Nuclear Theory
New submissions
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New submissions for Wed, 1 May 24
- [1] arXiv:2404.19355 [pdf, ps, other]
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Title: Statistical Theory of Neutron-Induced Nuclear Fission and of Heavy-Ion FusionAuthors: Hans A. WeidenmüllerSubjects: Nuclear Theory (nucl-th)
For both reactions we use an approach similar to that of compound-nucleus reaction theory. For neutron-induced fission, we describe the compound system generated by absorption of the neutron and the nuclear system near the scission point as two statistically independent systems governed by random-matrix theory. The systems are connected either by a barrier penetration factor or by a set of transition states above the barrier. Each system is coupled to a different set of channels. An analogous model is used for heavy-ion fusion. Assuming that (seen from the entrance channel) the system on the other side of the barrier is in the regime of strongly overlapping resonances, we obtain for fixed spin and parity closed-form analytical expressions for the total probability for fission and for fusion. Parts of these expressions can be calculated reliably within existing compound-nucleus reaction theory. The remaining parts are the probabilities for passage through or over the barrier. These may be determined theoretically from the liquid-drop model or experimentally from total fission or fusion cross sections.
- [2] arXiv:2404.19446 [pdf, other]
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Title: Exploring the potential of synthesizing unknown superheavy isotopes via cold-fusion reactions based on the dinuclear system modelComments: 10 pages, 6 figuresSubjects: Nuclear Theory (nucl-th)
To assess the potential of cold-fusion for synthesizing superheavy nuclei (SHN) with proton numbers 104-113, we systematically calculated 145 naturally occurring projectile-target combinations within the DNS model. Reactions predominantly show maximum cross-sections in the 1n to 2n channels, peaking near the Coulomb barrier with a sum of barrier and Q-value within 30 MeV. The maximum cross-section occurs below the Bass barrier, suggesting either the Bass model's limitation or significant deformation reducing the effective Coulomb barrier. Our calculations align well with experimental data, revealing that more neutron-rich projectiles slightly enhance fusion, though the effect is minor. For fixed targets (Pb, Bi), evaporation residue cross-sections decrease linearly with increasing projectile proton number, attributed to reduced fusion probability and lower fission barriers in heavier SHN. The touching potential $V_{\rm in}$ shows a linear trend with the product of projectile-target proton numbers, with neutron-rich systems exhibiting lower $V_{\rm in}$. Some reactions with $V_{\rm in} < V_{\rm S}$ may involve nucleon transfer before capture. Based on the DNS model, we identified optimal combinations and collision energies for synthesizing SHN with significant cross-sections. Collectively, our findings indicate that cold fusion is a promising avenue for creating proton-rich SHN around the drip line in the Z=104-113 region, offering distinct advantages over alternative mechanisms.
Cross-lists for Wed, 1 May 24
- [3] arXiv:2404.18993 (cross-list from hep-ph) [pdf, other]
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Title: Axion Searches Go Deep UndergroundComments: 6 pages, 2 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
We propose to investigate the time modulation of radioisotope decays deep underground as a method to explore axion dark matter. In this work, we focus on the $\alpha$-decay of heavy isotopes and develop a theoretical description for the $\theta$-dependence of $\alpha$-decay half-lives, which enables us to predict the time variation of $\alpha$-radioactivity in response to an oscillating axion dark matter background. To probe this scenario, we have recently constructed and installed a setup deep underground at the Gran Sasso Laboratory, based on the $\alpha$-decay of Americium-241. This prototype experiment, named RadioAxion-$\alpha$, will allow us to explore a broad range of oscillation's periods, from a few micro-seconds up to one year, thus providing competitive limits on the axion decay constant across 13 orders of magnitude in the axion mass, ranging from $10^{-9}$ eV to $10^{-20}$ eV after one month of data collection, and down to $10^{-22}$ eV after three years.
- [4] arXiv:2404.19008 (cross-list from hep-ph) [pdf, other]
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Title: Strongly vs. weakly coupled in-medium showers: energy stopping in large-$N_f$ QEDComments: 48 pages, 14 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
Inside a medium, showers originating from a very high-energy particle may develop via medium-induced splitting processes such as hard bremsstrahlung or pair production. During shower development, two consecutive splittings sometimes overlap quantum mechanically, so that they cannot be treated independently. Some of these effects can be absorbed into an effective value of a medium parameter known as $\hat q$. Previous calculations (with certain simplifying assumptions) have found that, after adjusting the value of $\hat q$, the leftover effect of overlapping splittings is quite small for purely gluonic large-$N_c$ showers but is very much larger for large-$N_f$ QED showers, at comparable values of $N\alpha$. Those works did not quite make for apples-to-apples comparisons: the gluon shower work investigated energy deposition from a gluon-initiated shower, whereas the QED work investigated charge-deposition from an electron-initiated shower. As a first step to tighten up the comparison, this paper investigates energy deposition in the QED case. Along the way, we develop a framework that should be useful in the future to explore whether the very small effect of overlapping splitting in purely gluonic showers is an artifact of having ignored quarks.
- [5] arXiv:2404.19123 (cross-list from hep-ph) [pdf, other]
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Title: CP Violation ProblemComments: 25 pages, 5 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
The strong CP violation problem has a long history emanating from its discovery 60 years ago in the decay of neutral kaons and the subsequent experimental and theoretical studies over several decades. We review herein experimental data that observe indirect CP violation of the order of $\sim10^{-3}$, as well as the discovery of direct CP violation of the order of $\sim10^{-6}$. The verification of CP violation in the decay of charged kaons was also observed. Data reflecting CP violation in the decays of $B$ and $D$ mesons have become very important and are also discussed in this review.
- [6] arXiv:2404.19414 (cross-list from hep-th) [pdf, other]
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Title: Toward the application of large-$N$ deconfinement to SU(3) QCDAuthors: Hiromasa WatanabeComments: 14 pages, 5 figures, Contribution to the proceedings of "Workshop on Noncommutative and Generalized Geometry in String Theory, Gauge Theory and Related Physical Models" in the Corfu Summer Institute 2023, 18 - 25 September 2023, Corfu, Greece, based on arXiv:2310.01940 [hep-th] and arXiv:2310.07533 [hep-th]Subjects: High Energy Physics - Theory (hep-th); High Energy Physics - Lattice (hep-lat); High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
It is generally known for $\mathrm{U}(N)$ gauge theory at finite temperature that phase transitions are manifested by taking the large-$N$ limit. Since the large-$N$ theory undergoes two thermodynamic phase transitions, a nontrivial intermediate phase can be realized in addition to the phases classified as the conventional confined and deconfined phases. In this talk, we discuss that a similar picture can be applied to QCD with $N=3$. In particular, we analyze the gauge configurations of lattice QCD calculations involving dynamical quarks and show the results of an analysis of the deviation due to finite-temperature effects from the Haar randomness expected at zero temperature in $\mathrm{SU}(N)$ gauge theory, using physical pictures suggested by the large-$N$ theory.
- [7] arXiv:2404.19746 (cross-list from hep-ph) [pdf, ps, other]
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Title: The Width of an Electron-Capture Neutrino Wave PacketSubjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
We expand on the methodology outlined in previous work that predicted the width of an antineutrino wave packet emerging from a beta-decaying nucleus, to the case of a neutrino from electron capture decay. Based on this result, we also respond to a recent Beryllium Electron capture in Superconducting Tunnel junctions Experiment (BeEST) paper which utilizes this previous work in forming their measurement of the neutrino wave packet width. According to our interpretation, the direct limit on the neutrino wave packet width from electron capture decay ($e^- + \mathrm{^{7}Be}\rightarrow\mathrm{^{7}Li+\nu_e}$) using the BeEST analysis should map to $\sigma_{\nu,x}>6.2\,\mathrm{pm}$ while our theoretical prediction is $\sigma_{\nu,x}\sim2.7\,\mathrm{nm}$.
Replacements for Wed, 1 May 24
- [8] arXiv:2310.01940 (replaced) [pdf, other]
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Title: A new perspective on thermal transition in QCDComments: v3. 18 pages, 5 figures, 1 table, final version published in PTEPSubjects: High Energy Physics - Theory (hep-th); High Energy Physics - Lattice (hep-lat); High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
- [9] arXiv:2311.13805 (replaced) [pdf, other]
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Title: Mass and radius of the most massive neutron star: The probe of the equation of state and perturbative QCDComments: 12 pages, 5 figures, PRD publishedJournal-ref: Phys. Rev. D 109, 083037 (2024)Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
- [10] arXiv:2401.13207 (replaced) [pdf, other]
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Title: Extracting transition generalized parton distributions from hard exclusive pion-nucleon scatteringComments: 7+2 pages, 9 figures; journal published versionJournal-ref: Phys. Rev. D 109, 074023 (2024)Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); High Energy Physics - Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
- [11] arXiv:2401.15402 (replaced) [pdf, other]
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Title: Universality for Three Bosons with Large, Negative Effective Range: Aspects and AddendaAuthors: Harald W. Griesshammer (George Washington U.)Comments: 10 pages LaTeX2e (pdflatex) including 6 figures as 7 .pdf files using includegraphics and sn-jnl class. Contribution to the Proceedings of the 25th European Conference of Few-Body Physics, Mainz, 30 July - 4 August 2023. Typographical updates onlySubjects: Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); Atomic and Molecular Clusters (physics.atm-clus); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
- [12] arXiv:2403.16389 (replaced) [pdf, other]
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Title: Illuminating Systematic Trends in Nuclear Data with Generative Machine Learning ModelsComments: New version uploaded after rewriting several sections for clarity and one new figure addedSubjects: Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
- [13] arXiv:2404.09511 (replaced) [pdf, other]
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Title: Bayesian inference of neutron-skin thickness and neutron-star observables based on effective nuclear interactionsComments: 10 pages, 7 figuresSubjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
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