Nuclear Theory·nucl-th

Thursday·August 5, 2021

8 papers—3 primary·5 cross-listed

01
[Submitted on 4 Aug 2021]
Anisotropic turbulence in relativistic plasmas
Abhisek Saha🇮🇳 · Soma Sanyal🇮🇳
Signs of turbulence have been observed at the relativistic heavy ion collision at high collision energies. We study the signatures of turbulence in this system and find that there are significant departures from isotropic turbulence in the initial stages of the collision. Since the anisotropic fluctuations are sub leading to the isotropic fluctuations, the Kolmogorov spectrum can usually be obtained even for the initial stages. However, the energy spectrum and the temperature fluctuations indicate deviations from isotropic turbulence. Since a strong momentum anisotropy exists between the transverse and the longitudinal plane, we study the energy density spectrum in these two planes. The geometrical anisotropy is reflected in the anisotropic turbulence generated in the rotating plasma and we find that the scaling exponent is different in the two planes. We find that the scaling exponents in the longitudinal plane are independent of centrality while the scaling exponent in the transverse plane depends on the centrality range. We also obtain the temperature spectrum in the initial stages. The spectrum deviates from the Gaussian spectra expected for an isotropic turbulence. All these seem to indicate that the large scale momentum anisotropy persists in the smaller length scales for the relativistic heavy ion collisions.
Comments:
8 figures. 9 pages Major revision, relativistic effects included
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2108.01847 [pdf]
Eur.Phys.J.Plus(2022)·1 citation
02
[Submitted on 4 Aug 2021]
Charmonium in electromagnetic and vortical fields
Jiaxing Zhao🇨🇳 · Shile Chen🇨🇳 · Pengfei Zhuang🇨🇳
Due to larger mass and earlier production, heavy quark(quarkonium) can be sensitive probes to investigate the fast decaying electromagnetic and vortical fields produced in heavy-ion collisions. The non-relativistic Schroedinger-like equation for heavy quarks under strong electromagnetic fields in the rotating frame is deduced and used to construct the two-body equation for the charmonium system. The effective potential between charm and anti-charm becomes anisotropic in electromagnetic and vortical fields, especially along the direction of the Lorentz force. The vorticity will affect this asymmetry property largely and catalyze the transition from strong interaction dominant bound state to electromagnetic and vortical interaction controlled anisotropic bound state. It is possible to be realized in high-energy nuclear collisions.
Comments:
Contribution to: SQM2021
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2108.02125 [pdf]
EPJ Web Conf.(2022)·1 citation
03
[Submitted on 4 Aug 2021]
Transient fluid dynamics with general matching conditions: a first study from the method of moments
Gabriel S. Rocha🇧🇷 · Gabriel S. Denicol🇧🇷
Recent works have revealed that matching conditions play a major role on general consistency properties of relativistic fluid dynamics such as causality, stability and wellposedness of the equations of motion. In this paper we derive transient fluid dynamics from kinetic theory, using the method of moments as proposed by Israel and Stewart, without imposing an specific matching condition. We then investigate how the equations of motion and their corresponding transport coefficients are affected by the choice of matching condition.
Comments:
20 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2108.02187 [pdf]
PRD(2021)·36 citations
04
[Submitted on 3 Aug 2021] (cross-list from hep-ph)
Extending Precision Perturbative QCD with Track Functions
Yibei Li🇨🇳 · Ian Moult🇺🇸 · Solange Schrijnder van Velzen🇳🇱 · Wouter J. Waalewijn🇳🇱 · Hua Xing Zhu🇨🇳
Collider experiments often exploit information about the quantum numbers of final state hadrons to maximize their sensitivity, with applications ranging from the use of tracking information (electric charge) for precision jet substructure measurements, to flavor tagging for nucleon structure studies. For such measurements, perturbative calculations in terms of quarks and gluons are insufficient, and non-perturbative track functions describing the energy fraction of a quark or gluon converted into a subset of hadrons (e.g., charged hadrons) must be incorporated. Unlike fragmentation functions, track functions describe correlations between hadrons and therefore satisfy complicated non-linear evolution equations whose structure has so far eluded calculation beyond the leading order. In this Letter, we develop an understanding of track functions and their interplay with energy flow observables beyond the leading order, allowing them to be used in state-of-the-art perturbative calculations for the first time. We identify a shift symmetry in the evolution of their moments that fixes their structure, and we explicitly compute the evolution of the first three moments at next-to-leading order, allowing for the description of up to three-point energy correlations. We then calculate the two-point energy correlator on charged particles at $O (α_{s}^{2})$ , illustrating explicitly that infrared singularities in perturbation theory are absorbed by moments of the track functions and also highlighting how these moments seamlessly interplay with modern techniques for perturbative calculations. Our results extend the boundaries of traditional perturbative QCD, enabling precision perturbative predictions for energy flow observables sensitive to the quantum numbers of hadronic states.
Comments:
5 pages, 3 figures + Supplemental Material
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2108.01674 [pdf]
PRL(2022)·93 citations
