Tue·Jul 29, 2025Tuesday·July 29, 2025

1. 01*

   Measurement of production branching ratio after muon nuclear capture reaction of Al and Si isotopes

   R. Mizuno🇯🇵 · M. Niikura🇯🇵 · T.Y. Saito🇯🇵 · T. Matsuzaki🇯🇵 · S. Abe🇯🇵 · H. Fukuda🇯🇵 · M. Hashimoto🇯🇵 · A. Hillier🇬🇧 · K. Ishida🇯🇵 · N. Kawamura🇯🇵 · S. Kawase🇯🇵 · T. Kawata🇯🇵 and 9 other authors

   Background: Muon nuclear capture is a reaction between a muon and a proton inside a nucleus through weak interactions. This reaction results in the formation of an excited nucleus, which subsequently de-excites by emitting several particles. Examination of the excited state allows for an investigation of the properties of nuclear excitation and particle emission in highly excited nuclei. Purpose: This study investigates muon nuclear capture of 27Al and 28,29,30Si, focusing on determining the absolute production branching ratio (BR) following muon nuclear capture and subsequent particle emissions. By measuring the absolute production BR, we can collect valuable information on the excitation energy distribution of muon nuclear capture. Methods: Measurements were conducted using the in-beam activation method at two pulsed muon facilities: RIKEN-RAL beamline and MLF at J-PARC. Absolute BRs were determined by measuring the number of muons irradiating the target using a plastic scintillator and the beta-delayed gamma-rays emitted from the produced nuclei using germanium detectors. Results: The absolute production branching ratios of muon nuclear capture on 27Al and 28,29,30Si were obtained with the highest accuracy to date. Predominant neutron emissions, even-odd atomic number dependence of particle emission probabilities, and influence of the neutron excess were observed. These results were compared with previous measurements and theoretical models and discussed regarding the excitation energy distribution, particle emission mechanism, and nuclear properties, such as resonance in the isovector transition. Conclusion: This study emphasizes the importance of considering nuclear structure effects, even-odd effects of proton and neutron numbers, neutron excess, nucleon pairing effect, and particle emission mechanisms, in the context of the muon nuclear capture reaction.

   nucl-exPRC(2025)·5 citations
2. 02*

   Nucleon charge radius measurement with low-energy electron scattering

   Clement Legris (1)🇯🇵 · Rika Danjo (1)🇯🇵 · Taiga Goke (1)🇯🇵 · Yuki Honda (1)🇯🇵 · Kengo Hotta (1)🇯🇵 · Rin Kagami (2)🇯🇵 · Hiroki Kobayashi (2)🇯🇵 · Michael Kohl (3)🇺🇸 · Yukie Maeda (4)🇯🇵 · Dominique Marchand (5)🇫🇷 · Edward Morris (6)🇬🇧 · Toshiya Muto (1)🇯🇵 and 7 other authors

   The charge radius is one of the most basic characteristics of the nucleons. The proton charge radius is especially of great importance for many applications such as the structure studies of the atomic nuclei, the determination of the Rydberg constant and QED tests. Its determination is thus a hot topic in several physics communities due to inconsistent results using electron scattering, atomic and muonic hydrogen spectroscopy. A new measurement of the proton and deuteron charge radii with low energy electron scattering is being conducted in the Research Center for Accelerator and Radioisotope Science (RARiS), Tohoku University, Japan. The current status of the experiment is discussed in the present paper.

   nucl-ex2 citations
3. 03*

   Vibrational Modes in Strongly Deformed Nuclei

   Y. Tsunoda🇯🇵 · T. Otsuka🇯🇵 · N. Shimizu🇯🇵 · T. Duguet🇫🇷 · Y. Utsuno🇯🇵 · T. Abe🇯🇵

   Low-energy vibrational excitations associated with the fluctuation of quadrupole deformed shapes are discussed within the frame of state-of-the-art Configuration Interaction calculations, actually performed via the Quasi-particle Vacua Shell Model version of the Monte Carlo Shell Model. Recently, low-lying $\gamma$ bands in heavy strongly deformed nuclei were shown to be rotational $K^P$ = 2${}^{+}$ excitations of triaxially deformed states (see T. Otsuka \etal, Eur. Phys. J. A 61, 126 (2025)) rather than vibrational excitations as traditionally interpreted. In this context, it is important to identify possible low-lying vibrational excitations and to characterize the excitation energy at which they emerge. Focusing on two typical examples, ${}^{166}$Er and ${}^{162}$Dy, vibrational states are indeed identified above the $\gamma$ band using an extended version of the so-called T-plot. The phenomenon of shape coexistence is also shown to produce low-lying states below such vibrational band heads. These results suggest novel and rich structures in heavy deformed nuclei. While experimental counterparts are seen for some of such states, others are predictions opening doors to future dedicated experiments.

   ↳ nucl-thnucl-ex3 citations
4. 04*

   Understanding the correlation between elliptic and triangular flow

   Mubarak Alqahtani🇸🇦 · Jean-Yves Ollitrault🇫🇷

   The relative correlation between the magnitudes of elliptic flow ($v_2$) and triangular flow ($v_3$) has been accurately measured in nucleus-nucleus collisions at the LHC collider. As a function of the centrality of the collision, it changes sign and varies non-monotonically. We show that this is naturally explained by two combined effects. The first effect is a skewness in initial-state fluctuations, which is quantified by the correlation between the geometry-driven elliptic deformation in the reaction plane and the fluctuation-driven triangularity ${\epsilon }_3$. We introduce an intensive measure of this skewness, which is generically of order unity and depends weakly on the system size and centrality. We evaluate its magnitude using Monte Carlo simulations of the initial state, which show that it is sensitive to the nucleon width. The second effect is the fluctuation of impact parameter relative to centrality classifiers used by experiment. The ATLAS collaboration uses two different centrality classifiers, the multiplicity $N_{ch}$ and the transverse energy $E_T$. We fit both sets of results for Pb+Pb collisions up to $\approx 40\%$ centrality with a single parameter, the intensive mixed skewness. Its value inferred from experiment agrees with theoretical expectations.

   ↳ nucl-thhep-exhep-phnucl-exPLB(2026)·2 citations
5. 05*

   Improvised Nuclear Weapons with 60%-Enriched Uranium

   Matt E. Caplan🇺🇸

   In this work we show that as little as 40 kg of 60%-enriched uranium can be used to build a crude nuclear weapon with a kiloton yield. While too large to fit on a missile, such a weapon could be delivered by shipping container. This analysis is motivated by the June 2025 Israeli and US attacks on Iran, especially the bombings of the nuclear facilities at Natanz, Fordow, and Isfahan. The Iranian stockpile of approximately 408 kg of 60%-enriched uranium is, at the time of writing, inaccessible to IAEA inspectors and stored in secret. The rapid clandestine relocation of this material in June 2025 creates an opportunity for aspiring nuclear terrorists to divert an amount that could be used in the construction of an improvised gun-type nuclear weapon in the style of Little Boy.

   ↳ physics.soc-phnucl-exphysics.pop-ph0 citations
6. 06*

   Understanding neutrino pion production with the GiBUU model

   Qiyu Yan🇨🇳 · Kaile Wen🇨🇳 · Kai Gallmeister🇩🇪 · Xianguo Lu🇬🇧 · Ulrich Mosel🇩🇪 · Yangheng Zheng🇨🇳

   Pion production is a major source of systematic uncertainty in neutrino oscillation measurements. We report a systematic investigation of neutrino-induced pion production using MINERvA and MicroBooNE data within the GiBUU theoretical framework. The analysis begins by establishing baseline model parameters using inclusive and pionless data from MINERvA, MicroBooNE, and T2K experiments. We then examine the role of in-medium effects, including resonance broadening and nucleon-nucleon final-state interactions. While agreement with individual datasets can be achieved through specific model configurations, we demonstrate the difficulty of a unified description across all experiments: MINERvA measurements prefer minimum in-medium modifications, whereas MicroBooNE data require the maximum in-medium enhancement, revealing the complexity and richness of the underlying nuclear dynamics.

   ↳ hep-exnucl-exnucl-thPRD(2025)·7 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.