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Physics Nuclear Experiment

nucl-ex Watch Nuclear Experiment

Tuesday 6 October

Nuclear Experiment

Charge exchange reactions with central and tensor interactions and nuclear matrix elements associated with double-beta-decay neutrinos and astro neutrinos

Hiroyasu Ejiri and Yoritaka Iwata

Nuclear matrix elements (NMEs) for neutrinoless beta-beta decays (DBD) and inverse-beta decays (IBD) are crucial for studying neutrino properties beyond and within the standard model by using DBDs and IBDs. The charge exchange nuclear reaction (CER) is a realistic probe for studying experimentally these NMEs. The present work shows for the first time an experimental way to extract the Gamow-Teller (GT) and tensor (T) NMEs associated with DBDs and IBDs from the q (momentum transfer) dependence of the CER cross-section by taking into accounts explicitly both the central and tensor interactions. The present method was applied for CERs on 71Ga used for the solar-neutrino and the Ga anomaly and on 100Mo and 128Te used for DBD and IBD. Impacts of the CER with the tensor interaction on the DBD and IBD NME studies are discussed.
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Nuclear Experiment

First Measurement of Compton Scattering on $^3\text{He}$ at HI$\gamma$S

J. Zhou, E. Mancil, M.W. Ahmed et al. (+27 more)

The world's first Compton scattering measurements on a $^3$He target were performed to probe neutron electromagnetic polarizabilities. Differential cross sections were measured at laboratory angles of $40^\circ$, $55^\circ$, $90^\circ$, $115^\circ$, $150^\circ$, using circularly polarized, quasi-monoenergetic photon beams at weighted mean energy values of 61.5 and 97.1 MeV from the High Intensity $\gamma$-ray Source at the Triangle Universities Nuclear Laboratory. Comparisons with chiral effective field theory show good agreement at 97.1 MeV but over-prediction at 61.5 MeV, motivating further theoretical development.
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All authors J. Zhou, E. Mancil, M.W. Ahmed, B. Crowe, G. Feldman, F.Q.L. Friesen, H. Gao, D. Godagama, H.W. Grießhammer, D. Hornidge, C.R. Howell, S. Jia, S. Estupinan Jimenez, H.J. Karwowski, M.A. Kovash, K.K.H. Leung, M. Lewis, Y. Liu, D. Markoff, C. Martin, J. McPherson, R. Mendez, S.F. Mikhailov, D.R. Phillips, M.H. Sikora, N. Walton, J. Wang, Y.K. Wu, B. Yu, Z.W. Zhao

Monday 5 October

Nuclear Experiment · Cross-listed from hep-ph

Neutral Pseudoscalar Mesons, Hadron Light-by-Light Scattering, and the Muon Anomalous Magnetic Moment

Cong-Cong Ye, Yu-Chen Hu, Minghui Ding et al. (+1 more)

Continuum Schwinger function methods\linebreak (CSM) are used to provide estimates of pseudoscalar meson pole contributions - $\mathsf P = \pi^0$, $\eta$, $\eta^\prime$, $\eta_c$, $\eta_b$ - to the muon anomalous magnetic moment. The analysis framework is benchmarked via successful applications to an array of other meson and nucleon properties. It uses the leading order CSM truncation, augmented by a parametrisation of non-Abelian anomaly effects, to deliver an internally consistent treatment of all the pseudoscalar–two-photon transition form factors required to complete such a calculation. Employing those form factor predictions, the following results are obtained (units $10^{-11}$): $a_\mu^{\pi^0} + a_\mu^{\eta} + a_\mu^{\eta^\prime} = 84.3(0.8)$ - a value lower than some other contemporary estimates; $a_\mu^{\eta_c} = 0.82(0.04)$; and a value of $a_\mu^{\eta_b}$ that is negligible. The total contribution is $\sum _{\mathsf P} a_\mu^{\mathsf P} = 85.1(0.8) / 10^{11}$. Our analysis suggests that this pole contribution to $a_\mu$ is still not known with precision better than 5%.
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All authors Cong-Cong Ye, Yu-Chen Hu, Minghui Ding, Craig D. Roberts

Nuclear Experiment

Evolution of high-spin states in neutron-rich $^{195-202}$Au isotopes approaching the $N=126$ shell closure

Y. Cho, Y. H. Kim, A. Navin et al. (+48 more)

Background: The nuclear structure in the region southwest of the doubly magic $^{208}$Pb is important to benchmark theoretical models relevant for neutron-rich heavy element formation and for the origin of the $A\approx195$ peak in the mass abundance distribution. Although neutron-rich Pb, Tl, and Hg ($Z=80-82$) isotopes are relatively well studied, experimental data for neutron-rich Au isotopes ($Z=79$) remain largely limited due to experimental challenges. Purpose: The purpose of this work is to investigate the evolution of the high-spin structure in neutron-rich Au isotopes near the $N=126$ shell closure and to characterize the underlying shell-model configurations, with a particular focus on the roles of the high-$j$ unique-parity $\pi h_{11/2}$ and $\nu i_{13/2}$ orbitals. Methods: Neutron-rich $^{195-202}$Au isotopes were produced using multi-nucleon transfer reactions of $^{198}$Pt($^{136}$Xe, $^{x}$I)$^{y}$Au at a beam energy of 7 MeV/u. %between a 7 MeV/u $^{136}$Xe beam and a $^{198}$Pt target at GANIL. Prompt and delayed $\gamma$-ray spectroscopy of isotopically identified reaction products was performed with a unique experimental setup combining the VAMOS++ large acceptance magnetic spectrometer, the AGATA HPGe $\gamma$-ray tracking array, and the CATLIFE detection system.
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All authors Y. Cho, Y. H. Kim, A. Navin, M. Rejmund, A. Lemasson, D. Ramos, E. Clement, C. Yuan, M. Liu, P. van Isacker, A. N. Andreyev, J. Dudouet, S. Choi, Y. Son, A. Mukherjee, D. Ackermann, G. de Angelis, S. Bae, R. Banik, S. Bhattacharya, S. Bhattacharyya, K. Chae, F. Didierjean, C. Fougeres G. de France, G. Fremont, J. Goupil, G. M. Gu, J. Ha, K. I. Hahn, Y. Hirayama, S. Jeong, C. H. Kim, M. J. Kim, S. H. Kim, W. Korten, P. Marini, H. Miyatake, M. Mukai, G. Mukherjee, T. Niwase, T. Otsuka, J. Park, R. M. Perez-Vidal, F. Recchia, K. Rezynkina, P. Schury, J. C. Thomas, D. T. Kattikat Melcom, I. Tsekhanovich, A. Utepov, Y. X. Watanabe

Nuclear Experiment · Cross-listed from nucl-th

Interplay between final-state nucleon distortion, nuclear transparency and intranuclear cascade models in neutrino event generators

R. González-Jiménez, A. Nikolakopoulos, J. McKean et al. (+7 more)

We present an overview of the relativistic distorted-wave impulse approximation (RDWIA) for lepton-nucleus scattering, with emphasis on its use as an elementary-vertex model in event generators. In the intermediate-energy regime, neutrino-nucleus event generators typically follow a two-step scheme: an elementary neutrino-hadron interaction is first generated, and the outgoing hadrons are then propagated through the nuclear medium using an intranuclear cascade (INC) model. Using exclusive and inclusive $(e,e'p)$ and $(e,e')$ data for several nuclei, we assess how nuclear effects should be distributed between these two stages. In particular, we identify which effects should be included in the elementary-vertex description and which can be treated more effectively by the INC, while addressing the consistency required between both components. We also discuss nuclear transparency in quasielastic scattering. We show that it is directly connected to $(e,e'p)$ data below the two-nucleon knockout threshold; and depends on the full nuclear density distribution and the initial position of the nucleon, therefore, it varies substantially with the shell from which the nucleon is removed. We demonstrate that this shell dependence can be incorporated straightforwardly into the INC component of event generators.
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All authors R. González-Jiménez, A. Nikolakopoulos, J. McKean, K. Niewczas, T. Franco-Munoz, J. García-Marcos, M. Hooft, N. Jachowicz, G. D. Megias, J. M. Udías

Nuclear Experiment

Threshold resonances in relativistic $^{16}$O and $^{22}$Ne dissociation

D.A. Artemenkov, N.K. Kornegrutsa, V.V. Rusakova et al. (+2 more)

The nuclear emulsion method is applied to study binary dissociation leading to the formation of $\alpha$-particles from $^{16}$O nuclei at 3.65 GeV per nucleon and $^{22}$Ne nuclei at 3.22 GeV per nucleon. The invariant mass distribution for the $^{16}$O$\to$$^{12}$C(0$^+_1$)+$\alpha$ channel indicates decays of the $^{16}$O(0$^+_6$) excitation, whose probability exceeds the estimate for the $^{12}$C(0$^+_2$)+$\alpha$ channel by a factor of 20. The invariant mass distribution for $^{22}$Ne$\to$$^{18}$O+$\alpha$ exhibits a peak corresponding to $^{22}$Ne excitations around 11.6 MeV.
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All authors D.A. Artemenkov, N.K. Kornegrutsa, V.V. Rusakova, A.A. Zaitsev, P.I. Zarubin

Sunday 4 October

Nuclear Experiment

Data-driven measurements of the beauty hadron production in p-Pb collisions at \sqrt{s_{\mathrm{NN}}} = 5.02 and 8.16 TeV

Liang Dong, Tianle Liu, Guangsheng Li et al. (+4 more)

Beauty-hadron production in proton-nucleus collisions is a particularly powerful probe of cold nuclear matter (CNM) effects: thanks to the large beauty-quark mass, the production is initiated in early hard scatterings and is calculable in perturbative QCD, while the modifications observed in nuclear collisions directly constrain the nuclear parton distribution functions (nPDFs) in a kinematic region complementary to that accessed by charm. Precisely quantifying these effects is a prerequisite for isolating possible signatures of quark-gluon plasma formation in heavy-ion collisions. In this work, the production of open beauty hadrons in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ and $8.16$~TeV is studied via a data-driven Bayesian unfolding of ALICE and LHCb measurements of non-prompt $D^{0}$ and J/$\psi$ mesons. The unfolded $p_{T}$- and $y$-differential cross sections are mutually consistent across decay channels and compatible with directly reconstructed beauty-hadron measurements. The nuclear modification factor $R_{pPb}$ is reported as a function of transverse momentum and rapidity, providing the first unfolding-based result spanning $-4.0 < y < 4.0$ of beauty-hadron $R_{pPb}$ covering the full rapidity range, with a precision comparable to or better than that of existing data. The results are compared with calculations based on nPDFs and can provide valuable constraints for future global nPDF fits. The total inclusive B hadron production cross section in p-Pb collisions is also reported. A weaker CNM suppression is observed for beauty hadrons than for charm hadrons, consistent with the expected mass hierarchy of cold-nuclear-matter effects.
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All authors Liang Dong, Tianle Liu, Guangsheng Li, Xiaozhi Bai, Fabrizio Grosa, Yifei Zhang, Jianhui Zhu

Nuclear Experiment · Cross-listed from nucl-th

Rapidity-dependent charge dynamics in high-energy nuclear collisions from dynamical core-corona initialization

Shin-ei Fujii, Yasuki Tachibana and Tetsufumi Hirano

We develop a new model that provides a unified description of the equilibration and subsequent transport of conserved charges, including baryon number, electric charge, and strangeness, as well as the dynamical formation and evolution of the quark-gluon plasma medium in high-energy nuclear collisions. This is achieved by extending the state-of-the-art model of dynamical core-corona initialization to incorporate phenomenological source terms for conserved charges within a full (3+1)-dimensional hydrodynamic framework; the updated model is referred to as DCCI3. Consequently, the model simultaneously describes the core (equilibrium) and corona (nonequilibrium), including their mutual interactions. We present a detailed construction of the DCCI3 model and employ it in numerical simulations of Pb+Pb collisions at $\sqrt{s_{NN}}=2.76~\mathrm{TeV}$ to investigate the resulting dynamics of matter and conserved charges, with particular emphasis on the longitudinal structure. We find that each of the chemical potentials exhibits sizable fluctuations around midrapidity, which challenges the conventional assumption of vanishing values as an oversimplification. Moreover, the baryon chemical potential increases sharply with rapidity and becomes comparable to the temperature at forward rapidities. This suggests that the Rapidity Scan (RS) approach in high-energy nuclear collisions can serve as a complementary probe to the Beam Energy Scan (BES) in exploring the QCD phase diagram.
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Nuclear Experiment · Cross-listed from nucl-th

Nuclear mass table in deformed relativistic Hartree-Bogoliubov theory in continuum, III: nuclei with $8 \leq Z \leq 120$

DRHBc Mass Table Collaboration: Peng Guo, Xiaojie Cao, Kangmin Chen et al. (+89 more)

The mass table in the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the PC-PK1 density functional has been established for nuclei with $8 \leq Z \leq 120$, extended from the previous works for even-even nuclei [Zhang et al. (DRHBc mass table collaboration), At. Data Nucl. Data Tables 144, 101488 (2022)] and for even-$Z$ nuclei [Guo et al. (DRHBc mass table collaboration), At. Data Nucl. Data Tables 158, 101661 (2024)]. The calculated binding energies, two- and one-nucleon separation energies, root-mean-square (rms) radii of neutron, proton, matter, and charge distributions, quadrupole deformations, neutron and proton Fermi surfaces, and the blocked neutron (proton) orbitals of odd-$N$ ($Z$) nuclei are tabulated and compared with the available experimental data. A total of 9495 nuclei are predicted to be bound, with an rms deviation of 1.444 MeV from the 2380 mass data. Good agreement with the available experimental pairing gaps, $\alpha$ decay energies, and charge radii is also achieved. The accuracies of the calculated nuclear masses and nucleon separation energies as well as the prediction for drip lines are compared with those obtained by other relativistic and nonrelativistic density functional calculations. It turns out that the DRHBc theory with PC-PK1 provides one of the best microscopic descriptions for nuclear masses. The systematics of nucleon separation energies, pairing gaps, pairing energies, two-nucleon gaps, $\alpha$ decay energies, rms radii, quadrupole deformations, potential energy curves, neutron density distributions, and neutron mean-field potentials are discussed.
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All authors DRHBc Mass Table Collaboration: Peng Guo, Xiaojie Cao, Kangmin Chen, Qibo Chen, Myung-Ki Cheoun, Yongbeom Choi, Wenmin Deng, Jianmin Dong, Pengxiang Du, Xiaokai Du, Kangda Duan, Xiaohua Fan, Wei Gao, Lisheng Geng, Xi Guo, Yixin Guo, Eunja Ha, Xiao-Tao He, Jinniu Hu, Rongyan Hu, Jingke Huang, Kun Huang, Yanan Huang, Zidan Huang, Xiaofei Jiang, Seonghyun Kim, Youngman Kim, Chang-Hwan Lee, Jenny Lee, Jian Li, Minglong Li, Zhipan Li, Zhengzheng Li, Zhanjiang Lian, Haozhao Liang, Boran Liu, Lang Liu, Xiao Lu, Chenjun Lv, Jie Meng, Myeong-Hwan Mun, Yifei Niu, Zhongming Niu, Cong Pan, Panagiota Papakonstantinou, Jing Peng, Xiaoying Qu, Tianshuai Shang, Xinle Shang, Caiwan Shen, Guofang Shen, Ting Sun, Tingting Sun, Wei Sun, Xiang-Xiang Sun, Chen Wang, Peng Wang, Sibo Wang, Yiran Wang, Yuanyuan Wang, Yumeng Wang, Jiawei Wu, Liang Wu, Xinhui Wu, Xuewei Xia, Yingfeng Xu, Yonghe Xue, Jiangming Yao, Yaochen Yang, Guixiang Ye, Lian Ye, To Chung Yiu, Jianghan Yu, Yangyang Yu, Wentao Zeng, Kaiyuan Zhang, Jinzhe, Zhang, Ning Zhang, Shijie Zhang, Shuangquan Zhang, Wei Zhang, Xiaoyan Zhang, Yanxin Zhang, Ying Zhang, Yingxun Zhang, Zhenhua Zhang, Qiang Zhao, Ruyou Zheng, Chang Zhou, Shan-Gui Zhou, Lianjian Zou

Saturday 3 October

Nuclear Experiment

Particle emission from $^{40}$Ar nuclei excited in fixed-target $^{208}$Pb+$^{40}$Ar UPC at the LHC

P. Jucha, M. Klusek-Gawenda, K. Mazurek et al. (+3 more)

Ultraperipheral collisions of heavy ions, dominated by the electromagnetic interaction, allow to investigate the photoproduction of baryons and mesons from the excited nuclei. At LHCb, thanks to the SMOG2 system, these studies can also be conducted in fixed-target collisions, exploiting a variety of target gases ranging from $^{4}$He to Xe. In the present work, we adapted our photonuclear model and the Giesen-Boltzmann-Uehling-Uhlenbeck (GiBUU) generator to study photoproduction of protons, neutrons as well as pions and kaons from excited $^{40}$Ar nuclei in fixed-target ultraperipheral collisions with the LHC $^{208}$Pb beam. We present predictions for the total and differential photoproduction cross sections in $p$ and $p_T$, both in the full phase-space and within the geometrical acceptance of the LHCb detector.
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All authors P. Jucha, M. Klusek-Gawenda, K. Mazurek, L. L. Pappalardo, K. Pysz, A. Szczurek

Nuclear Experiment · Cross-listed from hep-ph

Precision Electroweak Physics of Neutral Currents Below the Z-pole

Jens Erler and Krishna S. Kumar

We report on the status and prospects of precision weak neutral current interaction measurements in fixed target scattering, atomic parity violation, as well as future collider measurements at momentum transfer $\sqrt{Q^2} \ll M_Z$, including the experiments in parity-violating electron scattering under construction at Jefferson Laboratory and at Mainz that are expected to commence data collection in the very near future.
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Friday 2 October

Nuclear Experiment

First strength measurements of low-energy resonances in the $^{45}$Sc($p,\gamma$)$^{46}$Ti reaction and its astrophysical implications

R. S. Sidhu, R. J. deBoer, J. Görres et al. (+13 more)

The $^{45}$Sc($p,\gamma$)$^{46}$Ti reaction plays an important role in both hydrostatic and explosive nucleosynthesis. During hydrostatic oxygen and silicon burning in massive stars, including dynamic processes such as convective carbon-oxygen (C-O) shell mergers, it acts as a bottleneck that regulates the reaction flow in the Sc-Ti mass region. In oxygen-neon (ONe) novae, the ejecta indicate the production of elements up to the Fe group, as observed in V1974 Cygni, and the $^{45}$Sc($p,\gamma$)$^{46}$Ti reaction links nuclei above Ca to the Fe region. In core-collapse supernovae (CCSNe), it influences the production of the radioactive isotope $^{47}$Sc. At present, the thermonuclear reaction rate is based on statistical model calculations. In this work, we report on measurements of the $^{45}$Sc($p,\gamma$)$^{46}$Ti reaction performed using the 5~MV accelerator at the Nuclear Science Laboratory, University of Notre Dame, over a laboratory proton energy range of 526–1275~keV. We present the first direct measurements of the resonance strengths for six resonances at $E^{\rm lab}_{\rm R} = 917.4$, 1026.0, 1031.1, 1049.7, 1059.4 and 1257.5~keV, together with integrated resonance strengths at $E^{\rm lab} = 555$, 630, 700, 761 and 871~keV. For resonance energies below the lowest directly measured energy, available transfer-reaction data were used to estimate the resonance strengths. An updated thermonuclear reaction rate is derived, and its astrophysical implications are discussed.
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All authors R. S. Sidhu, R. J. deBoer, J. Görres, M. Wiescher, W. N. Catford, C. Dembski, C. R. Jones, Ó. E. López-López, G. Lotay, K. Manukyan, M. Matney, J. O'Neill, J. Rufino, A. T. Sanchez, M. Williams, L. Zimmer

Nuclear Experiment

Spin-Density Matrix Elements in the Reaction $\gamma p \to \rho^-\Delta^{++}$ at GlueX

Niklas Herrmann and Farah Afzal for the GlueX Collaboration

The GlueX experiment, located in Hall D at Jefferson Lab, aims to map the full spectrum of light-quark mesons with an emphasis on hybrid mesons, states in which the gluonic field is excited and contributes to the quantum numbers of the meson. The search for exotic hybrid mesons requires a detailed understanding of the underlying production mechanisms. Polarization observables, such as the spin-density matrix elements (SDMEs), are an important experimental tool to investigate these mechanisms. The measurement of the unpolarized and polarized SDMEs in the photoproduction of $\rho^-\Delta^{++}$ using GlueX data is reported. In this analysis, for the first time, the correct full formalism is applied in which the upper mesonic and lower baryonic systems are described by a joint spin-density matrix. A factorized model yields results consistent with those of the full model, suggesting that this simplified description may also be suitable for other reactions involving meson-baryon final states.
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Thursday 1 October

Nuclear Experiment · Cross-listed from hep-ph

How Quantum Is Bottomonium in the Quark-Gluon Plasma?

Nora Brambilla and Tom Magorsch

We study how much quantum structure bottomonium retains during its evolution in the quark-gluon plasma. Within the open quantum system framework, we simulate the Lindblad equation obtained from potential nonrelativistic QCD in the quantum Brownian regime. From the resulting real-time evolution of the bottomonium density matrix, we compute the Wigner transform and study its negativity as a measure of nonclassicality and a test of a key condition underlying classical Langevin-type approximations. We find that the medium suppresses the negativity, which nevertheless approaches a finite plateau close to that of the $1\mathrm{S}$ state. The overlaps with the excited $2\mathrm{S}$ and $3\mathrm{S}$ states arise from near-canceling positive and negative phase-space contributions, driven by negative regions in the Wigner transforms of the bound-state projectors, while the $1\mathrm{S}$ overlap is insensitive to such contributions. We further show that the position-space coherence is similarly suppressed and plateaus close to the 1S value. We trace the finite residual quantum structure to conditional purification: the medium preferentially dissolves weakly bound and unbound modes with large $\langle r^2\rangle$, driving the surviving singlet $\mathrm{S}$-wave ensemble toward the $1\mathrm{S}$ state. More broadly, these results reveal that classicalization is partial and observable dependent, a feature that is relevant across applications of open quantum system methods in fundamental physics.
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Nuclear Experiment · Cross-listed from hep-ph

Confronting $K^-d$ dynamics with kaonic atom measurements within a novel unitary framework

Albert Feijoo, Àngels Ramos and Juan Torres-Rincon

We study the low-energy interaction of negative kaons with deuterons using chiral $\bar{K}N$ interaction models (OR and BCN) as input. The three-body $K^-d$ amplitude is constructed within the Fixed-Center Approximation to the Faddeev equations, where the unitary constraints missing in the conventional approach are formally implemented with the incorporation of coherent multiple-scattering processes. The unitary procedure is extended to coupled channels including charge-exchange processes, as well as isospin-breaking effects through the use of physical particle masses. This provides a consistent description of the low-energy $K^-d$ amplitude and allows for the determination of the scattering length and the effective range. The resulting framework is then used to assess the compatibility of the BCN $\bar{K}N$ interaction model with the recent SIDDHARTA-2 measurements of kaonic hydrogen and kaonic deuterium through a bootstrap analysis. The procedure leads to a readjustment of the BCN parameterization which produces visible effects in several isospin-sensitive $\bar{K}N$ scattering observables, hence highlighting the additional information provided by the new kaonic-atom measurements to better constrain the poorly known isovector component of the ${\bar K}N$ interaction.
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Nuclear Experiment

Thick-target Yield of $^{65}$Cu($\alpha,n)^{68}$Ga Near Threshold and Implications for Nuclear Medicine, Deep Underground Detector Backgrounds, and Nucleosynthesis

Zach Meisel, Gula Hamad, Kristyn Brandenburg et al. (+8 more)

We report thick target yields of $^{65}{\rm Cu}(\alpha,n)^{68}{\rm Ga}$ from $\alpha$ energies $E_{\alpha}$$=$6.5–8~MeV measured via neutron-counting at the Edwards Accelerator Laboratory at Ohio University. Our results agree with prior results based on single-foil irradiations, while disagreeing with thick-target yields inferred from stacked-foil irradiations by up to an order of magnitude. Based on comparisons of our and prior measurements to Hauser-Feshbach calculations, we estimate the thick-target yield for $^{68}{\rm Ga}$ from $E_{\alpha}$=14~MeV impinging on 100%-enriched copper ($^{65}{\rm Cu}$) is 161$^{+5}_{-24}$~MBq/$\mu$Ah (for He$^{++}$), which is in agreement with the current IAEA estimate of 156~MBq/$\mu$Ah. At $E_{\alpha}$$=$8~MeV, where radioimpurity-free production of $^{68}{\rm Ga}$ could be realized with a natural copper target, our yield estimate is nearly 4$\times$ lower than the IAEA estimate. We find that the $^{65}{\rm Cu}(\alpha,n)$ cross section estimates presently employed for neutrino and dark matter detector backgrounds and the $^{65}{\rm Cu}(\alpha,n)$ astrophysical reaction rate recently recommended for nucleosynthesis calculations are in agreement with our measurement results.
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All authors Zach Meisel, Gula Hamad, Kristyn Brandenburg, Carl R. Brune, Don E. Carter, Joseph Derkin, Yenuel Jones-Alberty, Tom N. Massey, Doug Soltesz, Shiv K. Subedi, Alexander V. Voinov

Nuclear Experiment · Cross-listed from physics.acc-ph

The JO&Minna Framework: A Method to Interpret Depth Profiles of Activation

Edil Mustafin

A novel analytical framework, designated as the JO&Minna method, is presented for interpreting the depth profiles of residual activation induced by heavy-ion beams in thick structural materials. By combining the limiting fragmentation and factorization principles, the JO-factor formalism rigorously links the spatial distribution of projectile-like fragments to the range derivatives and electronic stopping powers. Furthermore, the Minna procedure establishes a mathematical link via profile differentiation and convolution analysis to reconstruct the original energy spectrum and energy spread of the fragments from the measured activity profiles. The methodology is benchmarked using experimental data for $^{46}\text{Sc}$ production from $^{238}\text{U}$ irradiation in aluminum, demonstrating a reliable and straightforward approach for extracting fragment production kinematics and energy distributions in accelerator materials research.
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Wednesday 30 September

Nuclear Experiment · Cross-listed from physics.data-an

Developing Multi-Dimensional, Sequential sWeighting Routines for Reaction Selection with Emphasis on Kaon Identification at CLAS12

A. Acar, M. Bashkanov, D.P. Watts et al. (+1 more)

In nuclear and particle physics experiments, event selection is often a multidimensional classification problem which involves several correlated observables. The widely used sWeight technique provides a statistically rigorous means of separating signal and background using discriminating variables, but its conventional formulation is generally applied to a single discriminating variable or a simultaneous multidimensional fit. In this paper we present a novel extension of the widely used sWeight technique, in which an arbitrary number of discriminating variables can be used to construct a multidimensional sequential framework. This method allows the extraction of signal distributions in controlled variables in a rigorous way. Particular attention is given to the treatment of signal and background correlations, as well as the propagation of statistical uncertainties through successive weighting stages. The method yields high-purity signal samples even in the presence of large and correlated backgrounds. As a benchmark application, the validity of this technique is demonstrated on kaon identification in a dataset collected with the CLAS12 detector at the Thomas Jefferson National Laboratory for cascade baryon searches. The final workflow is shown to be robust and consistent across different run periods and beam/detector conditions, demonstrating minimal systematical uncertainties associated with the method. Statistical uncertainties are proved to be evaluable using a bootstrap-based procedure. The method provides a general framework for multidimensional event weighting and is intended for application in complex analyses requiring robust signal selection in the presence of complex correlated backgrounds.
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All authors A. Acar, M. Bashkanov, D.P. Watts, M. Nicol

Nuclear Experiment · Cross-listed from physics.ins-det

Performance and quality testing of CBM RICH front-end electronics

Pavish Subramani, Christian Pauly, Joerg Foertsch et al. (+2 more)

This note describes the laboratory setup at the University of Wuppertal and its use to measure charge sharing crosstalk, perform high rate and high occupancy tests of MAPMT-DIRICH readout elec- tronics using a realistic detector setup, and also includes the analysis of induced electronic noise characteristics of a new iteration of the DIRICH power module to be used in the CBM RICH readout chain.
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All authors Pavish Subramani, Christian Pauly, Joerg Foertsch, Dennis Pfeifer, Karl-Heinz Kampert

Nuclear Experiment · Cross-listed from nucl-th

Are breakup reactions sensitive to spectroscopic factors? (Spoiler alert: they ain't)

Live-Palm Kubushishi and Pierre Capel

Halo nuclei are mostly studied through reactions. In breakup reactions, the projectile is sent upon a target, which induces the dissociation of the loosely-bound halo from the core of the nucleus. In most cases, a spectroscopic factor for the core-halo structure is inferred from experimental data. In this contribution, we present a new analysis of the Coulomb breakup of 11Be on 208Pb at 69A MeV measured at RIKEN. We use an effective multi-channel particle-rotor model of the projectile, which accounts for the excitation of the 10Be core. The calculations are in excellent agreement with the data, independently of the value of the spectroscopic factor. This confirms that breakup cross sections are insensitive to this value and that spectroscopic factors cannot be inferred from such measurements. In the near future, we plan to extend this idea to other reactions.
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Nuclear Experiment · Cross-listed from hep-ex

Measurement of prompt and non-prompt ${\rm D}^{\rm *+}$-meson spin alignment in pp collisions at $\sqrt{s}$ = 13.6 TeV$

ALICE Collaboration

A precise measurement of prompt and non-prompt ${\rm D}^{\rm *+}$-meson spin alignment with respect to the helicity and production axes in proton-proton (pp) collisions at $\sqrt{s} = 13.6$ TeV is presented, using data collected with the ALICE experiment at the LHC. The spin alignment is quantified by measuring the diagonal spin density matrix element $\rho_{\rm 00}$ for ${\rm D}^{\rm *+}$ mesons at midrapidity ($|y|<0.8$). The measurement is performed in the transverse-momentum ($p_{\rm T}$) range $3<p_{\rm T}<100$ GeV/$c$ for prompt ${\rm D}^{\rm *+}$ mesons and $3<p_{\rm T}<30$ GeV/$c$ for non-prompt ${\rm D}^{\rm *+}$ mesons, respectively. The measured $\rho_{\rm 00}$ values for prompt ${\rm D}^{\rm *+}$ mesons are consistent with the unpolarised expectation of $1/3$ over the entire $p_{\rm T}$ range, indicating no evidence of spin alignment. In contrast, $\rho_{\rm 00}$ of non-prompt ${\rm D}^{\rm *+}$ mesons exhibit a deviation from $1/3$, consistent with expectations from weak beauty-hadron decays and well described by PYTHIA 8 simulations coupled with the EvtGen decay package. These results confirm and extend previous measurements, providing a precise baseline for future studies of ${\rm D}^{\rm *+}$ spin alignment in heavy-ion collisions.
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Nuclear Experiment

Probing jet quenching via the correlation of groomed jet substructure observables in Pb$-$Pb and pp collisions

ALICE Collaboration

A measurement of the correlation between the splitting angle $\theta_{\rm g}$ and the momentum-sharing fraction $z_{\rm g}$ of the first hard splitting in a parton shower in pp collisions and 0$-$10% central Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5 TeV with the ALICE detector is reported. Charged-particle jets are reconstructed using the anti-$k_{\rm T}$ algorithm with a jet resolution parameter $R$ = 0.2, in the transverse-momentum range $60 \leq p_{\rm T,ch\;jet} < 80$ GeV/$c$. The Soft Drop grooming algorithm is used to identify the first splitting in the parton shower. Jets observed in Pb$-$Pb collisions are narrower than in pp collisions. This effect is more pronounced for balanced than for unbalanced jets. No significant modification of the momentum-sharing fraction is observed for jets with small opening angles. In contrast, there is a hint that jets with a large opening angle may be less balanced in transverse momentum in Pb$-$Pb collisions compared to pp collisions. The correlations between $\theta_{\rm g}$ and $z_{\rm g}$ are well described in pp collisions by PYTHIA 8 and POWHEG while HERWIG shows too few jets with large opening angle. In Pb$-$Pb collisions the measurement is compared to a variety of models. The measurement is insensitive to the different implementations of medium response. Inclusion of elastic scatterings, as implemented in the HYBRID model is preferred to describe the unbalanced jets with large $\theta_{\rm g}$ in Pb$-$Pb collisions. The balanced jets, however, are less sensitive to elastic scatterings.
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Nuclear Experiment · Cross-listed from physics.ins-det

Measurement of the $^{39}$Ar specific activity in atmospheric argon with DArT at the Canfranc Underground Laboratory

P. Agnes, H. O. Back, S. Bharat et al. (+41 more)

We report the measurement of the $^{39}$Ar specific activity of atmospheric argon using DArT, a low-background single-phase liquid-argon detector read out by cryogenic silicon photomultipliers, at the Canfranc Underground Laboratory (LSC) in Spain. DArT was first filled with atmospheric argon and then with a sample of underground argon of known radioactivity from the DarkSide-50 experiment. The underground argon serves as a background reference in this measurement, making the result robust because we do not rely on background simulations. We measure the $^{39}$Ar specific activity with both a cut-and-count method and a binned maximum-likelihood fit, yielding consistent results. We obtain $a_{\text{AAr}}= 0.955 \pm 0.008~\text{Bq}/\text{kg}$. This result agrees with previous measurements from other experiments and provides the most precise determination of the $^{39}$Ar specific activity in atmospheric argon to date. It also validates DArT as a key component of the DArTInArDM experiment at LSC, which aims to measure the $^{39}$Ar activity of the argon extracted from deep underground wells in Colorado (USA) for the Darkside-20k and LEGEND-1000 experiments at Laboratori Nazionali del Gran Sasso in Italy.
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All authors P. Agnes, H. O. Back, S. Bharat, W. M. Bonivento, M. Boulay, M. Caboni, N. Canci, N. Cargioli, P. Castello, S. Cebrián, L. Consiglio, R. Crampton, D. Diaz Mairena, D. Franco, I. Fuente-Ortega, F. Gabriele, D. Gahan, C. Galbiati, P. Garcia Abia, T. Hessel, S. Horikawa, A. Ianni, G. Korga, M. Kuźniak, L. Luzzi, A. Marasciulli, M. Martínez, P. Organtini, A. Ortiz de Solórzano, R. Pavarani, P. Pegoraro, V. Pesudo Fortes, M. Razeti, O. U. Rehman, L. Romero, D. Sablone, E. Sánchez García, R. Santorelli, C. Seoane, J. Sosiak, S. Sulis, C. Tierney, S. Tullio, G. Vera Díaz

Nuclear Experiment · Cross-listed from nucl-th

Advancing Nuclear Physics with Machine Learning and Artificial Intelligence

Wanbing He, Qingfeng Li, Yugang Ma et al. (+3 more)

Machine learning (ML) and artificial intelligence (AI) are becoming powerful tools in scientific research across various disciplines. In this review, we summarize recent progress in AI-assisted studies of nuclear structure and reaction observables, heavy-ion collisions and dense nuclear matter properties, many-body wave functions, experimental facilities and data analysis. This review focus on new progress since the last review in 2023, and machine learning in nuclear physics is evolving from purely data inferences to physics informed learning. Future directions on the integration of physical knowledge with modern learning architectures, large foundation models and other emerging methods are also reviewed. These developments suggest that AI is enabling and advancing new approaches towards most challenging nuclear physics problems.
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All authors Wanbing He, Qingfeng Li, Yugang Ma, Zhongming Niu, Junchen Pei, Yingxun Zhang

Tuesday 29 September

Nuclear Experiment · Cross-listed from nucl-th

Nuclear Deep Inelastic Scattering around $x=0.3$

S.A. Kulagin and R. Petti

Deep-inelastic scattering (DIS) data on nuclei, from deuterium to lead, indicate that nuclear effects on the partonic structure of bound nucleons are remarkably small around $x=0.3$, where valence-quark distributions peak. We present the results of a global analysis of DIS data on the cross-section ratios $\sigma^A/\sigma^{{}^2\text{H}}$ in the range $0.25 \leq x \leq 0.35$, revealing a remarkable cancellation of nuclear effects across the entire range of nuclear targets. We also discuss the interpretation of such an observation within a microscopic model of nuclear modifications of the structure functions.
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Nuclear Experiment · Cross-listed from nucl-th

Effective Contact Theory for Exotic Loosely Bound States in Strongly Interacting Expanding Matter

Xiaofeng Wang, Zebo Tang, Zhangbu Xu et al. (+2 more)

Short-distance correlations generate universal relations that can be independent of microscopic details. Tan's contact is a prominent example, connecting close pairs, high-momentum constituents, and bound-state formation across atomic, condensed-matter, and nuclear systems. Whether an analogous universality governs the nonequilibrium freeze-out of relativistic QCD matter is an open question. We develop an effective contact theory that relates the production of loosely bound states to continuum two-particle correlations in heavy-ion collisions. The construction replaces the hard relative-momentum cutoff of conventional coalescence by a regulated Bethe–Peierls kernel: freeze-out localization fixes its momentum scale, while the composite yield fixes its contact residue. Bound and continuum observables then become projections of a common two-particle density matrix rather than independent phenomena. Coulomb-bound $K\mu$ atoms provide an ideal realization because their atomic, production, and source scales are widely separated. A contact-theory analysis of STAR $d\Lambda$ correlations supplies a first bound–continuum consistency test and demonstrates how inferred near-threshold parameters can depend on the finite expanding source. The framework establishes a general strategy for relating coalescence, correlations, and exotic bound states in strongly interacting expanding matter.
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All authors Xiaofeng Wang, Zebo Tang, Zhangbu Xu, Chi Yang, Wangmei Zha

Nuclear Experiment · Cross-listed from hep-ex

Search for $\boldsymbol{\pi_1(1600)}$ in a three-pion system at GlueX

Ilia Belov and Farah Afzal

The GlueX experiment in Hall D at Jefferson Lab enables studies of the light meson spectrum in $\gamma p$ interactions with a linearly polarized photon beam. GlueX aims in particular to search for hybrid mesons that have exotic quantum numbers and therefore cannot be classified as conventional hadrons. We present the search for the $\pi_1(1600)$ meson by means of a partial-wave analysis of the $\pi^{+}\pi^{-}\pi^{-}$ system produced off the $\Delta^{++}$-baryon. Data with the selected three-pion final state are fitted in bins of $m_{3\pi}$ as coherent sums of partial-wave amplitudes defined in the reflectivity basis. The properties of $a_{2}^{-}(1320)$ production are investigated through the extracted signal in the $\rho\,\pi^{-}$ $D$-waves. In this analysis, the overall $m_{3\pi}$ lineshape will be extracted for each of the model contributions. The main interest lies in establishing the existence of a resonant $1^{-+}$ contribution in the $\rho\,\pi^{-}$ $P$-wave configuration.
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Nuclear Experiment

$\pi$-QCD; Proposal for Experiments at the GSI Pion Beam Facility

HADES Collaboration: R. Abou Yassine, J. Adamczewski-Musch, G. Appagere et al. (+126 more)

We propose to investigate the dynamics of hadronic matter in the strong QCD regime using the pion-beam facility at GSI in conjunction with HADES. This program will study hadron physics through elementary pion-nucleon interactions up to $\sqrt{s}\approx$2.35 GeV, bridging cold matter research with detailed analyses of exclusive reactions. Our goals include exploring baryon resonance formation and their electromagnetic structures. This will complement photo-production experiments (e.g., ELSA) and enhance our understanding of emissivity in dense, hot hadronic matter. Key topics include examining baryon couplings to mesons and virtual photons, analyzing hyperon weak decays in exclusive reactions, and using Partial Wave Analyses with differential cross sections and polarization observables to achieve unprecedented precision in baryon-meson coupling data ($\rho$N, $\omega$N). Furthermore, e$^{+}$e$^{-}$ production measurements off nucleons will provide insight into the electromagnetic transition form factors of baryons in the time-like region, revealing the role of vector mesons ($\rho$, $\omega$). Reactions on nuclear targets allow for detailed studies of hadron properties, including vector-meson line shapes and strengths in cold nuclear matter. These measurements provide a critical reference for the interpretation of results from the hot and dense environment created in $A+A$ collisions. This research also has broader implications. It will contribute to the modeling of neutrino-nucleus interactions, facilitate unprecedented investigations into hypernuclei formation, and enhance our understanding of strong interaction dynamics across different energy regimes.
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All authors HADES Collaboration: R. Abou Yassine, J. Adamczewski-Musch, G. Appagere, M. Becker, A. Blanco, C. Blume, M. Bohman, Y. Bondar, L. Chlad, I. Ciepał, S. Deb, M. D. Doncel Monasterio, M. Duerr, W. Esmail, L. Fabbietti, M. Firlej, T. Fiutowski, A. M. Foda, J. Förtsch, P. Fonte, J. Friese, I. Fröhlich, T. Galatyuk, R. Gernhäuser, M. Grunwald, D. Grzonka, M. Gumberidze, S. Harabasz, T. Heinz, C. Höhne, F. Hojeij, R. Holzmann, M. Idzik, B. Kämpfer, K.-H. Kampert, B. Kardan, V. Kedych, S. Kim, V. Kladov, A. Kodym, M. Kohls, J. Kolas, A. Koperwas-Władyszewska, G. Korcyl, G. Kornakov, W. Krueger, A. Kugler, R. Lalik, S. Lebedev, T. Leontiou, S. Linev, F. Linz, L. Lopes, M. Lorenz, A. Malige, P. Marciniewski, J. Markert, T. Matulewicz, S. Mehat, J.G. Messchendorp, V. Metag, J. Michel, A. Molenda, J. Moron, C. Müntz, A. Mukherjee, M. Nabroth, A. Opíchal, J. Orliński, J.-H. Otto, M. Papenbrock, Y. Parpottas, M. Parschau, S. Pattnaik, C. Pauly, D. Pawlowska-Szymanska, V. Pechenov, O. Pechenova, G. Perez Andrade, J. Phan, K. Piasecki, J. Pietraszko, T. Povar, M. Prędota, K. Prościński, A. Prozorov, W. Przygoda, B. Ramstein, N. Rathod, J. T. Rieger, J. Ritman, A. Rost, A. Rustamov, S. Sahu, P. Salabura, J. Saraiva, K. Scharmann, N. Schild, K. Schönning, E. Schwab, F. Seck, I. Selyuzhenkov, J. Smyrski, M. Sobiella, S. Spies, A. Sreejith, A. Strach, H. Ströbele, J. Stroth, P. Subramani, K. Sumara, O. Svoboda, K. Swientek, J. Taylor, P. E. Tegner, P. Tlusty, M. Traxler, S. Treliński, I. C. Udrea, F. Ulrich-Pur, V. Wagner, A.A. Weber, E. Weiler, C. Wendisch, D. Wielanek, P. Wintz, H.P. Zbroszczyk, M. Zieliński, P. Zumbruch

Nuclear Experiment · Cross-listed from hep-ex

Trace isotopes set the neutron horizon of liquid argon

Yasser Maghrbi

Near 57 keV, destructive interference makes argon-40 almost transparent to neutrons. The 0.4% of argon-36 and argon-38 in natural argon then supply over 90% of its opacity, amplified 230-fold. Published transmission data rule out the argon-36 evaluation FLUKA uses by default, even with every other isotope made transparent, and bound its cross section in the window to 2-11 b. In a DUNE-scale detector, switching to the data-consistent evaluations moves the fiducial fraction of argon-41 calibration captures by 9-13% while the total yield changes by only 2%: the effect is on where captures occur, not how many.
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Nuclear Experiment · Cross-listed from nucl-th

Wigner and mirror correlations in nuclear mass predictions with kernel ridge regression

X. H. Wu

Wigner- and mirror-correlated kernel ridge regression (WKRR) and its odd-even extension WKRRoe are developed to improve nuclear mass predictions. The Wigner and mirror correlations are encoded entirely in the kernel functions without introducing more weight parameters. For experimentally known nuclear masses, WKRRoe achieves a leave-one-out root-mean-square deviation of 98.0 keV, which falls below the often-quoted 100-keV scale discussed in connection with chaos-related limits. The gain is mainly concentrated in light nuclei near $N=Z$ and is especially large for mirror pairs. Further tests show that WKRRoe can potentially improve predictions for experimentally unknown nuclei near $N=Z$, particularly when their mirror partners have already been measured.
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