05
[Submitted on 3 Aug 2021] (cross-list from nucl-ex)
Investigation of the background in coherent $J / ψ$ production at the EIC
Wan Chang🇨🇳 · Elke-Caroline Aschenauer🇺🇸 · Mark D. Baker🇺🇸 · Alexander Jentsch🇺🇸 · Jeong-Hun Lee🇺🇸 · Zhoudunming Tu🇺🇸 · Zhongbao Yin🇨🇳 · Liang Zheng🇨🇳
Understanding various fundamental properties of nucleons and nuclei are among the most important scientific goals at the upcoming Electron-Ion Collider (EIC). With the unprecedented opportunity provided by the next-generation machine, the EIC might provide definitive answers to many standing puzzles and open questions in modern nuclear physics. Here we investigate one of the golden measurements proposed at the EIC, which is to obtain the spatial gluon density distribution within a lead ( $P b$ ) nucleus. The proposed experimental process is the exclusive $J / ψ$ vector-meson production off the $P b$ nucleus - $e + P b \to e^{'} + J / ψ + P b^{'}$ . The Fourier transformation of the momentum transfer $∣ t ∣$ distribution of the coherent diffraction is the transverse gluon spatial distribution. In order to measure it, the experiment has to overcome an overwhelmingly large background arising from the incoherent diffractive production, where the nucleus $P b^{'}$ mostly breaks up into fragments of particles in the far-forward direction close to the hadron-going beam rapidity. In this paper, we systematically study the rejection of incoherent $J / ψ$ production by vetoing products from these nuclear breakups - protons, neutrons, and photons, which is based on the BeAGLE event generator and the most up-to-date EIC Far-forward Interaction Region design. The achieved vetoing efficiency, the ratio between the number of vetoed events and total incoherent events, ranges from about 80% - 99% depending on $∣ t ∣$ , which can resolve at least the first minimum of the coherent diffractive distribution based on the Sar $t$ re model. Experimental and accelerator machine challenges as well as potential improvements are discussed.
Comments:
Manuscript with 12 pages, including 8 figures and 3 tables
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.01694 [pdf]
PRD(2021)·28 citations
06
[Submitted on 4 Aug 2021] (cross-list from hep-ph)
New form of kernel in equation for Nakanishi function
V.A. Karmanov🇷🇺
The Bethe-Salpeter amplitude $Φ (k, p)$ is expressed, by means of the Nakanishi integral representation, via a smooth function $g (γ, z)$ . This function satisfies a canonical equation $g = N g$ . However, calculations of the kernel $N$ in this equation, presented previously, were restricted to one-boson exchange and, depending on method, dealt with complex multivalued functions. Although these difficulties are surmountable, but in practice, they complicate finding the unambiguous result. In the present work, an unambiguous expression for the kernel $N$ in terms of real functions is derived. For the one-boson scalar exchange, the explicit formula for $N$ is found. With this equation and kernel, the binding energies, calculated previously, are reproduced. Their finding, as well as calculation of the Bethe-Salpeter amplitude in the Minkowski space, become not more difficult than in the Euclidean one. The method can be generalized to any kernel given by irreducible Feynman graph. This generalization is illustrated by example of the cross-ladder kernel.
Comments:
10 pages, 1 figure, accepted for publication in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.01853 [pdf]
PRD(2021)·5 citations
07
[Submitted on 4 Aug 2021] (cross-list from hep-ph)
JAM small- $x$ helicity phenomenology
Daniel Adamiak🇺🇸
We present the first-ever description the world data on the $g_{1}^{p, n}$ structure function at small Bjorken $x$ using evolution equations in $x$ derived from first principles QCD. This is a Monte-Carlo analysis within the JAM global framework that allows us to fit all existing polarized DIS data below $x < 0.1$ as well as predict future measurements of small $x$ $g_{1}^{p, n}$ at the EIC. This is a necessary step in determining the quark helicity PDFs and, ultimately, the quark contribution to the proton spin.
Comments:
9 pages, 4 figures, 1 logo, to appear in proceedings of DIS 2021. Version 2, fixed some errors and typos, included additional citations
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.02070 [pdf]
1 citation
08
[Submitted on 4 Aug 2021] (cross-list from hep-ph)
Soft-photon radiative corrections to the $e^{-} p \to e^{-} p l^{-} l^{+}$ process
Matthias Heller🇩🇪 · Niklas Keil🇩🇪 · Marc Vanderhaeghen🇩🇪
We calculate the leading-order QED radiative corrections to the process $e^{-} p \to e^{-} p l^{-} l^{+}$ in the soft-photon approximation, in two different energy regimes which are of relevance to extract nucleon structure information. In the low-energy region, this process is studied to better constrain the hadronic corrections to precision muonic Hydrogen spectroscopy. In the high-energy region, the beam-spin asymmetry for double virtual Compton scattering allows to directly access the Generalized Parton Distributions. We find that the soft-photon radiative corrections have a large impact on the cross sections and are therefore of paramount importance to extract the nucleon structure information from this process. For the forward-backward asymmetry the radiative corrections are found to affect the asymmetry only around or below the 1\% level, whereas the beam-spin asymmetry is not affected at all in the soft-photon approximation, which makes them gold-plated observables to extract nucleon structure information in both the low- and high-energy regimes.
Comments:
32 pages, 25 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.02088 [pdf]
PRD(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE