Nuclear Theory·nucl-th

Monday·November 13, 2023

6 papers—3 primary·3 cross-listed

01
Coherent interactions of a fast proton with a short-range $N N$ correlation in the nucleus
A.B. Larionov🇷🇺 · Yu.N. Uzikov🇷🇺
Nuclear structure at short $N N$ -distances is still poorly understood. In particular, the full quantum structure of the nucleus with a correlated $N N$ -pair is a challenge to theory. So far, model descriptions have been limited to the average mean-field picture of the remaining nuclear system after removing the $N N$ -pair. In the recent experiment of the BM@N Collaboration at JINR \cite{Patsyuk:2021fju}, the reactions $^{12} \mbox C (p, 2 p n_{s})^{10} \mbox B$ and $^{12} \mbox C (p, 2 p p_{s})^{10} \mbox B e$ induced by the hard elastic $pp$ scattering were studied. Here, $n_{s}$ or $p_{s}$ denote the undetected slow nucleon in the rest frame of $^{12} \mbox C$ . In contrast to the previous experiments, the residual bound nucleus was also detected which requires a new level of theoretical understanding. In the present work, we apply the technique of fractional parentage coefficients of the translationally-invariant shell model (TISM) to calculate the spectroscopic amplitude of the system $N N - B$ where $B$ is the remaining nuclear system. The spectroscopic amplitude enters the full amplitude of a nuclear reaction. The relative $N N - B$ wave function is no longer a free parameter of the model but is uniquely related to the internal state of $B$ . The interaction of the target proton with the $N N$ -pair is considered in the impulse approximation. We also include the initial- and final state interactions of absorptive type as well as the single charge exchange processes. Our calculations are in a reasonable agreement with the BM@N data.
nucl-thhep-exhep-phnucl-exPRC(2024)·2 citations
02
Neutron Skins: Weak Elastic Scattering and Neutron Stars
Juliette M. Mammei🇨🇦 · Charles J. Horowitz🇺🇸 · Jorge Piekarewicz🇺🇸 · Brendan Reed🇺🇸 · Concettina Sfienti🇩🇪
The recently completed PREX-2 campaign - which measured the weak form factor of lead at an optimal momentum transfer - has confirmed that the neutron skin of lead is relatively large and has provided a precise determination of the interior baryon density of a heavy nucleus. In turn, the measured form factor can be related to various nuclear and neutron-star properties. Astrophysical observations by the NICER mission have benefited from improvements in flux, energy resolution, and notably, timing resolution. NICER has the capability to measure pulse profile data, which enables simultaneous mass-radius determinations. During the next decade, measurements in astrophysics, gravitational wave astronomy, and nuclear physics are expected to provide a wealth of more precise data. In this review we provide an overview of the current state of neutron skin measurements and offer insights into the prospects for the future.
nucl-thnucl-exAnn.Rev.Nucl.Part.Sci.(2024)·17 citations
03
Quantum Fluctuations Drive Angular Momenta in Nuclear Fission
M. H. Zhou · S. Y. Chen · Z. Y. Li · M. S. Smith · Z. P. Li
Quantum fluctuations are ubiquitous and play crucial roles across various scales and systems, such as the Big Bang, black hole dynamics, quantum phase transitions in microscopic many-body systems, and so on. Nuclear fission manifests as a complex nuclear shape stretching until it splits into fragments with substantial angular momenta, also exhibiting complex quantum fluctuations and specifically shape fluctuations. For over 40 years, researchers have puzzled how the fission fragment angular momenta are generated dynamically from (almost) zero spin, as well as the particular role played by quantum fluctuations. Here, for the first time, we report the quantum shape fluctuations that drive fragment angular momenta during nuclear fission, based on a global, microscopic, and dynamical simulation. The calculated probability distributions of fragment angular momenta are in good agreement with the experimental measurements, and the sawtooth-like mass dependence of average angular momenta is reproduced very well. It is noteworthy to find that the shape fluctuations -- multiple rotations, vibrations, and their couplings -- drive the generation and chaotic evolution of fragment angular momenta during fission fragment formation and induce strong correlations between angular momentum orientations of partner fragments at small, medium, and large opening angles ( $ϕ_{L H} \approx 3 0^{\circ}, 9 0^{\circ}, 16 0^{\circ}$ ). Our work not only deepens the fundamental understanding of the nuclear fission mechanism but also has implications for the $γ$ -ray heating problem in nuclear reactors and the synthesis of superheavy elements.
nucl-th4 citations
04
First Detailed Calculation of Atmospheric Neutrino Foregrounds to the Diffuse Supernova Neutrino Background in Super-Kamiokande
Bei Zhou🇺🇸 · John F. Beacom🇺🇸
The Diffuse Supernova Neutrino Background (DSNB) -- a probe of the core-collapse mechanism and the cosmic star-formation history -- has not been detected, but its discovery may be imminent. A significant obstacle for DSNB detection in Super-Kamiokande (Super-K) is detector backgrounds, especially due to atmospheric neutrinos (more precisely, these are foregrounds), which are not sufficiently understood. We perform the first detailed theoretical calculations of these foregrounds in the range 16--90 MeV in detected electron energy, taking into account several physical and detector effects, quantifying uncertainties, and comparing our predictions to the 15.9 livetime years of pre-gadolinium data from Super-K stages I--IV. We show that our modeling reasonably reproduces this low-energy data as well as the usual high-energy atmospheric-neutrino data. To accelerate progress on detecting the DSNB, we outline key actions to be taken in future theoretical and experimental work. In a forthcoming paper, we use our modeling to detail how low-energy atmospheric-neutrino events register in Super-K and suggest new cuts to reduce their impact.
↳ hep-phastro-ph.HEhep-exnucl-thPRD(2024)·21 citations
05
Floquet insulators and lattice fermions beyond naive time discretization
Thomas Iadecola🇺🇸 · Srimoyee Sen🇺🇸 · Lars Sivertsen🇺🇸
Periodically driven quantum systems known as Floquet insulators can host topologically protected bound states known as " $π$ modes" that exhibit response at half the frequency of the drive. Such states can also appear in undriven lattice field theories when time is discretized as a result of fermion doubling, raising the question of whether these two phenomena could be connected. Recently, we demonstrated such a connection at the level of an explicit mapping between the spectra of a continuous-time Floquet model and a discrete-time undriven lattice fermion model. However, this mapping relied on a symmetry of the single-particle spectrum that is not present for generic drive parameters. Inspired by the example of the temporal Wilson term in lattice field theory, in this paper we extend this mapping to the full drive parameter space by allowing the parameters of the discrete-time model to be frequency-dependent. The spectra of the resulting lattice fermion models exactly match the quasienergy spectrum of the Floquet model in the thermodynamic limit. Our results demonstrate that spectral features characteristic of beyond-equilibrium physics in Floquet systems can be replicated in static systems with appropriate time discretization.
↳ quant-phcond-mat.mes-hallhep-lathep-th+1PRResearch(2024)·4 citations
06
Holographic Odderon at TOTEM ?
Florian Hechenberger🇦🇹 · Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
We consider the contribution of the Odderon to diffractive $pp$ and $p p ˉ$ elastic scattering at large center of mass energy. We identify the Odderon and Pomeron with the Reggeized $1^{\pm-}$ and $2^{++}$ glueballs in the bulk, respectively. We use for the gravity dual description the repulsive wall model, to account for the proper Gribov diffusion for off-forward scattering. The eikonalized and unitarized amplitudes exhibit a vanishingly small rho-parameter, and a slope parameter fixed by twice the closed string slope. The results for the differential and total cross sections are compared to the empirical results reported recently by the TOTEM collaboration.
↳ hep-phhep-thnucl-thPRD(2024)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Coherent interactions of a fast proton with a short-range NN correlation in the nucleus

Neutron Skins: Weak Elastic Scattering and Neutron Stars

Quantum Fluctuations Drive Angular Momenta in Nuclear Fission

First Detailed Calculation of Atmospheric Neutrino Foregrounds to the Diffuse Supernova Neutrino Background in Super-Kamiokande

Floquet insulators and lattice fermions beyond naive time discretization

Holographic Odderon at TOTEM ?

Affiliations

Coherent interactions of a fast proton with a short-range $N N$ correlation in the nucleus