Nuclear Theory·nucl-th

Tuesday·September 14, 2021

11 papers—5 primary·6 cross-listed

01
[Submitted on 10 Sept 2021]
Off-of-equilibrium effects on Kurtosis Along Strangeness-Neutral Trajectories
Travis Dore🇺🇸 · Jamie Karthein🇺🇸 · Debora Mroczek🇺🇸 · Paolo Parotto🇩🇪 · Jacquelyn Noronha-Hostler🇺🇸 · Claudia Ratti🇺🇸
The Beam Energy Scan program at the Relativistic Heavy Ion Collider (RHIC) is searching for the QCD critical point. The main signal for the critical point is the kurtosis of the distribution of proton yields obtained on an event-by-event basis where one expects a peak at the critical point. However, its exact behavior is still an open question due to out-of-equilibrium effects and uncertainty in the equation of state. Here we use a simplistic hydrodynamic model that enforces strangeness-neutrality, selecting trajectories that pass close to the critical point. We vary the initial conditions to estimate the effect of out-of-equilibrium hydrodynamics on the kurtosis signal.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2109.05098 [pdf]
EPJ Web Conf.(2022)·4 citations
02
[Submitted on 11 Sept 2021]
Transverse momentum analysis of collective motion in relativistic nuclear collisions
P. Danielewicz🇺🇸 · G. Odyniec (LBL)🇺🇸
Novel transverse-momentum technique is used to analyse charged-particle exclusive data for collective motion in the Ar+KCl reaction at 1.8 GeV/nucl. Previous analysis of this reaction, employing the standard sphericity tensor, revealed no significant effect. In the present analysis, collective effects are observed, and they are substantially stronger than in the Cugnon cascade model, but weaker than in the hydrodynamical model.
Comments:
Preprint version, serving as a reference for another work (14 pages, 3 figures). This version contains, in particular, calculation of second-order azimuthal moments of particle distributions, in the elements of the sphericity tensor, not in the journal. The editor insisted on shortening of the paper, while the referee insisted on additional explanations, so something had to go
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2109.05308 [pdf]
PLB(1985)·504 citations
03
[Submitted on 11 Sept 2021]
Fock space dualities
K. Neergård
Several cases of Fock space duality occurring in the theory of many-body systems in general and nuclei in particular are discussed. All of them are special cases of a general duality theorem proved in mathematics by Howe in the 1970s. Dualities on a fermion Fock space between orthogonal Lie algebras and related groups, including an o-Pin duality recently discovered by the author, present a nice, symmetric pattern.
Comments:
Presented at The International Workshop "Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects" (SDANCA-21), 16-18 September 2021, Sofia, Bulgaria
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2109.05335 [pdf]
Bulg.J.Phys.(2021)·2 citations
04
[Submitted on 11 Sept 2021]
Comparison of different relativistic models applied to dense nuclear matter
R. Somasundaram🇫🇷 · J. Margueron🇫🇷 · G. Chanfray🇫🇷 · H. Hansen🇫🇷
We explore three different classes of relativistic approaches applied to the description of dense nuclear matter: a Walecka-type relativistic mean field model (RMF), an extension including an effective chiral potential (RMF-C) and a further extension with a chiral potential and confinement effects (RMF-CC). The parameters of the latter are controlled by fundamental properties such as the chiral potential, Lattice-QCD predictions, the quark sub-structure, as well as empirical properties at nuclear matter saturation. While these models are calibrated to the same properties at saturation density, they differ in their predictions as the density increases. We take care of parameter uncertainties and propagate them to our predictions for symmetric nuclear matter by employing Bayesian statistics. We show that RMF and RMF-C share common features as the density increases, while RMF-CC behaves differently. For instance, the scalar field at $6 n_{sat}$ reaches $\sim 20$ MeV for RMF-CC while it is larger than $\sim 70$ MeV for RMF and RMF-C. Interestingly, we also show that, by fixing the $ρ$ coupling constant from the quark structure of the nucleon, these three models reproduce only half of the empirical symmetry energy.
Comments:
18 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2109.05374 [pdf]
EPJA(2022)·11 citations
05
[Submitted on 13 Sept 2021]
Quenching of Gamow-Teller strengths and two particle -- two hole configurations
Danilo Gambacurta🇮🇹 · Marcella Grasso🇫🇷
We apply the charge-exchange subtracted second random-phase approximation (SSRPA), based on Skyrme functionals, to investigate Gamow-Teller resonances in several closed-shell and closed-subshell nuclei, located in different regions of the nuclear chart. After having discussed the SSRPA findings obtained within different approximation schemes in $^{48}$ Ca, we compare our results with {\it{ab-initio}} coupled-cluster predictions available for C and O isotopes, where two-body currents are included. Our integrated strenghts, obtained by using one-body transition operators, are lower compared to the corresponding {\it{ab-initio}} results. This indicates that, within our model, quenching effects are mainly driven by the inclusion of two particle - two hole configurations and that the role of a two-body contribution in the transition operator is less important than in the coupled-cluster approach. By analyzing heavier nuclei, $^{90}$ Zr and $^{132}$ Sn, we confirm the same conclusions that we have recently drawn for $^{48}$ Ca: the inclusion of two particle - two hole configurations is very effective in our model for providing strengths which are significantly more quenched than in other theoretical models and, thus, in better agreement with the experimental measurements. This occurs because two particle - two hole configurations have a density which strongly increases with the excitation energy. Their inclusion thus pushes a significant amount of the strength to higher energies, compared to what happens in other theoretical models, reducing in this way the cumulative sum of the strength up to excitation energies around 20-30 MeV.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2109.06064 [pdf]
PRC(2022)·15 citations
06
[Submitted on 10 Sept 2021] (cross-list from hep-ph)
Space-time structure of 3+1D color fields in high energy nuclear collisions
Andreas Ipp🇦🇹 · David I. Müller🇦🇹 · Soeren Schlichting🇩🇪 · Pragya Singh🇩🇪
We perform an analytic calculation of the color fields in heavy-ion collisions by considering the collision of longitudinally extended nuclei in the dilute limit of the Color Glass Condensate effective field theory of high-energy QCD. Based on general analytic expressions for the color fields in the future light cone, we evaluate the rapidity profile of the transverse pressure within a simple specific model of the nuclear collision geometry and compare our results to 3+1D classical Yang-Mills simulations.
Comments:
27 pages, 3 figures; v2 & v3: fixed typos
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.05028 [pdf]
PRD(2021)·32 citations
07
[Submitted on 11 Sept 2021] (cross-list from hep-ph)
Charged particle to photon ratio in heavy-ion collisions at RHIC: a different point of view
Mohammad Asif Bhat🇮🇳 · Supriya Das🇮🇳
We report an alternative explanation of the variation of charged particle to photon ratio in Cu+Cu collisions and Au+Au collisions from 1.4 $\pm$ 0.1 to 1.2 $\pm$ 0.1 at $s_{NN}$ = 62.4 GeV and 200 GeV respectively in STAR experiment at RHIC. Based on the theoretical predictions and experimental results we argue that the additional contribution of direct photons at $s_{NN}$ = 200 GeV in both Cu+Cu and Au+Au collisions are improving the ratio $\frac{N _{c h}}{N _{γ}}$ to 1.2 $\pm$ 0.1 from 1.4 $\pm$ 0.1.
Comments:
20 pages , 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.05204 [pdf]
0 citations
08
[Submitted on 12 Sept 2021] (cross-list from hep-ph)
Impacts of EMC effects on the D meson modification factor in equilibrating QGP
A. Mirjalili🇮🇷 · J. Sheibani🇮🇷 · K. Javidan🇮🇷 · R. Gharaei🇮🇷 · Shahin Atashbar Tehrani🇮🇷
In this article we employ the nuclear EMC effect to extract the parton distribution functions (PDFs) inside the Lead (Pb) and Gold (Au) nuclei. Extracted PDFs are utilized to obtain the transverse momentum dependent (TMD) ones, using the computing codes like Pythia 8 or MCFM-10. Through this procedure TMDPDFs for charm and bottom quarks in Au at $s_{N N} = 200 G e V$ , Pb at $s_{N N} = 2.76 T e V$ and $s_{N N} = 5.02 T e V$ are calculated. To evaluate the validity of results and investigate the influence of nuclear EMC effect, the numerated TMDs are used as input to estimate heavy quark modification factor $R_{AA}$ at transverse plane $P_{T}$ . This observable is calculated through numerical solution of the Fokker-Planck equation. For this purpose we need to extract the drag and diffusion coefficients, using the hard thermal loop correction. It is done in the frame work of the relativistic hydrodynamics up to the third order approximation of gradient expansion. The results are compared with same solutions when the input PFDs are considered inside the unbounded protons where the nuclear effect is not included. The comparison indicates a significant improvement of computed $R_{AA}$ with available experimental data when the EMC effect is considered.
Comments:
16 pages 6 figures 1 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.05597 [pdf]
Eur.Phys.J.Plus(2022)·2 citations
09
[Submitted on 13 Sept 2021] (cross-list from hep-ph)
Coalescence, the thermal model and multi-fragmentation: The energy and volume dependence of light nuclei production in heavy ion collisions
Paula Hillmann🇩🇪 · Katharina Käfer🇩🇪 · Jan Steinheimer🇩🇪 · Volodymyr Vovchenko🇺🇸 · Marcus Bleicher🇩🇪
We present results of a phase space coalescence approach within the UrQMD transport and -hybrid model for a very wide range of beam energies from SIS to LHC. The coalescence model is able to qualitatively describe the whole range of experimental data with a fixed set of parameters. Some systematic deviations are observed for very low beam energies where the role of feed down from heavier nuclei and multi-fragmentation becomes relevant. The coalescence results are mostly very close to the thermal model fits. However, both the coalescence approach as well as thermal fits are struggling to simultaneously describe the triton multiplicities measured with the STAR and ALICE experiment. The double ratio of $tp / d^{2}$ , in the coalescence approach, is found to be essentially energy and centrality independent for collisions of heavy nuclei at beam energies of $E_{lab} > 10 A$ GeV. On the other hand the clear scaling of the $d / p^{2}$ and $t / p^{3}$ ratios with the systems volume is broken for peripheral collisions, where a canonical treatment and finite size effects become more important.
Comments:
10 pages, 9 figures, version accepted for publication. J. Phys. G: Nucl. Part. Phys (2022)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.05972 [pdf]
J.Phys.G(2022)·40 citations
10
[Submitted on 13 Sept 2021] (cross-list from hep-th)
Chiral Vortical Effect in Extended Rarita-Schwinger Field Theory and Chiral Anomaly
G. Yu. Prokhorov🇷🇺 · O. V. Teryaev🇷🇺 · V. I. Zakharov🇷🇺
We consider the theory of Rarita-Schwinger field interacting with a field with spin 1/2, in the case of finite temperature, chemical potential and vorticity, and calculate the chiral vortical effect for spin 3/2. We have clearly demonstrated the role of interaction with the spin 1/2 field, the contribution of the terms with which to CVE is 6. Since the contribution from the Rarita-Schwinger field is -1, the overall coefficient in CVE is 6-1=5, which corresponds to the recent prediction of a gauge chiral anomaly for spin 3/2. The obtained values for the coefficients $μ^{2}$ and $T^{2}$ are proportional to each other, but not proportional to the spin, which indicates a possible new universality between the temperature-related and the chemical potential-related vortical effects. The results obtained allow us to speculate about the relationship between the gauge and gravitational chiral anomalies.
Comments:
11 pages
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2109.06048 [pdf]
PRD(2022)·11 citations
11
[Submitted on 13 Sept 2021] (cross-list from nucl-ex)
Remeasuring the anomalously enhanced $B (E 2; 2^{+} \to 1^{+})$ in $^{8} Li$
S. L. Henderson · T. Ahn · P. J. Fasano · A. E. McCoy · S. Aguilar · D. T. Blankstein · L. Caves · A. C. Dombos · R. K. Grzywacz · K. L. Jones · S. Jin · R. Kelmar and 5 other authors
The large reported $E 2$ strength between the $2^{+}$ ground state and $1^{+}$ first excited state of $\isotope [8] L i$ , $B (E 2; 2^{+} \to 1^{+}) = 55 (15) e^{2} \fm^{4}$ , presents a puzzle. Unlike in neighboring $A = 7 - 9$ isotopes, where enhanced $E 2$ strengths may be understood to arise from deformation as rotational in-band transitions, the $2^{+} \to 1^{+}$ transition in $^{8}$ Li cannot be understood in any simple way as a rotational in-band transition. Moreover, the reported strength exceeds \textit{ab initio} predictions by an order of magnitude. In light of this discrepancy, we revisited the Coulomb excitation measurement of this strength, now using particle- $γ$ coincidences, yielding a revised $B (E 2; 2^{+} \to 1^{+})$ of $19 (_{- 6}^{+ 7}) (2)$ ~e $^{2}$ fm $^{4}$ . We explore how this value compares to what might be expected in the limits of rotational models. While the present value is about a factor of three smaller than previously reported, it remains anomalously enhanced.
Comments:
21 pages, 5 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2109.06081 [pdf]
PRC(2024)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE