})$ and the interpretation of $Δ v_{2} (A_{ch})$ in terms of the CMW is delicate.
nucl-thnucl-exPRC(2020)·14 citations
09
Global sensitivity analysis of bulk properties of an atomic nucleus
Andreas Ekström🇸🇪 · Gaute Hagen
We perform a global sensitivity analysis of the binding energy and the charge radius of the nucleus $^{16}$ O to identify the most influential low-energy constants in the next-to-next-to-leading order chiral Hamiltonian with two- and three-nucleon forces. For this purpose we develop a subspace-projected coupled-cluster method using eigenvector continuation [Frame D. et al., Phys. Rev. Lett. 121, 032501 (2018)]. With this method we compute the binding energy and charge radius of $^{16}$ O at more than one million different values of the 16 low-energy constants in one hour on a standard laptop. For relatively small subspace projections, the root-mean-square error is about 1% compared to full space coupled-cluster results. We find that 58(1)% of the variance in the energy can be apportioned to a single contact-term in the $^{3} S_{1}$ -wave, whereas the radius depends sensitively on several low-energy constants and their higher-order correlations. The results identify the most important parameters for describing nuclear saturation, and help prioritize efforts for uncertainty reduction of theoretical predictions. The achieved acceleration opens up for an array of computational statistics analyses of the underlying description of the strong nuclear interaction in nuclei across the Segré chart.
nucl-thPRL(2019)·132 citations

Affiliations

first authorsco-authorsvia INSPIRE