Nuclear Theory·nucl-th

Tuesday·May 17, 2022

8 papers—6 primary·2 cross-listed

01
New Insights into Backbending in the Symmetry-adapted Framework
Nicholas D. Heller · Grigor H. Sargsyan · Kristina D. Launey · Calvin W. Johnson · Tomáš Dytrych · Jerry P. Draayer
We provide new insights into backbending phenomenon within the symmetry-adapted framework which naturally describes the intrinsic deformation of atomic nuclei. For $^{20} Ne$ , the canonical example of backbending in light nuclei, the ab initio symmetry-adapted no-core shell model shows that while the energy spectrum replicates the backbending from experimental energies under the rigid rotor assumption, there is no change in the intrinsic deformation or intrinsic spin of the yrast band around the backbend. For the traditional example of $^{48} Cr$ , computed in the valence shell with empirical interactions, we confirm a high-spin nucleus that is effectively spherical, in agreement with previous models. However, we find that this spherical distribution results, on average, from an almost equal mixing of deformed prolate shapes with deformed oblate and triaxial shapes. Microscopic calculations confirm the importance of spin alignment and configuration mixing, but surprisingly unveil no anomalous increase in moment of inertia. This finding opens the path toward further understanding the rotational behavior and moment of inertia of medium-mass nuclei.
nucl-thPRC(2023)·10 citations
02
Modeling survival probabilities of superheavy nuclei at high excitations
C.Y. Qiao · J.C. Pei
This work investigated the first-chance survival probabilities of highly excited compound superheavy nuclei in the prospect of synthesizing new superheavy elements. The main feature of our modelings is the adoption of microscopic temperature dependent fission barriers in calculations of fission rates. A simple derivation is demonstrated to elucidate the connection between Bohr-Wheeler statistical model and imaginary free energy method, obtaining a new formula for fission rates. The best modeling is chosen with respect to reproducing the experimental fission probability of $^{210}$ Po. Systematic studies of fission and survival probabilities of No, Fl, Og, and $Z$ =120 compound nuclei are performed. Results show large discrepancies by different models for survival probabilities of superheavy nuclei although they are close for $^{210}$ Po. We see that the first-chance survival probabilities of $Z$ =120 are comparable to that of Fl and Og.
nucl-thPRC(2022)·7 citations
03
Uncertainty Quantification in Breakup Reactions
Özge Sürer · Filomena M. Nunes · Matthew Plumlee · Stefan M. Wild
Breakup reactions are one of the favored probes to study loosely bound nuclei, particularly those in the limit of stability forming a halo. In order to interpret such breakup experiments, the continuum discretized coupled channel method is typically used. In this study, the first Bayesian analysis of a breakup reaction model is performed. We use a combination of statistical methods together with a three-body reaction model (the continuum discretized coupled channel method) to quantify the uncertainties on the breakup observables due to the parameters in the effective potential describing the loosely bound projectile of interest. The combination of tools we develop opens the path for a Bayesian analysis of not only breakup processes, but also a wide array of complex processes that require computationally intensive reaction models.
nucl-thphysics.data-anPRC(2022)·22 citations
04
Fluctuations in the canonical ensemble of an Abelian charge
Bengt Friman (Darmstadt, GSI)🇩🇪 · Krzysztof Redlich (Wroclaw U.)🇵🇱
We study fluctuations in the canonical ensemble, where the net baryon number is exactly conserved. The focus is on cumulants and factorial cumulants linked to the baryon and antibaryon multiplicities and their sum or difference in full phase-space as well as in subsystems. In particular, we connect the fluctuations of the net baryon number in a subsystem, relevant for fluctuation studies in nucleus-nucleus collisions, with fluctuations of the baryon and antibaryon numbers of the total system. We derive analytic expressions for factorial cumulants of arbitrary order. Compact results are obtained in terms of cumulants of the baryon number of the total system. Moreover, we derive the asymptotic forms of the factorial cumulants of baryon and antibaryon multiplicities in the high- and low-temperature limits and discuss the results in the context of heavy-ion collision experiments.
nucl-thhep-ph7 citations
05
Probe the color screening in proton-nucleus collisions with complex potentials
Liuyuan Wen🇨🇳 · Xiaojian Du🇨🇳 · Shuzhe Shi🇨🇳 · Baoyi Chen🇨🇳
Color screening and parton inelastic scattering modify the heavy-quark antiquark potential in the medium that consists of particles from quantum chromodynamics (QCD), leading to suppression of quarkonium production in relativistic heavy-ion collisions. Due to small charm/anti-charm ( $c c ˉ$ ) pair production number in proton-nucleus (pA) collisions, the correlation between different $c c ˉ$ pairs is negligible, which makes the Schrödinger equation viable for tracking the evolution of only one $c c ˉ$ pair. We employ the time-dependent Schrödinger equation with in-medium $c c ˉ$ potential to study the evolution of charmonium wave functions in the hydrodynamic like QCD medium produced in pA collisions. We explore different parametrizations of real and imaginary parts of $c c ˉ$ potential and calculate the nuclear modification factors ( $R_{pA}$ ) of $J / ψ$ and $ψ (2 S)$ in $s_{N N} = 5.02$ TeV energy p-Pb collisions at Large Hadron Collider (LHC). Comparing a strong and a weak screening scenario with experimental data in this approach, we arrive at the conclusion that the color screening is weak at temperature close to deconfined phase transition. Moreover, the imaginary part of the potential is crucial to describe the experimental data which is consistent with widely studied semi-classical approaches where the dissociation rates are essential.
nucl-thCPC(2022)·17 citations
06
A fluid-dynamic approach to heavy-quark diffusion in the quark-gluon plasma
F. Capellino🇩🇪 · A. Beraudo🇮🇹 · A. Dubla🇩🇪 · S. Floerchinger🇺🇸 · S. Masciocchi🇩🇪 · J. Pawlowski🇩🇪 · I. Selyuzhenkov🇩🇪
A fluid-dynamic approach to the diffusion of heavy quarks in the quark--gluon plasma (QGP) is presented. Specifically, we analyze the Fokker-Planck equation for the momentum transport of heavy quarks from a fluid perspective and use a mapping to second-order fluid-dynamics to determine conductivities and relaxation times governing their spatial diffusion. By investigating the relation between the two approaches, we provide new insights concerning the level of local thermalization of charm and bottom quarks inside the expanding QGP. Our results indicate that a fluid-dynamic description of diffusion is feasible for charm quarks at least for the latest stages of the fireball evolution.
nucl-thPRD(2022)·26 citations
07
Power Counting Energy Flow Polynomials
Pedro Cal🇩🇪 · Jesse Thaler🇺🇸 · Wouter J. Waalewijn🇳🇱
Power counting is a systematic strategy for organizing collider observables and their associated theoretical calculations. In this paper, we use power counting to characterize a class of jet substructure observables called energy flow polynomials (EFPs). EFPs provide an overcomplete linear basis for infrared-and-collinear safe jet observables, but it is known that in practice, a small subset of EFPs is often sufficient for specific jet analysis tasks. By applying power counting arguments, we obtain linear relationships between EFPs that hold for quark and gluon jets to a specific order in the power counting. We test these relations in the parton shower generator Pythia, finding excellent agreement. Power counting allows us to truncate the basis of EFPs without affecting performance, which we corroborate through a study of quark-gluon tagging and regression.
↳ hep-phhep-exnucl-thJHEP(2022)·12 citations
08
Exclusive production of a pair of high transverse momentum photons in pion-nucleon collisions for extracting generalized parton distributions
Jian-Wei Qiu🇺🇸 · Zhite Yu🇺🇸
We show that exclusive production of a pair of high transverse momentum photons in pion-nucleon collisions can be systematically studied in QCD factorization approach if the photon's transverse momentum $q_{T}$ with respect to the colliding pion is much greater than $Λ_{QCD}$ . We demonstrate that the leading power non-perturbative contributions to the scattering amplitudes of this exclusive process are process-independent and can be systematically factorized into universal pion's distribution amplitudes (DAs) and nucleon's generalized parton distributions (GPDs), which are convoluted with corresponding infrared safe and perturbatively calculable short-distance hard parts. The correction to this factorized expression is suppressed by powers of $1/ q_{T}$ . We demonstrate quantitatively that this new type of exclusive processes is not only complementary to existing processes for extracting GPDs, but also capable of providing an enhanced sensitivity to the dependence of both DAs and GPDs on the active parton's momentum fraction $x$ . We also introduce additional, but the same type of exclusive observables to enhance our capability to explore GPDs, in particular, their $x$ -dependence.
↳ hep-phhep-latnucl-thJHEP(2022)·68 citations

Affiliations

first authorsco-authorsvia INSPIRE