Nuclear Theory·nucl-th

Friday·April 14, 2023

10 papers—6 primary·4 cross-listed

01
Four-Body Systems at Large Cutoffs in Effective Field Theory
Xincheng Lin
Four-body systems are studied using an effective field theory with two- and three-body contact interactions. A method to systematically address deep trimers (three-body bound states that are more tightly bound than four-body bound/resonant states) in four-body calculations is developed using a diagrammatic approach. Previous calculations were limited by the existence of deep trimers, which this work overcomes. For cold $^{4}$ He atoms, binding energies of 526.1(5)~mK and 128.517(1)~mK are obtained at leading order for the tetramer ground and excited states, respectively, where errors come from the truncation of three-body partial waves. Tetramer binding energies and decay widths are also computed approaching the unitary limit. In the unitary limit, there are two tetramers associated with each trimer of binding energy $B_{3}^{(0)}$ . The binding energy and decay width for the associated tetramer ground state are $E_{4}^{(0)} = 4.60 (1) B_{3}^{(0)}$ and $Γ_{4}^{(0)} /2 = 0.0160 (1) B_{3}^{(0)}$ , respectively, and for the associated tetramer excited state, $E_{4}^{(1)} = 1.0022 (3) B_{3}^{(0)}$ and $Γ_{4}^{(1)} /2 = 2.57 (2) \times 1 0^{- 4} B_{3}^{(0)}$ , respectively. This calculation is a gateway to higher-order and/or more-body calculations in nuclear and atomic systems.
nucl-thPRC(2024)·3 citations
02
A generalized hydrodynamizing initial stage for Heavy Ion Collisions
Govert Nijs🇺🇸 · Wilke van der Schee🇨🇭
We present an extended Bayesian analysis using Trajectum where the initial condition can now include binary scaling. For the far-from-equilibrium evolution before hydrodynamics we introduce an interpolation between free streaming and a holographically inspired evolution that exhibits fast hydrodynamization. We find strong evidence that binary scaling is incompatible with experimental data and find evidence that the holographic far-from-equilibrium evolution is preferred. We end with a discussion on several changes and improvements in the Bayesian framework.
nucl-thhep-phnucl-ex30 citations
03
Enlarged deformation region in neutron-rich Zr isotopes by the second intruder orbit
W. Horiuchi · T. Inakura · S. Michimasa · M. Tanaka
Nuclear deformations and density profiles of neutron-rich even-even Zr isotopes are investigated using the Skyrme-Hartree-Fock-Bogoliubov method. Large quadrupole and hexadecapole deformations are predicted along with large enhancement of the total reaction cross sections at the neutron number $N = 60$ -74. Strong nuclear deformation starting at $N = 60$ is induced by the occupation of the intruder orbit with the asymptotic quantum number $[n n_{z} Λ] Ω$ = [550]1/2 originating from the spherical $0 h_{11/2}$ orbit. The deformation region is further enlarged from $N = 72$ to 74 owing to the occupation of the next intruder orbit with [530]1/2 originating from the spherical $1 f_{7/2}$ orbit. This characteristic nuclear deformation is crucially reflected in the systematic behavior of the nuclear radii and the density profiles near the nuclear surface.
nucl-thPRC(2023)·6 citations
04
Faddeev Calculation of $_{Λ}^{3}$ H incorporating 2{\pi}-exchange $Λ$ NN Interaction
H. Kamada🇯🇵 · M. Kohno🇯🇵 · K. Miyagawa🇯🇵
Faddeev calculations of hypertriton ( $_{Λ}^{3}$ H) separation energy are performed, incorporating $2 π$ -exchange $Λ$ NN three-baryon force. Repulsive contributions of the three-baryon force in the order of 20 keV are found, depending on the NN interactions employed. The effect is not negligible compared with the small separation-energy of $_{Λ}^{3}$ H.
nucl-thnucl-exPRC(2023)·9 citations
05
Least action description of dynamic pairing correlations in the fission of Curium and Californium isotopes based on the Gogny energy density functional
R. Rodriguez-Guzman · L.M. Robledo · C.A. Jimenez-Hoyos · N. C. Hernandez
The impact of dynamic pairing correlations and their interplay with Coulomb antipairing effects on the systematic of the spontaneous fission half-lives for the nuclei $^{240 - 250}$ Cm and $^{240 - 250}$ Cf is analyzed, using a hierarchy of approximations based on the parametrization D1M of the Gogny energy density functional (EDF). First, the constrained Hartree-Fock-Bogoliubov (HFB) approximation is used to compute deformed mean-field configurations, zero-point quantum corrections and collective inertias either by using the Slater approximation to Coulomb exchange and neglecting Coulomb antipairing or by fully considering the exchange and pairing channels of the Coulomb interaction. Next, the properties of the {\it{least action}} and {\it{least energy}} fission paths are compared. In the {\it{least action}} case, pairing is identified as the relevant degree of freedom in order to minimize the action entering the Wentzel-Kramers-Brillouin (WKB) approximation to the tunneling probability through the fission barrier. Irrespective of the treatment of Coulomb exchange and antipairing, it is shown that the {\it{least action}} path obtained taking into account the pairing degree of freedom leads to stronger pairing correlations that significantly reduce the spontaneous fission half-lives $t_{S F}$ improving thereby the comparison with the experiment by several orders of magnitude. It is also shown that the Coulomb antipairing effect is, to a large extent, washed out by the {\it{least action}} procedure and therefore the $t_{S F}$ values obtained by the two different treatments of the Coulomb exchange and pairing are of similar quality.
nucl-thPRC(2023)·8 citations
06
Hyperspherical cluster model for bosons: application to sub-threshold halo states in helium drops
N.K. Timofeyuk
To describe long-range behaviour of one particle removed from a few- or a many-body system, a hyperspherical cluster model has been developed. It has been applied to the ground and first excited states of helium drops with five, six, eight and ten atoms interacting via a two-body soft gaussian potential. Convergence of the hyperspherical cluster harmonics expansion is studied for binding energies, root-mean-squared radii and overlaps of the wave functions of two helium drops differing by one atom. It was shown that with increasing model space the functional form of such overlaps at large distances converges to the correct asymptotic behaviour. The asymptotic normalization coefficients that quantify the overlaps' amplitudes in this region are calculated. It was also shown that in the first excited state one helium atom stays far apart from the rest forming a two-body molecule, or a halo. The probability of finding the halo atom in the classically-forbidden region of space depends on the definition of the latter and on the number of atoms in the drop. The total norm of the overlap integrals, the spectroscopic factor, represents the number of partitions of a many-body state into a chosen state of the system with one particle removed. The spectroscopic factors have been calculated and their sum rules are discussed giving a further insight into the structure of helium drops.
nucl-thcond-mat.quant-gasphysics.atm-clusphysics.atom-ph+1Few Body Syst.(2023)·1 citation
07
Analytic Solution for the Revised Helicity Evolution at Small $x$ and Large $N_{c}$ : New Resummed Gluon-Gluon Polarized Anomalous Dimension and Intercept
Jeremy Borden🇺🇸 · Yuri V. Kovchegov🇺🇸
We construct an exact analytic solution of the revised small- $x$ helicity evolution equations derived recently. The equations we solve are obtained in the large- $N_{c}$ limit (with $N_{c}$ the number of quark colors) and are double-logarithmic (summing powers of $α_{s} ln^{2} (1/ x)$ with $α_{s}$ the strong coupling constant and $x$ the Bjorken $x$ variable). Our solution provides small- $x$ , large- $N_{c}$ expressions for the flavor-singlet quark and gluon helicity parton distribution functions (PDFs) and for the $g_{1}$ structure function, with their leading small- $x$ asymptotics given by \begin{align} \Delta \Sigma (x, Q^2) \sim \Delta G (x, Q^2) \sim g_1 (x, Q^2) \sim \left( \frac{1}{x} \right)^{\alpha_h} , \notag \end{align} where the exact analytic expression we obtain for the intercept $α_{h}$ can be approximated by $α_{h} = 3.66074 \frac{α _{s} N _{c}}{2 π}$ . Our solution also yields an all-order (in $α_{s}$ ) resummed small- $x$ anomalous dimension $Δ γ_{GG} (ω)$ which agrees with all the existing fixed-order calculations (to three loops). Notably, our anomalous dimension is different from that obtained in the infrared evolution equation framework developed earlier by Bartels, Ermolaev, and Ryskin (BER), with the disagreement starting at four loops. Despite the previously reported agreement at two decimal points based on the numerical solution of the same equations, the intercept of our large- $N_{c}$ helicity evolution and that of BER disagree beyond that precision, with the BER intercept at large $N_{c}$ given by a different analytic expression from ours with the numerical value of $α_{h}^{B E R} = 3.66394 \frac{α _{s} N _{c}}{2 π}$ . We speculate on the origin of this disagreement.
↳ hep-phnucl-thPRD(2023)·41 citations
08
Bayesian inference of the path-length dependence of jet energy loss
Jordan Wu🇺🇸 · Weiyao Ke🇺🇸 · Xin-Nian Wang🇺🇸
A simple model for medium modification of the jet function can be used to extract the jet energy loss distribution through a parameterized form. We carry out a comprehensive Bayesian analysis of the world data on single inclusive jet spectra in heavy-ion collisions at both RHIC and LHC energies. We extract the average jet energy loss $⟨ Δ E ⟩$ as a function of jet transverse momentum $p_{T}$ for each collision system and centrality independently. Assuming jet energy loss is proportional to the initial parton density $ρ \sim d N_{ch} / d η / π R_{eff}^{2}$ as estimated from the pseudorapidity density of charged hadron multiplicity $d N_{ch} / d η$ and the effective system size $R_{eff} \sim N_{part}^{1/3}$ given by the number of participant nucleons $N_{part}$ , the scaled average jet energy loss $⟨ Δ E ⟩ / ρ \sim R_{eff}^{0.59} p_{T}^{0.13} ln p_{T}$ for jet cone-size $R = 0.4$ is found to have a momentum dependence that is slightly stronger than a logarithmic form while the system size or length dependence is slower than a linear one. The fluctuation of jet energy loss is, however, independent of the initial parton density or the system size.
↳ hep-phnucl-thPRC(2023)·17 citations
09
Kinematical higher-twist corrections in $γ^{*} \to M_{1} M_{2} γ$ : Neutral meson production
Bernard Pire🇫🇷 · Qin-Tao Song🇨🇳
We carry out the calculation of kinematical higher-twist corrections to the cross section of $γ^{*} \to M_{1} M_{2} γ$ up to twist 4, where $M_{i}$ is a scalar or pseudoscalar neutral meson. The three independant helicity amplitudes are presented in terms of the twist-2 generalized distribution amplitudes (GDAs), which are important non-perturbative quantities for understanding the 3D structure of hadrons. Since this process can be measured by BESIII in $e^{+} e^{-}$ collisions, we perform the numerical estimate of the kinematical higher-twist corrections by using the kinematics of BESIII. We adopt the $π π$ GDA extracted from Belle measurements and the asymptotic $π π$ GDA to study the size of the kinematical corrections in the case of pion meson pair, and a model $η η$ GDA is used to see the impact of target mass corrections $O (m^{2} / s)$ for $γ^{*} \to η η γ$ . Our results show that the kinematical higher-twist corrections account for $\sim 20%$ of the cross sections at BESIII on the average, and it is necessary to include them if one tries to extract GDAs from experimental measurements precisely. We also comment the case of $π^{0} η$ production which is important for the search of hybrid mesons.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·9 citations
10
Anisotropic flow and the valence quark skeleton of hadrons
Meijian Li🇪🇸 · Wenyang Qian🇪🇸 · Bin Wu🇪🇸 · Hong Zhang🇨🇳
We study transverse momentum anisotropies, in particular, the elliptic flow $v_{2}$ due to the interference effect sourced by valence quarks in high-energy hadron-hadron collisions. Our main formula is derived as the high-energy (eikonal) limit of the impact-parameter dependent cross section in quantum field theory, which agrees with that in terms of the impact parameter in the classical picture. As a quantitative assessment of the interference effect, we calculate $v_{2}$ in the azimuthal distribution of gluons at a comprehensive coverage of the impact parameter and the transverse momentum in high-energy pion-pion collisions. In a broad range of the impact parameter, a sizable amount of $v_{2}$ , comparable with that produced due to saturated dense gluons or final-state interactions, is found to develop. In our calculations, the valence sector of the pion wave function is obtained numerically from the Basis Light-Front Quantization, a non-perturbative light-front Hamiltonian approach. And our formalism is generic and can be applied to other small collision systems like proton-proton collisions.
↳ hep-phnucl-thJHEP(2023)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE