Nuclear Theory·nucl-th

Wednesday·October 19, 2022

8 papers—3 primary·5 cross-listed

01
Fission Fragments Mass Yields of Actinide Nuclei
Krzysztof Pomorski · Bożena Nerlo-Pomorska
A new, rapidly convergent Fourier over spheroid parametrization is developed to describe the shape of a fissioning nucleus: its elongation, non-axiality and left-right asymmetry and neck formation. The 4D Potential Energy Surfaces (PES) of even-even actinide nuclei are evaluated within the macro-micro model. The Langevin trajectories generated on such PESs allow for obtaining the fission fragments' mass and kinetic energy yields. The charge equilibration at the scission configuration and the post-scission neutron emission are also discussed.
nucl-thnucl-exActa Phys.Polon.Supp.(2023)·8 citations
02
First-order QCD transition in a primordial magnetic field
Gaoqing Cao🇨🇳
Recalling the expectation of an extremely strong primordial magnetic field $H$ , we recheck transitions among the phases of chiral symmetry restoration ( $χ S R$ ), chiral symmetry breaking ( $χ S B$ ), and pion superfluidity ( $π S F$ )in the QCD epoch of the early Universe. For homogeneous phases in a finite $H$ , a sensible scheme is adopted to determine the phase boundaries of $π S F$ , which is also superconductivity phase itself. In the first part, the QCD phase diagrams are studied in detail within the chiral effective Polyakov-Nambu--Jona-Lasinio model and the transitions involving $π S F$ are found to be of first order at relatively small $H$ . As expected from the Meissner effect, the regime of $π S F$ shrinks with increasing $H$ and completely vanishes beyond a threshold value. In the second part, the bubble dynamics is illuminated for the stronger first-order transition, $χ S R \to π S F$ , in the more convenient Polyakov-quark-meson model. The coupled equations of motion of pion condensate and magnetic field are solved consistently to give the bubble structure. Then, based on bubble collisions, we explore gravitational wave (GW) emission by developing a simple toy model in advance; and the characteristic frequency of the relic GW is estimated to be of the order $0.1 - 1 K$ or $1 0^{9} - 1 0^{10} Hz$ in our galaxy.
nucl-thgr-qchep-phPRD(2023)·7 citations
03
Extended superscaling with two-particle emission in electron and neutrino scattering
V.L. Martinez-Consentino🇪🇸 · J.E. Amaro🇪🇸 · P.R. Casale🇪🇸 · I. Ruiz Simo🇪🇸
An extended superscaling analysis of quasielastic electron scattering data is proposed by parametrizing the scaling function as the sum of a symmetric function corresponding to the emission of a single particle plus a contribution from the phase space of two-particle emission. The phase space of two-particle emission (2p2h) is multiplied by a q-dependent parameter that has been fitted to describe the tail behavior of the scaling function. This approach allows for an alternative description of the quasielastic electron scattering data, incorporating the contributions from both single-particle and two-particle emission processes induced by the one-body current and explaining the asymmetry of the scaling function. In a factorized schematic model based on the independent-pair approximation, the 2p2h parameter is related to the high-momentum distribution of the pair averaged over 2p-2h excitations. However, in the phenomenological fitting approach undertaken here, this coefficient includes other contributions such as interference with two-body currents and effects of the final-state interactions. We present predictions for the inclusive two-nucleon emission cross section induced by electrons and neutrinos.
nucl-thhep-phPRD(2023)·14 citations
04
Bjorken sum rule with hyperasymptotic precision
Cesar Ayala🇨🇱 · Antonio Pineda🇪🇸
We obtain an improved determination of the normalization of the leading infrared renormalon of the Bjorken sum rule: $Z_{B} (n_{f} = 3) = - 0.407 \pm 0.119$ . Estimates of higher order terms of the perturbative series are given. We compute the Bjorken sum rule with hyperasymptotic precision by including the leading terminant, associated with the first infrared renormalon. We fit the experimental data to the operator product expansion theoretical prediction with $f^_{3}^{PV}$ as the free parameter. We obtain a good agreement with the experiment with $f^_{3}^{PV} \times 1 0^{3} = 3 2_{- 196}^{+ 187} GeV^{2}$ for $Q^{2} \geq 1$ GeV $^{2}$ .
↳ hep-phnucl-thPRD(2022)·17 citations
05
Beautiful and Charming Energy Correlators
Evan Craft🇺🇸 · Kyle Lee🇺🇸 · Bianka Meçaj🇺🇸 · Ian Moult🇺🇸
Understanding the detailed structure of energy flow within jets, a field known as jet substructure, plays a central role in searches for new physics, and precision studies of QCD. Many applications of jet substructure require an understanding of jets initiated by heavy quarks, whose description has lagged behind remarkable recent progress for massless jets. In this Letter, we initiate a study of correlation functions of energy flow operators on beauty and charm jets to illuminate the effects of the intrinsic mass of the elementary particles of QCD. We present a factorization theorem incorporating the mass of heavy quarks, and show that the heavy quark jet functions for energy correlators have a simple structure in perturbation theory. Our results achieve the very first full next-to-leading-logarithmic calculation of the heavy quark jet substructure observable at the LHC. Using this framework, we study the behavior of the correlators, and show that they exhibit a clear transition from a massless scaling regime, at precisely the scale of the heavy quark mass. This manifests the long-sought-after dead-cone effect and illustrates fundamental effects from the intrinsic mass of beauty and charm quarks in a perturbative regime, before they are confined inside hadrons. Our theoretical framework for studying energy correlators using heavy jets has many exciting applications for improving the description of mass effects in next generation parton shower event generators, probing the QGP, and studying heavy flavor fragmentation functions.
↳ hep-phhep-exnucl-exnucl-thPRD(2026)·100 citations
06
Effective model for pure Yang-Mills theory on $T^{2} \times R^{2}$ with Polyakov loops
Daiki Suenaga🇯🇵 · Masakiyo Kitazawa🇯🇵
We investigate the phase diagram and thermodynamics of $S U (N)$ pure Yang-Mills theory on a manifold $T^{2} \times R^{2}$ with an effective model that includes two Polyakov loops along two compactified directions. We find that a rich phase structure can appear owing to the spontaneous breaking of two center symmetries for $N = 2$ and $3$ . Thermodynamic quantities are obtained in the model and compared with recent lattice results. It is shown that two Polyakov loops play significant roles in thermodynamics on $T^{2} \times R^{2}$ .
↳ hep-phhep-lathep-thnucl-thPRD(2023)·5 citations
07
Towards the finite-volume spectrum of the Roper resonance
Daniel Severt🇩🇪
The finite-volume energy levels corresponding to the Roper resonance based on a two-flavor chiral effective Lagrangian at leading one-loop order are investigated. It is shown that the Roper mass can be extracted from these levels for not too large lattice volumes. Further, to include three-body $N π π$ dynamics, a non-relativistic effective field theory for the Roper resonance within a covariant particle-dimer picture is introduced. This particle-dimer approach is a suitable framework to investigate three-particle scattering relevant for the Roper channel. The appearing dimer fields are analyzed, the energy levels of the Roper resonance in a finite volume are calculated and compared to the results from the chiral effective Lagrangian.
↳ hep-lathep-phnucl-thPoS(2023)·4 citations
08
Gluon Parton Distribution of the Nucleon from 2+1+1-Flavor Lattice QCD in the Physical-Continuum Limit
Zhouyou Fan🇺🇸 · William Good🇺🇸 · Huey-Wen Lin🇺🇸
We present the first physical-continuum limit $x$ -dependent nucleon gluon distribution from lattice QCD using the pseudo-PDF approach, on lattice ensembles with $2 + 1 + 1$ flavors of highly improved staggered quarks (HISQ), generated by MILC Collaboration. We use clover fermions for the valence action on three lattice spacings $a \approx 0.9$ , 0.12 and 0.15~fm and three pion masses $M_{π} \approx 220$ , 310 and 690~MeV, with nucleon two-point measurements numbering up to $O (1 0^{6})$ and nucleon boost momenta up to 3~GeV. We study the lattice-spacing and pion-mass dependence of the reduced pseudo-ITD matrix elements obtained from the lattice calculation, then extrapolate them to the continuum-physical limit before extracting $xg (x) / ⟨ x ⟩_{g}$ . We use the gluon momentum fraction $⟨ x ⟩_{g}$ calculated from the same ensembles to determine the nucleon gluon unpolarized PDF $xg (x)$ for the first time entirely through lattice-QCD simulation. We compare our results with previous single-ensemble lattice calculations, as well as selected global fits.
↳ hep-lathep-phnucl-thPRD(2023)·35 citations

Affiliations

first authorsco-authorsvia INSPIRE