Nuclear Theory·nucl-th

Thursday·May 26, 2022

14 papers—7 primary·7 cross-listed

01
[Submitted on 24 May 2022]
Electromagnetic measurement of the temperature of quark-gluon plasma produced in central ultrarelativistic nuclear collisions
Jean-François Paquet🇺🇸 · Steffen A. Bass🇺🇸
Ultrarelativistic collisions of large nuclei produce a short-lived plasma of deconfined quarks and gluons. Of all the GeV-energy photons detected in these nuclear collisions, only a small number are emitted directly by the quark-gluon plasma. The characteristic near-exponential energy spectrum of these photons is often associated with an effective temperature whose interpretation is complicated by spacetime averaging, Doppler shifts and other factors. We show that the Doppler shift's effect on the slope of the photon spectrum is generally modest and can either increase or decrease the slope, in contrast to the commonly assumed blue-shifting of the photon spectrum. We make the case that a minimal degree of modelling of quark-gluon plasma expansion provides a reasonable mapping between the slope of the photon energy spectrum and the maximum temperature of the plasma, as long as the slope is extracted at a reasonably high photon energy and thermal photons can be isolated from non-thermal sources. Validating our approach using state-of-the-art numerical calculations of photon production, we highlight the challenges of contamination from non-thermal sources.
Comments:
19 pages, 9 figures; focused paper on inverse slope rather than spectrum; extended discussion of the role of Doppler shift and non-thermal sources
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2205.12299 [pdf]
9 citations
02
[Submitted on 25 May 2022]
Influence of the Pauli exclusion principle on the alpha decay
M. M. Amiri · O. N. Ghodsi
In this study, the effects of repulsive nucleon-nucleon interactions arising from the Pauli exclusion principle were examined regarding the half-lives of heavy even-even nuclei with $84 \leq Z \leq 92$ . The Pauli exclusion principle is applied to our investigations by renormalizing the nucleon-nucleon interactions according to the Bohr-Sommerfeld quantization condition. It is also applied to the double-folding ( $D F$ ) formalism as a modification term by investigating the kinetic energy variation at the overlapping regions between the densities of the alpha and daughter nuclei. The standard deviation for the calculated half-lives from their corresponded experimental data is 0.340 for the renormalized DF formalism. Its value reduces to 0.309 for the DF formalism modified with the kinetic energy contribution estimated by the extended Thomas-Fermi approach. The calculated $α$ decay half-lives are more consistent with experimental data if the kinetic energy contribution is associated with the DF formalism.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.12497 [pdf]
PRC(2020)·13 citations
03
[Submitted on 25 May 2022]
Continuum Skyrme Hartree-Fock-Bogoliubov theory with Green's function method for neutron-rich Ca, Ni, Zr, Sn isotopes
En-Bo Huo · Ting-Ting Sun · Ke-Ran Li · Xiao-Ying Qu · Ying Zhang
The possible exotic nuclear properties in the neutron-rich Ca, Ni, Zr, and Sn isotopes are explored with the continuum Skyrme Hartree-Fock-Bogoliubov theory formulated with the Green's function method. The available experimental two-neutron separation energies $S_{2n}$ and one-neutron separation energies $S_{n}$ are well reproduced. Much shorter drip lines predicted by $S_{n}$ are obtained compared with those by $S_{2n}$ . The systematic studies of the neutron pairing energies $- E_{pair}$ shown that values of the odd- $A$ nuclei are much smaller in comparison with those of the neighboring even-even nuclei due to the absent contribution of pairing energy by the unpaired odd neutron. By investigating the single-particle structures, the rms radii and the density distributions, the possible halo structures in the neutron-rich Ca, Ni, and Sn isotopes are predicted, in which the sharp increases of rms radii with significant deviations from the traditional $r \propto A^{1/3}$ rule and very diffuse spatial distributions in densities are observed. By analyzing the contributions of different partial waves to the total neutron density $ρ_{l j} (r) / ρ (r)$ , the orbitals locating around the Fermi surface especially those with low angular momenta are found the main reason causing the extended nuclear density and large rms radii. Finally, the numbers of the neutrons $N_{λ}$ ~( $N_{0}$ ) occupied above the Fermi surface $λ_{n}$ ~(in the continuum) are discussed, the behaviors of which are basically consistent with those of pairing energy, supporting the key role of the pairing correlations in the halo phenomena.
Comments:
10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.12560 [pdf]
Nucl.Sci.Tech.(2023)·18 citations
04
[Submitted on 25 May 2022]
Surface energy coefficient of a N2LO Skyrme energy functional : a semiclassical Extended Thomas-Fermi approach
P. Proust🇫🇷 · Y. Lallouet🇫🇷 · D. Davesne🇫🇷 · J. Meyer🇫🇷
We generalize to N2LO Skyrme functionals the semi-classical approach of Grammaticos and Voros in order to calculate the Extended Thomas Fermi expressions of the new densities and currents appearing at the N2LO level. Within a one dimensional symmetric semi infinite nuclear matter model and using a simple Fermi-like density profile, we obtain an easy-to-use formula for the surface energy including the contributions of the central, density-dependent and spin-orbit terms up to $ℏ^{2}$ . Such a formula can be easily used as a first attempt to constrain the surface properties of new N2LO Skyrme parametrizations. The N2LO parametrization tested in this paper is shown to exhibit a shift (compared to a full Hartree-Fock calculation) which is quantitatively similar to the one obtained with the traditional Skyrme parametrizations.
Comments:
19 pages, 3 figures, to be published
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.12651 [pdf]
PRC(2022)·3 citations
05
[Submitted on 25 May 2022]
Uncertainty evaluation of peak energy of giant dipole resonance propagated from uncertainties of Skyrme parameters
Tsunenori Inakura
We evaluate uncertainty of peak energy of giant dipole resonance (GDR), propagated from uncertainty of parameters of Skyrme interaction. The Monte Carlo calculation of the random phase approximation using randomized Skyrme parameters is performed. Under the condition that the correlations between each of the Skyrme parameters is considered, the GDR peak energy has the uncertainty of $\sim$ 1 MeV irrespective of nuclear mass and is strongly correlated with the Skyrme parameters, in present calculations. This serves a guide for a new parametrization of effective interactions.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.12671 [pdf]
EPJ Web Conf.(2023)·2 citations
06
[Submitted on 25 May 2022]
Machine learning the deuteron: new architectures and uncertainty quantification
J Rozalén Sarmiento · J W T Keeble · A Rios
We solve the ground state of the deuteron using a variational neural network ansatz for the wave function in momentum space. This ansatz provides a flexible representation of both the $S$ and the $D$ states, with relative errors in the energy which are within fractions of a percent of a full diagonalisation benchmark. We extend the previous work on this area in two directions. First, we study new architectures by adding more layers to the network and by exploring different connections between the states. Second, we provide a better estimate of the numerical uncertainty by taking into account the final oscillations at the end of the minimisation process. Overall, we find that the best performing architecture is the simple one-layer, state-independent network. Two-layer networks show indications of overfitting, in regions that are not probed by the fixed momentum basis where calculations are performed. In all cases, the error associated to the model oscillations around the real minimum is larger than the stochastic initialisation uncertainties. The conclusions that we draw can be generalised to other quantum mechanics settings.
Comments:
17 pages, 6 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.12795 [pdf]
Eur.Phys.J.Plus(2024)·7 citations
07
[Submitted on 25 May 2022]
Critical net-baryon fluctuations in an expanding system
Grégoire Pihan🇫🇷 · Marcus Bluhm🇫🇷 · Masakiyo Kitazawa🇯🇵 · Taklit Sami🇫🇷 · Marlene Nahrgang🇫🇷
In this work we study the consequences of a longitudinal Bjorken expansion and a Hubble-like temperature cooling scenario on a 1+1D non-linear model of the diffusive dynamics of fluctuations in the net-baryon density. The equilibrium behavior of the fluctuations is fully encoded in the temperature dependence of the susceptibilities on the crossover side both in the vicinity of the assumed location of the critical point and at vanishing baryo-chemical potential in-line with lattice QCD calculations. We demonstrate the great sensitivity of the fluctuation observables on the dynamics, in particular on the diffusion length and the freeze-out conditions. While the critical signals are visible and the critical region is broadened by the expansion, a too small diffusion length can strongly reduce the amplitude of the signals. We propose to search for significant anti-correlations of baryons at intermediate rapidity experimentally and to map out the rapidity dependence of the fourth-order cumulant, which in the presence of a critical point (and only in its presence) has a pronounced minimum at intermediate rapidities.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2205.12834 [pdf]
PRC(2023)·24 citations
08
[Submitted on 24 May 2022] (cross-list from hep-ph)
One-loop matching for gluon lattice TMDs
Stella T. Schindler🇺🇸 · Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸
Transverse-momentum-dependent parton distributions (TMDs) can be calculated from first principles by computing a related set of Euclidean lattice observables and connecting them via a factorization formula. This work focuses on the leading-power factorization formula connecting the lattice quasi-TMD and continuum Collins TMD for gluons. We calculate the one-loop gluon matching coefficient, which is known to be independent of spin and exhibits no mixing with quarks. We demonstrate that this coefficient satisfies Casimir scaling with respect to the quark matching coefficient at one-loop order. Our result facilitates reliable lattice QCD calculations of gluon TMDs.
Comments:
11 pages, 2 figures, v2: updates to match journal
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2205.12369 [pdf]
JHEP(2022)·24 citations
09
[Submitted on 24 May 2022] (cross-list from hep-ph)
Designing Observables for Quantum Interference in Jets at Subleading Color
Andrew J. Larkoski🇺🇸
The large- $N_{c}$ or topologically planar limit of gauge theories can be considered as a classical limit because all gauge bosons are distinguishable particles and therefore cannot exhibit interference. Quantum effects due to the flow of color therefore arise starting at subleading in $1/ N_{c}$ . We introduce kinematic observables explicitly sensitive to effects at subleading color formed from the ratio of interfering to squared color-ordered amplitudes. Such observables are in general not infrared and collinear safe, so we introduce angular observables defined from appropriate multi-point energy correlators motivated by the form of color-ordered amplitudes. We demonstrate that color interference effects are manifest as sinusoidal oscillation in the simplest system, a collinear jet with three particles, and show the limitations of predicting this observable in all-purpose, leading-color parton shower Monte Carlos.
Comments:
19 pages, 5 figures; v2: updated comparison to parton shower simulation; v3: title change and other minor changes, SciPost version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2205.12375 [pdf]
SciPost Phys.(2023)·4 citations
10
[Submitted on 25 May 2022] (cross-list from hep-ph)
New aspect of chiral and axial breaking in QCD
Chuan-Xin Cui🇨🇳 · Mamiya Kawaguchi🇨🇳 · Jin-Yang Li🇨🇳 · Shinya Matsuzaki🇨🇳 · Akio Tomiya🇯🇵
Violation of the $U (1)$ axial symmetry in QCD is stricter than the chiral $S U (2)$ breaking, simply because of the presence of the quantum axial anomaly. If the QCD gauge coupling is sent to zero, the strength of the $U (1)$ axial breaking coincides with that of the chiral $S U (2)$ breaking, which we shall in short call an axial-chiral coincidence. This coincidence is trivial since QCD then becomes a non-interacting theory. Actually, there exists another limit in the QCD parameter space, where an axial-chiral coincidence occurs even with nonzero QCD gauge coupling, that can be dubbed a nontrivial coincidence: it is the case with the massive light quarks $(m_{l} \neq = 0)$ and the massless strange quark ( $m_{s} = 0$ ), due to the flavor-singlet nature of the topological susceptibility. This coincidence is robust and tied to the anomalous chiral Ward-Takahashi identity, which is operative even at hot QCD. This implies that the chiral $S U (2)$ symmetry is restored simultaneously with the $U (1)$ axial symmetry at high temperatures. This simultaneous restoration is independent of $m_{l} (\neq = 0)$ , hence is irrespective to the order of the chiral phase transition. In this paper, we discuss how the real-life QCD can be evolved from the nontrivial chiral-axial coincidence limit, by working on a Nambu-Jona-Lasinio model with the $U (1)$ axial anomaly contribution properly incorporated. It is shown that at high temperatures the large differences between the restorations of the chiral $S U (2)$ symmetry and the $U (1)$ axial symmetry for two light quarks and a sufficiently large current mass for the strange quark is induced by a significant interference of the topological susceptibility. Thus the deviation from the nontrivial coincidence, which is monitored by the strange quark mass controlling the topological susceptibility, provides a new way of understanding the chiral $S U (2)$ and $U (1)$ axial breaking in QCD.
Comments:
23 pages, 11 figures, some references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2205.12479 [pdf]
Particles(2024)·10 citations
11
[Submitted on 25 May 2022] (cross-list from hep-lat)
Centre Vortex Structure of QCD-Vacuum Fields and Confinement
Derek Leinweber🇦🇺 · James Biddle🇦🇺 · Waseem Kamleh (University of Adelaide)🇦🇺
The non-trivial ground-state vacuum fields of QCD form the foundation of matter. Using modern visualisation techniques, this presentation examines the microscopic structure of these fields. Of particular interest are the centre vortices identified within the ground-state fields of lattice QCD. Our current focus is on understanding the manner in which dynamical fermions in the QCD vacuum alter the centre-vortex structure. The impact of dynamical fermions is significant and provides new insights into the role of centre vortices in underpinning both confinement and dynamical chiral symmetry breaking in QCD.
Comments:
10 pages, 7 figures with 4 3D interactive. XXXIII International (Online) Workshop on High Energy Physics, "Hard Problems of Hadron Physics: Non-Perturbative QCD & Related Quests" November 8-12, 2021. arXiv admin note: substantial text overlap with arXiv:2204.04825
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2205.12518 [pdf]
SciPost Phys.Proc.(2022)·4 citations
12
[Submitted on 25 May 2022] (cross-list from hep-ph)
Faddeev fixed-center approximation to the $D D ˉ K$ system and the hidden charm $K_{c c ˉ} (4180)$ state
Xiang Wei🇨🇳 · Qing-Hua Shen🇨🇳 · Ju-Jun Xie🇨🇳
We perform a theoretical study on the $D D ˉ K$ three body system, using the fixed center approximation to the Faddeev equations, considering the interaction between $D$ and $K$ , $D$ and $D ˉ$ from the chiral unitary approach. We assume the scattering of $K$ meson on a clusterized system $D D ˉ$ , where a scalar meson $X (3720)$ could be formed. Thanks to the strong $D K$ interaction, where the scalar $D_{s 0}^{*} (2317)$ meson is dynamically generated, a resonance structure shows up in the modulus squared of the three body $K$ - $(D D ˉ)_{X (3720)}$ scattering amplitude and supports that a $D D ˉ K$ bound state can be formed. The result is in agreement with previous theoretical studies, which claim a new excited hidden charm $K$ meson, $K_{c c ˉ} (4180)$ with quantum numbers $I (J^{P}) = \frac{1}{2} (0^{-})$ and mass about $4180$ MeV. It is expected that these theoretical results motivate its search in experimental measurements.
Comments:
6 pages, 5 figures. Typos fixed, more discussions added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2205.12526 [pdf]
EPJC(2022)·19 citations
13
[Submitted on 25 May 2022] (cross-list from hep-lat)
Towards the chiral phase transition in the Roberge-Weiss plane
F. Cuteri🇩🇪 · J. Goswami🇯🇵 · F. Karsch🇩🇪 · Anirban Lahiri🇩🇪 · M. Neumann🇩🇪 · O. Philipsen🇩🇪 · Christian Schmidt🇩🇪 · A. Sciarra🇩🇪
We discuss the interplay between chiral and center sector phase transitions that occur in QCD with an imaginary quark chemical potential $μ = i (2 n + 1) π T /3$ . Based on a finite size scaling analysis in (2+1)-flavor QCD using HISQ fermions with a physical strange quark mass and a range of light quark masses, we show that the endpoint of the line of first-order Roberge-Weiss (RW) transitions between center sectors is second order for light quark masses $m_{l} \geq m_{s} /320$ , and that it belongs to the $3$ -d, $Z (2)$ universality class. The operator for the chiral condensate behaves like an energy-like operator in an effective spin model for the RW phase transition. As a consequence, for any non-zero value of the quark mass, the chiral condensate will have an infinite slope at the RW phase transition temperature, $T_{R W}$ . Its fluctuation, the disconnected chiral susceptibility, behaves like the specific heat in $Z (2)$ symmetric models and diverges in the infinite volume limit at the RW phase transition temperature $T_{R W}$ for any non-zero value of the light quark masses. Our analysis suggests the critical temperatures for the RW phase transition and the chiral phase transition coincide in the RW plane. On lattices with temporal extent $N_{τ} = 4$ , we find in the chiral limit $T_{χ} = T_{R W} = 195 (1)$ MeV.
Comments:
17 pages
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2205.12707 [pdf]
PRD(2022)·29 citations
14
[Submitted on 25 May 2022] (cross-list from quant-ph)
Variational thermal quantum simulation of the lattice Schwinger model
Xu-Dan Xie🇨🇳 · Xingyu Guo🇨🇳 · Hongxi Xing🇨🇳 · Zheng-Yuan Xue🇨🇳 · Dan-Bo Zhang🇨🇳 · Shi-Liang Zhu🇨🇳
Confinement of quarks due to the strong interaction and the deconfinement at high temperatures and high densities are a basic paradigm for understanding the nuclear matter. Their simulation, however, is very challenging for classical computers due to the sign problem of solving equilibrium states of finite-temperature quantum chromodynamical systems at finite density. In this paper, we propose a variational approach, using the lattice Schwinger model, to simulate the confinement or deconfinement by investigating the string tension. We adopt an ansatz that the string tension can be evaluated without referring to quantum protocols for measuring the entropy in the free energy. Results of numeral simulation show that the string tension decreases both along the increasing of the temperature and the chemical potential, which can be an analog of the phase diagram of QCD. Our work paves a way for exploiting near-term quantum computers for investigating the phase diagram of finite-temperature and finite density for nuclear matters.
Subjects:
Quantum Physics (quant-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2205.12767 [pdf]
PRD(2022)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE