Mon·Nov 24, 2025Monday·November 24, 2025

1. 01*

   Backward-angle electroproduction of ${\eta }^{\prime }$ mesons off protons at $W=2.13\text{GeV}$ and $Q^2=0.46{\left(\text{GeV}/c\right)}^2$

   T. Akiyama (1)🇯🇵 · P. Bydžovský (2)🇨🇿 · T. Gogami (3)🇯🇵 · K. Itabashi (4)🇯🇵 · S. Nagao (5,6)🇯🇵 · S. N. Nakamura (1,5,6)🇯🇵 · K. Okuyama (1)🇯🇵 · B. Pandey (7,8)🇺🇸 · D. Skoupil (2)🇨🇿 · K. N. Suzuki (3)🇯🇵 · L. Tang (7,9)🇺🇸 · D. Abrams (10)🇺🇸 and 74 other authors

   The electroproduction of ${\eta }^{\prime }$ mesons from a ${}^1\mathrm{H}$ target at $W=2.13\text{GeV}$, $Q^2=0.46{\left(\text{GeV}/c\right)}^2$ and $\cos {\theta }_{{\gamma }^{\ast }{\eta }^{\prime }}^{\text{CM}}\approx -1$ has been experimentally measured. The differential cross section of virtual-photoproduction has been obtained as $4.4\pm 0.8\left(\text{stat.}\right)\pm 0.4\left(\text{sys.}\right)\text{nb/sr}$ in the One-Photon-Exchange Approximation. This value is one-sixth of that of real-photoproduction at backward angles. A comparison with newly-developed isobar model calculations not only shows validity of the theoretical framewark employed, but also imposes new constrains on coupling strength between the ${\eta }^{\prime }p$ final state and nucleon resonances.

   nucl-exPTEP·4 citations
2. 02*

   Maris polarization in the ($p,pd$) reaction

   Yoshiki Chazono🇯🇵

   Proton-induced knockout reactions at intermediate energies provide a clean probe for nuclear clusters. The Maris polarization, which is the effective polarization of a particle inside a nucleus arising from nuclear absorption and spin-orbit coupling, has been used in proton knockout to determine the total angular momentum $j$ of the removed protons. However, its manifestation in cluster knockout remains unexplored. We theoretically demonstrated that the Maris polarization can be observed via the vector analyzing power $A_y$ of the proton-induced deuteron knockout (p,pd) reaction in imbalanced kinematics. First, we computed the spin correlation coefficient $C_{y,y}$ of p-d elastic scattering, which is an elementary process, to identify suitable kinematics for the Maris polarization. Subsequently, we calculated the $A_y$ values of the (p,pd) reaction at 250 MeV for deuteron-cluster orbits with $j=1$, $2$, and $3$. The large positive $C_{y,y}$ values at p-d scattering angles of $\sim 40^{\circ }$ are consistent with the experimental data. In the corresponding (p,pd) kinematics, the signs of $A_y$ for $j=3$ and $1$ orbits are positive and negative, respectively, indicating effective upward and downward polarizations of the deuterons in the nucleus. The $A_y$ value for $j=2$ orbit lies between those for the other two orbits, which can also be explained by the Maris polarization, with the deuteron being knocked out from regions near the poles of the $y$-axis. These results are nearly independent of the deuteron internal state and the nucleon-nucleon effective interactions adopted. We theoretically demonstrated that the Maris polarization occurs in the (p,pd) reaction under imbalanced kinematics. This work may lead to the establishment of the concept of deuteron-cluster orbit. Further experimental and theoretical studies are required to improve the quantitative understanding of this effect.

   ↳ nucl-thnucl-ex0 citations
3. 03*

   Geometry-induced azimuthal anisotropy in coherent $J/\psi$ photoproduction

   Ding Yu Shao🇨🇳 · Han-Qing Yu🇨🇳 · Cheng Zhang🇨🇳 · Jian Zhou🇨🇳

   Azimuthal anisotropies in heavy-ion collisions are conventionally interpreted as signatures of hydrodynamic flow. We demonstrate that in peripheral collisions, a significant $\cos 2\varphi$ asymmetry in the decay leptons of coherently photoproduced $J/\psi$ mesons arises purely from the initial-state geometry of the nuclear electromagnetic field. This modulation originates from the linear polarization of coherent photons, which is radially aligned in impact parameter space and transferred to the vector meson. By employing light-cone perturbation theory within the dipole formalism, we calculate the centrality dependence of this asymmetry for collisions at RHIC and LHC energies. Our predictions quantitatively reproduce STAR data. This observable thus provides a rigorous benchmark for distinguishing electromagnetic initial-state effects from collective medium dynamics.

   ↳ hep-phnucl-exnucl-thPRD(2026)·4 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.