Mon·Sep 19, 2022Monday·September 19, 2022

1. 01*

   Probing a light dark sector at future lepton colliders via invisible decays of the SM-like and dark Higgs bosons

   Gholamhossein Haghighat🇮🇷 · Mojtaba Mohammadi Najafabadi🇮🇷 · Kodai Sakurai🇯🇵 · Wen Yin🇯🇵

   A renormalizable UV model for Axion-Like Particles (ALPs) or hidden photons, that may explain the dark matter usually involves a dark Higgs field which is a singlet under the standard model (SM) gauge group. The dark sector can couple to the SM particles via the portal coupling between the SM-like Higgs and dark Higgs fields. Through this coupling, the dark sector particles can be produced in either the early universe or the collider experiments. Interestingly, not only the SM-like Higgs boson can decay into the light dark bosons, but also a light dark Higgs boson may be produced and decay into the dark bosons in a collider. In this paper, we perform the first collider search for invisible decays by taking both the Higgs bosons into account. We use a multivariate technique to best discriminate the signal from the background. We find that a large parameter region can be {probed} at the International Linear Collider (ILC) operating at the center-of-mass energy of 250 GeV. In particular, even when the SM-like Higgs invisible decay is a few orders of magnitude below the planned sensitivity reaches of the ILC and the high luminosity LHC (HL-LHC), the scenario can be probed by the invisible decay of the dark Higgs boson produced via a similar diagram. Measuring the dark Higgs boson decay into the dark sector will be a smoking gun signal of the light dark sector. A similar search of the dark sector would be expected in, e.g., Cool Copper Collider (C${}^3$), Circular Electron Positron Collider (CEPC), Compact Linear Collider (CLIC) and {Future Circular electron-positron Collider (FCC-ee).

   hep-phPRD(2023)·17 citations
2. 02*

   Two-Loop Electroweak Corrections with Fermion Loops to $e^{+}{e}^{-}\to ZH$

   Ayres Freitas🇺🇸 · Qian Song🇺🇸

   We present a complete calculation of the next-to-next-to-leading (NNLO) electroweak corrections involving closed fermion loops to the $e^{+}{e}^{-}\to ZH$ process. This has been achieved by using a semi-numerical technique for the two-loop vertex and box diagrams, which is based on Feynman parameters and dispersion relations for one of the two sub-loops. UV divergences are treated with suitable subtraction terms. Numerical results for the unpolarized differential and integrated cross-section at center-of-mass energy $\sqrt{s}=240\text{GeV}$ are provided. Combining the NNLO contributions with one and two closed fermions loops, they are found to increase the NLO cross-section by 0.7\%.

   hep-phPRL(2023)·22 citations
3. 03*

   Brownian Axion-like particles

   Shuyang Cao🇺🇸 · Daniel Boyanovsky🇺🇸

   We study the non-equilibrium dynamics of a pseudoscalar axion-like particle (ALP) weakly coupled to degrees of freedom in thermal equilibrium by obtaining its reduced density matrix. Its time evolution is determined by the in-in effective action which we obtain to leading order in the (ALP) coupling but to \emph{all orders} in the couplings of the bath to other fields within or beyond the standard model. The effective equation of motion for the (ALP) is a Langevin equation with noise and friction kernels obeying the fluctuation dissipation relation. A ``misaligned'' initial condition yields damped coherent oscillations, however, the (ALP) population increases towards thermalization with the bath. As a result, the energy density features a mixture of a cold component from misalignment and a hot component from thermalization with proportions that vary in time $(cold)e^{-\Gamma t}+(hot)(1-e^{-\Gamma t})$, providing a scenario wherein the ``warmth'' of the dark matter evolves in time from colder to hotter. As a specific example we consider the (ALP)-photon coupling $ga\vec{E}\cdot \vec{B}$ to lowest order, valid from recombination onwards. For $T\gg m_a$ the long-wavelength relaxation rate is substantially enhanced ${\Gamma }_T=\frac{g^2{m}_a^{2}T}{16\pi }$. The ultraviolet divergences of the (ALP) self-energy require higher order derivative terms in the effective action. We find that at high temperature, the finite temperature effective mass of the (ALP) is $m_a^2(T)=m_a^2(0)[1-(T/T_c{)}^4]$, with $T_c\propto \sqrt{m_a(0)/g}$, \emph{suggesting} the possibility of an inverted phase transition, which when combined with higher derivatives may possibly indicate exotic new phases. We discuss possible cosmological consequences on structure formation, the effective number of relativistic species and birefringence of the cosmic microwave background.

   hep-phastro-ph.COhep-thquant-phPRD(2022)·15 citations
4. 04*

   New Constraints on Macroscopic Dark Matter Using Radar Meteor Detectors

   Pawan Dhakal🇺🇸 · Steven Prohira🇺🇸 · Christopher V. Cappiello🇨🇦 · John F. Beacom🇺🇸 · Scott Palo🇮🇳 · John Marino🇺🇸

   We show that dark-matter candidates with large masses and large nuclear interaction cross sections are detectable with terrestrial radar systems. We develop our results in close comparison to successful radar searches for tiny meteoroids, aggregates of ordinary matter. The path of a meteoroid (or suitable dark-matter particle) through the atmosphere produces ionization deposits that reflect incident radio waves. We calculate the equivalent radar echoing area or `radar cross section' for dark matter. By comparing the expected number of dark-matter-induced echoes with observations, we set new limits in the plane of dark-matter mass and cross section, complementary to pre-existing cosmological limits. Our results are valuable because (A) they open a new detection technique for which the reach can be greatly improved and (B) in case of a detection, the radar technique provides differential sensitivity to the mass and cross section, unlike cosmological probes.

   hep-phastro-ph.COastro-ph.EPPRD(2023)·17 citations
5. 05*

   Understanding template methods for top polarisation measurements

   J. A. Aguilar-Saavedra🇪🇸

   Top polarisation measurements at the LHC are often performed using template methods. I discuss the role of quantum interference between polarisation states - which is mostly overlooked in the literature. Furthermore, I argue which is the correct definition of the `templates' of definite polarisations, in order to match the experimental measurements with meaningful theoretical predictions.

   hep-phhep-ex1 citation
6. 06*

   Study of corrections for anomalous coupling limits due to the possible background BSM contributions

   Artur E. Semushin🇷🇺 · Evgeny Yu. Soldatov🇷🇺

   The search of the anomalous couplings is one of the possible ways to find any deviation from the Standard Model. The effective field theory is used to parameterize the anomalous couplings in the Lagrangian with the operators of higher dimensions, constructed from the SM fields. In the classical way, the limits on the Wilson coefficients of these operators are set based on beyond the Standard Model contributions induced for signal process, whereas the ones induced for background processes are assumed to be negligible. This article provides a study of the corrections to the limits on Wilson coefficients by accounting beyond the Standard Model contributions induced for background processes. The studies of $Z(\nu \bar{\nu })\gamma jj$ and $W(\ell \nu )\gamma jj$ productions in $pp$ collisions with $\sqrt{s}=13$ TeV and conditions of the ATLAS experiment at the LHC are used as example. Cases of collected during Run II and expected from Run III integrated luminosities of 139 fb${}^{-1}$ and 300 fb${}^{-1}$ are considered. The expected 95% CL limits on coefficients $f_{\text{T0}}/{\Lambda }^4$, $f_{\text{T5}}/{\Lambda }^4$, $f_{\text{M0}}/{\Lambda }^4$ and $f_{\text{M2}}/{\Lambda }^4$ are obtained both in classical way and in the way, where the corrections from background anomalous contributions are applied. Corrected one-dimensional limits from $Z(\nu \bar{\nu })\gamma jj$ and $W(\ell \nu )\gamma jj$ productions are up to 9.1% and 4.4% (depending on operator) tighter than the classical ones respectively. Corrected combined limits are up to 3.0% (depending on operator) tighter than the classical ones. Corrections to two-dimensional limits are also obtained, corrected contours are more stringent, than the classical ones, and the maximal improvement is of 17.2%.

   hep-phhep-exSymmetry(2022)·3 citations
7. 07*

   Constraints on $Z^{\prime }$ solutions to the flavor anomalies with trans-Planckian asymptotic safety

   Abhishek Chikkaballi🇵🇱 · Wojciech Kotlarski🇵🇱 · Kamila Kowalska🇵🇱 · Daniele Rizzo🇵🇱 · Enrico Maria Sessolo🇵🇱

   Motivated by the flavor anomalies in $b\to s$ transitions, we embed minimal models with a $Z^{\prime }$ gauge boson, vector-like fermions, and a singlet scalar in the framework of trans-Planckian asymptotic safety. The presence of a fixed point in the renormalization group flow of the models' parameters leads to predictions for the $\gamma /Z^{\prime }$ kinetic mixing, the New Physics Yukawa couplings, and the quartic couplings of the scalar potential. We derive the constraint on the kinetic mixing from the most recent high-mass dilepton resonance searches at the LHC, showing that this bound is often inescapable in this framework, unless the U(1) charges conspire to forbid the radiative generation of kinetic mixing. In the latter case, the parameter space consistent with the flavor anomalies can still be probed in depth by direct LHC searches for heavy vector-like quarks and leptons. We derive the current exclusion bounds and projections for future high-luminosity runs.

   hep-phJHEP(2023)·22 citations
8. 08*

   Theory of Neutrino Physics -- Snowmass TF11 (aka NF08) Topical Group Report

   André de Gouvêa🇺🇸 · Irina Mocioiu🇺🇸 · Saori Pastore🇺🇸 · Louis E. Strigari🇺🇸 · L. Alvarez-Ruso🇪🇸 · A. M. Ankowski🇺🇸 · A. B. Balantekin🇺🇸 · V. Brdar🇺🇸 · M. Cadeddu🇮🇹 · S. Carey🇺🇸 · J. Carlson🇺🇸 · M.-C. Chen🇺🇸 and 35 other authors

   This is the report for the topical group Theory of Neutrino Physics (TF11/NF08) for Snowmass 2021. This report summarizes the progress in the field of theoretical neutrino physics in the past decade, the current status of the field, and the prospects for the upcoming decade.

   hep-phastro-ph.HEnucl-th18 citations
9. 09*

   Report of the Topical Group on Electroweak Precision Physics and Constraining New Physics for Snowmass 2021

   Alberto Belloni · Ayres Freitas · Junping Tian · Juan Alcaraz Maestre Aram Apyan · Bianca Azartash-Namin · Paolo Azzurri · Swagato Banerjee · Jakob Beyer · Saptaparna Bhattacharya · Jorge de Blas · Alain Blondel · Daniel Britzger and 56 other authors

   The precise measurement of physics observables and the test of their consistency within the standard model (SM) are an invaluable approach, complemented by direct searches for new particles, to determine the existence of physics beyond the standard model (BSM). Studies of massive electroweak gauge bosons (W and Z bosons) are a promising target for indirect BSM searches, since the interactions of photons and gluons are strongly constrained by the unbroken gauge symmetries. They can be divided into two categories: (a) Fermion scattering processes mediated by s- or t-channel W/Z bosons, also known as electroweak precision measurements; and (b) multi-boson processes, which include production of two or more vector bosons in fermion-antifermion annihilation, as well as vector boson scattering (VBS) processes. The latter categories can test modifications of gauge-boson self-interactions, and the sensitivity is typically improved with increased collision energy. This report evaluates the achievable precision of a range of future experiments, which depend on the statistics of the collected data sample, the experimental and theoretical systematic uncertainties, and their correlations. In addition it presents a combined interpretation of these results, together with similar studies in the Higgs and top sector, in the Standard Model effective field theory (SMEFT) framework. This framework provides a model-independent prescription to put generic constraints on new physics and to study and combine large sets of experimental observables, assuming that the new physics scales are significantly higher than the EW scale.

   hep-phhep-ex27 citations
10. 10*

    Constraining Dark Matter Substructure With Gaia Wide Binaries

    Edward D. Ramirez🇺🇸 · Matthew R. Buckley🇺🇸

    We use a catalogue of stellar binaries with wide separations (up to 1 pc) identified by the Gaia satellite to constrain the presence of extended substructure within the Milky Way galaxy. Heating of the binaries through repeated encounters with substructure results in a characteristic distribution of binary separations, allowing constraints to be placed independent of the formation mechanism of wide binaries. Across a wide range of subhalo density profiles, we show that subhalos with masses $\gtrsim 65M_{\odot }$ and characteristic length scales similar to the separation of these wide binaries cannot make up 100% of the Galaxy's dark matter. Constraints weaken for subhalos with larger length scales and are dependent on their density profiles. For such large subhalos, higher central densities lead to stronger constraints. Subhalos with density profiles similar to those expected from cold dark matter must be at least $\sim 5,000$ times denser than predicted by simulation to be constrained by the wide binary catalogue.

    hep-phastro-ph.GAMNRAS(2023)·19 citations
11. 11*

    Odd-parity perturbations in the most general scalar-vector-tensor theory

    Yolbeiker Rodríguez Baez🇨🇱 · Manuel Gonzalez-Espinoza🇨🇱

    In the context of the most general scalar-vector-tensor theory, we study the stability of static spherically symmetric black holes under linear odd-parity perturbations. We calculate the action to second order in the linear perturbations to derive a master equation for these perturbations. For this general class of models, we obtain the conditions of no-ghost and Laplacian instability. Then, we study in detail the generalized Regge-Wheeler potential of particular cases to find their stability conditions.

    ↳ gr-qcastro-ph.COhep-phhep-thClass.Quant.Grav.(2023)·3 citations
12. 12*

    Isotropic cosmic birefringence from early dark energy

    Kai Murai🇯🇵 · Fumihiro Naokawa🇯🇵 · Toshiya Namikawa🇯🇵 · Eiichiro Komatsu🇩🇪

    A tantalizing hint of isotropic cosmic birefringence has been found in the $EB$ cross-power spectrum of the cosmic microwave background (CMB) polarization data with a statistical significance of $3\sigma$. A pseudoscalar field coupled to the CMB photons via the Chern-Simons term can explain this observation. The same field may also be responsible for early dark energy (EDE), which alleviates the so-called Hubble tension. Since the EDE field evolves significantly during the recombination epoch, the conventional formula that relates $EB$ to the difference between the $E$- and $B$-mode auto-power spectra is no longer valid. Solving the Boltzmann equation for polarized photons and the dynamics of the EDE field consistently, we find that currently favored parameter space of the EDE model yields a variety of shapes of the $EB$ spectrum, which can be tested by CMB experiments.

    ↳ astro-ph.COgr-qchep-phPRD(2023)·75 citations
13. 13*

    Plasma dynamics at the Schwinger limit and beyond

    Gert Brodin🇸🇪 · Haidar Al-Naseri🇸🇪 · Jens Zamanian🇸🇪 · Greger Torgrimsson🇸🇪 · Bengt Eliasson🇬🇧

    Strong field physics close to or above the Schwinger limit are typically studied with vacuum as initial condition, or by considering test particle dynamics. However, with a plasma present initially, quantum relativistic mechanisms such as Schwinger pair-creation are complemented by classical plasma nonlinearities. In this work we use the Dirac-Heisenberg-Wigner formalism to study the interplay between classical and quantum mechanical mechanisms for ultra-strong electric fields. In particular, the effects of initial density and temperature on the plasma oscillation dynamics are determined.

    ↳ physics.plasm-phhep-phPRE(2023)·26 citations
14. 14*

    $\mathcal{P}\mathcal{T}$-symmetric $-g{\phi }^4$ theory

    Wen-Yuan Ai🇬🇧 · Carl M. Bender🇺🇸 · Sarben Sarkar🇬🇧

    The scalar field theory with potential $V(\phi )=\frac{1}{2}{m}^2{\phi }^2-\frac{1}{4}g{\phi }^4$ ($g>0$) is ill defined as a Hermitian theory but in a non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric framework it is well defined, and it has a positive real energy spectrum for the case of spacetime dimension $D=1$. While the methods used in the literature do not easily generalize to quantum field theory, in this paper the path-integral representation of a $\mathcal{P}\mathcal{T}$-symmetric $-g{\phi }^4$ theory is shown to provide a unified formulation for general $D$. A new conjectural relation between the Euclidean partition functions $Z^{\mathcal{P}\mathcal{T}}(g)$ of the non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric theory and $Z_{\mathrm{Herm}}(\lambda )$ of the $\lambda {\phi }^4$ ($\lambda >0$) Hermitian theory is proposed: $\log Z^{\mathcal{P}\mathcal{T}}(g)=\frac{1}{2}\log Z_{\mathrm{Herm}}(-g+\mathrm{i}{0}^{+})+\frac{1}{2}\log Z_{\mathrm{Herm}}(-g-\mathrm{i}{0}^{+})$. This relation ensures a real energy spectrum for the non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric $-g{\phi }^4$ field theory. A closely related relation is rigorously valid in $D=0$. For $D=1$, using a semiclassical evaluation of $Z^{\mathcal{P}\mathcal{T}}(g)$, this relation is verified by comparing the imaginary parts of the ground-state energy $E_0^{\mathcal{P}\mathcal{T}}(g)$ (before cancellation) and $E_{0,\mathrm{Herm}}(-g\pm \mathrm{i}{0}^{+})$.

    ↳ hep-thhep-phquant-phPRD(2022)·46 citations
15. 15*

    Automated consistent truncations and stability of flux compactifications

    David Andriot🇫🇷 · Paul Marconnet🇫🇷 · Muthusamy Rajaguru🇺🇸 · Timm Wrase🇺🇸

    Classical flux compactifications contribute to a well-controlled corner of the string landscape, therefore providing an important testing ground for a variety of conjectures. We focus here on type II supergravity compactifications on 6d group manifolds towards 4d maximally symmetric spacetimes. We develop a code where the truncation to left-invariant scalars and the dimensional reduction to a 4d theory are automated, for any possible configuration of Op-planes and Dp-branes. We then prove that any such truncation is consistent. We further compute the mass spectrum and analyse the stability of many de Sitter, Minkowski or anti-de Sitter solutions, as well as their consistency with swampland conjectures.

    ↳ hep-thgr-qchep-phJHEP(2022)·23 citations
16. 16*

    Fundamental Physics in Small Experiments

    T. Blum🇺🇸 · P. Winter🇺🇸 · T. Bhattacharya🇺🇸 · T.Y. Chen🇺🇸 · V. Cirigliano🇺🇸 · D. DeMille🇺🇸 · A. Gerarci · N.R. Hutzler🇺🇸 · T.M. Ito🇺🇸 · O. Kim🇰🇷 · R. Lehnert🇺🇸 · W.M. Morse🇺🇸 · Y.K. Semertzidis🇰🇷

    High energy physics aims to understand the fundamental laws of particles and their interactions at both the largest and smallest scales of the universe. This typically means probing very high energies or large distances or using high-intensity beams, which often requires large-scale experiments. A complementary approach is offered through high-precision measurements in small- and mid-scale size experiments, often at lower energies. The field of such high-precision experiments has seen tremendous progress and importance for particle physics for at least two reasons. First, they exploit synergies to adjacent areas of particle physics and benefit by many recent advances in experimental techniques. Together with intensified phenomenological explorations, these advances led to the realization that challenges associated with weak couplings or the expected suppression factors from the mass scale of new physics can be overcome with such methods. Second, many of these measurements add a new set of particle physics phenomena and observables that can be reached compared to the more conventional methodologies using high energies. Combining high-precision, smaller-scale measurements with the large-scale efforts therefore casts a wider and tighter net for possible effects originating from physics beyond the Standard Model. This report presents a broad set of small-scale research projects that could provide key new precision measurements in the areas of electric dipole moments, magnetic dipole moments, fermion flavor violation, tests of spacetime symmetries, and tests with gravity. The growing impact of these high-precision studies in high energy physics and the complementary input they provide compared to large-scale efforts warrants strong support over the next decades. In particular, EDM searches are expected to improve sensitivities by four or more orders of magnitude in the next decade or two.

    ↳ hep-exhep-lathep-ph3 citations
17. 17*

    Reinterpretation and Long-Term Preservation of Data and Code

    Stephen Bailey🇺🇸 · K.S. Cranmer🇺🇸 · Matthew Feickert🇺🇸 · Rob Fine🇺🇸 · Sabine Kraml🇫🇷 · Clemens Lange🇨🇭

    Careful preservation of experimental data, simulations, analysis products, and theoretical work maximizes their long-term scientific return on investment by enabling new analyses and reinterpretation of the results in the future. Key infrastructure and technical developments needed for some high-value science targets are not in scope for the operations program of the large experiments and are often not effectively funded. Increasingly, the science goals of our projects require contributions that span the boundaries between individual experiments and surveys, and between the theoretical and experimental communities. Furthermore, the computational requirements and technical sophistication of this work is increasing. As a result, it is imperative that the funding agencies create programs that can devote significant resources to these efforts outside of the context of the operations of individual major experiments, including smaller experiments and theory/simulation work. In this Snowmass 2021 Computational Frontier topical group report (CompF7: Reinterpretation and long-term preservation of data and code), we summarize the current state of the field and make recommendations for the future.

    ↳ physics.comp-phhep-ph4 citations
18. 18*

    Beam Energy Dependence of Triton Production and Yield Ratio (${\mathrm{N}}_t\times {\mathrm{N}}_p/{\mathrm{N}}_d^2$) in Au+Au Collisions at RHIC

    STAR Collaboration: M. I. Abdulhamid🇪🇬 · B. E. Aboona🇺🇸 · J. Adam🇨🇿 · J. R. Adams🇺🇸 · G. Agakishiev🇷🇺 · I. Aggarwal🇮🇳 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · A. Aitbaev🇷🇺 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · A. Aparin🇷🇺 and 345 other authors

    We report the triton ($t$) production in mid-rapidity ($|y|<$ 0.5) Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$= 7.7--200 GeV measured by the STAR experiment from the first phase of the beam energy scan at the Relativistic Heavy Ion Collider (RHIC). The nuclear compound yield ratio (${\mathrm{N}}_t\times {\mathrm{N}}_p/{\mathrm{N}}_d^2$), which is predicted to be sensitive to the fluctuation of local neutron density, is observed to decrease monotonically with increasing charged-particle multiplicity ($d{N}_{ch}/d\eta$) and follows a scaling behavior. The $d{N}_{ch}/d\eta$ dependence of the yield ratio is compared to calculations from coalescence and thermal models. Enhancements in the yield ratios relative to the coalescence baseline are observed in the 0\%-10\% most central collisions at 19.6 and 27 GeV, with a significance of 2.3$\sigma$ and 3.4$\sigma$, respectively, giving a combined significance of 4.1$\sigma$. The enhancements are not observed in peripheral collisions or model calculations without critical fluctuation, and decreases with a smaller $p_T$ acceptance. The physics implications of these results on the QCD phase structure and the production mechanism of light nuclei in heavy-ion collisions are discussed.

    ↳ nucl-exhep-exhep-phhep-th+1PRL(2023)·92 citations
19. 19*

    Impact of large-mass constraints on the properties of neutron stars

    Christian Ecker🇩🇪 · Luciano Rezzolla🇩🇪

    The maximum mass of a nonrotating neutron star, $M_{\mathrm{TOV}}$, plays a very important role in deciphering the structure and composition of neutron stars and in revealing the equation of state (EOS) of nuclear matter. Although with a large-error bar, the recent mass estimate for the black-widow binary pulsar PSR J0952-0607, i.e. $M=2.35\pm 0.17M_{\odot }$, provides the strongest lower bound on $M_{\mathrm{TOV}}$ and suggests that neutron stars with very large masses can in principle be observed. Adopting an agnostic modelling of the EOS, we study the impact that large masses have on the neutron-star properties. In particular, we show that assuming $M_{\mathrm{TOV}}\gtrsim 2.35M_{\odot }$ constrains tightly the behaviour of the pressure as a function of the energy density and moves the lower bounds for the stellar radii to values that are significantly larger than those constrained by the NICER measurements, rendering the latter ineffective in constraining the EOS. We also provide updated analytic expressions for the lower bound on the binary tidal deformability in terms of the chirp mass and show how larger bounds on $M_{\mathrm{TOV}}$ lead to tighter constraints for this quantity. In addition, we point out a novel quasi-universal relation for the pressure profile inside neutron stars that is only weakly dependent from the EOS and the maximum-mass constraint. Finally, we study how the sound speed and the conformal anomaly are distributed inside neutron stars and show how these quantities depend on the imposed maximum-mass constraints.

    ↳ astro-ph.HEgr-qchep-phMNRAS(2022)·70 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.