Wed·Aug 27, 2025Wednesday·August 27, 2025

1. 01*

   Exploring Data-Driven Corrections for $\varphi$-Meson Global Spin Alignment Measurements

   C.W. Robertson🇺🇸 · Yicheng Feng🇺🇸 · Fuqiang Wang🇺🇸

   Non-central heavy ion collisions generate large orbital angular momentum (OAM), providing opportunities to study spin phenomena such as the global spin alignment of vector mesons. Such studies are expected to reveal properties of the quark-gluon plasma produced in these collisions. Global spin alignment of vector mesons, such as the $\varphi$-meson, can be measured by the $00^{\mathrm{th}}$ coefficient of the spin density matrix, ${\rho }_{00}$, via the polar angle of the decay kaon momentum in the parent rest frame with respect to the OAM direction of the collision. A deviation of ${\rho }_{00}$ from the isotropic value of $1/3$ indicates a finite spin alignment. The reported signal of ${\rho }_{00}-1/3$ is on the order of $\sim 1\%$ and therefore corrections for finite detector performance and acceptance, which are expected to be on the order of a few tenths of a percent, are important. Additional complications in the detector corrections may arise from the $\varphi$-meson azimuthal anisotropy which could become intertwined with the detector efficiency. Typically, detector corrections for global spin alignment of vector mesons are performed with Monte-Carlo (MC) methods using detector simulation packages such as GEANT, however it is unclear if such methods can be trusted at the needed level of precision. In this paper, we investigate an alternative, data-driven approach in correcting for detector effects. This approach utilizes detector effects on combinatorial kaon pairs from $\varphi$-meson decays that fall within the $\varphi$-meson mass window, which can be obtained through statistical identification of decay kaons in real data analysis. We examine the degree of success of such a data-driven approach using toy-model MC simulations as well as its shortcomings.

   nucl-ex1 citation
2. 02*

   A New Evidence of Interplay Between Tetrahedral and Octahedral Symmetries and Symmetry Breaking: Exotic Rotational Bands in ${}^{152}$Sm

   S. Basak🇮🇳 · D. Kumar🇮🇳 · T. Bhattacharjee🇮🇳 · I. Dedes🇵🇱 · J. Dudek🇵🇱 · A. Pal🇮🇳 · S. S. Alam🇮🇳 · A. Saha🇮🇳 · A. K. Sikdar🇮🇳 · J. Nandi🇮🇳 · Shabir Dar🇮🇳 · A. Baran🇵🇱 and 21 other authors

   We report on an experimental evidence for a new, second tetrahedral band in ${}_{62}^{152}$Sm${}_{90}^{}$. It was populated via fusion evaporation reaction, ${}^{150}\mathrm{Nd}(\alpha ,2n{)}^{152}$Sm, employing 26 MeV beam of $\alpha$ particles from K-130 cyclotron at Variable Energy Cyclotron Centre, Kolkata, India. The newly observed possible mixed parity sequence with absence of E2 and strong indication of E3 transitions is consistent with the spectroscopic criteria for a tetrahedral-symmetry rotational band that could be constructed from the allowed spin-parity assignments. This structure differs from the structure of the band previously found in the same nucleus, the new one manifesting tetrahedral symmetry not accompanied by the octahedral one. Our new experimental results are interpreted in terms of group representation theory and collective nuclear-motion theory of Bohr. We propose to generalize the notion of the tetrahedral vibrational bands and believe that our new experimental results support a number of theory predictions related to nuclear tetrahedral symmetry published earlier and bring a new light into the issue of spontaneous symmetry breaking in heavy nuclei.

   nucl-exnucl-thPRC(2025)·7 citations
3. 03*

   Beam-Normal Single-Spin Asymmetry in ${}^{208}$Pb at low energy: discrepancy resolved or new kinematic puzzle?

   A. Esser🇩🇪 · N. Kozyrev · K. Aulenbacher🇩🇪 · S. Baunack · M. Dehn · A. Del Vincio · L. Doria🇩🇪 · M. Hoek🇩🇪 · F. Keil · F. Maas🇩🇪 · H. Merkel🇩🇪 · M. Mihovilovic🇸🇮 and 8 other authors

   A longstanding discrepancy between measured and predicted beam-normal single-spin asymmetries $A_n$ in elastic electron scattering off ${}^{208}$Pb has challenged our understanding of two-photon exchange (TPE) in heavy nuclei. We report a new measurement at 570 MeV and $Q^2$=0.04 $Ge{V}^2$/$c^2$, yielding$A_n=(-9.1\pm 2.1\text{(stat)}\pm 0.7\text{(syst)})\mathrm{ppm}$. This nonzero value contrasts with previous results at higher energies and suggests a kinematic dependence of TPE effects not captured by current theory, prompting a reevaluation of earlier interpretations.

   nucl-exhep-exnucl-thPRL(2025)·4 citations
4. 04*

   Two-flavored heavy-light mesons' nuclear bound states

   G. N. Zeminiani🇧🇷 · K. Tsushima🇧🇷

   We calculate the $B^{-}$-, $\overline{B^0}$-, $D^{+}$-, $D^0$-, $K^{-}$-, and $\overline{K^0}$-${}^{12}$C bound state energies by solving the Klein-Gordon (K;G.) equation in momentum space, and also obtain the corresponding coordinate space radial wave functions. The strong Lorentz scalar and vector potentials in ${}^{12}$C are calculated using a local density approximation, where the scalar potentials are obtained based on the mass shifts of the respective mesons in nuclear matter. The mesons' mass shifts, the ${}^{12}$C nuclear density distributions, the strong potentials as well as the Coulomb potentials, are calculated by the quark-meson coupling (QMC) model.

   ↳ nucl-thhep-exhep-phnucl-exPoS(2026)·0 citations
5. 05*

   Contribution of Subthreshold States to the Residual Energy Distribution of ${}^{159}$Dy

   Tadafumi Kishimoto🇯🇵 · Toru Sato🇯🇵

   We investigate the residual energy distribution in the electron capture (EC) process of ${}^{159}$Dy, emphasizing the role of subthreshold atomic states, which have typically been omitted in conventional spectral analyses. By incorporating these energetically forbidden hole states into the spectral function $P(E)$, we demonstrate a significant enhancement - over an order of magnitude - in the EC rate near the zero-momentum neutrino emission region. This enhancement increases further with larger $Q$ values, contrary to standard expectations. Our analysis shows that $P(E)$ can be experimentally determined, resolving ambiguities near the endpoint and enabling new approaches to 'ultra-low $Q$ value' EC reactions for neutrino mass studies.

   ↳ nucl-thhep-phnucl-exPRL(2025)·1 citation
6. 06*

   Baselines for Abelian Charge Fluctuations in Nuclear Collisions:Theory and Comparison with Experimental Data

   Bengt Friman🇩🇪 · Krzysztof Redlich🇵🇱 · Anar Rustamov🇩🇪

   We investigate fluctuations in the canonical ensemble of an Abelian charge, such as baryon number. Our focus is on cumulants and factorial cumulants of baryon and antibaryon multiplicity distributions, including their sum and difference, in both the full phase space and subsystems. In particular, we establish a correlation between net-baryon number fluctuations within a subsystem, which is pertinent for fluctuation analyses in nucleus-nucleus collisions, and fluctuations of baryon and antibaryon numbers in the total system. We derive analytical expressions for factorial cumulants of arbitrary order and present concise results in terms of the cumulants of the total baryon number. To account for dynamics beyond global conservation, we introduce local attractive and repulsive multi-particle interactions within a phenomenological framework. A comparison of calculated and generated cumulants with STAR and HADES data indicates that multiparticle interactions play a decisive role in the description of observed fluctuation patterns. At high collision energies, the data are well-reproduced by incorporating repulsive two-proton interactions, while at lower energies, attractive three-particle interactions become essential. Furthermore, our framework facilitates realistic event generation, enabling a direct comparison with experimental measurements.

   ↳ nucl-thhep-exhep-phnucl-exJHEP(2026)·11 citations
7. 07*

   Dual-polarization structure and nuclear structure effect on $\Lambda$ polarization

   X. G. Deng🇨🇳 · Y. G. Ma🇨🇳

   We report a novel manifestation of spin-vorticity interplay in relativistic heavy-ion collisions. Using ${}^{16}$O+${}^{197}$Au at $\sqrt{s_{\mathrm{NN}}}=7.7$ GeV as a test case, we show that the $\Lambda$ hyperon exhibits a clear dual-polarization structure, observed here in central ${}^{16}$O + ${}^{197}$Au collisions for the first time. The polarization is further highly sensitive to the intrinsic nuclear geometry: different $\alpha$-cluster configurations of ${}^{16}$O, ranging from chain-like to tetrahedral, lead to distinct polarization patterns across centralities. In particular, the backward rapidity region and peripheral events display striking structure-dependent variations, including opposite angular distributions of local polarizations $P_x$ and $P_y$ compared with a spherical reference. These findings reveal that nuclear clustering leaves measurable imprints on hyperon spin alignment in relativistic collisions. Our results open a promising avenue for probing nuclear structure in short-lived systems and highlight a new spin-sensitive mechanism relevant for upcoming experiments at RHIC and future facilities.

   ↳ nucl-thnucl-ex2 citations
8. 08*

   Quantifying fluctuation signatures of the QCD critical point using maximum entropy freeze-out

   Jamie M. Karthein🇺🇸 · Maneesha Sushama Pradeep🇺🇸 · Krishna Rajagopal🇺🇸 · Mikhail Stephanov🇺🇸 · Yi Yin🇨🇳

   A key question about the QCD phase diagram is whether there is a critical point somewhere on the boundary between the hadronic and quark-gluon plasma phases, and if so where. Heavy-ion collisions offer a unique opportunity to search for signatures of such a critical point by analyzing event-by-event fluctuations in particle multiplicities. To draw meaningful conclusions from experimental data, a theoretical framework is needed to link QCD thermodynamics with the particle spectra and correlations observed in detectors. The Equation of State (EoS) of QCD near a critical point can be related to the universal Gibbs free energy of the 3D Ising model using four currently unknown non-universal mapping parameters whose values are determined by the microscopic details of QCD. We utilize the maximum entropy approach to freeze-out the fluctuations in order to make estimates for factorial cumulants of proton multiplicities, assuming thermal equilibrium, for a family of EoS with a 3D Ising-like critical point, varying the microscopic inputs that determine the strength and structure of the critical features. We quantify the effect of the non-universal mapping parameters, and the distance between the critical point and the freeze-out curve, on the factorial cumulants of proton multiplicities.

   ↳ nucl-thhep-phnucl-exPRD(2026)·12 citations
9. 09*

   Finite-volume analysis and universal scaling signatures near the chiral phase transition in (2+1)-flavor QCD

   Sabarnya Mitra🇩🇪 · Frithjof Karsch🇩🇪

   For quantifying the universal properties of the chiral phase transition in QCD through numerical calculations on a discrete space-time lattice, one needs to perform controlled extrapolations to the continuum and infinite-volume limits followed by an extrapolation to the limit of massless light quarks. We discuss here, the results on the latter two limits at still finite lattice spacings. We use here for chiral symmetry breaking, an improved order parameter free of additive and multiplicative divergences and we analyse its volume and quark mass dependence. Comparing to the expected universal behavior in the chiral limit, we quantify deviations from the universal finite-size scaling behavior as function of the light to strange quark mass ratio.

   ↳ hep-lathep-phhep-thnucl-ex+1EPJ Web Conf.(2026)·3 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.