Thu·Aug 21, 2025Thursday·August 21, 2025

1. 01*

   New Upper Bounds on Exotic Neutron Spin-Electron Spin Interactions via Neutron Spin Rotation Measurements in a Compensated Ferrimagnet

   T. Mulkey🇺🇸 · K. N. Lopez🇺🇸 · C. D. Hughes🇺🇸 · B. Hill🇺🇸 · M. Van Meter🇺🇸 · H. Wijeratne🇺🇸 · J. C. Long🇺🇸 · M. Sarsour🇺🇸 · W. M. Snow🇺🇸 · K. Li🇺🇸 · R. Parajuli🇺🇸 · S. Samiei🇺🇸 and 7 other authors

   We report a search for exotic spin-spin interactions between neutrons and electrons which could signal new physics beyond the Standard Model using slow neutron polarimetric imaging through a dense medium of polarized electrons. Our dense polarized electron target is a ferrimagnet held at its magnetic compensation temperature, which realizes a polarized electron ensemble with zero net magnetization. We sought the spin rotation of transversely polarized neutrons from a neutron spin-electron spin interaction of the form $V_2=-g_A^e{g}_A^n\frac{\hslash c}{4\pi }{\vec{\sigma }}_e\cdot {\vec{\sigma }}_n\frac{e^{-r/{\lambda }_c}}{r}$, where $g_A^e$ and $g_A^n$ are the electron and neutron axial couplings, $\overrightarrow{{\sigma }_e}$ and $\overrightarrow{{\sigma }_n}$ are the electron and neutron spin, and ${\lambda }_c$ is the interaction range for an exotic axial vector interaction from massive spin-1 boson exchange of mass $\hslash c/{\lambda }_c$. The resulting average neutron spin rotation angle per unit length, $\frac{d{\bar{\varphi }}_{F5}}{dz}=[0.41\pm 6.30(stat.)\pm 4.4(sys.)]\times 10^{-3}$ rad/m, is consistent with zero. Our novel approach improves the previous upper limits on the coupling constant product $g_A^e{g}_A^n$ by several orders of magnitude in the poorly explored $10^{-8}\le {\lambda }_c\le 10^{-2}$ range.

   nucl-excond-mat.mtrl-scihep-exquant-phPRL(2026)·1 citation
2. 02*

   Probing hadronization with the charge correlator ratio in $p$+$p$, $Ru$+$Ru$ and $Zr$+$Zr$ collisions at STAR

   Youqi Song (STAR Collaboration)🇺🇸

   The parton-to-hadron transition, known as hadronization, is dominated by non-perturbative Quantum Chromodynamics (QCD) effects and thus challenging to study from first-principle calculations. On the other hand, experimental studies of observables sensitive to hadronization could provide valuable input. The charge correlator ratio $r_c$ studies the charge correlation between the leading two hadrons in jets and is sensitive to hadronization effects. With data taken at $\sqrt{s_{\mathrm{NN}}}=200$ GeV at STAR, we measure $r_c$ in $p$+$p$ collisions to probe for string-like fragmentation, and in $Ru$+$Ru$ and $Zr$+$Zr$ collisions to probe for potential modification to hadronization in the Quark-Gluon Plasma (QGP). These measurements, compared with various model predictions, are expected to distinguish between phenomenological model descriptions for hadronization in vacuum, and provide insight into jet-medium interaction in the QGP.

   nucl-exEPJ Web Conf.(2025)·0 citations
3. 03*

   Structure of the doubly magic nuclei ${}^{208}$Pb and ${}^{266}$Pb from ab initio computations

   Francesca Bonaiti🇺🇸 · Gaute Hagen🇺🇸 · Thomas Papenbrock🇺🇸

   Theoretical studies indicate that the superheavy neutron-rich nucleus ${}_{82}^{266}$Pb${}_{184}$ is doubly magic and at the neutron drip line. While its density distributions and single-particle energies have been computed, the structure of this nucleus is yet unknown. We perform ab initio computations of ${}^{266}$Pb using an interaction from an effective field theory of quantum chromodynamics tuned only on properties of nuclei with $A\le 4$. We validate our theoretical framework by computing the first $2^{+}$ and $3^{-}$ excited states of ${}^{208}$Pb, finding agreement with experimental data. We confirm that ${}^{266}$Pb is doubly magic and show that its $3^{-}$ state, located below the $2^{+}$ state, exhibits an excitation gap of 2.6 MeV with respect to the ground state. Our calculations also suggest that this nucleus is at the neutron drip line.

   ↳ nucl-thnucl-ex29 citations
4. 04*

   Enhancing Neutron Measurement Accuracy with Bubble Detectors at Laser-Driven Neutron Sources

   Stefan Scheuren · Maria Angeles Millán-Callado · Jonas Kohl · Tim T. Jäger · Markus Roth🇩🇪 · Christian Rödel · Aaron Alejo · Florian Kroll · Karl Zeil · Arnd Junghans🇩🇪 · Carlos Guerrero🇪🇸 · Benedikt Schmitz

   Bubble detectors are widely used to measure neutron flux from laser-driven sources employing a pitcher-catcher setup, due to their insensitivity to intense $\gamma$-ray backgrounds and strong electromagnetic pulses (EMP).\\ This paper presents a method to account for the neutron energy-dependent response of bubble detectors, enabling accurate conversion of bubble counts into neutron flux at the detector location. The proposed method is based on the accurate reconstruction of the response function using a surrogate model. The resulting model is convoluted with the (normalized) expected/measured neutron spectrum to obtain an effective measure of the bubble detector's response, herein referred to as effective $c$ or $c_{\text{eff}}$. This effective value for the response is energy-independent after the convolution. In this way, our approach includes the spectral distribution of neutrons arriving at the detector to determine the integral neutron flux. Analyzing our experimental results obtained at the DRACO PW laser and comparing the results to previously used methods to obtain neutron fluxes from bubble detectors returns a reduction in neutron flux of up to \SI{31}{\%}. Results from the method detailed in this paper agree with in-depth experimental setup Monte Carlo simulations, with deviations of less than \SI{10}{\%}. We furthermore discuss the inherent limitations of our method with regard to its uncertainty and highlight the influence of neutron scattering in bubble detector measurements. For our experimental setup at the DRACO laser, up to \SI{47}{\%} of the detected neutrons arrive at the detector after undergoing at least one scattering event.

   ↳ physics.ins-detnucl-ex0 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.