Nuclear Theory·nucl-th

Monday·October 16, 2023

6 papers—2 primary·4 cross-listed

03
[Submitted on 12 Oct 2023] (cross-list from hep-ph)
Heavy flavor as a probe of hot QCD matter produced in proton-proton collisions
Jiaxing Zhao🇫🇷 · Joerg Aichelin🇫🇷 · Pol Bernard Gossiaux🇫🇷 · Klaus Werner🇫🇷
The creation of a quark-gluon plasma (QGP) is expected in heavy ion collisions. It came as a surprise that proton-proton collisions at ultrarelativistic energies show as well a ``QGP-like'' behavior and signs of the creation of a fluid, although the corresponding system size is not more than a few cubic femtometers. Even more surprisingly, also heavy flavor particles seem to be part of the fluid or at least interact with it. In this paper, we will investigate in a quantitative way this ``collective behavior'' of heavy flavor, by employing the newly developed EPOS4HQ approach, which has proven to be compatible with basic experimental data of light flavor hadrons. We will investigate all observables, which may manifest collectivity, as particle spectra, elliptic flow, baryon-to-meson ratios, and two-particle correlations, and compare the results with experimental data. We will try to disentangle initial state effects, those being due to interactions between charm quarks and plasma partons, and final state effects (hadronization).
Comments:
9 pages, 14 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.08684 [pdf]
PRD(2024)·42 citations
04
[Submitted on 12 Oct 2023] (cross-list from astro-ph.SR)
The intermediate neutron capture process: IV. Impact of nuclear model and parameter uncertainties
S. Martinet · A. Choplin · S. Goriely · L. Siess
We investigate both the systematic and statistical uncertainties associated with theoretical nuclear reaction rates of relevance during the i-process and explore their impact on the i-process elemental production, and subsequently on the surface enrichment, for a low-mass low-metallicity star during the early AGB phase. We use the TALYS reaction code (Koning et al. 2023) to estimate both the model and parameter uncertainties affecting the photon strength function and the nuclear level densities, hence the radiative neutron capture rates. The STAREVOL code (Siess et al. 2006) is used to determine the impact of nuclear uncertainties on the i-process nucleosynthesis in a 1 $M_{⊙}$ [Fe/H] = - 2.5 model star during the proton ingestion event in the early AGB phase. A large nuclear network of 1160 species coherently coupled to the transport processes is solved to follow the i-process nucleosynthesis. We find that the non-correlated parameter uncertainties lead the surface abundances uncertainties of element with $Z \geq 40$ to range between 0.5 and 1.0 dex, with odd- $Z$ elements displaying higher uncertainties. The correlated model uncertainties are of the same order of magnitude, and both model and parameter uncertainties have an important impact on potential observable tracers such as Eu and La. Both the correlated model and uncorrelated parameter uncertainties need to be estimated coherently before being propagated to astrophysical observables through multi-zone stellar evolution models. Many reactions are found to affect the i-process predictions and will require improved nuclear models guided by experimental constraints. Priority should be given to the reactions influencing the observable tracers.
Comments:
Accepted: October 11, 2023 \\ 14 Pages, 14 Figures, 2 Tables
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2310.08694 [pdf]
Astron.Astrophys.(2024)·16 citations
05
[Submitted on 13 Oct 2023] (cross-list from hep-lat)
Lattice computation of the Kugo-Ojima correlation function
Nuno Miguel Rebelo Brito🇵🇹
As of today, color confinement in Quantum Chromodynamics remains a mystery from the theoretical point of view. So far, no analytical proof of color confinement has been found and the mechanism that confines colored states from the space of physical states is still unknown. Taichiro Kugo and Izumi Ojima proposed such confinement mechanism, using as basis the BRST-symmetry and derived the requirements for the realization of this mechanism. One such requirement, which happens to be the non-trivial one, is that a special correlation function, the Kugo-Ojima correlation function $u (p^{2})$ , approaches $- 1$ at the origin ( $p^{2} = 0)$ . This correlation function can be obtained on the lattice within the lattice formulation of gauge theories. The present work consists on lattice results for this correlation function on the Landau gauge. We present results obtained from 4 symmetric large volume lattices $(3 2^{4}, 4 8^{4}, 6 4^{4}, 8 0^{4})$ with $β = 6.0$ on the Landau gauge. A test on the transversality of the Kugo-Ojima correlation function is also performed, along with some statistical considerations of the results. The results present further evidence that the Kugo-Ojima confinement scenario is not realized on the lattice and that the Kugo-Ojima correlation function, in the Landau gauge, is transverse. Our findings align qualitatively with existing literature.
Comments:
Master's Degree Dissertation, 72 Pages, 10 Figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.09010 [pdf]
2 citations
06
[Submitted on 13 Oct 2023] (cross-list from hep-ph)
Low-energy matrix elements of heavy-quark currents
Harvey B. Meyer🇩🇪
In QCD at energies well below a heavy-quark threshold, the heavy-quark vector current can be represented via local operators made of the lighter quarks and of the gluon fields. We extract the leading perturbative matching coefficients for the two most important sets of operators from known results. As an application, we analytically determine the $O (α_{s}^{3}) m_{c}^{2} / m_{b}^{2}$ effect of the bottom quark current on the $R (s)$ ratio below the bottom but above the charm threshold. For the low-energy representation of the charm quark current, the two most important operators are given by the total divergence of dimension-six gluonic operators. We argue that the charm magnetic moment of the nucleon is effectively measuring the forward matrix elements of these gluonic operators and predict the corresponding bottom magnetic moment. Similarly, the contribution of the charm current to $R (s \approx 1 GeV^{2})$ , which is associated with quark-disconnected diagrams, is dominantly determined by the decay constants of the $ω$ and $ϕ$ mesons with respect to the two gluonic operators.
Comments:
14 pages, 2 figures; corrected Eq. 2, expanded the discussion at beginning of section 2, added comment on four-fermion operators at end of section 3
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2310.09085 [pdf]
EPJC(2023)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Heavy flavor as a probe of hot QCD matter produced in proton-proton collisions

The intermediate neutron capture process: IV. Impact of nuclear model and parameter uncertainties

Lattice computation of the Kugo-Ojima correlation function

Low-energy matrix elements of heavy-quark currents

Affiliations