Nuclear Theory·nucl-th

Tuesday·October 8, 2019

16 papers—9 primary·7 cross-listed

01
[Submitted on 5 Oct 2019]
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.
Comments:
13 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1910.02266 [pdf]
PRC(2019)·39 citations
02
[Submitted on 7 Oct 2019]
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.
Comments:
5 pages, 6 figures, 1 table, a talk presented at PHOTON2019, Frascati, Italy, June 3-7, 2019
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1910.02690 [pdf]
Frascati Phys.Ser.(2019)·0 citations
03
[Submitted on 7 Oct 2019]
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.
Comments:
9 pages, 3 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.02695 [pdf]
EPJA(2020)·21 citations
04
[Submitted on 7 Oct 2019]
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.
Comments:
V3: 10 pages, 4 figures. Published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1910.02700 [pdf]
JHEP(2024)·41 citations
05
[Submitted on 7 Oct 2019]
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.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
1910.02728 [pdf]
PRD(2019)·36 citations
06
[Submitted on 7 Oct 2019]
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.
Comments:
14 pages
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1910.02755 [pdf]
NPA(2019)·3 citations
07
[Submitted on 7 Oct 2019]
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.
Comments:
5 pages, 5 figures, preprint
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1910.02864 [pdf]
PRL(2020)·61 citations
08
[Submitted on 7 Oct 2019]
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.
Comments:
9 pages and 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1910.02896 [pdf]
PRC(2020)·14 citations
09
[Submitted on 7 Oct 2019]
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.
Comments:
6 pages, 3 figures, Supplemental Material provided as ancillary material
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.02922 [pdf]
PRL(2019)·132 citations
10
[Submitted on 21 May 2019] (cross-list from hep-ph)
Flavor-changing hyperon decays with light invisible bosons
Gang Li🇹🇼 · Jhih-Ying Su🇹🇼 · Jusak Tandean🇹🇼
We consider the strangeness-changing decays of hyperons into another baryon and missing energy which is carried away by a pair of invisible spinless bosons. Pursuing a model-independent approach and taking into account constraints from the kaon sector, we find that these hyperon modes can have large rates, especially if the bosons have parity-odd effective couplings to light quarks. In that case the rates could attain values which are well within the expected reach of the currently running BESIII experiment. Since the branching fractions of hyperon decays with missing energy are tiny in the standard model, observing them at ongoing or upcoming facilities would likely be indicative of new physics. In addition, we show that the kaon restrictions may be weakened or absent if the bosons have nonnegligible mass. Specifically, if the bosons interact with the quarks solely via an axial-vector current, in the mass region from about 115 to 175 MeV the constraints from rare kaon decays no longer apply and a couple of the hyperon modes become the only direct probes of such interactions. We also make comparisons with the previously explored new-physics scenario where the invisible particles are spin-1/2 fermions.
Comments:
15 pages, 3 figures, slightly modified, matches journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1905.08759 [pdf]
PRD(2019)·12 citations
11
[Submitted on 3 Oct 2019] (cross-list from hep-ph)
Chiral instabilities & the onset of chiral turbulence in QED plasmas
Mark Mace🇫🇮 · Niklas Mueller🇺🇸 · Sören Schlichting🇩🇪 · Sayantan Sharma🇮🇳
We present a first principles study of chiral plasma instabilities and the onset of chiral turbulence in QED plasmas far from equilibrium. By performing classical-statistical lattice simulations of the microscopic theory, we show that the generation of strong helical magnetic fields from a helicity imbalance in the fermion sector proceeds via three distinct phases. During the initial linear instability regime the helicity imbalance of the fermion sector causes an exponential growth(damping) of magnetic field modes with right(left) handed polarization, for which we extract the characteristic growth (damping) rates. Secondary growth of unstable modes accelerates the helicity transfer from fermions to gauge fields and ultimately leads to the emergence of a self-similar scaling regime characteristic of decaying turbulence, where magnetic helicity is efficiently transferred to macroscopic length scales. Within this turbulent regime the evolution of magnetic helicity spectrum can be described by an infrared power-spectrum with spectral exponent $κ$ and dynamical scaling exponents $α, β$ , which we determine from our simulations.
Comments:
published in Physical Review Letters, 13 pages, 9 figures (incl. supplemental material). Details of lattice implementation and numerical analysis strategy significantly expanded
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1910.01654 [pdf]
PRL(2020)·45 citations
12
[Submitted on 4 Oct 2019] (cross-list from hep-ph)
Transition Distribution Amplitudes : from JLab to EIC
L. Szymanowski🇵🇱 · B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇷🇺
Baryon-to-meson Transition Distribution Amplitudes extend both the concepts of generalized parton distributions and baryon distribution amplitudes encoding valuable complementary information on the 3-dimensional hadronic structure. The recent analysis of backward meson electroproduction at JLab supports the hope to perform femto-photography of hadrons from a brand new perspective.and in particular opens a new domain for EIC experiments.
Comments:
4 pages, 3 figures, proccedings of the INT program 18-3 : Probing Nucleons and Nuclei in High Energy Collisions, to be published by World Scientific
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1910.01979 [pdf]
2 citations
13
[Submitted on 4 Oct 2019] (cross-list from hep-ph)
Improved opacity expansion for medium-induced parton splitting
Yacine Mehtar-Tani🇺🇸 · Konrad Tywoniuk🇳🇴
We present a new expansion scheme to compute the rate for parton splittings in dense and finite QCD media. In contrast to the standard opacity expansion, our expansion is performed around the harmonic oscillator whose characteristic frequency depends on the typical transverse momentum scale generated in the splitting. The first two orders account for the high frequency regime that is dominated by single hard scatterings together with the regime of multiple soft scatterings at low frequency. This work generalizes the findings of Ref. \cite{Mehtar-Tani:2019tvy} beyond the leading logarithmic approximation allowing to account also for the Bethe-Heitler regime and compare to the full numerical results from Ref. \cite{CaronHuot:2010bp}. We investigate the sensitivity of our results to varying the separation scale that defines the leading order. Finally, the application to Monte Carlo event generators is discussed.
Comments:
16 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1910.02032 [pdf]
JHEP(2020)·70 citations
14
[Submitted on 5 Oct 2019] (cross-list from cond-mat.stat-mech)
The Concealed Voter Model is in the Voter Model universality class
Rosalba Garcia-Millan
The Concealed Voter Model (CVM) is an extension of the original Voter Model, where two different opinions compete until consensus is reached. In the CVM, agents express an opinion not only publicly, they also hold a private opinion, which they may disclose or change. In this paper I derive the critical exponents of both models via renormalised field theory and show that both belong to the compact directed percolation universality class.
Comments:
9 pages, 2 figures
Subjects:
Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
1910.02315 [pdf]
J.Stat.Mech.(2020)·2 citations
15
[Submitted on 6 Oct 2019] (cross-list from hep-th)
Bridging the Chiral symmetry and Confinement with Singularity
Yoon-Seok Choun🇰🇷 · Sang-Jin Sin🇰🇷
We consider a holographic quark model where the confinement is a consequence of the quark condensate. Surprisingly, the equation of motion of our holographic model can be mapped to the old spin-less bag model. Both models correctly reproduce the linear Regge trajectory of hadrons for zero quark mass. For the case of non-zero quark mass, the model lead us to Heun's equation. The mass term is precisely the origin of the higher singularity, which changes the system behavior drastically. Our result can shed some light on why the chiral transition is so close to the confinement transition. In the massive case, the Schroedinger equation is exactly solvable, but only if a surprising new quantization condition, additional to the energy quantization, is applied.
Comments:
Accepted by Physics Letters B
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1910.02383 [pdf]
PLB(2020)·4 citations
16
[Submitted on 7 Oct 2019] (cross-list from hep-ph)
On the shape of the $d ˉ - u ˉ$ asymmetry
A. Accardi · C.E. Keppel · S. Li · W. Melnitchouk · J.F. Owens
Using data from a recent reanalysis of neutron structure functions extracted from inclusive proton and deuteron deep-inelastic scattering (DIS), we re-examine the constraints on the shape of the $d ˉ - u ˉ$ asymmetry in the proton at large parton momentum fractions $x$ . A global analysis of the proton-neutron structure function difference from BCDMS, NMC, SLAC and Jefferson Lab DIS measurements, and of Fermilab Drell-Yan lepton-pair production cross sections, suggests that existing data can be well described with $d ˉ > u ˉ$ for all values of $x$ currently accessible. We compare the shape of the fitted $d ˉ - u ˉ$ distributions with expectations from nonperturbative models based on chiral symmetry breaking, which can be tested by upcoming Drell-Yan data from the SeaQuest experiment at larger values of $x$ .
Comments:
17 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1910.02931 [pdf]
PLB(2020)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE