Wed·Dec 25, 2024Wednesday·December 25, 2024

1. 01*

   Improving $\pi \pi$ dispersive analyses and resonance determination with Forward Dispersion Relations

   P. Rabán🇪🇸 · J.R. Peláez🇪🇸 · J. Ruiz de Elvira🇪🇸

   We present preliminary results of an improved pion-pion scattering dispersive analysis that includes: a refined treatment of inelasticities, the introduction of G-waves, the extension of Forward Dispersion Relations as constraints up to 1.6 GeV, and data description up to roughly 1.8 GeV. Additionally, we impose Roy-like dispersion relations. As a result, we obtain three reliable solutions corresponding to three different datasets. From the Forward Dispersion Relation output, we extract resonance pole parameters in a parameterization-independent way using continued fractions.

   hep-phhep-exhep-latnucl-thPoS(2025)·0 citations
2. 02*

   Supernova Remnants with Mirror Dark Matter and Hyperons

   Adamu Issifu🇧🇷 · Prashant Thakur🇮🇳 · Franciele M. da Silva🇧🇷 · Kau D. Marquez🇵🇹 · Débora P. Menezes🇧🇷 · M. Dutra🇧🇷 · O. Lourenço🇧🇷 · Tobias Frederico🇧🇷

   For the first time, we use relativistic mean-field (RMF) approximation with density-dependent couplings, adjusted by the DDME2 parameterization, to investigate the effects of dark matter on supernova remnants. We calculate the nuclear equation of state for nuclear and dark matter separately, under the thermodynamic conditions related to the evolution of supernova remnants. A mirrored model is adopted for dark matter, and its effect on remnant matter is studied using a two-fluid scenario. At each stage of the remnant evolution, we assume that dark and ordinary matter have the same entropy and lepton fraction, and a fixed proportion of dark matter mass fraction is added to the stellar matter to observe its effects on some microscopic and macroscopic properties of the star. We observe that dark matter in the remnant core reduces the remnant's maximum mass, radius, and tidal deformability. Moreover, dark matter heats the remnant matter and alters particle distributions, thereby decreasing its isospin asymmetry and increasing the sound speed through the matter.

   hep-phPRD(2025)·18 citations
3. 03*

   Physical interpretation of large Lorentz violation via Weyl semimetals

   Alan Kostelecky🇺🇸 · Ralf Lehnert🇺🇸 · Marco Schreck🇧🇷 · Babak Seradjeh🇺🇸

   The physical intepretation of effective field theories of fundamental interactions incorporating large Lorentz violation is a long-standing challenge, known as the concordance problem. In condensed-matter physics, certain Weyl semimetals with emergent Lorentz invariance exhibit large Lorentz violation, thereby offering prospective laboratory analogues for exploration of this issue. We take advantage of the mathematical equivalence between the descriptions of large Lorentz violation in fundamental and condensed-matter physics to investigate the primary aspects of the concordance problem, which arise when the coefficients for Lorentz violation are large or the observer frame is highly boosted. Using thermodynamic arguments, we present a physical solution to the concordance problem and explore some implications.

   hep-phcond-mat.mes-hallNew J.Phys.(2025)·16 citations
4. 04*

   Low-Energy Neutrino-Nucleus Scattering and New Physics

   S. Carey🇺🇸 · V. Pandey🇺🇸

   The interactions of low-energy neutrinos with nuclei provide a unique window to explore various Standard Model (SM) and Beyond the Standard Model (BSM) processes. In particular, the recent observation of coherent elastic neutrino-nucleus scattering (CEvNS), predicted over five decades ago, has generated significant interest across disciplines. With its high cross section and suitability for compact detectors, particularly with stopped pion neutrinos, CEvNS offers a powerful probe for light, weakly coupled new physics. Ongoing global experimental efforts now aim to leverage CEvNS to test SM predictions and search for BSM signals, where deviations in event rates or spectra could reveal new physics. We present here an estimate of the number of recoil events obtained from CEvNS using the current and upcoming liquid argon based experiments. Furthermore, the event rate due to the inclusion of neutrino magnetic moment is also discussed.

   hep-phhep-exnucl-exnucl-th1 citation
5. 05*

   Zee model in a non-holomorphic modular $A_4$ symmetry

   Takaaki Nomura🇨🇳 · Hiroshi Okada🇨🇳

   We study a Zee model in a non-holomorphic modular $A_4$ flavor symmetry in which we find good predictions in both the cases of normal and inverted hierarchy. Parameter reduction on neutrino sector occurs due to large mass hierarchies between charged-leptons mass eigenvalues and new singly-charged bosons in addition to this flavor symmetry. As a result, we have two complex free parameters including modulus $\tau$. We show several predictions in terms of verifiable observables such as Dirac CP, Majorana phases, sum of the neutrino masses, and the effective mass for neutrino double beta decay in addition to demonstrating allowed regions for our input parameters.

   hep-phPLB(2025)·21 citations
6. 06*

   Forbidden neutrinogenesis

   Shinya Kanemura🇯🇵 · Shao-Ping Li🇯🇵

   The origin of neutrino masses can be simply attributed to a new scalar beyond the Standard Model. We demonstrate that leptogenesis can explain the baryon asymmetry of the universe already in such a minimal framework, where the electroweak scalar is favored to enhance the baryon asymmetry. Different from traditional leptogenesis, the realization here exploits the thermal behavior of leptons at finite temperatures, which is otherwise kinetically forbidden in vacuum. We present detailed calculations of the CP asymmetry in the Schwinger-Keldysh Closed-Time-Path formalism, and compute the asymmetry evolution via the Kadanoff-Baym equation. Such minimal forbidden neutrinogenesis establishes a direct link between the baryon asymmetry and the CP-violating phase from neutrino mixing, making the scenario a compelling target in neutrino oscillation experiments. Complementary probes from cosmology, flavor physics and colliders are also briefly discussed.

   hep-phJHEP(2025)·6 citations
7. 07*

   Heavy-Quark Spin Symmetry Violation effects in Charmed Baryon Production

   Nantana Monkata🇹🇭 · Prin Sawasdipol🇹🇭 · Nongnapat Ponkhuha🇹🇭 · Ratirat Suntharawirat🇹🇭 · Ahmad Jafar Arifi🇯🇵 · Daris Samart🇹🇭

   In this work, we investigate the Heavy-Quark Spin Symmetry (HQSS) exhibited in the effective Lagrangians governing the three-point interactions of $D$ mesons, charmed baryons, and nucleons. We first construct the effective Lagrangians, and there are 12 distinct terms. As a result, we observe that the invariant Lagrangian under HQSS manifests exclusively in the pseudoscalar $D$ mesons coupling to nucleons and ${\Lambda }_c$ baryons, whereas nucleons and ${\Sigma }_c$ (${\Sigma }_c^{\ast }$) baryons only couple with vector $D$ mesons. By taking into account the violated heavy-quark spin transformation, one can recover all interactions from the effective Lagrangians. Furthermore, we compute the differential cross-sections of the $p\bar{p}\to Y_c{\bar{Y}}_c^{\prime }$ scatterings, where $Y_c,{\overline{Y_c}}^{\prime }={\Lambda }_c,{\Sigma }_c,{\Sigma }_c^{\ast }$, to reveal the residue of the violating HQSS (VHQSS) on charmed baryon production. Ultimately, by accounting for VHQSS, we aim for precise predictions of production rates, which are essential for the High-Energy Storage Ring (HESR) experiments at the Facility for Antiproton and Ion Research (FAIR).

   hep-phnucl-th0 citations
8. 08*

   Global analysis of Sivers and Collins asymmetries within the TMD factorization

   Chunhua Zeng🇨🇳 · Hongxin Dong🇨🇳 · Tianbo Liue · Peng Sun🇨🇳 · Yuxiang Zhao🇨🇳

   We present a global analysis of Sivers functions, transversity distribution functions, and Collins fragmentation functions within the transverse momentum dependent factorization. This analysis encompasses the latest data from semi-inclusive deep inelastic scattering, Drell-Yan, and W/Z-boson production processes as recently reported by the COMPASS and STAR Collaborations. Upon integrating the new data into our fitting, the precision of the extracted d and dbar quark Sivers and transversity distributions, as well as the tensor charge, is notably improved.

   hep-ph8 citations
9. 09*

   Halo-dependent Anharmonic Effects in Collective Excitation for Light Dark Matter Direct Detection

   Jun Guo🇨🇳 · Lei Wu🇨🇳 · Bin Zhu🇨🇳

   Phonon, the collective excitation of lattice vibration in the crystal, has been put forward as a means to search for light dark matter. However, the accurate modeling of the multi-phonon production process is challenging in theory. The anharmonicity of the crystal must be taken into account, as it has a significant impact on dark matter-nucleus scattering cross section in the low dark matter mass region. Notably, such an effect is sensitive to the velocity distribution of the dark matter halo. In this work, we consider the potential dark matter substructures indicated by the recent Gaia satellite observation and investigate their impact on the anharmonicity of the silicon crystal. By employing the likelihood analysis with the Asimov dataset, we present the expected sensitivity of dark matter-nucleus interactions, which can differ from the standard halo model by a factor of 2-3.

   hep-phSCPMA(2025)·5 citations
10. 10*

    About Matter Effects on Neutrino Mixing Matrix Phases

    Pedro Cunha de Holanda🇧🇷 · Macello Jales de Carvalho Fonseca Filho · Eduardo Walter da Silva

    As is widely known, the flavour and mass eigenbasis in neutrino sector can be related by a reduced unitary matrix, described by 3 real parameters and one phase, for Dirac neutrinos, and 2 extra phases if neutrinos are Majorana particles. Neutrino flavour oscillation experiments are insensitive to Majorana phases, which leads to using the PMNS matrix with only one phase to describe flavour transitions. In this paper, we point out one feature of such choice that is commonly ignored: when neutrinos propagate in matter, the reduced unitary matrix PMNS does not properly diagonalize the neutrino system. We present some numerical calculations and analytical estimations to illustrate such statement, and discuss some scenarios where this effect can be probed.

    hep-ph0 citations
11. 11*

    Large and small hierarchies from finite modular symmetries

    Tetsutaro Higaki🇯🇵 · Junichiro Kawamura🇰🇷 · Tatsuo Kobayashi🇯🇵 · Kaito Nasu🇯🇵 · Riku Sakuma🇯🇵

    We study the moduli stabilization by the radiative corrections due to the moduli dependent vector-like masses invariant under the finite modular symmetry. The radiative stabilization mechanism can stabilize the modulus $\tau$ of the finite modular symmetry ${\Gamma }_N$ ($N\in \mathbb{N}$) at $\mathrm{Im}\tau \gg 1$, where the shift symmetry $\tau \to \tau +1$ remains unbroken approximately. The shift symmetry can be considered as the residual ${\mathbb{Z}}_N$ symmetry which realizes the Froggatt-Nielsen mechanism with the hierarchy parameter $e^{-2\pi \mathrm{Im}\tau /N}\ll 1$. In this work, we study the stabilization of multiple moduli fields, so that various hierarchical values of the modular forms coexist in a model. For example, one modulus stabilized at $\mathrm{Im}{\tau }_1\sim 3$ is responsible for the hierarchical structure of the quarks and leptons in the Standard Model, and another modulus stabilized at $\mathrm{Im}{\tau }_2\sim 15$ can account for the flatness of the $\mathrm{Re}{\tau }_2$ direction which may be identified as the QCD axion.

    hep-phhep-thJHEP(2025)·2 citations
12. 12*

    Study on Toponium: Spectrum and Associated Processes

    Sheng-Juan Jiang🇨🇳 · Bai-Qing Li🇨🇳 · Guang-Zhi Xu🇨🇳 · Kui-Yong Liu🇨🇳

    In this paper, we calculate the toponium spectrum in the potential model with the screened effects. Coulombic part is dominant for toponium, and the coefficient of the Coulomb potential is chosen from lattice QCD calculations at an infinite quark mass in accord with the ultrasoft scale choice. We also derive the relative E1 transitions, decays, and production.

    hep-ph20 citations
13. 13*

    Higgs Decays to $Z\gamma$ and $\gamma \gamma$ in the Flavor-Gauged Two Higgs Doublet Model

    Feng-Zhi Chen🇨🇳 · Qiaoyi Wen🇨🇳 · Fanrong Xu🇨🇳

    This work examines the $h\to Z\gamma$ and $h\to \gamma \gamma$ decays in the flavor-gauged two Higgs doublet model (FG2HDM), which augments the Standard Model (SM) with an additional scalar doublet, a singlet, and a $U(1{)}^{\prime }$ flavor gauge symmetry. Beyond the SM spectrum, FG2HDM predicts five additional physical scalars and a new neutral gauge boson, $Z^{\prime }$. We demonstrate that while both decay channels are sensitive to charged Higgs loops, $h\to Z\gamma$ is uniquely modified by fermion-antifermion-$Z$ ($f\bar{f}Z$) vertex corrections. These vertex corrections further impact top-quark observables and the flavor-changing neutral current (FCNC) process $b\to s{\ell }^{+}{\ell }^{-}$. Our analysis identifies a viable parameter space ($m_{H^{\pm }}>200$~GeV and ${\lambda }_{h{H}^{+}{H}^{-}}<0$) consistent with current $1\sigma$ experimental limits, where the signal strength ${\mu }_{\gamma \gamma }$ remains the primary constraint on scalar sector parameters. Regarding the $f\bar{f}Z$ couplings, we delineate the allowed regions in the ${\mathcal{Q}}_{tL}$-${\mathcal{Q}}_{tR}$ plane by evaluating the leading top-quark contributions, revealing that $b\to s{\ell }^{+}{\ell }^{-}$ imposes the most stringent bounds. Finally, we highlight that the $14\%$ projected precision for ${\mu }_{Z\gamma }$ at the High-Luminosity LHC (HL-LHC) will significantly enhance sensitivity to the FG2HDM.

    hep-phhep-exCPC(2026)·3 citations
14. 14*

    Fermion masses and mixings and charged lepton flavor violation in a 3-3-1 model with inverse seesaw

    A. E. Cárcamo Hernández🇨🇱 · D. T. Huong🇻🇳 · H. N. Long🇻🇳 · Daniel Salinas-Arizmendi🇨🇱

    We present a extension of the 3-3-1 gauge model supplemented by an $A_4$ flavor symmetry and cyclic discrete symmetries, including $Z_2$, $Z_2^{\prime }$, $Z_3$, $Z_4$, $Z_7$ and $Z_{10}$. The model successfully reproduces the observed SM fermion mass hierarchies and mixing patterns in quark and lepton sectors. The smallness of the active neutrino masses is explained through an inverse seesaw mechanism, enabled by the introduction of right-handed and sterile Majorana neutrinos. In the quark sector, flavor-changing neutral currents (FCNCs) arise at tree level exclusively for up-type quarks via the new heavy neutral gauge boson exchange, leading to strong constraints from $D^0$ - ${\bar{D}}^0$ mixing. The charged lepton sector exhibits sizeable flavor-violating effects, especially in the $\mu \to e\gamma$ decay, mediated by loops involving heavy neutrinos, new charged gauge bosons as well as charged scalars. We perform a detailed numerical fit of fermion masses and mixing parameters and identify viable regions of parameter space consistent with experimental data on CKM and PMNS mixing matrices. The model predicts branching ratios for charged lepton flavor violating decays and $\mu$-$e$ conversion rates within the sensitivity of future experiments.

    hep-phPTEP(2025)·3 citations
15. 15*

    Production of ${\eta }_b$ in ultra-peripheral $PbPb$ collisions

    C.N. Azevedo🇧🇷 · F.C. Sobrinho🇧🇷 · F.S. Navarra🇧🇷

    Very recently, the two-photon decay width of the ${\eta }_b$ meson was computed with lattice QCD methods. This decay has not yet been measured. The knowledge of this width allows for the calculation of the ${\eta }_b$ production cross section through photon-photon interactions in ultra-peripheral $PbPb$ collisions. In this work we present this calculation, which is the first application of the lattice result. Since UPCs are gaining an increasing attention of the heavy ion community, we take the opportunity to perform a comprehensive study of the different ways of defining ultra-peripheral collisions and of the different ways to treat the equivalent photon flux.

    hep-phPRC(2025)·1 citation
16. 16*

    Non-radial oscillations of hadronic neutron stars, quark stars, and hybrid stars : Calculation of $f$, $p$, and $g$ mode frequencies

    Atanu Guha🇰🇷 · Debashree Sen🇰🇷 · Chang Ho Hyun🇰🇷

    The composition and equation of state (EoS) of dense matter relevant to compact stars are quite inconclusive. However, certain observational constraints on the structural properties of compact stars help us constrain the EoS to a fair extent. Moreover, gravitational asteroseismology gives a notion of the composition and EoS of compact stars. The next generation gravitational wave (GW) detectors are likely to detect several oscillation mode frequencies of the GWs. In this work we compute the fundamental ($f$) and the first pressure ($p_1$) mode frequencies ($f_f$ and $f_{p1}$, respectively) with different compositions viz., hadronic, quark, and hybrid star (HS) matter. For HSs, we also study the gravity ($g$) mode frequency ($f_g$). For each phase we also study the correlation between the oscillation frequencies of 1.4 $M_{\odot }$ and 2.01 $M_{\odot }$ compact stars with other different properties. We find that various possible composition of compact stars substantially affects the oscillation frequencies. However, the mass-scaled angular $f$ mode frequency (${\omega }_{f}M$) varies universally with compactness ($C$) for all hadronic, quark and hybrid stars. The $f$ mode frequency ($f_{f_{1.4}}$) of the canonical 1.4 $M_{\odot }$ compact star, obtained with different composition, is quite correlated with the canonical radius ($R_{1.4}$) and tidal deformability (${\Lambda }_{1.4}$) while $f_{p_{1.4}}$ is well correlated with slope parameter of the symmetry energy. We also show that $f_{g_{1.4}}$ of the HSs varies almost linearly with ${\Lambda }_{1.4}$. Should $g$ modes be detected, they could not only support the existence of HSs, but $f_g$ could be useful to understand the strength of quark repulsion in HSs.

    hep-phastro-ph.HEnucl-thEPJC(2025)·11 citations
17. 17*

    The allowed baryon to baryon-meson strong transitions

    A. R. Olamaei🇮🇷 · S. Rostami🇮🇷 · K. Azizi🇮🇷

    We investigate the kinematically allowed baryon to baryon-meson strong transitions in all the light and heavy sectors. We consider only the ground state on-shell particles in the baryonic and mesonic channels. In the case of mesons, only the well-established pseudoscslar and vector nonets are involved. For the baryons, we consider the ground state spin 1/2 and 3/2 baryons. Using all the restrictions and conservation laws, a \texttt{mathematica}/ \texttt{python} code selects the allowed strong channels among many possible transitions. Using the strong coupling constants defining these transitions, we estimate the strong width and beaching fraction at each channel, that may help ongoing experimental and theoretical investigations.

    hep-phhep-exhep-latEPJC(2025)·0 citations
18. 18*

    Diffuse Neutrino Signals from Dark Stars Seeding Super-Massive Black Holes

    Thomas Schwemberger🇺🇸 · Volodymyr Takhistov🇯🇵

    Dark stars (DSs) -- first stars powered by dark-matter (DM) heating rather than fusion -- could form in the early Universe. They can grow to $\gtrsim 10^5{M}_{\odot }$ masses and collapse into seeds of supermassive black holes (SMBHs). We demonstrate that diffuse neutrino flux generated by DSs can be observable in existing experiments and have energies reaching hundreds of MeV, providing novel window for probing SMBH progenitors. We establish first constraints on DSs and DM annihilations powering them using data from Super-Kamiokande and IceCube neutrino experiments, and consistent with James Webb Space Telescope observations. Upcoming experiments such as Hyper-Kamiokande, DUNE, JUNO will be able to explore DS properties with enhanced sensitivity.

    hep-phastro-ph.COastro-ph.HEhep-exApJL(2025)·2 citations
19. 19*

    Gravitational Waves from Particles Produced from Bubble Collisions in First-Order Phase Transitions

    Keisuke Inomata🇺🇸 · Marc Kamionkowski🇺🇸 · Kentaro Kasai🇯🇵 · Bibhushan Shakya🇩🇪

    We discuss a new source of gravitational waves (GWs) from first-order phase transitions. The collisions of bubbles of the new phase can efficiently produce particles that couple to the background field undergoing the transition, thereby transferring a significant fraction of the released vacuum energy into a distribution of inhomogeneous and dynamic particle populations that persist long after the bubbles have disappeared. We study the GWs produced by such particle distributions, showing that GWs arise from the quadrupolar anisotropy in the radiation emitted from the bubble collisions, and present a semi-analytical calculation of the two-point correlation function for the associated energy distributions. We find that this new contribution can qualitatively modify the overall GW signal from such phase transitions, creating a distinct shift in the spectral slope at low frequencies that could be observed by future GW experiments. It is therefore important to take this new contribution into account for any transition where the background field has significant self-coupling or couplings to other fields that could lead to efficient particle production at bubble collision.

    ↳ astro-ph.COgr-qchep-phPRD(2025)·23 citations
20. 20*

    Using the Th III Ion for a Nuclear Clock and Searches for New Physics

    V. A. Dzuba🇦🇺 · V. V. Flambaum🇦🇺

    The 229Th nucleus possesses a unique low-frequency transition at 8.4 eV, which is being considered for the development of an extremely accurate nuclear clock. We investigate an electronic bridge process in the Th III ion, where nuclear excitation occurs via electronic transitions, and demonstrate that a proper choice of laser frequencies can lead to 10,000 enhancement of this effect. Electrons also reduce 1.7 times the lifetime of the nuclear excited state. Additionally, the electronic structure of the Th III ion exhibits features that make it particularly useful for probing new physics. Notably, it contains a metastable state connected to the ground state via a weak M2 transition, which can be utilized for quantum information processing, as well as searches for oscillating axion field, violation of local Lorentz invariance, test of the Einstein's equivalence principle, and measurement of nuclear weak quadrupole moment. The electronic states of the ion present a unique case of level crossing involving the 5f, 6d, and 7s single-electron states. This crossing renders the transition frequencies highly sensitive to potential time-variation of the fine-structure constant.

    ↳ physics.atom-phhep-phnucl-thPRA(2025)·4 citations
21. 21*

    Notes on Quasinormal Modes of charged de Sitter Blackholes from Quiver Gauge Theories

    Pujun Liu🇨🇳 · Rui-Dong Zhu🇨🇳

    We give the connection formulae for ordinary differential equations with 5 and 6 (and in principle can be generalized to more) regular singularities from the data of instanton partition functions of quiver gauge theories. We check the consistency of these connection formulae by numerically computing the quasinormal modes (QNMs) of Reissner-Nordström de Sitter (RN-dS) blackhole. Analytic expressions are obtained for all the families of QNMs, including the photon-sphere modes, dS modes, and near-extremal modes. We also argue that a similar method can be applied to the dS-Kerr-Newman blackhole.

    ↳ hep-thastro-ph.HEgr-qchep-ph+2JHEP(2025)·7 citations
22. 22*

    Quasinormal modes of black holes embedded in halos of matter

    Laura Pezzella🇮🇹 · Kyriakos Destounis🇮🇹 · Andrea Maselli🇮🇹 · Vitor Cardoso🇩🇰

    We investigate the (axial) quasinormal modes of black holes embedded in generic matter profiles. Our results reveal that the axial QNMs experience a redshift when the black hole is surrounded by various matter environments, proportional to the compactness of the matter halo. Our calculations demonstrate that for static black holes embedded in galactic matter distributions, there exists a universal relation between the matter environment and the redshifted vacuum quasinormal modes. In particular, for dilute environments the leading order effect is a redshift $1+U$ of frequencies and damping times, with $U\sim -\mathcal{C}$ the Newtonian potential of the environment at its center, which scales with its compactness $\mathcal{C}$.

    ↳ gr-qcastro-ph.GAastro-ph.HEhep-ph+1PRD(2025)·77 citations
23. 23*

    Dirac-Schwinger Quantization for Emergent Magnetic Monopoles?

    A. Farhan (1) · M. Saccone (2) · B.F.L. Ward (1) ((1) Department of Physics and Astronomy, Baylor University, Waco, TX, USA, (2) Croputation, Santa Fe, NM, USA)🇺🇸

    In Refs.[1-4] Dirac and Schwinger showed the existence of a magnetic monopole required a charge quantization condition which we write following Dirac as $\frac{eg}{4\pi \hslash }=\frac{n}{2},n=0,\pm 1,\pm 2,\dots$. Here, $g$ is the magnetic monopole charge and $e$ is the electric charge of the positron. Recently, in Refs. [5,6], it has been shown experimentally that frustrated spin-ice systems exhibit 'emergent' magnetic monopoles. We show that, within the experimental errors, the respective magnetic charges obey the Dirac-Schwinger quantization condition. Possible implications are discussed.

    ↳ cond-mat.str-elhep-phPLB(2025)·0 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.