Nuclear Theory·nucl-th

Wednesday·February 3, 2021

8 papers—1 primary·7 cross-listed

01
[Submitted on 2 Feb 2021]
Trace of $Λ (1405)$ resonance in low energy $K^{-} +^{3} He \to (π^{0} Σ^{0}) + d$ reaction
J. Esmaili🇮🇷 · S. Marri🇮🇷 · M. Raeisi🇮🇷 · A. Naderi Beni🇮🇷
In present work, we investigated $K^{-} +^{3} He$ reaction at low energies. The coupled-channel Faddeev AGS equations were solved for $K ˉ N d - π Σ d$ three-body system in momentum representation to extract the scattering amplitudes. To trace the signature of the $Λ$ (1405) resonance in the $π Σ$ invariant mass, the deuteron energy spectrum for $K^{-} +^{3} He \to π Σ d$ reaction was obtained. Different types of $K ˉ N - π Σ$ potentials based on phenomenological and chiral SU(3) approaches were used. As a remarkable result of this investigation, it was found that the deuteron energy spectrum, reflecting the $Λ$ (1405) mass distribution and width, depends quite sensitively on the $K ˉ N - π Σ$ model of interaction. Hence accurate measurements of the $π Σ$ mass distribution have the potential to discriminate between possible mechanisms at work in the formation of the $Λ$ (1405).
Comments:
9 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2102.01677 [pdf]
EPJA(2021)·3 citations
02
[Submitted on 1 Feb 2021] (cross-list from hep-ph)
Origin and Resummation of Threshold Logarithms in the Lattice QCD Calculations of PDFs
Xiang Gao🇺🇸 · Kyle Lee🇺🇸 · Swagato Mukherjee🇺🇸 · Charles Shugert🇺🇸 · Yong Zhao🇺🇸
Many present lattice QCD approaches to calculate the parton distribution functions (PDFs) rely on a factorization formula or effective theory expansion of certain Euclidean matrix elements in boosted hadron states. In the quasi- and pseudo-PDF methods, the matching coefficient in the factorization or expansion formula includes large logarithms near the threshold, which arise from the subtle interplay of collinear and soft divergences of an underlying 3D momentum distribution. We use the standard prescription to resum such logarithms in the Mellin-moment space at next-to-leading logarithmic accuracy, which also accounts for the DGLAP evolution, and we show that it can suppress the PDF at large $x$ . Unlike the deep inelastic scattering and Drell-Yan cross sections, the resummation formula is away from the Landau pole. We then apply our formulation to reanalyze the recent lattice results for the pion valence PDF, and find that within the current data sensitivity, the effect of threshold resummation is marginal for the accessible moments and the PDF at large $x$ .
Comments:
15 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2102.01101 [pdf]
PRD(2021)·62 citations
03
[Submitted on 1 Feb 2021] (cross-list from hep-ph)
Deuterium scattering experiments in CTEQ global QCD analyses: a comparative investigation
A. Accardi🇺🇸 · T. J. Hobbs🇺🇸 · X. Jing🇺🇸 · P. M. Nadolsky🇺🇸
Experimental measurements in deep-inelastic scattering and lepton-pair production on deuterium targets play an important role in the flavor separation of $u$ and $d$ (anti)quarks in global QCD analyses of the parton distribution functions (PDFs) of the nucleon. We investigate the impact of theoretical corrections accounting for the light-nuclear structure of the deuteron upon the fitted $u, d$ -quark, gluon, and other PDFs in the CJ15 and CT18 families of next-to-leading order CTEQ global analyses. The investigation is done using the $L_{2}$ sensitivity statistical method, which provides a common metric to quantify the strength of experimental constraints on various PDFs and ratios of PDFs in the two distinct fitting frameworks. Using the $L_{2}$ sensitivity and other approaches, we examine the compatibility of deuteron data sets with other fitted experiments under varied implementations of the deuteron corrections. We find that freely-fitted deuteron corrections modify the PDF uncertainty at large momentum fractions and will be relevant for future PDFs affecting electroweak precision measurements.
Comments:
28 pages, 13 multi-panel figures, 4 tables; updated to published version with comparisons to NNLO corrections and scale variations
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2102.01107 [pdf]
EPJC(2021)·31 citations
04
[Submitted on 1 Feb 2021] (cross-list from hep-ph)
A Standard Model Explanation for the "ATOMKI Anomaly"
A. Aleksejevs🇨🇦 · S. Barkanova🇨🇦 · Yu.G. Kolomensky🇺🇸 · B. Sheff🇺🇸
Using the $e^{+} e^{-}$ pair spectrometer at the 5 MV Van de Graaff accelerator at the Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Krasznahorkay et al. have claimed a 6.8 $σ$ excess at high $e^{+} e^{-}$ opening angles in the internal pair creation isoscalar transition $^{8} Be (18.15) \to^{8} Be e^{+} e^{-}$ . A hypothetical gauge boson with the mass circa $17$ MeV, "X17", has been proposed as an explanation for the excess. We show that the observed experimental structure can be reproduced within the Standard Model by adding the full set of second-order corrections and the interference terms to the Born-level decay amplitudes considered by Krasznahorkay et al. We implement a detailed model of the ATOMKI detector, and also show how experimental selection and acceptance bias exacerbate the apparent difference between the experimental data and the Born-level prediction.
