Nuclear Theory·nucl-th

Monday·December 2, 2019

17 papers—11 primary·6 cross-listed

01
Toward Initial Conditions of Conserved Charges Part II: The ICCING Monte Carlo Algorithm
Patrick Carzon🇺🇸 · Mauricio Martinez🇺🇸 · Matthew D. Sievert🇺🇸 · Douglas E. Wertepny🇮🇱 · Jacquelyn Noronha-Hostler🇺🇸
At top collider energies where baryon stopping is negligible, the initial state of heavy ion collisions is overall charge neutral and predominantly composed of gluons. Nevertheless, there can also be significant local fluctuations of the baryon number, strangeness, and electric charge densities about zero, perturbatively corresponding to the production of quark/antiquark pairs. These previously ignored local charge fluctuations can permit the study of charge diffusion in the quark-gluon plasma (QGP), even at top collider energies. In this paper we present a new model denoted ICCING (Initial Conserved Charges in Nuclear Geometry) which can reconstruct the initial conditions of conserved charges in the QGP by sampling a ( $g \to q q ˉ$ ) splitting probability over the initial energy density. We find that the new charge distributions generally differ from the bulk energy density; in particular, the strangeness distribution is significantly more eccentric than standard bulk observables and appears to be associated with the geometry of hot spots in the initial state. The new information provided by these conserved charges opens the door to studying a wealth of new charge- and flavor-dependent correlations in the initial state and ultimately the charge transport parameters of the QGP.
nucl-thhep-phPRC(2022)·43 citations
02
Impact of uncertainties of unbound $^{10}$ Li on the ground state of two-neutron halo $^{11}$ Li
Jagjit Singh · W. Horiuchi
Recently, the energy spectrum of $^{10}$ Li was measured upto 4.6 MeV, via one-neutron transfer reaction d( $^{9}$ Li, p) $^{10}$ Li. Considering the ambiguities on the $^{10}$ Li continuum spectrum with reference to new data, we report the configuration mixing in the ground state of the two-neutron halo nucleus $^{11}$ Li for two different choices of the $^{9}$ Li $+$ n potential. For the present study, we employ a three-body (core $+$ n $+$ n) structure model developed for describing the two-neutron halo system by explicit coupling of unbound continuum states of the subsystem (core $+$ n), and discuss the two-neutron correlations in the ground state of $^{11}$ Li.
nucl-thSciPost Phys.Proc.(2020)·1 citation
03
Improved many-body expansions from eigenvector continuation
Pepijn Demol🇧🇪 · Thomas Duguet🇧🇪 · Andreas Ekström🇸🇪 · Mikael Frosini🇫🇷 · Kai Hebeler🇩🇪 · Sebastian König🇩🇪 · Dean Lee🇺🇸 · Achim Schwenk🇩🇪 · Vittorio Somà🇫🇷 · Alexander Tichai🇫🇷
Quantum many-body theory has witnessed tremendous progress in various fields, ranging from atomic and solid-state physics to quantum chemistry and nuclear structure. Due to the inherent computational burden linked to the ab initio treatment of microscopic fermionic systems, it is desirable to obtain accurate results through low-order perturbation theory. In atomic nuclei however, effects such as strong short-range repulsion between nucleons can spoil the convergence of the expansion and make the reliability of perturbation theory unclear. Mathematicians have devised an extensive machinery to overcome the problem of divergent expansions by making use of so-called resummation methods. In large-scale many-body applications such schemes are often of limited use since no a priori analytical knowledge of the expansion is available. We present here eigenvector continuation as an alternative resummation tool that is both efficient and reliable because it is based on robust and simple mathematical principles.
nucl-thcond-mat.str-elPRC(2020)·66 citations
04
Derivation of the Strutinsky method from the least squares principle
B. Mohammed-Azizi
The main purpose of this paper is to rigorously establish the Strutinsky method from the least squares principle. Thus, it is the mathematical basis of this method (aspect often neglected) which is revisited in an extensive way. Some formulas previously given without demonstration or in a simplified way are set out here with all the details. In this respect, the most important mathematical properties of the averaging functions are also established in this paper. When some conditions are met, it turns out that Strutinsky's method is nothing more than a polynomial moving average of the semi-classical level density.
nucl-thIJMPE(2020)·0 citations
05
Two photon transition form factors of neutral pseudoscalar mesons
Minghui Ding🇮🇹 · Daniele Binosi🇮🇹 · Khépani Raya🇨🇳 · Lei Chang🇨🇳 · Craig D. Roberts🇨🇳
Starting from the axial vector Ward-Green-Takahashi identity, and the necessity of preserving this identity when attempting to calculate the properties describing pseudoscalar mesons, we describe a Bethe-Salpeter kernel which takes into account the non-Abelian anomaly and therefore is suitable to describe the flavor mixing states $η, η^{'}$ . We then report results for the two photon transition form factors of $η, η^{'}$ , and compare them with existing experimental data.
nucl-thhep-ph0 citations
06
Neutrino-deuteron scattering: Uncertainty quantification and new $L_{1, A}$ constraints
Bijaya Acharya🇩🇪 · Sonia Bacca🇩🇪
We study neutral- and charged-current (anti)neutrino-induced dissociation of the deuteron at energies from threshold up to 150 MeV by employing potentials, as well as one- and two-body currents, derived in chiral effective field theory ( $χ$ EFT). We provide uncertainty estimates from $χ$ EFT truncations of the electroweak current, dependences on the $χ$ EFT cutoff and variations in the pool of fit data used to fix the low-energy constants of $χ$ EFT. At 100 MeV of incident (anti)neutrino energy, these uncertainties amount to about 2-3\% and are smaller than the sensitivity of the cross sections to the single-nucleon axial form factor, which amounts to 5\% if one varies the range of the nucleon axial radius within the bands determined by recent lattice quantum chromodynamics evaluations and phenomenological extractions. We conclude that a precise determination of the nucleon axial form factor is required for a high-precision calculation of the neutrino-deuteron cross sections at energies higher than 100 MeV. By matching our low-energy $χ$ EFT results to those of pionless effective field theory ( $π$ EFT), we provide new constraints for the counterterm $L_{1, A}$ that parameterizes the strength of the axial two-body current in $π$ EFT. We obtain a value of $4. 9_{- 1.5}^{+ 1.9} fm^{3}$ at renormalization scale set to pion mass, which is compatible with, albeit narrower than, previous experimental determinations, and comparable to a recent lattice quantum chromodynamics calculation.
nucl-thhep-phPRC(2020)·35 citations
07
Bose-Einstein condensate of alpha particles in the ground state of nuclear matter?
L. M. Satarov · M. I. Gorenstein · I. N. Mishustin · H. Stoecker
The phase diagram of isospin-symmetric chemically equilibrated mixture of alpha particles and nucleons is studied in the mean-field approximation. Skyrme-like parametrization is used for the mean-field potentials as functions of partial densities of nucleons and alphas. We find that there is a threshold value a* of the parameter a(N-alpha) which describes the attractive interaction between alpha-particles and nucleons. At a(N-alpha)<a* the ground state of nuclear matter at zero temperature behaves as a pure system of interacting nucleons, whereas at a(N-alpha)>a* the nuclear ground state includes also a nonzero fraction of alphas. We demonstrate that the equation of state of such alpha-N system includes both the first-order liquid-gas phase transitions and the Bose-Einstein condensation of alpha particles.
nucl-thPRC(2020)·13 citations
08
Studying the effect of the hadronic phase in nuclear collisions with PYTHIA and UrQMD
André Vieira da Silva🇧🇷 · Christian Bierlich🇩🇰 · David Dobrigkeit Chinellato🇧🇷 · Jun Takahashi🇧🇷
In this work, we couple Pb-Pb events simulated with the PYTHIA Angantyr event generator at $s_{NN} = 2.76$ and $5.02$ ~TeV with the hadronic cascade simulator UrQMD to study the effect of the hadronic phase on observables such as charged-particle multiplicity densities, transverse momentum spectra and identified particle ratios, giving special emphasis to short-lived resonances.
nucl-thnucl-exSpringer Proc.Phys.(2020)·6 citations
09
Unveiling the structure of pseudoscalar mesons
Khépani Raya🇨🇳 · Lei Chang🇨🇳 · Minghui Ding🇮🇹 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳
A valuable approach to the analysis of hadron physics observables is provided by QCD's equations-of-motion; namely, the Dyson-Schwinger equations. Drawing from a diverse collection of predictions, we revisit: $γ γ^{*} \to$ neutral pseudoscalar transition form factors, their corresponding valence-quark distribution amplitudes and a recent result on the pion distribution functions.
nucl-thhep-ph2 citations
10
Machine learning the deuteron
J. W. T. Keeble · A. Rios
We use machine learning techniques to solve the nuclear two-body bound state problem, the deuteron. We use a minimal one-layer, feed-forward neural network to represent the deuteron S- and D-state wavefunction in momentum space, and solve the problem variationally using ready-made machine learning tools. We benchmark our results with exact diagonalisation solutions. We find that a network with 6 hidden nodes (or 24 parameters) can provide a faithful representation of the ground state wavefunction, with a binding energy that is within 0.1% of exact results. This exploratory proof-of-principle simulation may provide insight for future potential solutions of the nuclear many-body problem using variational artificial neural network techniques.
nucl-thphysics.comp-phPLB(2020)·61 citations
11
Radial flow induced by inhomogeneous magnetic field in heavy ion collisions
Mohsen Haddadi Moghaddam🇮🇹 · Behnam Azadegan🇮🇷 · Ahmad Farzaneh Kord🇮🇷 · Wanda M. Alberico🇮🇹
In this paper, we study the effects of an in-homogeneous magnetic field on the quark gluon plasma dynamics, within the Magneto-Hydrodynamic framework. We have investigated the effect of an inhomogeneous external magnetic field on the transverse expansion of in-viscid fluid created in high energy nuclear collisions. Transverse velocity and energy density are modified by the presence of the magnetic field. This effects can also influence the transverse momentum spectrum for particles at the freeze-out surface. In this context we obtained an interesting comparison with data extracted from heavy-ion collisions.
nucl-thhep-phSpringer Proc.Phys.(2020)·0 citations
12
Weak structure functions in $ν_{l} - N$ and $ν_{l} - A$ scattering with nonperturbative and higher order perturbative QCD effects
F. Zaidi🇮🇳 · H. Haider🇺🇸 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳 · I. Ruiz Simo🇪🇸
We study the effect of various perturbative and nonperturbative QCD corrections on the free nucleon structure functions ( $F_{i N}^{W I} (x, Q^{2}); i = 1 - 3$ ) and their implications in the determination of nuclear structure functions. The evaluation of the nucleon structure functions has been performed by using the MMHT 2014 PDFs parameterization, and the TMC and HT effects are incorporated following the works of Schienbein et al. and Dasgupta et al., respectively. These nucleon structure functions are taken as input in the determination of nuclear structure functions. The numerical calculations for the $ν_{l} / ν ˉ_{l} - A$ DIS process have been performed by incorporating the nuclear medium effects like Fermi motion, binding energy, nucleon correlations, mesonic contributions, shadowing and antishadowing in several nuclear targets such as carbon, polystyrene scintillator, iron and lead which are being used in MINERvA, and in argon nucleus which is relevant for the ArgoNeuT and DUNE experiments. The differential scattering cross sections $\frac{d ^{2} σ _{A}^{W I}}{d x d y}$ and $(\frac{d σ _{A}^{W I}}{d x} / \frac{d σ _{C H}^{W I}}{d x})$ have also been studied in the kinematic region of MINERvA experiment. The theoretical results are compared with the recent experimental data of MINERvA and the earlier data of NuTeV, CCFR, CDHSW and CHORUS collaborations. Moreover, a comparative analysis of the present results for the ratio $(\frac{d σ _{A}^{W I}}{d x} / \frac{d σ _{C H}^{W I}}{d x})$ , and the results from the MC generator GENIE and other phenomenological models of Bodek and Yang, and Cloet et al., has been performed in the context of MINERvA experiment. The predictions have also been made for $ν ˉ_{l} - A$ cross section relevant for MINERvA experiment.
↳ hep-phnucl-thPRD(2020)·23 citations
13
J/ $ψ$ p Scattering Length from GlueX Threshold Measurements
Igor Strakovsky (GWU)🇺🇸 · Denis Epifanov (Budker Ins)🇷🇺 · Lubomir Pentchev (JLab)🇺🇸
The quality of the recent GlueX $J / ψ$ photoproduction data from Hall~D at Jefferson Laboratory, and the proximity of the data to the energy threshold, gives access to a variety of interesting physics aspects. As an example, an estimation of the $J / ψ$ -nucleon scattering length $α_{J / ψ p}$ is provided within the vector meson dominance model. It results in $∣ α_{J / ψ p} ∣ = (3.08 \pm 0.55 (stat.) \pm 0.45 (syst.))$ ~mfm.
↳ hep-phhep-exnucl-exnucl-thPRC(2020)·46 citations
14
Deconfined, Massive Quark Phase at High Density and Compact Stars: A Holographic Study
Kazem Bitaghsir Fadafan🇮🇷 · Jesus Cruz Rojas🇬🇧 · Nick Evans🇬🇧
In Hoyos et al. (arXiv:1603.02943) a holographic D3/D7 system was used to describe a deconfined yet massive quark phase of QCD at finite density, concluding that the equation of state of such a phase was not stiff enough to support exotic dense stars. That analysis used a hard quark mass to represent the dynamical mass and assumed a conformal gauge background. Here we phenomenologically adjust the D3/D7 system to include a running anomalous dimension for the quark condensate. This introduces a dynamical mechanism for chiral symmetry breaking yet the model still has a deconfined massive phase at intermediate densities. We show that these systems, dependent on the running profile in the deep IR, generate much stiffer equations of state and non-monotonic behaviour in the speed of sound. The results suggest that these equations of state may be closer to supporting hybrid stars with quark cores.
↳ hep-phhep-thnucl-thPRD(2020)·64 citations
15
Gluon Radiation from a classical point particle II: dense gluon fields
K. Kajantie🇫🇮 · Larry D. McLerran🇺🇸 · Risto Paatelainen🇫🇮
The goal of this paper is to extend the results of Ref. [1], where formulae were derived for gluonic radiation for a high energy nucleus colliding with a classical colored particle. In Ref. [1], we computed the amplitudes for radiation in the fragmentation region of the particle for a dilute gluonic field. In this paper, we compute the radiation by solving the fluctuation equations of the dense background field in a specific gauge which makes it simple to solve the asymptotic radiation from an initial condition immediately after the passage of the nucleus. We identify and compute two components of gluon radiation, a bulk component which extends to the central region and bremsstrahlung, which may give rise to an experimentally observable intensity peak in the target fragmentation region.
↳ hep-phnucl-thPRD(2020)·9 citations
16
Charmed excited baryons with heavy-quark spin symmetry
L. Tolos🇩🇪 · J. Nieves🇪🇸 · R. Pavao🇪🇸
Recently five $Ω_{c}$ excited states have been reported by the LHCb Collaboration, four of them corroborated by Belle. The Belle Collaboration has also discovered in 2017 one excited $Ξ_{c}$ with mass of 2930 MeV. In view of these recent detections, we analyze the possible molecular description of these states, using a unitarized baryon-meson model that incorporates both chiral and heavy-quark spin symmetries in a consistent manner. We pay a special attention to the renormalization procedure, so as to determine the robustness of our predictions. Within our model, we generate dynamically several $Ω_{c}$ and $Ξ_{c}$ states. We find that, at least, three of our $Ω_{c}$ states can be identified with the experimental ones and have spin-parity $J = 1/ 2^{-}$ or $J = 3/ 2^{-}$ . Moreover, we find a plausible molecular description of not only the $Ξ_{c} (2930)$ state, but also $Ξ_{c} (2790)$ , $Ξ_{c} (2815)$ and $Ξ_{c} (2970)$ , reported in the PDG. Interestingly, we determine that $Ξ_{c} (2930)$ and $Ξ_{c} (2970)$ are heavy-quark spin partners with $J = 1/ 2^{-}$ and $J = 3/ 2^{-}$ , respectively, while obtaining that $Ξ_{c} (2930)$ , $Ω_{c} (3090)$ or the $Ω_{c} (3119)$ , and $Σ_{c} (2800)$ would belong to the same SU(3) multiplet.
↳ hep-phhep-exnucl-exnucl-th0 citations
17
The enigmatic $Δ (1600)$ resonance
B. Golli🇸🇮
Our recently proposed model of the $Δ (1600)$ resonance, in which the dominant component is a quasi-bound state of the $Δ (1232)$ and the pion, is confronted with a similar model of the $N^{*} (1440)$ resonance as its counterpart in the P11 partial wave. We stress an essentially different mechanism responsible for generating the two resonances.
↳ hep-phnucl-thBled Workshops Phys.(2019)·0 citations

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