Nuclear Theory·nucl-th

Tuesday·February 15, 2022

11 papers—6 primary·5 cross-listed

01
Multi-channel experimental and theoretical constraints for the $^{116}$ Cd( $^{20}$ Ne, $^{20}$ F) $^{116}$ In charge exchange reaction at 306 MeV
S. Burrello🇩🇪 · S. Calabrese🇮🇹 · F. Cappuzzello🇮🇹 · D. Carbone🇮🇹 · M. Cavallaro🇮🇹 · M. Colonna🇮🇹 · J. A. Lay🇪🇸 · H. Lenske🇩🇪 · C. Agodi🇮🇹 · J. L. Ferreira🇧🇷 · S. Firat🇹🇷 · A. Hacisalihoglu🇹🇷 and 34 other authors
Charge exchange (CE) reactions offer a major opportunity to excite nuclear isovector modes, providing clues about the nuclear interaction in the medium. Moreover, double charge exchange (DCE) reactions are proving to be a tempting tool to access nuclear transition matrix elements (NME) related to double beta-decay processes. Through a multi-channel experimental analysis and a consistent theoretical approach of the $^{116}$ Cd( $^{20}$ Ne, $^{20}$ F) $^{116}$ In single charge exchange (SCE) reaction at 306 MeV, we aim at disentangling from the experimental cross section the contribution of the competing mechanisms, associated with second or higher order sequential transfer and inelastic processes. We measured excitation energy spectra and absolute cross sections for elastic + inelastic, one-proton transfer and SCE channels, using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. For the first two channels, we also extracted the experimental cross section angular distributions. The experimental data are compared with theoretical predictions obtained by performing two-step distorted wave Born approximation and coupled reaction channel calculations. We employ spectroscopic amplitudes for single-particle transitions derived within a large-scale shell model approach and different optical potentials for modeling the initial and the final state interactions. The present study significantly mitigates the possible model dependence existing in the description of these complex reaction mechanisms, thanks to the reproduction of several channels at once. In particular, our work demonstrates that the two-step transfer mechanisms produce a non negligible contribution to the total cross section of the $^{116}$ Cd( $^{20}$ Ne, $^{20}$ F) $^{116}$ In reaction channel, although a relevant fraction is still missing, being ascribable to the direct SCE mechanism, which is not addressed here.
nucl-thnucl-exPRC(2022)·35 citations
02
Scaling properties of exclusive vector meson production cross section from gluon saturation
Gregory Matousek🇺🇸 · Vladimir Khachatryan🇺🇸 · Jinlong Zhang🇨🇳
It is already known from phenomenological studies that in exclusive deep-inelastic scattering off nuclei there appears to be a scaling behavior of vector meson production cross section in both nuclear mass number, $A$ , and photon virtuality, $Q^{2}$ , which is strongly modified due to gluon saturation effects. In this work we continue those studies in a realistic setup based upon using the Monte Carlo event generator Sar{\em t}re. We make quantitative predictions for the kinematics of the Electron-Ion Collider, focusing on this $A$ and $Q^{2}$ scaling picture, along with establishing a small region of squared momentum transfer, $t$ , where there are signs of this scaling that may potentially be observed at the EIC. Our results are represented as pseudo-data of vector meson production diffractive cross section and/or their ratios, which are obtained by parsing data collected by the event generator through smearing functions, emulating the proposed detector resolutions for the future EIC.
nucl-thhep-phnucl-exEur.Phys.J.Plus(2023)·2 citations
03
Theory of kaon-nuclear systems
Tetsuo Hyodo🇯🇵 · Wolfram Weise🇩🇪
The strong interaction between an antikaon and a nucleon is at the origin of various interesting phenomena in kaon-nuclear systems. In particular, the interaction in the isospin $I = 0$ channel is sufficiently attractive to generate a quasi-bound state, the $Λ (1405)$ resonance, below the $K ˉ N$ threshold. Based on this picture, it may be expected that the $K ˉ N$ interaction also generates quasi-bound states in kaon-nuclear systems, sometimes called kaonic nuclei. At the same time, the $K ˉ N$ quasi-bound picture of the $Λ (1405)$ is also related to the discussion of hadronic molecules in hadron spectroscopy. Here an overview is presented of the theoretical studies developed for kaon-nucleon and kaon-nuclear systems. We start from the modern understanding of the $Λ (1405)$ resonance. We then discuss the $K ˉ N$ interaction and various aspects of few-body kaonic nuclei. Heavier kaon-nuclear systems are examined from the viewpoint of nuclear many-body physics, with focus on the properties of antikaons in nuclear matter. Related topics, such as the $K^{-} p$ momentum correlation functions in high-energy collisions and the studies of kaonic atoms, are also discussed.