Comments:
7 pages, 10 figures. v2 corrects small typos and replaces images with vector graphics
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2102.01127 [pdf]
36 citations
05
[Submitted on 1 Feb 2021] (cross-list from hep-lat)
Finite temperature properties of QCD with two flavors and three, four and five colors
Thomas DeGrand🇺🇸
I present a numerical study of the crossover between the low temperature chirally broken phase and the high temperature chirally restored phase in $S U (N_{c})$ gauge theory with $N_{c} = 3 - 5$ colors and $N_{f} = 2$ degenerate fermion flavors. Fermion masses span a range of intermediate values (represented by the squared ratio of pseudoscalar to vector meson masses $(m_{P S} / m_{V})^{2} \sim 0.25$ to 0.63). Observables include the temperature dependent chiral condensate and screening masses. At each fermion mass these quantities show nearly identical temperature dependence across $N_{c}$ .
Comments:
published version, small changes from v.1, 24 pages, 9 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2102.01150 [pdf]
PRD(2021)·15 citations
06
[Submitted on 1 Feb 2021] (cross-list from hep-ph)
Fresh extraction of the proton charge radius from electron scattering
Zhu-Fang Cui🇨🇳 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳 · Sebastian M. Schmidt🇩🇪
We present a novel method for extracting the proton radius from elastic electron-proton ( $e p$ ) scattering data. The approach is based on interpolation via continued fractions augmented by statistical sampling and avoids any assumptions on the form of function used for the representation of data and subsequent extrapolation onto $Q^{2} ≃ 0$ . Applying the method to extant modern $e p$ data sets, we find that all results are mutually consistent and, combining them, arrive at $r_{p} = 0.847 (8)$ fm. This result compares favourably with values obtained from contemporary measurements of the Lamb shift in muonic hydrogen, transitions in electronic hydrogen, and muonic deuterium spectroscopy.
Comments:
7 pages, 4 figures. Version accepted for publication in Phys. Rev. Lett
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2102.01180 [pdf]
PRL(2021)·41 citations
07
[Submitted on 2 Feb 2021] (cross-list from hep-ph)
First Saturation Correction in High Energy Proton-Nucleus Collisions: I. Time evolution of classical Yang-Mills fields beyond leading order
Ming Li🇺🇸 · Vladimir V. Skokov🇺🇸
In high energy proton-nucleus collisions, the single- and double-inclusive soft gluon productions at the leading order have been calculated and phenomenologically studied in various approaches for many years. These studies do not take into account the saturation and multiple rescatterings in the field of the proton. The first saturation correction to these leading order results (the terms that are enhanced by the combination $α_{s}^{2} μ^{2}$ , where $μ^{2}$ is the proton's color charge squared per unit transverse area) has not been completely derived despite recent attempts using a diagrammatic approach. This paper is the first in a series of papers towards analytically completing the first saturation correction to physical observables in high energy proton-nucleus collisions. Our approach is to analytically solve the classical Yang-Mills equations in the dilute-dense regime using the Color Glass Condensate effective theory and compute physical observables constructed from classical gluon fields. In the current paper, the Yang-Mills equations are solved perturbatively in the field of the dilute object (the proton). Next-to-leading order and next-to-next-to-leading order analytic solutions are explicitly constructed. A systematic way to obtain all higher order analytic solutions is outlined
Comments:
53 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2102.01594 [pdf]
JHEP(2021)·16 citations
08
[Submitted on 2 Feb 2021] (cross-list from hep-ph)
Forces within hadrons on the light front
Adam Freese🇺🇸 · Gerald A. Miller🇺🇸
In this work, we find the light front densities for momentum and forces, including pressure and shear forces, within hadrons. This is achieved by deriving relativistically correct expressions relating these densities to the gravitational form factors $A (t)$ and $D (t)$ associated with the energy momentum tensor. The derivation begins from the fundamental definition of density in a quantum field theory, namely the expectation value of a local operator within a spatially-localized state. We find that it is necessary to use the light front formalism to define a density that corresponds to internal hadron structure. When using the instant form formalism, it is impossible to remove the spatial extent of the hadron wave function from any density, and -- even within instant form dynamics -- one does not obtain a Breit frame Fourier transform for a properly defined density. Within the front formalism, we derive new expressions for various mechanical properties of hadrons, including the mechanical radius, as well as for stability conditions. The multipole ansatz for the form factors is used as an example to illustrate all of these findings.
Comments:
2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2102.01683 [pdf]
PRD(2021)·93 citations

Affiliations

first authorsco-authorsvia INSPIRE