Fri·Aug 21, 2020Friday·August 21, 2020

1. 01*

   Sensing Higgs cascade decays through memory

   Christoph Englert🇬🇧 · Malcolm Fairbairn🇬🇧 · Michael Spannowsky🇬🇧 · Panagiotis Stylianou🇬🇧 · Sreedevi Varma🇬🇧

   Beyond the Standard Model scenarios with extensions of the Higgs sector typically predict new resonances that can undergo a series of cascade decays to detectable Standard Model particles. On one hand, sensitivity to such signatures will contribute to the full reconstruction of the extended Higgs potential if a new physics discovery will be made. On the other hand, such cascade decays could be dominant decay channels, thus being potentially the best motivated signatures to achieve a new physics discovery in the first place. In this work, we show how the long short-term memory that is encoded in the cascade decays' phenomenology can be exploited in discriminating the signal from the background, where no such information is present. In parallel, we demonstrate for theoretically motivated scenarios that such an approach provides improved sensitivity compared to more standard analyses, where only information about the signal's final state kinematics is included.

   hep-phhep-exPRD(2020)·13 citations
2. 02*

   Dark matter in minimal dimensional transmutation with multicritical-point principle

   Yuta Hamada🇫🇷 · Hikaru Kawai🇯🇵 · Kin-ya Oda🇯🇵 · Kei Yagyu🇯🇵

   We investigate a model with two real scalar fields that minimally generates exponentially different scales in an analog of the Coleman-Weinberg mechanism. The classical scale invariance -- the absence of dimensionful parameters in the tree-level action, required in such a scale generation -- can naturally be understood as a special case of the multipoint criticality principle. This two-scalar model can couple to the Standard Model Higgs field to realize a maximum multiplicity of criticality for field values around the electroweak scale, providing a generalization of the classical scale invariance to a wider class of criticality. As a bonus, one of the two scalars can be identified as Higgs-portal dark matter. We find that this model can be consistent with the constraints from dark matter relic abundance, its direct detection experiments, and the latest LHC data, while keeping the perturbativity up to the Planck scale. We then present successful benchmark points satisfying all these constraints: The mass of dark matter is a few TeV, and its scattering cross section with nuclei is of the order of $10^{-9}$ pb, reachable in near future experiments. The mass of extra Higgs boson $H$ is smaller than or of the order of 100 GeV, and the cross section of $e^{+}{e}^{-}\to ZH$ can be of fb level for collision energy 250 GeV, targetted at future lepton colliders.

   hep-phJHEP(2021)·12 citations
3. 03*

   Numerical solutions to Giovannini's parton branching equation up to TeV energies at the LHC

   Z. Ong🇸🇬 · P. Agarwal🇸🇬 · H. W. Ang🇸🇬 · A. H. Chan🇸🇬 · C. H. Oh🇸🇬

   Giovannini's parton branching equation is integrated numerically using the 4th-order Runge-Kutta method. Using a simple hadronisation model, a charged-hadron multiplicity distribution is obtained. This model is then fitted to various experimental data up to the TeV scale to study how the Giovannini parameters vary with collision energy and type. The model is able to describe hadronic collisions up to the TeV scale and reveals the emergence of gluonic activity as the centre-of-mass energy increases. A prediction is made for $\sqrt{s}$ = 14 TeV.

   hep-phMod.Phys.Lett.A(2020)·3 citations
4. 04*

   R-Symmetric Flipped SU(5)

   Koichi Hamaguchi🇯🇵 · Shihwen Hor🇯🇵 · Natsumi Nagata🇯🇵

   We construct a supersymmetric flipped SU(5) grand unified model that possesses an $R$ symmetry. This $R$ symmetry forbids dangerous non-renormalizable operators suppressed by a cut-off scale up to sufficiently large mass dimensions so that the SU(5)-breaking Higgs field develops a vacuum expectation value of the order of the unification scale along the $F$- and $D$-flat directions, with the help of the supersymmetry-breaking effect. The mass terms of the Higgs fields are also forbidden by the $R$ symmetry, with which the doublet-triplet splitting problem is solved with the missing partner mechanism. The masses of right-handed neutrinos are generated by non-renormalizable operators, which then yield a light neutrino mass spectrum and mixing through the seesaw mechanism that are consistent with neutrino oscillation data. This model predicts one of the color-triplet Higgs multiplets to lie at an intermediate scale, and its mass is found to be constrained by proton decay experiments to be $\gtrsim 5\times 10^{11}$ GeV. If it is $\lesssim 10^{12}$ GeV, future proton decay experiments at Hyper-Kamiokande can test our model in the $p\to {\pi }^0{\mu }^{+}$ and $p\to K^0{\mu }^{+}$ decay modes, in contrast to ordinary grand unified models where $p\to {\pi }^0{e}^{+}$ or $p\to K^{+}\bar{\nu }$ is the dominant decay mode. This characteristic prediction for the proton decay branches enables us to distinguish our model from other scenarios.

   hep-phJHEP(2020)·12 citations
5. 05*

   Constraints on new physics from an improved calculation of parity violation in ${}^{133}$Cs

   B. K. Sahoo🇮🇳 · B. P. Das🇯🇵

   We report the result of our calculation of the nuclear spin-independent parity violating electric dipole transition amplitude ($E{1}_{PV}$) for the $6s{}^2{S}_{1/2}-7s{}^2{S}_{1/2}$ transition in ${}^{133}$Cs to an accuracy of 0.3\% using a variant of the perturbed relativistic coupled-cluster theory. In the present work, we treat the contributions of both the low-lying and high-lying excited states to the above mentioned amplitude on the same footing, thereby overcoming the limitations of previous high accuracy relativistic coupled cluster calculations. We obtain an accurate value for the vector polarizability ($\beta$) for the above transition and by combining it with the results from our present calculation of $E{1}_{PV}$ and the latest measurement of $Im(E{1}_{PV}/\beta )$, we extract the nuclear weak charge ($Q_W$); and analyze its deviation from its value in the Standard Model (SM) in order to constrain certain scenarios of new physics beyond the SM.

   hep-phnucl-thphysics.atom-phphysics.comp-ph8 citations
6. 06*

   Enhanced CP asymmetries in $B\to K{\mu }^{+}{\mu }^{-}$

   Damir Bečirević🇫🇷 · Svjetlana Fajfer🇸🇮 · Nejc Košnik🇸🇮 · Aleks Smolkovič🇸🇮

   We show that the current values of $R_K^{\exp }$ and $R_{K^{\ast }}^{\exp }$ can be accommodated by allowing a nonzero New Physics coupling $\delta C_9^{\mu \mu }$ to be complex, both in the scenario in which only $\delta C_9^{\mu \mu }$ is affected, and in the scenario with complex $\delta C_{9,10}^{\mu \mu }$ satisfying $\delta C_9^{\mu \mu }=-\delta C_{10}^{\mu \mu }$. A presence of the weak CP-violating phase can then be tested by measuring the CP-asymmetry, ${\mathcal{A}}_{\mathrm{CP}}$. We show that this asymmetry is enhanced around the peak of each $c\bar{c}$-resonance, and in fact more pronounced in the close vicinity of $J/\psi$ and $\psi (2S)$. Therefore, measuring ${\mathcal{A}}_{\mathrm{CP}}$ before and after the resonances' peak could be revelatory of the CP-violation that originates from beyond the Standard Model, or to be a significant constrain when building a realistic scenario of New Physics.

   hep-phhep-exEPJC(2020)·25 citations
7. 07*

   Exploring possible triangle singularities in the ${\Xi }_b^{-}\to K^{-}J/\psi \Lambda$ decay

   Chao-Wei Shen🇨🇳 · Hao-Jie Jing🇨🇳 · Feng-Kun Guo🇨🇳 · Jia-Jun Wu🇨🇳

   We analyze possible singularities in the $J/\psi \Lambda$ invariant mass distribution of the ${\Xi }_b^{-}\to K^{-}J/\psi \Lambda$ process via triangle loop diagrams. Triangle singularities in the physical region are found in 18 different triangle loop diagrams. Among those with ${\Xi }^{\ast }$-charmonium-$\Lambda$ intermediate states, the one from the ${\chi }_{c1}\Xi (2120)\Lambda$ loop, which is located around 4628 MeV, is found the most likely to cause observable effects. One needs $S$- and $P$-waves in ${\chi }_{c1}\Lambda$ and $J/\psi \Lambda$ systems, respectively, when the quantum numbers of these systems are $1/2^{+}$ or $3/2^{+}$. When the quantum numbers of the $\Xi (2120)$ are $J^P=1/2^{+}$, $1/2^{-}$ or $3/2^{+}$, the peak structure should be sharper than the other $J^P$ choices. This suggests that although the whole strength is unknown, we should pay attention to the contributions from the ${\Xi }^{\ast }$-charmonium-$\Lambda$ triangle diagram if structures are observed in the $J/\psi \Lambda$ invariant mass spectrum experimentally. In addition, a few triangle diagrams with the $D_{s1}^{\ast }(2700)$ as one of the intermediate particles can also produce singularities in the $J/\psi \Lambda$ distribution, but at higher energies above 4.9 GeV.

   hep-phSymmetry(2020)·40 citations
8. 08*

   Non-Oscillatory No-Scale Inflation

   John Ellis🇬🇧 · Dimitri V. Nanopoulos🇺🇸 · Keith A. Olive🇺🇸 · Sarunas Verner🇺🇸

   We propose a non-oscillatory no-scale supergravity model of inflation (NO-NO inflation) in which the inflaton does not oscillate at the end of the inflationary era. Instead, the Universe is then dominated by the inflaton kinetic energy density (kination). During the transition from inflation to kination, the Universe preheats instantly through a coupling to Higgs-like fields. These rapidly annihilate and scatter into ultra-relativistic matter particles, which subsequently dominate the energy density, and reheating occurs at a temperature far above that of Big Bang Nucleosynthesis. After the electroweak transition, the inflaton enters a tracking phase as in some models of quintessential inflation. The model predictions for cosmic microwave background observables are consistent with Planck 2018 data, and the density of gravitational waves is below the upper bound from Big Bang Nucleosynthesis. We also find that the density of supersymmetric cold dark matter produced by gravitino decay is consistent with Planck 2018 data over the expected range of supersymmetric particle masses.

   hep-phastro-ph.COhep-thJCAP(2021)·19 citations
9. 09*

   Electric Dipole Moments, New Forces and Dark Matter

   Pavel Fileviez Perez🇺🇸 · Alexis D. Plascencia🇺🇸

   New sources of CP violation beyond the Standard Model are crucial to explain the baryon asymmetry in the Universe. We discuss the impact of new CP violating interactions in theories where a dark matter candidate is predicted by the cancellation of gauge anomalies. In these theories, the constraint on the dark matter relic density implies an upper bound on the new symmetry breaking scale from which all new states acquire their masses. We investigate in detail the predictions for electric dipole moments and show that if the relevant CP-violating phase is large, experiments such as the ACME collaboration will be able to fully probe the theory.

   hep-phhep-exhep-thJHEP(2021)·13 citations
10. 10*

    Accidental SO(10) axion from gauged flavour

    Luca Di Luzio🇩🇪

    An accidental U(1) Peccei-Quinn (PQ) symmetry automatically arises in a class of SO(10) unified theories upon gauging the SU(3)${}_f$ flavour group. The PQ symmetry is protected by the ${\mathbb{Z}}_4\times {\mathbb{Z}}_3$ center of $\text{SO(10)}\times {\text{SU(3)}}_f$ up to effective operators of canonical dimension six. However, high-scale contributions to the axion potential posing a PQ quality problem arise only at $d=9$. In the pre-inflationary PQ breaking scenario the axion mass window is predicted to be $m_a\in [7\times 10^{-8},10^{-3}]$ eV, where the lower end is bounded by the seesaw scale and the upper end by iso-curvature fluctuations. A high-quality axion, that is immune to the PQ quality problem, is obtained for $m_a\gtrsim 0.02$ eV. We finally offer a general perspective on the PQ quality problem in grand unified theories.

    hep-phhep-thJHEP(2020)·34 citations
11. 11*

    Tetraquarks with open charm favor

    Yaoyao Xue🇨🇳 · Xin Jin🇨🇳 · Hongxia Huang🇨🇳 · Jialun Ping🇨🇳

    Inspired by the recent report of the exotic states $X_0(2900)$ and $X_1(2900)$ with four different quark flavors in the $D^{-}{K}^{+}$ invariant mass distributions of the decay process $B^{+}\to D^{+}{D}^{-}{K}^{+}$ by the LHCb collaboration, we systematically investigate the tetraquarks composed of $ud\bar{s}\bar{c}$ with meson-meson and diquark-antidiquark structures in the quark delocalization color screening model. We find that the $X_0(2900)$ can be interpreted as the molecular state $\overline{D^{\ast }}{K}^{\ast }$ with $I{J}^P=00^{+}$. Moreover, two bound states are obtained by the channel coupling calculation, with energies $2341.2$ MeV for $I{J}^P=00^{+}$ and $2489.7$ MeV for $I{J}^P=01^{+}$, respectively. We also extend our study to the $uc\bar{d}\bar{s}$ systems and find that there is no any bound state, so the $D_{s0}(2317)$ cannot be identified as the $DK$ molecular state in present calculation. Besides, several resonance states with the diquark-antidiquark configuration are possible in both $ud\bar{s}\bar{c}$ and $uc\bar{d}\bar{s}$ systems. All these open charm bound states and resonances are worth searching in the future experiments.

    hep-phPRD(2021)·47 citations
12. 12*

    From Chiral Kinetic Theory To Relativistic Viscous Spin Hydrodynamics

    Shuzhe Shi🇨🇦 · Charles Gale🇨🇦 · Sangyong Jeon🇨🇦

    In this work, we start with chiral kinetic theory and construct the spin hydrodynamic framework for a chiral spinor system. Using the 14-moment expansion formalism, we obtain the equations of motion of second-order dissipative relativistic fluid dynamics with non-trivial spin polarization density. In a chiral spinor system, the spin alignment effect could be treated in the same framework as the Chiral Vortical Effect (CVE). However, the quantum corrections due to fluid vorticity induce not only CVE terms in the vector/axial charge currents but also corrections to the stress tensor. In this framework, viscous corrections to the hadron spin polarization are self-consistently obtained, which will be important for the precise prediction of the polarization rate for the observed hadrons, e.g. $\Lambda$-hyperon.

    ↳ nucl-thhep-phPRC(2021)·144 citations
13. 13*

    Precision Metrology Meets Cosmology: Improved Constraints on Ultralight Dark Matter from Atom-Cavity Frequency Comparisons

    Colin J. Kennedy🇺🇸 · Eric Oelker🇺🇸 · John M. Robinson🇺🇸 · Tobias Bothwell🇺🇸 · Dhruv Kedar🇺🇸 · William R. Milner🇺🇸 · G. Edward Marti🇺🇸 · Andrei Derevianko🇺🇸 · Jun Ye🇺🇸

    We conduct frequency comparisons between a state-of-the-art strontium optical lattice clock, a cryogenic crystalline silicon cavity, and a hydrogen maser to set new bounds on the coupling of ultralight dark matter to Standard Model particles and fields in the mass range of $10^{-16}$ $-$ $10^{-21}$ eV. The key advantage of this two-part ratio comparison is the differential sensitivities to time variation of both the fine-structure constant and the electron mass, achieving a substantially improved limit on the moduli of ultralight dark matter, particularly at higher masses than typical atomic spectroscopic results. Furthermore, we demonstrate an extension of the search range to even higher masses by use of dynamical decoupling techniques. These results highlight the importance of using the best performing atomic clocks for fundamental physics applications as all-optical timescales are increasingly integrated with, and will eventually supplant, existing microwave timescales.

    ↳ physics.atom-phastro-ph.IMhep-phphysics.opticsPRL(2020)·211 citations
14. 14*

    Measurement of $\gamma$+jet and ${\pi }^0$+jet in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV with the STAR experiment

    Nihar Ranjan Sahoo (for the STAR Collaboration)🇨🇳

    We present the semi-inclusive measurement of charged jets recoiling from direct-photon and ${\pi }^0$ triggers in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV, using a dataset with integrated luminosity 13 $\mathrm{n}{\mathrm{b}}^{-1}$ recorded by the STAR experiment in 2014. The photon and ${\pi }^0$ triggers are selected within transverse energy (${\mathrm{E}}_{\mathrm{T}}^{\mathrm{trig}}$) between 9 GeV and 20 GeV. Charged jets are reconstructed with the anti-$k_{\mathrm{T}}$ algorithm with resolution parameters R = 0.2 and 0.5. A Mixed-Event technique developed previously by STAR is used to correct the recoil jet yield for uncorrelated background, enabling recoil jet measurements over a broad ${\mathrm{p}}_{\mathrm{T},\mathrm{jet}}$ range. We report fully corrected charged-jet yields recoiling from direct-photon and ${\pi }^0$ triggers for the above two jet radii and also discuss the jet R dependence of in-medium parton energy loss at the top RHIC energy.

    ↳ nucl-exhep-exhep-phnucl-thPoS(2021)·7 citations
15. 15*

    Emergent particles and gauge fields in quantum matter

    Ben J. Powell🇦🇺

    I give a pedagogical introduction to some of the many particles and gauge fields that can emerge in correlated matter. The standard model of materials is built on Landau's foundational principles: adiabatic continuity and spontaneous symmetry breaking. These ideas lead to quasiparticles that inherit their quantum numbers from fundamental particles, Nambu-Goldstone bosons, the Anderson-Higgs mechanism, and topological defects in order parameters. I then describe the modern discovery of physics beyond the standard model. Here, quantum correlations (entanglement) and topology play key roles in defining the properties of matter. This can lead to fractionalised quasiparticles that carry only a fraction of the quantum numbers that define fundamental particles. These particles can have exotic properties: for example Majorana fermions are their own antiparticles, anyons have exchange statistics that are neither bosonic nor fermionic, and magnetic monopoles do not occur in the vacuum. Gauge fields emerge naturally in the description of highly correlated matter and can lead to gauge bosons. Relationships to the standard model of particle physics are discussed.

    ↳ cond-mat.str-elcond-mat.quant-gascond-mat.supr-conhep-ph+1Contemp.Phys.(2020)·12 citations
16. 16*

    Probing Fundamental Symmetries of Deformed Nuclei in Symmetric Top Molecules

    Phelan Yu🇺🇸 · Nicholas R. Hutzler🇺🇸

    Precision measurements of Schiff moments in heavy, deformed nuclei are sensitive probes of beyond Standard Model $T,P$-violation in the hadronic sector. While the most sensitive limits on Schiff moments to date are set with diamagnetic atoms, polar polyatomic molecules can offer higher sensitivities with unique experimental advantages. In particular, symmetric top molecular ions possess $K$-doublets of opposite parity with especially small splittings, leading to full polarization at low fields, internal co-magnetometer states useful for rejection of systematic effects, and the ability to perform sensitive searches for $T,P$-violation using a small number of trapped ions containing heavy exotic nuclei. We consider the symmetric top cation ${}^{225}$RaOCH${}_3^{+}$ as a prototypical and candidate platform for performing sensitive nuclear Schiff measurements and characterize in detail its internal structure using relativistic ab initio methods. The combination of enhancements from a deformed nucleus, large polarizability, and unique molecular structure make this molecule a promising platform to search for fundamental symmetry violation even with a single trapped ion.

    ↳ physics.atom-phhep-exhep-phPRL(2021)·47 citations
17. 17*

    Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$

    H.Fonvieille (1) · J. Beričič (2) · L. Correa (1)(3) · M. Benali (1) · P. Achenbach (3) · C. Ayerbe Gayoso (3) · J.C. Bernauer (4)(5) · A. Blomberg (6) · R. Böhm (3) · D. Bosnar (7) · L. Debenjak (2) · A. Denig (3) and 27 other authors

    Background: Generalized polarizabilities (GPs) are important observables to describe the nucleon structure, and measurements of these observables are still scarce. Purpose: This paper presents details of a virtual Compton scattering (VCS) experiment, performed at the A1 setup at the Mainz Microtron by studying the $ep\to ep\gamma$ reaction. The article focuses on selected aspects of the analysis. Method: The experiment extracted the $P_{LL}-P_{TT}/ϵ$ and $P_{LT}$ structure functions, as well as the electric and magnetic GPs of the proton, at three new values of the four-momentum transfer squared $Q^2$: 0.10, 0.20 and 0.45 GeV${}^2$. Results: We emphasize the importance of the calibration of experimental parameters. The behavior of the measured $ep\to ep\gamma$ cross section is presented and compared to the theory. A detailed investigation of the polarizability fits reveals part of their complexity, in connection with the higher-order terms of the low-energy expansion. Conclusions: The presented aspects are elements which contribute to minimize the systematic uncertainties and improve the precision of the physics results.

    ↳ nucl-exhep-phnucl-thPRC(2021)·9 citations
18. 18*

    Lattice gauge theory and dynamical quantum phase transitions using noisy intermediate scale quantum devices

    Simon Panyella Pedersen🇩🇰 · Nikolaj Thomas Zinner🇩🇰

    Lattice gauge theories are a fascinating and rich class of theories relating to the most fundamental models of particle physics, and as experimental control on the quantum level increases there is a growing interest in non-equilibrium effects such as dynamical quantum phase transitions. To demonstrate how these physical theories can be accessed in near-term quantum devices, we study the dynamics of a (1+1)D U(1) quantum link model following quenches of its mass-term. We find that the system undergoes dynamical quantum phase transitions for all system sizes considered, even the smallest where the dynamics can be solved analytically. We devise a gauge invariant string order parameter whose zeros correlates with the structure of the Loschmidt amplitude, making the order parameter useful for experimental study in near-term devices. The zeros of the Loschmidt amplitude as well as the zeros of our order parameter are revealed by vortices in their phases, which can be counted by a topologically invariant winding number. With noisy intermediate scale quantum devices in mind, we propose a class of superconducting circuits for the general implementation of U(1) quantum link models. The principles of these circuits can be generalized to implement other, more complicated gauge symmetries. Furthermore, the circuit can be modularly scaled to any lattice configuration. Simulating the circuit dynamics with realistic circuit parameters we find that it implements the target dynamics with a steady average fidelity of $99.5\%$ or higher. Finally, we consider readout of the circuit using a method that yields information about all the degrees of freedom with resonators coupled dispersively to only a subset of them. This constitutes a direct and relatively straightforward protocol to access both Loschmidt amplitudes and the order parameter.

    ↳ quant-phcond-mat.str-elhep-lathep-phPRB(2021)·21 citations
19. 19*

    Early evolution constrained by high-$p_T$ QGP tomography

    Stefan Stojku🇷🇸 · Jussi Auvinen🇷🇸 · Marko Djordjevic🇷🇸 · Pasi Huovinen🇷🇸 · Magdalena Djordjevic🇷🇸

    We show that high-$p_T$ $R_{AA}$ and $v_2$ are sensitive to the early expansion dynamics, and that the high-$p_T$ observables prefer delayed onset of energy loss and transverse expansion. To calculate high-$p_T$ $R_{AA}$ and $v_2$, we employ our newly developed DREENA-A framework, which combines state-of-the-art dynamical energy loss model with 3+1-dimensional hydrodynamical simulations. The model applies to both light and heavy flavor, and we predict a larger sensitivity of heavy flavor observables to the onset of transverse expansion. This presents the first time when bulk QGP behavior has been constrained by high-$p_{\perp }$ observables and related theory, i.e., by so-called QGP tomography.

    ↳ nucl-thhep-phPRC(2022)·23 citations
20. 20*

    Effects of a quark chemical potential on the analytic structure of the gluon propagator

    Yui Hayashi🇯🇵 · Kei-Ichi Kondo🇯🇵

    We perform complex analyses of the gluon propagator at nonzero quark chemical potential in the long-wavelength limit, using an effective model with a gluon mass term of the Landau-gauge Yang-Mills theory, which is a Landau-gauge limit of the Curci-Ferrari model with quantum corrections being included within the one-loop level. We mainly investigate complex poles of the gluon propagator, which could be relevant to confinement. Around typical values of the model parameters, we show that the gluon propagator has one or two pairs of complex conjugate poles depending on the value of the chemical potential. In addition to a pair similar to that in the case of zero chemical potential, a new pair appears near the real axis when the chemical potential is roughly between the effective quark mass and the effective gluon mass of the model. We discuss possible interpretations of these poles. Additionally, we prove the uniqueness of analytic continuation of the Matsubara propagator to a class of functions that vanish at infinity and are holomorphic except for a finite number of complex poles and singularities on the real axis.

    ↳ hep-thhep-phPRD(2021)·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.