nucl-thhep-ph15 citations
04
Reply to Comment on "Phase-space consideration on barrier transmission in a time-dependent variational approach with superposed wave packets"
Akira Ono
In the paper by Hasegawa, Hagino and Tanimura (HHT) [Phys. Lett. B 808 (2020) 135693, arXiv:2006.06944], they concluded that quantum tunneling was simulated by a time-dependent generator coordinate method (TDGCM). In contrast, difficulties of TDGCM in describing quantum tunneling were pointed out by Ono in the paper [Phys. Lett. B 826 (2022) 136931, arXiv:2201.02966]. Recently, HHT submitted a comment [arXiv:2202.00513v1], by which they appear to give some counterarguments to Ono's paper. Here I examine their arguments, reviewing the main points of Ono's paper. The confusion in HHT's arguments may be mostly resolved by recognizing how the wave packets interfere with each other when they are coherently superposed.
nucl-th1 citation
05
Asymmetric nuclear matter in relativistic mean-field models with isoscalar- and isovector-meson mixing
Tsuyoshi Miyatsu🇰🇷 · Myung-Ki Cheoun🇰🇷 · Koichi Saito🇯🇵
Using the relativistic mean-field model with nonlinear couplings between the isoscalar and isovector mesons, we study the properties of isospin-asymmetric nuclear matter. Not only the vector mixing, $ω_{μ} ω^{μ} ρ_{ν} ρ^{ν}$ , but also the quartic interaction due to the scalar mesons, $σ^{2} δ^{2}$ , is taken into account to investigate the density dependence of nuclear symmetry energy, $E_{sym}$ , and the neutron-star properties. It is found that the $δ$ meson increases $E_{sym}$ at high densities, whereas the $σ$ - $δ$ mixing makes $E_{sym}$ soft above the saturation density. Furthermore, the $δ$ meson and its mixing have a large influence on the radius and tidal deformability of a neutron star. In particular, the $σ$ - $δ$ mixing reduces the neutron-star radius, and, thus, the present calculation can simultaneously reproduce the dimensionless tidal deformabilities of a canonical $1.4 M_{⊙}$ neutron star observed from the binary neutron star merger, GW170817, and from the compact binary coalescence, GW190814.
nucl-thastro-ph.HEnucl-exApJ(2022)·41 citations
06
Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions
Hermann Wolter (1)🇩🇪 · Maria Colonna (2)🇮🇹 · Dan Cozma (3)🇷🇴 · Pawel Danielewicz (4,5)🇺🇸 · Che Ming Ko (6)🇺🇸 · Rohit Kumar (4)🇺🇸 · Akira Ono (7)🇯🇵 · ManYee Betty Tsang (4,5)🇺🇸 · Jun Xu (8,9)🇨🇳 · Ying-Xun Zhang (10,11)🇨🇳 · Elena Bratkovskaya (12,13)🇩🇪 · Zhao-Qing Feng (14)🇨🇳 and 40 other authors
Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.
nucl-thnucl-exPPNP(2022)·161 citations
07
A dispersive analysis of $η^{'} \to π^{+} π^{-} γ$ and $η^{'} \to ℓ^{+} ℓ^{-} γ$
Simon Holz🇩🇪 · Christoph Hanhart🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪
We present a dispersive representation of the $η^{'}$ transition form factor that allows one to account, in a consistent way, for the effects of $ρ$ - $ω$ mixing in both the isoscalar and the isovector contributions. Using this formalism, we analyze recent data on $η^{'} \to π^{+} π^{-} γ$ to constrain the isovector part of the form factor, individually and in combination with data for the pion vector form factor. As a first application, we use our results, in combination with the most recent input for the isoscalar part of the form factor, to predict the corresponding spectrum of $η^{'} \to ℓ^{+} ℓ^{-} γ$ , in particular we find the slope parameter $b_{η^{'}} = 1.431 (23) GeV^{- 2}$ . With forthcoming data on the latter process, our results establish the necessary framework to improve the evaluation of the $η^{'}$ -pole contribution to the anomalous magnetic moment of the muon using experimental input from both $η^{'}$ decay channels.
↳ hep-phhep-exnucl-thEPJC(2022)·61 citations
08
Production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ mesons in hadronic matter
Li-Yuan Li🇨🇳 · Xiao-Ming Xu🇨🇳 · H. J. Weber🇺🇸
We present the first study of production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ mesons in hadronic matter. Quark interchange between two colliding charmed mesons leads to the production of the three mesons. We calculate unpolarized cross sections for the reactions, $D D ˉ \to ρR$ , $D D ˉ^{*} \to π R$ , $D D ˉ^{*} \to ρR$ , $D^{*} D ˉ \to π R$ , $D^{*} D ˉ \to ρR$ , $D^{*} D ˉ^{*} \to π R$ , and $D^{*} D ˉ^{*} \to ρR$ , where $R$ stands for $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ . In the temperature region covering hadronic matter the peak cross sections of producing $ψ (4040)$ are similar to or larger than the ones of producing $ψ (4415)$ , and the latter are generally larger than those of producing $ψ (4160)$ . With the cross sections we establish new master rate equations for $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ . The equations are solved for central Pb-Pb collisions at $s_{N N} = 5.02$ TeV at the Large Hadron Collider. Solutions of the equations show that the $ψ (4040)$ number density at kinetic freeze-out of hadronic matter is larger than the $ψ (4415)$ number density which is larger than the $ψ (4160)$ number density.
↳ hep-phhep-exnucl-exnucl-thPRD(2022)·2 citations
09
Artificial Dynamical Effects in Quantum Field Theory
S. J. Brodsky🇺🇸 · A. Deur🇺🇸 · C. D. Roberts🇨🇳
In Newtonian mechanics, inertial pseudoforces - or fictitious forces - appear in systems studied in non-Galilean reference frames; e.g., a centrifugal force seems to arise if the dynamics is analyzed in a rotating reference frame. The equivalent of Galilean invariance for relativistic kinematics is Poincaré invariance; analogous artificial effects may arise in relativistic quantum field theory (QFT) if a system is studied in a framework violating Poincaré invariance. We highlight how such issues complicate the traditional canonical quantization of QFTs and can lead to a subjective description of natural phenomena. In fact, if the system involves the strong interaction, obtaining objective results can become an intractable problem using canonical quantization because the pseudoforces are essentially nonperturbative. In contrast, the treatment of the same problem using light-front (LF) quantization is free of spurious pseudoeffects because Poincaré invariance is manifest; thus the treatment of strong interaction problems becomes simpler. These statements are illustrated using several examples: the Gerasimov-Drell-Hearn (GDH) relation, a fundamental feature of QFT; the absence of any measurable impact of Lorentz contraction in high-energy collisions; and the fictitious character of vacuum fluctuation contributions to the cosmological constant.
↳ hep-phhep-lathep-thnucl-thNature Rev.Phys.(2022)·27 citations
10
Doubly heavy tetraquarks in a chiral-diquark picture
Yonghee Kim🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵
Energy spectrum of doubly heavy tetraquarks, $T_{QQ}$ ( $QQ q ˉ q ˉ$ with $Q = c, b$ and $q = u, d, s$ ), is studied in the potential chiral-diquark model. Using the chiral effective theory of diquarks and the quark-diquark-based potential model, the $T_{bb}$ , $T_{cc}$ , and $T_{c b}$ tetraquarks are described as a three-body system composed of two heavy quarks and an antidiquark. We find several $T_{bb}$ bound states, while no $T_{cc}$ and $T_{c b}$ (deep) bound state is seen. We also study the change of the $T_{QQ}$ tetraquark masses under restoration of chiral symmetry.
↳ hep-phhep-exnucl-thPRD(2022)·54 citations
11
Energy dependence of the proton geometry in exclusive vector meson production
Arjun Kumar🇮🇳 · Tobias Toll🇮🇳
The gluon radius of the proton is expected to increase at small gluon momentum fractions $x$ , an effect which has hitherto not been considered in the dipole model framework. We investigate the energy dependence of exclusive $J / ψ$ , $ϕ$ , and $ρ$ production by introducing three models for $x$ dependence of the gluon thickness function. We allow the transverse width of the proton to increase as $x$ decreases, using novel parametrisations in the spherical proton and the hotspot model. We compare these with a model where the number of hotspots increases as $x$ decreases and confront the models with HERA data. The models exhibit clear differences in the slope of the $t$ -spectra and in the cross section ratios between coherent and incoherent events. Comparisons to $t$ -slopes and $W_{γ p}$ measurements show a preference for models where the proton's size increases as $x$ decreases.
↳ hep-phnucl-thPRD(2022)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE