Nuclear Theory·nucl-th

Friday·December 23, 2022

11 papers—3 primary·8 cross-listed

01
Microscopic Calculation of Fission Product Yields for Odd-Mass Nuclei
N. Schunck · M. Verriere · G. Potel Aguilar · R. C. Malone · J. A. Silano · A. P. D. Ramirez · A. P. Tonchev
Fission data are essential inputs to reaction networks involved in nucleosynthesis simulations and nuclear forensics. In such applications as well as in the description of multi-chance fission, the characteristics of fission for odd-mass nuclei are just as important as those for even-even nuclei. The fission theories that aim at explicitly describing fission dynamics are typically based on some variant of the nuclear mean-field theory. In such cases, the treatment of systems with an odd number of particles is markedly more involved, both formally and computationally. In this article, we use the blocking prescription of the Hartree-Fock-Bogoliubov theory with Skyrme energy functionals to compute the deformation properties of odd-mass uranium isotopes. We show that the resulting fission fragment distributions depend quite significantly on the spin of the odd neutron. By direct calculation of the spin distribution of the fissioning nucleus, we propose a methodology to rigorously predict the charge and mass distributions in odd-mass nuclei.
nucl-thPRC(2023)·12 citations
02
Smallest drop of QGP: Thermodynamic properties in p-Pb collisions
Fernando G. Gardim🇧🇷 · Renata Krupczak🇧🇷 · Tiago Nunes da Silva🇧🇷
The extreme conditions of temperature and density produced in ultrarelativistic collisions of heavy nuclei facilitate the formation of the most fundamental fluid in the universe, the deconfined phase of Quantum Chromodynamics called quark-gluon plasma. Despite the extensive experimental evidence collected over the past decade of its production in colliding systems such as Au-Au and Pb-Pb, establishing quark-gluon plasma formation in the collision of smaller systems, such as p-Pb, remains an open question. In this study, we describe the evolution of matter formed in p-Pb collisions at 5.02 TeV using a state-of-the-art hybrid model based on viscous relativistic hydrodynamics. We investigate the thermodynamic properties of the medium and final state observables. Our findings are compared with experimental data and first-principles calculations derived from lattice quantum chromodynamics. The results support the formation of a collective phase of strongly interacting matter in high-multiplicity p-Pb collisions.
nucl-thhep-phPRC(2024)·14 citations
03
Anisotropic electron transport in the nuclear pasta phase
Mateus R. Pelicer🇧🇷 · Marco Antonelli🇫🇷 · Débora P. Menezes🇧🇷 · Francesca Gulminelli🇫🇷
The presence of nuclear pasta is expected to modify the transport properties in the mantle of neutron stars. The non-spherical geometry of the pasta nuclear clusters leads to anisotropies in the collision frequencies, impacting the thermal and electrical conductivity. We derive analytical expressions for the anisotropic collision frequencies using the Boltzmann equation in the relaxation time approximation. The average parallel, perpendicular and Hall electrical conductivities are computed in the high-temperature regime above crustal melting, considering incoherent elastic electron-pasta scattering and randomly oriented pasta structures. Numerical values are obtained at different densities and temperatures by using the IUFSU parametrization of the non-linear Walecka model to determine the crustal structure. We find that the anisotropy of the collision frequencies grows with the length of the pasta structures and, independently of the magnetic field, the presence of rod and slab phases decreases the conductivity by more than one order of magnitude. Our numerical results indicate that, even if the pasta structures might survive above the crustal melting point, no strong anisotropies are to be expected in the conduction properties in this temperature regime, even in the presence of a very high magnetic field.
nucl-thastro-ph.HEcond-mat.dis-nnMNRAS(2023)·10 citations
04
Gluon PDF for the proton using the twisted mass formulation of lattice QCD
Joseph Delmar🇺🇸 · Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾
We present results of the x-dependence of the unpolarized gluon PDF for the proton. We use an $N_{f} = 2 + 1 + 1$ ensemble of maximally twisted mass fermions with clover improvement and the Iwasaki improved gluon action. The quark masses are tuned so that the pion mass is 260 MeV. We use a $3 2^{3} \times 64$ lattice size with a lattice spacing $a = 0.093$ fm giving a spatial extent of 3 fm. We employ the pseudo-distribution approach and obtain the light-cone Ioffe time distribution (ITD) combining data for nucleon momentum boosts up to 1.67 GeV and Wilson line lengths, $z$ , up to 0.56 fm. We explore systematic effects such as the dependence on the maximum value of $z$ entering the fits to obtain the gluon PDF.
↳ hep-lathep-thnucl-thPoS(2023)·3 citations
05
Theory of non-linear diffusion with a physical gapped mode
Navid Abbasi🇨🇳 · Matthias Kaminski🇺🇸 · Omid Tavakol🇨🇦
In a system with one conserved charge the charge diffusion is modified by non-linear self-interactions within an effective field theory (EFT) of diffusive fluctuations. We include the slowest ultraviolet (UV) mode, constructing a UV-regulated EFT. The relaxation time of this UV mode is protected from renormalization, as supported by experimental data in a bad metal system. Furthermore, the retarded density-density Green's function acquires four branch points, eventually increasing the range of applicability. We discuss the fate of long-time-tails as well as implications for the quark gluon plasma.
↳ hep-thcond-mat.stat-mechcond-mat.str-elnucl-ex+1PRL(2024)·23 citations
06
Non-Hermitian topological Fermi superfluid near the $p$ -wave unitary limit
Hiroyuki Tajima · Yuta Sekino · Daisuke Inotani · Akira Dohi · Shigehiro Nagataki · Tomoya Hayata
We theoretically discuss the non-Hermitian superfluid phase transition in one-dimensional two-component Fermi gases near the $p$ -wave Feshbach resonance accompanied by the two-body loss associated with the dipolar relaxation. For the first time we point out that this system gives us an opportunity to explore the interplay among various non-trivial properties such as universal thermodynamics at divergent $p$ -wave scattering length, topological phase transition at vanishing chemical potential, and non-Hermitian Bardeen-Cooper-Schrieffer(BCS) to Bose-Einstein condensate (BEC) transition, in a unified manner. In the BCS phase, the loss-induced superfluid-normal transition occurs when the exceptional point appears in the effective non-Hermitian Hamiltonian. In the BEC phase, the diffusive gapless mode can be regarded as a precursor of the instability of the superfluid state. Moreover, we show that the superfluid state is fragile against the two-body loss near the topological phase transition point.
↳ cond-mat.quant-gascond-mat.supr-connucl-thquant-phPRA(2023)·10 citations
07
Dynamics of quarks and gauge fields in the lowest-energy states in QCD and QED
Andrew V. Koshelkin🇷🇺 · Cheuk-Yin Wong🇺🇸
The dynamics of quarks and gauge fields in the lowest energy states in QCD and QED interactions is studied by compactifying the (3+1)D space-time to the (1+1)D space-time with cylindrical symmetry and by combining Schwinger's longitudinal confinement in (1+1)D with Polyakov's transverse confinement in (2+1)D. Using the action integral, we separate out the transverse and longitudinal degrees of freedom. By solving the derived transverse and longitudinal equations, we study the QCD and QED collective excitations. In addition to the well known QCD low-energy states, we find stable collective QED excitations showing up as massive QED-confined mesons, in support of previous studies. In particular, the masses of the recently observed X17 particle at about 17 MeV and the E38 particle at about 38 MeV are calculated in the developed approach, in good agreement with experimental results.
↳ hep-phnucl-thPoS·2 citations
08
Analysis of rescattering effects in $3 π$ final states
Dominik Stamen🇩🇪 · Tobias Isken🇩🇪 · Bastian Kubis🇩🇪 · Mikhail Mikhasenko🇩🇪 · Malwin Niehus🇩🇪
Decays into three particles are often described in terms of two-body resonances and a non-interacting spectator particle. To go beyond this simplest isobar model, crossed-channel rescattering effects need to be accounted for. We quantify the importance of these rescattering effects in three-pion systems for different decay masses and angular-momentum quantum numbers. We provide the amplitude decompositions for four decay processes with total $J^{P C} = 0^{--}$ , $1^{--}$ , $1^{-+}$ , and $2^{++}$ , all of which decay predominantly as $ρ π$ states. Two-pion rescattering is described in terms of an Omnès function, which incorporates the $ρ$ resonance. Inclusion of crossed-channel effects is achieved by solving the Khuri-Treiman integral equations. The unbinned log-likelihood estimator is used to determine the significance of the rescattering effects beyond two-body resonances; we compute the minimum number of events necessary to unambiguously find these in future Dalitz-plot analyses. Kinematic effects that enhance or dilute the rescattering are identified for the selected set of quantum numbers and various masses.
↳ hep-phhep-exnucl-thEPJC(2023)·25 citations
09
Unobservability of the topological charge in nonabelian gauge theory: Ward-Takahashi identity and phenomenological aspects
Nodoka Yamanaka🇯🇵
We argue that the topological charge of nonabelian gauge theory is unphysical. To show this statement, we use the Adler-Bardeen theorem and the Becchi-Rouet-Stora-Tyutin symmetry which are warranted by the perturbative finiteness of the chiral anomaly, thus being free of Gribov ambiguity. In addition to the original argument using the unphysical gauge field component collinear to the spatial derivative of the gauge function, we show the unobservability of the topological charge using the Ward-Takahashi identity. We then present the consequences of this finding and show the consistency with many physical pictures and ideas that have been developed around the topology of nonabelian gauge theory. The most important ones are the resolution of the Strong CP problem, the unobservability of topological instantons, the physical relevance of the axial $U (1)$ symmetry, the independence of the vacuum energy on the vacuum angle, and the impossibility to realize the sphaleron induced baryogenesis and chiral magnetic effects. The axial $U (1)$ symmetry and the unphysical $θ$ -term imply that the physical complex phase of the Cabibbo-Kobayashi-Maskawa matrix is the sole source of CP violation in the standard model. The unphysical sphaleron also means that the lepton number is phenomenologically free from the baryon number, and their violations may be modeled separately. We also comment on the consistency with the results of lattice calculations.
↳ hep-phhep-lathep-thnucl-th16 citations
10
Towards a Unified Model of Neutrino-Nucleus Interactions
Omar Benhar🇮🇹 · Camillo Mariani🇺🇸
The achievement of the goals of the ongoing and future accelerator-based neutrino experiments - notably the determination of CP violating phase in the lepton sector - will require the development of advanced models of neutrino-nucleus interactions. In this review, we summarise the present status of experimental studies of neutrino-nucleus scattering, and discuss the developments and perspectives of the theoretical approach based on factorisation of the nuclear cross section, which has recently emerged as a promising framework for the description of the variety of processes contributing to the detected signals.
↳ hep-phhep-exnucl-thEPJA(2023)·3 citations
11
Resonant contributions to polarized proton structure functions
A. N. Hiller Blin🇩🇪 · V. I. Mokeev🇺🇸 · W. Melnitchouk🇺🇸
Nucleon resonance contributions to the polarized proton $g_{1}$ and $g_{2}$ structure functions are computed from resonance electroexcitation amplitudes extracted from CLAS exclusive meson electroproduction data. Including resonances in the mass range up to 1.75 GeV, and taking into account the interference between excited states, we compare the resonant contributions with the polarized proton structure function and polarization asymmetry data from Jefferson Lab 6 GeV measurements. All resonance-like structure observed in the polarized structure functions and asymmetries can be attributed to the resonant contributions, confirming their essential role in the behavior of $g_{1}$ and $g_{2}$ in the resonant region over the entire range $Q^{2} < 7.5$ GeV $^{2}$ covered by the measurements. Comparing the resonance contributions with the $g_{1}$ and $g_{2}$ structure functions computed from parton distribution functions extrapolated from the deep-inelastic region, we also quantify the degree to which quark-hadron duality holds for $g_{1}$ and $g_{2}$ and their moments.
↳ hep-phhep-exnucl-thPRC(2023)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE