Tue·Aug 12, 2025Tuesday·August 12, 2025

1. 01*

   Characterizing radial flow fluctuations in relativistic heavy-ion collisions at top RHIC and LHC energies

   Lipei Du🇺🇸

   We present a systematic investigation of the transverse-momentum differential radial flow fluctuations observable $v_0(p_T)$ in relativistic heavy-ion collisions at top RHIC ($\sqrt{s_{\mathrm{NN}}}=200$ GeV) and LHC ($\sqrt{s_{\mathrm{NN}}}=2.76$ and 5.02 TeV) energies. Using a multistage hydrodynamic model, we assess the sensitivity of $v_0(p_T)$ to a wide range of physical effects, including bulk and shear viscosities, off-equilibrium corrections at particlization, the presence of a hadronic afterburner, and the nucleon size in the initial conditions. By employing complementary rescaling strategies, we demonstrate how different physical effects leave distinct imprints on the shape of $v_0(p_T)$. A combined double-rescaling of $v_0(p_T)/v_0$ versus $p_T/⟨p_T⟩$ reveals a universality across a wide range of energies and model assumptions in the low-$p_T$ regime, a robust signature of collective behavior. This allows us to disentangle the universal dynamics of the bulk medium from model-specific features that emerge at higher $p_T$. Our results establish $v_0(p_T)$ as a powerful and complementary observable for constraining QGP transport properties and initial-state granularity, offering a unique probe of the created QCD medium.

   nucl-exhep-phnucl-thPRC(2026)·16 citations
2. 02*

   Ultra-pure Nickel for Structural Components of Low-Radioactivity Instruments

   T. J. Roosendaal · C. T. Overman · G. S. Ortega · T. D. Schlieder · N. D. Rocco · L. K. S. Horkley · K. P. Hobbs · K. Harouaka · J. L. Orrell · P. Acharya · A. Amy · E. Angelico and 114 other authors

   The next generation of rare-event search experiments in nuclear and particle physics demand structural materials combining exceptional mechanical strength with ultra-low levels of radioactive contamination. This study evaluates chemical vapor deposition (CVD) nickel as a candidate structural material for such applications. Manufacturer-supplied CVD Ni grown on aluminum substrates underwent tensile testing before and after welding alongside standard Ni samples. CVD Ni exhibited a planar tensile strength of ~600 MPa, significantly surpassing standard nickel. However, welding and heat treatment were found to reduce the tensile strength to levels comparable to standard Ni, with observed porosity in the welds likely contributing to this reduction. Material assay via inductively coupled plasma mass spectrometry (ICP-MS) employing isotope-dilution produced measured bulk concentration of 232-Th, 238-U, and nat-K at the levels of ~70 ppq, <100 ppq, and ~900 ppt, respectively, which is the lowest reported in nickel. Surface-etch profiling uncovered higher concentrations of these contaminants extending ~10 micrometer beneath the surface, likely associated with the aluminum growth substrate. The results reported are compared to the one other well documented usage of CVD Ni in a low radioactive background physics research experiment and a discussion is provided on how the currently reported results may arise from changes in CVD fabrication or testing process. These results establish CVD Ni as a promising low-radioactivity structural material, while outlining the need for further development in welding and surface cleaning techniques to fully realize its potential in large-scale, low radioactive background rare-event search experiments.

   nucl-exNucl.Instrum.Meth.A(2026)·2 citations
3. 03*

   Puzzle for the Vector Meson Threshold Photoproduction

   Igor Strakovsky (GWU)🇺🇸

   High-statistics total cross sections for the vector meson photoproduction at the threshold: $\gamma p\to \omega p$ (from A2 at MAMI, ELPH, and CBELSA/TAPS), $\gamma p\to \varphi p$ (from CLAS and LEPS), and $\gamma p\to J/\psi p$ (from GlueX) allow one to extract the absolute value of vector meson nucleon scattering length using Vector Meson Dominance (VMD) model. The ``young'' vector meson hypothesis may explain the fact that the obtained scattering length value for the nucleon $\varphi$-meson compared to the typical hadron size of approximately $\sim 1\mathrm{fm}$ indicates that the proton is more transparent for the $\varphi$-meson compared to the $\omega$-meson and is much less transparent than the $J/\psi$-meson. The extended analysis of ${\rm Y}$-meson photoproduction using quasi-data from the QCD approach is in perfect agreement with the light-meson findings using experimental data. Future high-quality experiments by EIC and EicC will have the opportunity to evaluate cases for $J/\psi$- and ${\rm Y}$-mesons. It allows one to understand the dynamics of $c\bar{c}$ and $b\bar{b}$ production at the threshold. The ability of J-PARC to measure ${\pi }^{-}p\to \varphi n$ and ${\pi }^{-}p\to J/\psi n$, which are free from the VMD model, is considered.

   ↳ hep-phhep-exnucl-exnucl-thPoS(2025)·0 citations
4. 04*

   Partial pressure and susceptibilities of charmed sector in the van der Waals hadron resonance gas model

   Kangkan Goswami🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇲🇽 · Raghunath Sahoo🇮🇳

   We investigate the general susceptibilities in the charm sector by using the van der Waals hadron resonance gas model (VDWHRG). We argue that the ideal hadron resonance gas (HRG), which assumes no interactions between hadrons, and the excluded volume hadron resonance gas (EVHRG), which includes only repulsive interactions, fail to explain the lQCD data at very high temperatures. In contrast, the VDWHRG model, incorporating both attractive and repulsive interactions, extends the degree of agreement with lQCD up to nearly 180 MeV. We estimate the partial pressure in the charm sector and study charm susceptibility ratios in a baryon-rich environment, which is tricky for lattice quantum chromodynamics (lQCD) due to the fermion sign problem. Our study further solidifies the notion that the hadrons shouldn't be treated as non-interacting particles, especially when studying higher order fluctuations, but rather one should consider both attractive and repulsive interactions between the hadrons.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2026)·2 citations
5. 05*

   Vector meson dominance in photon structure functions at small $x$ from holography

   Wei Gao🇨🇳 · Siming Liu🇨🇳 · Wenbin Lin🇨🇳 · Akira Watanabe🇯🇵

   We investigate the photon structure functions via the photon-photon and photon-vector meson scattering within the framework of holographic QCD, focusing on the small Bjorken $x$ region and assuming that the Pomeron exchange dominates. The quasi-real photon structure functions are formulated as the convolution of the known U(1) vector field wave function with the Brower-Polchinski-Strassler-Tan (BPST) Pomeron exchange kernel in the five-dimensional AdS space. Assuming the vector meson dominance, the photon structure functions can be calculated in a different way with the BPST kernel and vector meson gravitational form factor, which can be obtained in a bottom-up AdS/QCD model, for the Pomeron-vector meson coupling. It is shown that the obtained $F_2$ structure functions in the both ways agree with the experimental data, which implies the realization of the vector meson dominance within the present model setup. Calculations for the longitudinal structure function and the longitudinal-to-transverse ratio are also presented.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2025)·0 citations
6. 06*

   Production and spectroscopy of cold radioactive molecules

   Chandler J. Conn · Phelan Yu🇺🇸 · Madison I. Howard · Yuxi Yang · Chaoqun Zhang🇺🇸 · Arian Jadbabaie🇺🇸 · Aikaterini Gorou · Alyssa N. Gaiser🇺🇸 · Timothy C. Steimle · Lan Cheng🇺🇸 · Nicholas R. Hutzler🇺🇸

   Molecules with heavy, radioactive nuclei promise extreme sensitivity to fundamental nuclear and particle physics. However, these nuclei are available in limited quantities, which challenges their use in precision measurements. Here we demonstrate the gas-phase synthesis, cryogenic cooling, and high-resolution laser spectroscopy of radium monohydroxide, monodeuteroxide, and monofluoride molecules (${}^{226}$RaOH, ${}^{226}$RaOD, and ${}^{226}$RaF) in a tabletop apparatus by combining novel radioactive target production protocols, optically driven chemistry in a cryogenic buffer gas, and low-background spectroscopic detection methods. The molecules are cooled in the lab frame, creating conditions that are the same starting points as many current molecular precision measurement and quantum information experiments. This approach is readily applied to a wide range of species and establishes key capabilities for molecular quantum sensing of exotic nuclei.

   ↳ physics.atom-phnucl-exphysics.chem-phScience(2026)·9 citations
7. 07*

   The DNA of nuclear models: How AI predicts nuclear masses

   Kate A. Richardson🇺🇸 · Sokratis Trifinopoulos🇨🇭 · Mike Williams🇺🇸

   Obtaining high-precision predictions of nuclear masses, or equivalently nuclear binding energies, $E_b$, remains an important goal in nuclear-physics research. Recently, many AI-based tools have shown promising results on this task, some achieving precision that surpasses the best physics models. However, the utility of these AI models remains in question given that predictions are only useful where measurements do not exist, which inherently requires extrapolation away from the training (and testing) samples. Since AI models are largely black boxes, the reliability of such an extrapolation is difficult to assess. We present an AI model that not only achieves cutting-edge precision for $E_b$, but does so in an interpretable manner. For example, we find that (and explain why) the most important dimensions of its internal representation form a double helix, where the analog of the hydrogen bonds in DNA here link the number of protons and neutrons found in the most stable nucleus of each isotopic chain. Furthermore, we show that the AI prediction of $E_b$ can be factorized and ordered hierarchically, with the most important terms corresponding to well-known symbolic models (such as the famous liquid drop). Remarkably, the improvement of the AI model over symbolic ones can almost entirely be attributed to an observation made by Jaffe in 1969 based on the structure of most known nuclear ground states. The end result is a fully interpretable data-driven model of nuclear masses based on physics deduced by AI.

   ↳ nucl-thcs.AIcs.LGnucl-ex3 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.