Nuclear Theory·nucl-th

Monday·January 24, 2022

8 papers—3 primary·5 cross-listed

01
[Submitted on 21 Jan 2022]
Neutron skin in $^{48}$ Ca determined from p+ $^{48}$ Ca and $^{48}$ Ca+ $^{12}$ C scattering
Shingo Tagami · Tomotsugu Wakasa · Maya Takechi · Jun Matsui · Masanobu Yahiro
In our previous paper, we determined $r_{skin}^{208} (exp) = 0.278 \pm 0.035$ ~fm from $σ_{R}$ for p+ $^{208}$ Pb scattering, using the Kyushu (chiral) $g$ -matrix folding model with the densities calculated with D1S-GHFB with the angular momentum projection (AMP). The value agrees with that of PREX2. Reaction cross sections $σ_{R}$ are available for p+ $^{48}$ Ca scattering, whereas interaction cross sections $σ_{I}$ are available for $^{48}$ Ca + $^{12}$ C scattering. As for $^{48}$ Ca, the high-resolution $E 1$ polarizability experiment ( $E 1$ pE) yields $r_{skin}^{48} (E 1 pE) = 0.14 \sim 0.20 fm$ . We determine $r_{skin}^{48} (exp)$ from the data on $σ_{R}$ for p+ $^{48}$ Ca scattering and from the data on $σ_{I}$ for $^{48}$ Ca+ $^{12}$ C scattering. We use the Kyushu $g$ -matrix folding model with the densities calculated with the D1M-GHFB+AMP densities. The D1M-GHFB+AMP proton and neutron densities are scaled so as to reproduce the data under the condition that the radius $r_{p}$ of the scaled proton density equals the data $r_{p} (exp)$ determined from the electron scattering. We deduce skin values $r_{skin} = r_{n} (exp) - r_{p} (exp)$ from the resulting $r_{n} (exp)$ and the $r_{p} (exp)$ determined from electron scattering. The same procedure is taken for D1S-GHFB+AMP. We regard $r_{skin}^{48} (E 1 pE)$ as a reference skin value. Using the reference skin value and taking D1M-GHFB+AMP, we determine $r_{skin}^{48} (exp) = 0.158 \pm 0.025$ ~fm for p+ $^{48}$ Ca scattering and $0.160 \pm 0.058$ ~fm for $^{48}$ Ca + $^{12}$ C scattering. We take the weighted mean and its error for the two skin values. The result is $r_{skin}^{48} (exp) = 0.158 \pm (0.023)_{exp} \pm (0.012)_{th} fm$ .
Comments:
arXiv admin note: substantial text overlap with arXiv:2107.06441
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2201.08541 [pdf]
6 citations
02
[Submitted on 21 Jan 2022]
Controlling extrapolations of nuclear properties with feature selection
Rodrigo Navarro Perez · Nicolas Schunck
Predictions of nuclear properties far from measured data are inherently imprecise because of uncertainties in our knowledge of nuclear forces and in our treatment of quantum many-body effects in strongly-interacting systems. While the model bias can be directly calculated when experimental data is available, only an estimate can be made in the absence of such measurements. Current approaches to compute the estimated bias quickly lose predictive power when input variables such as proton or neutron number are extrapolated, resulting in uncontrolled uncertainties in applications such as nucleosynthesis simulations. In this letter, we present a novel technique to identify the input variables of machine learning algorithms that can provide robust estimates of model bias. Our process is based on selecting input variables, or features, based on their probability distribution functions across the entire nuclear chart. We illustrate our approach on the problem of quantifying the model bias in nuclear binding energies calculated with Density Functional Theory (DFT). We show that feature selection can systematically improve theoretical predictions without increasing uncertainties.
Comments:
Manuscript: 6 pages. Supplemental material: 3 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.08835 [pdf]
PLB(2022)·11 citations
03
[Submitted on 21 Jan 2022]
Electric and Magnetic Moments and Transition Probabilities in $^{208}$ Pb $\pm 1$ Nuclei
V. Tselyaev · N. Lyutorovich · J. Speth · G. Martinez-Pinedo · K. Langanke · P.-G. Reinhard
We present moments and transition probabilities in the neighboring odd-mass nuclei of $^{208}$ Pb calculated fully self-consistently from the s.p. properties of $^{208}$ Pb with polarization corrections from its excitations, both given from previous Skyrme-Hartree-Fock and RPA calculations. The electric results agree nicely with the data with two very interesting exceptions. In the magnetic case we obtain similar results. We discuss also polarization contributions to the $l$ -forbidden $M 1$ transitions, which are, however, much too small compared to the data. With a modified external field operator which accounts effectively for mesonic and many-body effects the description of the data can be substantially improved.
Comments:
12 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.08838 [pdf]
3 citations
04
[Submitted on 18 Jan 2022] (cross-list from hep-th)
Current-induced inverse symmetry breaking and asymmetric critical phenomena at current-driven tricritical point
Masataka Matsumoto🇨🇳 · Shin Nakamura🇯🇵
We study critical phenomena associated with a spontaneous chiral symmetry breaking in current-driven non-equilibrium steady states by using holography. We find that the critical exponents $(γ, ν)$ at the tricritical point are asymmetric between the chiral symmetry restored phase and the broken phase. Their values in the broken phase are different from those of the mean-field theory, whereas other critical exponents are the mean-field values. The phase diagram with respect to temperature and current density shows a re-entrant structure: the broken chiral symmetry is restored again at low temperatures in the presence of current density.
Comments:
v1: 10 pages, 8 figures; v2: 9 pages, 8 figures, version published in PRD
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
2201.06894 [pdf]
PRD(2022)·6 citations
05
[Submitted on 20 Jan 2022] (cross-list from hep-ph)
Factorization connecting continuum and lattice TMDs
Markus A. Ebert🇩🇪 · Stella T. Schindler🇺🇸 · Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸
Transverse-momentum-dependent parton distribution functions (TMDs) can be studied from first principles by a perturbative matching onto lattice-calculable quantities: so-called lattice TMDs, which are a class of equal-time correlators that includes quasi-TMDs and TMDs in the Lorentz-invariant approach. We introduce a general correlator that includes as special cases these two Lattice TMDs and continuum TMDs, like the Collins scheme. Then, to facilitate the derivation of a factorization relation between lattice and continuum TMDs, we construct a new scheme, the Large Rapidity (LR) scheme, intermediate between the Collins and quasi-TMDs. The LR and Collins schemes differ only by an order of limits, and can be matched onto one another by a multiplicative kernel. We show that this same matching also holds between quasi and Collins TMDs, which enables us to prove a factorization relation between these quantities to all orders in $α_{s}$ . Our results imply that there is no mixing between various quark flavors or gluons when matching Collins and quasi TMDs, making the lattice calculation of individual flavors and gluon TMDs easier than anticipated. We cross-check these results explicitly at one loop and discuss implications for other physical-to-lattice scheme factorizations.
Comments:
33 pages + appendices, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2201.08401 [pdf]
JHEP(2022)·55 citations
06
[Submitted on 20 Jan 2022] (cross-list from hep-ph)
Event-by-event jet anisotropy and hard-soft tomography of the quark-gluon plasma
Yayun He🇨🇳 · Wei Chen🇨🇳 · Tan Luo🇪🇸 · Shanshan Cao🇨🇳 · Long-Gang Pang🇨🇳 · Xin-Nian Wang🇨🇳
Suppression of jet spectra or jet quenching in high-energy heavy-ion collisions is caused by jet energy loss in the dense medium. The azimuthal anisotropy of jet energy loss in non-central heavy-ion collisions can lead to jet anisotropy which in turn can provide insight into the path-length dependence of jet quenching. This is investigated within the Linear Boltzmann Transport (LBT) model which simulates both elastic scattering and medium-induced gluon radiation based on perturbative QCD for jet shower and medium recoil partons as well as radiated gluons as they propagate through the quark-gluon plasma (QGP). The dynamical evolution of the QGP in each event of heavy-ion collisions is provided by the (3+1)D CLVisc hydrodynamic model with fully fluctuating initial conditions. This framework has been shown to describe the suppression of single inclusive jet spectra well. We calculate in this study the elliptic ( $v_{2}^{jet}$ ) and triangular ( $v_{3}^{jet}$ ) anisotropy coefficients of the single inclusive jet spectra in Pb+Pb collisions at the LHC energies. We investigate the colliding energy, centrality, jet transverse momentum dependence of the jet anisotropy, as well as their event-by-event correlation with the flow coefficients of the soft bulk hadrons. An approximate linear correlation between jet and bulk $v_{2}$ is found. Effect of the bulk $v_{n}$ fluctuation on $v_{n}^{jet}$ is found negligible. The jet-induced medium excitation, which is influenced by radial flow, is shown to enhance $v_{2}^{jet}$ and the enhancement increases with the jet cone size. The jet elliptic anisotropy $v_{2}^{jet}$ is also found to be slightly enhanced by the shear viscosity of the bulk medium in comparison to the LBT results when jets propagate through an ideal hydrodynamic QGP medium.
Comments:
19 pages in RevTex with 26 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2201.08408 [pdf]
PRC(2022)·35 citations
07
[Submitted on 20 Jan 2022] (cross-list from hep-ph)
Critical point particle number fluctuations from molecular dynamics
Volodymyr A. Kuznietsov🇺🇦 · Oleh Savchuk🇺🇦 · Mark I. Gorenstein🇺🇦 · Volker Koch🇺🇸 · Volodymyr Vovchenko🇺🇸
We study fluctuations of particle number in the presence of critical point by utilizing molecular dynamics simulations of the classical Lennard-Jones fluid in a periodic box. The numerical solution of the $N$ -body problem naturally incorporates all correlations, exact conservation laws, and finite size effects, allowing us to study the fluctuation signatures of the critical point in a dynamical setup. We find that large fluctuations associated with the critical point are observed when measurements are performed in coordinate subspace, but, in the absence of collective flow and expansion, are essentially washed out when momentum cuts are imposed instead. We put our findings in the context of event-by-event fluctuations in heavy-ion collisions.
Comments:
16 pages, 9 figures, to be published in Physical Review C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
2201.08486 [pdf]
PRC(2022)·27 citations
08
[Submitted on 21 Jan 2022] (cross-list from hep-ph)
Tsallis statistics and thermofractals: applications to high energy and hadron physics
Eugenio Megias🇪🇸 · Evandro Andrade II🇧🇷 · Airton Deppman🇧🇷 · Arnaldo Gammal🇧🇷 · Debora P. Menezes🇧🇷 · Tiago Nunes da Silva🇧🇷 · Varese S. Timóteo🇧🇷
We study the applications of non-extensive Tsallis statistics to high energy and hadron physics. These applications include studies of $pp$ collisions, equation of state of QCD, as well as Bose-Einstein condensation. We also analyze the connections of Tsallis statistics with thermofractals, and address some of the conceptual aspects of the fractal approach, which are expressed in terms of the renormalization group equation and the self-energy corrections to the parton mass. We associate these well-known concepts with the origins of the fractal structure in the quantum field theory.
Comments:
16 pages, 8 figures. Talk given by E.Megias at the 10th International Conference on New Frontiers in Physics (ICNFP 2021), 23 Aug - 7 Oct 2021, Kolymbari, Crete, Greece
Subjects:
High Energy Physics — Phenomenology (hep-ph); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2201.08771 [pdf]
Int.J.Mod.Phys.A(2023)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE