Nuclear Theory·nucl-th

Wednesday·December 6, 2023

11 papers—3 primary·8 cross-listed

04
[Submitted on 4 Dec 2023] (cross-list from hep-ph)
Learning PDFs through Interpretable Latent Representations in Mellin Space
Brandon Kriesten🇺🇸 · T. J. Hobbs🇺🇸
Representing the parton distribution functions (PDFs) of the proton and other hadrons through flexible, high-fidelity parametrizations has been a long-standing goal of particle physics phenomenology. This is particularly true since the chosen parametrization methodology can play an influential role in the ultimate PDF uncertainties as extracted in QCD global analyses; these, in turn, are often determinative of the reach of experiments at the LHC and other facilities to non-standard physics, including at large $x$ , where parametrization effects can be significant. In this study, we explore a series of encoder-decoder machine-learning (ML) models with various neural-network topologies as efficient means of reconstructing PDFs from meaningful information stored in an interpretable latent space. Given recent effort to pioneer synergies between QCD analyses and lattice-gauge calculations, we formulate a latent representation based on the behavior of PDFs in Mellin space, i.e., their integrated moments, and test the ability of various models to decode PDFs from this information faithfully. We introduce a numerical package, $PDFdecoder$ , which implements several encoder-decoder models to reconstruct PDFs with high fidelity and use this tool to explore strengths and pitfalls of neural-network approaches to PDF parametrization. We additionally dissect patterns of learned correlations between encoded Mellin moments and reconstructed PDFs which suggest opportunities for further improvements to ML-based approaches to PDF parametrizations and uncertainty quantification.
Comments:
22 pages, 11 figures; updated link to public code, https://github.com/ML4HEP-Theory/PDFDecoder
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2312.02278 [pdf]
PRD(2025)·14 citations
05
[Submitted on 4 Dec 2023] (cross-list from hep-ph)
Hints of Entanglement Suppression in Hyperon-Nucleon Scattering
Qiaofeng Liu🇺🇸 · Ian Low🇺🇸
Hyperon ( $Y = Σ, Λ$ )-nucleon ( $N = n, p$ ) interactions are crucial for understanding the existence of neutron stars heavier than two solar masses. Amid renewed experimental efforts, we study $Y N$ scatterings from the perspective of quantum information, focusing on whether spin entanglement is suppressed in the s-wave channel, which is observed in $n p$ scattering and leads to enhanced global symmetries. Using global fits of phase shifts from experimental data, we find hints of entanglement suppression among the eight flavor channels in the strangeness $S = - 1$ sector, similar to the $n p$ case. One exception is the $Σ^{+} p$ channel, where conflicting global fits lead to inconclusive outcome. We then propose ''quantum'' observables in $Σ^{+} p$ scattering to help resolve the differing global fits.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2312.02289 [pdf]
PLB(2024)·36 citations
06
[Submitted on 5 Dec 2023] (cross-list from quant-ph)
Calculation of Relativistic Single-Particle States
D. Wingard · B. Kónya · Z.Papp
A computational method is proposed to calculate bound and resonant states by solving the Klein-Gordon and Dirac equations for real and complex energies, respectively. The method is an extension of a non-relativistic one, where the potential is represented in a Coulomb-Sturmian basis. This basis facilitates the exact analytic evaluation of the Coulomb Green's operator in terms of a continued fraction. In the extension to relativistic problems, we cast the Klein-Gordon and Dirac equations into an effective Schrödinger form. Then the solution method is basically an analytic continuation of non-relativistic quantities like the angular momentum, charge, energy and potential into the effective relativistic counterparts.
Comments:
10 pages
Subjects:
Quantum Physics (quant-ph); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
2312.02500 [pdf]
Few Body Syst.(2023)·0 citations
07
[Submitted on 5 Dec 2023] (cross-list from hep-th)
Stress inside the pion in holographic light-front QCD
Yang Li🇨🇳 · James P. Vary🇺🇸
In this work, we propose a method to compute the gravitational form factor $D (Q^{2})$ in holographic QCD by exploiting the remarkable correspondence between semi-classical light-front QCD and semi-classical field theories in wrapped spacetime in 5D. The use of light-front holography bridges physics at large $Q^{2}$ as attained in light-front QCD and physics at small $Q^{2}$ where the coupling to scalar and tensor fields, i.e. glueballs, are dominant. As an application, we compute the $D$ -term for the pion, and compare the results with recent lattice simulations.
Comments:
6 pages, 1 figure. Published on PRD as a letter
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2312.02543 [pdf]
PRD(2024)·25 citations
08
[Submitted on 5 Dec 2023] (cross-list from hep-ph)
Shedding light on charmonium
Zhiguo Wang🇨🇳 · Meijian Li🇪🇸 · Yang Li🇨🇳 · James P. Vary🇺🇸
We investigate E1 radiative transitions within charmonium in a relativistic approach based on light-front QCD. In quantum field theory, two sets of processes are pure E1: $χ_{c 0} \to J / ψ γ$ ( $ψ \to χ_{c 0} γ$ ) and $h_{c} \to η_{c} γ$ ( $η_{c}^{'} \to h_{c} γ$ ), both involving the $P$ -wave charmonia. We compute the E1 radiative decay widths as well as the corresponding transition form factors of various processes including those involving $2 P$ states. These observables provide an access to the microscopic structures of the $P$ -wave charmonium. We show that our parameter-free predictions are in excellent agreement with the experimental measurements as well as lattice simulations whenever available.
Comments:
Values of decay widths are provided in the supplementary file
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2312.02604 [pdf]
PRD(2024)·7 citations
09
[Submitted on 5 Dec 2023] (cross-list from astro-ph.IM)
A Framework for Exploring Nuclear Physics Sensitivity in Numerical Simulations
Zhi Chen · Eric T. Johnson · Max Katz · Alexander Smith Clark · Brendan Boyd · Michael Zingale
We describe the AMReX-Astrophysics framework for exploring the sensitivity of astrophysical simulations to the details of a nuclear reaction network, including the number of nuclei, choice of reaction rates, and approximations used. This is explored by modeling a simple detonation with the Castro simulation code. The entire simulation methodology is open-source and GPU-enabled.
Subjects:
Instrumentation and Methods for Astrophysics (astro-ph.IM); Nuclear Theory (nucl-th)
arXiv:
2312.02836 [pdf]
J.Phys.Conf.Ser.(2024)·1 citation
10
[Submitted on 5 Dec 2023] (cross-list from hep-lat)
Shallow Bound States and Hints for Broad Resonances with Quark Content $b ˉ c ˉ u d$ in $B$ - $D ˉ$ and $B^{*}$ - $D ˉ$ Scattering from Lattice QCD
Constantia Alexandrou🇨🇾 · Jacob Finkenrath🇨🇾 · Theodoros Leontiou🇨🇾 · Stefan Meinel🇺🇸 · Martin Pflaumer🇩🇪 · Marc Wagner🇩🇪
We present the first determination of the energy dependence of the $B$ - $D ˉ$ and $B^{*}$ - $D ˉ$ isospin-0, $S$ -wave scattering amplitudes both below and above the thresholds using lattice QCD, which allows us to investigate rigorously whether mixed bottom-charm $b ˉ c ˉ u d$ tetraquarks exist as bound states or resonances. The scattering phase shifts are obtained using Lüscher's method from the energy spectra in two different volumes. To ensure that no relevant energy level is missed, we use large, symmetric $7 \times 7$ and $8 \times 8$ correlation matrices that include, at both source and sink, $B^{(*)}$ - $D ˉ$ scattering operators with the lowest three or four possible back-to-back momenta in addition to local $b ˉ c ˉ u d$ operators. We fit the energy dependence of the extracted scattering phase shifts using effective-range expansions. We observe sharp peaks in the $B^{(*)}$ - $D ˉ$ scattering rates close to the thresholds, which are associated with shallow bound states, either genuine or virtual, a few MeV or less below the $B^{(*)}$ - $D ˉ$ thresholds. In addition, we find hints for resonances with masses of order $100$ MeV above the thresholds and decay widths of order $200$ MeV.
Comments:
5 pages + 10 pages of references and supplemental material. Added estimates of bound-state probabilities and improved calculation of bound-state mass uncertainties
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2312.02925 [pdf]
PRL(2024)·36 citations
11
[Submitted on 5 Dec 2023] (cross-list from hep-lat)
The Chiral Separation Effect from lattice QCD at the physical point
Bastian B. Brandt🇩🇪 · Gergely Endrődi🇩🇪 · Eduardo Garnacho-Velasco🇩🇪 · Gergely Markó🇩🇪
In this paper we study the Chiral Separation Effect by means of first-principles lattice QCD simulations. For the first time in the literature, we determine the continuum limit of the associated conductivity using 2+1 flavors of dynamical staggered quarks at physical masses. The results reveal a suppression of the conductivity in the confined phase and a gradual enhancement toward the perturbative value for high temperatures. In addition to our dynamical setup, we also investigate the impact of the quenched approximation on the conductivity, using both staggered and Wilson quarks. Finally, we highlight the relevance of employing conserved vector and anomalous axial currents in the lattice simulations.
Comments:
26 pages, 8 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2312.02945 [pdf]
JHEP(2024)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE