Mon·Jan 23, 2023Monday·January 23, 2023

1. 01*

   Dark Matter Phenomenology in 2HDMS

   Gudrid Moortgat-Pick🇩🇪 · Juhi Dutta🇩🇪 · Cheng Li🇩🇪 · Merle Schreiber🇩🇪 · Sheikh F. Tabira🇩🇪 · Julia Ziegler🇩🇪

   The constituents of dark matter are still an unresolved puzzle. Several Beyond Standard Model (BSM) Physics offer suitable candidates. In this study here we consider the Two Higgs Doublet model augmented with a complex scalar singlet (2HDMS) and focus on the dark matter phenomenology of 2HDMS with the complex scalar singlet as the dark matter candidate. The parameter space allowed from existing experimental constraints from dark matter, flavour physics and collider searches has been studied. The discovery potential for such a 2HDMS at HL-LHC and at future $e^{+}{e}^{-}$ colliders has been worked out.

   hep-phSciPost Phys.Proc.(2023)·2 citations
2. 02*

   Dark photon effect on the rare kaon decay $K_L\to {\pi }^0\nu \bar{\nu }$

   X. G. Wang🇦🇺 · A. W. Thomas🇦🇺

   We present an analysis of the effect of a dark photon on the rare kaon decay $K_L\to {\pi }^0\nu \bar{\nu }$. All relevant couplings of the dark photon to the Standard Model particles are derived explicitly in terms of the dark photon mass and the mixing parameter. We find that the dark photon yields no more than a few percent correction to the Standard Model branching ratio $\mathrm{Br}(K_L\to {\pi }^0\nu \bar{\nu })$ in the region of interest.

   hep-phhep-exJ.Phys.G(2023)·13 citations
3. 03*

   Asymptotic freedom using a gluon mass as a regulator

   J. J. Galvez-Viruet🇪🇸 · M. Gomez-Rocha🇪🇸

   Front-Form Hamiltonian dynamics provides a framework in which QCD's vacuum is simple and states are boost invariant. However, canonical expressions are divergent and must be regulated in order to establish well-defined eigenvalue problems. The Renormalization Group Procedure for Effective Particles (RGPEP) provides a systematic way of finding counterterms and obtaining regulated Hamiltonians. Among its achievements is the description of asymptotic freedom, with a running coupling constant defined as the coefficient in front of the three gluon-vertex operators in the regulated Hamiltonian. However, the obtained results need a deeper understanding, since the coupling exhibits a finite dependence on the regularization functions, at least at the third-order term in the perturbative expansion. Here we present a similar derivation using a different regularization scheme based on massive gluons. The procedure can be extended to incorporate contributions from virtual fermions.

   hep-phEPJ Web Conf.(2022)·1 citation
4. 04*

   Accommodating muon $(\mathbf{g}-2)$ and leptogenesis in a scotogenic model

   A. Alvarez🇩🇪 · A. Banik🇩🇪 · R. Cepedello🇩🇪 · B. Herrmann🇫🇷 · W. Porod🇩🇪 · M. Sarazin🇫🇷 · M. Schnelke🇩🇪

   We present a detailed study of a scotogenic model accommodating dark matter, neutrino masses and the anomalous magnetic moment of the muon while being consistent with the existing constraints on flavour violating decays of the leptons. Moreover, this model offers the possibility to explain the baryon asymmetry of the Universe via leptogenesis. We determine the viable regions of the model's parameter space in view of dark matter and flavour constraints using a Markov Chain Monte Carlo setup combined with a particular procedure to accommodate neutrino masses and the anomalous magnetic moment of the muon at the same time. We also discuss briefly the resulting collider phenomenology.

   hep-phJHEP(2023)·21 citations
5. 05*

   Scalar dark matter induced oscillation of permanent-magnet field

   I.M. Bloch🇺🇸 · D. Budker🇩🇪 · V.V. Flambaum🇦🇺 · I.B. Samsonov🇦🇺 · A.O. Sushkov🇺🇸 · O. Tretiak🇩🇪

   Scalar-field dark matter models imply small oscillations of fundamental constants. These oscillations could result in observable variations of the magnetic field in a permanent magnet. We propose an experiment for detection of this type of dark matter through searches of oscillations of magnetic field of permanent magnets with a SQUID magnetometer or a low-noise radiofrequency amplifier. We show that this experiment may have comparable sensitivity to leading experiments searching for variations of fundamental constants in the range of frequencies from a few Hz to about 1 MHz. We also discuss applicability of the approach of variations of fundamental constants for accounting for the interaction with scalar dark matter.

   hep-phastro-ph.COcond-mat.otherphysics.atom-phPRD(2023)·11 citations
6. 06*

   Repercussion of the $a_0(1710)$ [$a_0(1817)$] resonance and future developments

   E. Oset🇪🇸 · L. R. Dai🇨🇳 · L. S. Geng🇨🇳

   In this paper, we discuss the significance and prospect for the newly discovered a0(1710)[a0(1817)] resonance state at BESIII experiment, in which they reported the observation of a scalar meson of spin-parity $J^P=0^{+}$ with isospin $I=1$, branded as $a_0(1817)$. This state may be the same particle as the $a_0(1710)$ observed by the BaBar experiment earlier. As early as 2008, we found that f0(1710) can be regarded as a $K^{\ast }{\bar{K}}^{\ast }$ molecular state based on the chiral unitary theory, and there is a partner state $a_0(1710)$ with an isospin $I=1$. Our theoretical prediction based on this picture is in good agreement with the latest BESIII data, which further supports the molecular state picture of $a_0(1710)[a_0(1817)]$. If it is indeed the isospin partner state of $f_0(1710)$, this would rule out $f_0(1710)$ as a glueball candidate. This paper briefly reviews the relevant theoretical studies and suggests new experiments to further examine the nature of $a_0(1710)[a_0(1817)]$.

   hep-phSci.Bull.(2023)·19 citations
7. 07*

   Probe of a Randall-Sundrum-like model from muon pair production at high energy muon collider

   S.C. İnan🇹🇷 · A.V. Kisselev🇹🇷

   We have examined inclusive ${\mu }^{+}{\mu }^{-}\to {\mu }^{+}{\mu }^{-}+E_{\mathrm{miss}}$ and annihilation ${\mu }^{+}{\mu }^{-}\to {\mu }^{+}{\mu }^{-}$ processes at future high energy muon colliders in the framework of the Randall-Sundrum-like model with a small curvature of space-time. The collision energies of 3 TeV, 14 TeV and, 100 TeV are addressed. Both differential and total cross sections are calculated, and exclusion bounds on a 5-dimensional gravity scale are obtained depending on collision energy and integrated luminosity of the muon colliders.

   hep-phhep-exJ.Phys.G(2025)·10 citations
8. 08*

   Dark matter production from two evaporating PBH distributions

   Arnab Chaudhuri🇮🇳 · Baradhwaj Coleppa🇮🇳 · Kousik Loho🇮🇳

   Particulate Dark Matter (DM), completely isolated from the Standard Model particle sector, can be produced in the early universe from Primordial Black Hole (PBH) evaporation. However, Big Bang Nucleosynthesis (BBN) observations put an upper bound on the initial mass of PBH requiring the PBH to evaporate completely before the advent of BBN. DM particles in the mass range $\sim (1-10^9)$ GeV can not explain the observed relic abundance for an early matter dominated universe due to this BBN constraint. However, this assumes the presence of only one monochromatic PBH mass distribution in the early universe. In this work, we explore the simple possibility of achieving the observed relic with DM masses from the above mentioned range for an early matter dominated era with two monochromatic evaporating PBH mass distributions and demonstrate that the fermionic DM masses consistent with BBN change slightly.

   hep-phPRD(2023)·21 citations
9. 09*

   Search for the dipole portal of heavy neutral leptons at future colliders

   Maksym Ovchynnikov🇩🇪 · Jing-Yu Zhu🇩🇪

   In this paper, we study the potential of future colliders to explore the parameter space of heavy neutral leptons (HNLs) through the dipole portal. We consider hadron colliders such as the LHC in the high luminosity phase and FCC-hh, and lepton colliders, such as FCC-ee. We consider various signatures for the HNLs, including the missing energy signature and displaced decays, and discuss the complementarity between the hadron and lepton colliders. In particular, we find that thanks to a much clearer environment, FCC-ee may search for the HNLs with masses up to $\simeq 30\text{ GeV}$ and proper lifetimes $c{\tau }_N\gtrsim 1\text{ cm}$, which is well beyond the reach of the experiments to be launched in the next decade.

   hep-phJHEP(2023)·21 citations
10. 10*

    Photo-production of lowest ${\Sigma }_{1/2^{-}}^{\ast }$ state within the Regge-effective Lagrangian approach

    Yun-He Lyu🇨🇳 · Han Zhang🇨🇳 · Neng-Chang Wei🇨🇳 · Bai-Cian Ke🇨🇳 · En Wang🇨🇳 · Ju-Jun Xie🇨🇳

    Since the lowest ${\Sigma }^{\ast }$ state, with quantum numbers spin-parity $J^P=1/2^{-}$, is far from established experimentally and theoretically, we have performed a theoretical study on the ${\Sigma }_{1/2^{-}}^{\ast }$ photo-production within the Regge-effective Lagrangian approach. Taking into account that the ${\Sigma }_{1/2^{-}}^{\ast }$ couples to the $\bar{K}N$ channel, we have considered the contributions from the $t$-channel $K$ exchange diagram. Moreover, these contributions from $t$-channel $K^{\ast }$ exchange, $s$-channel nucleon pole, $u$-channel $\Sigma$ exchange, and the contact term, are considered. The differential and total cross sections of the process $\gamma n\to K^{+}{\Sigma }_{1/2^{-}}^{\ast -}$ are predicted with our model parameters. The results should be helpful to search for the ${\Sigma }_{1/2^{-}}^{\ast }$ state experimentally in future.

    hep-phnucl-thCPC(2023)·10 citations
11. 11*

    Electroweak Sphaleron in a Magnetic field

    Jaakko Annala🇫🇮 · Kari Rummukainen🇫🇮

    Using lattice simulations we calculate the rate of baryon number violating processes, the sphaleron rate, in the Standard Model with an external (hyper)magnetic field for temperatures across the electroweak cross-over, focusing on the broken phase. Additionally, we compute the Higgs expectation value and the pseudocritical temperature. The electroweak cross-over shifts to lower temperatures with increasing external magnetic field, bringing the onset of the suppression of the baryon number violation with it. When the hypermagnetic field reaches the magitude $B_Y\approx 2T^2$ the cross-over temperature is reduced from $160$ GeV to $145$ GeV. In the broken phase for small magnetic fields the rate behaves quadratically as a function of the magnetic flux. For stronger magnetic fields the rate reaches a linear regime which lasts until the field gets strong enough to restore the electroweak symmetry where the symmetric phase rate is reached.

    hep-phastro-ph.COhep-latPRD(2023)·18 citations
12. 12*

    Lepton Flavor Specific Extended Higgs Model

    B. L. Gonçalves🇵🇹 · Matthew Knauss🇺🇸 · Marc Sher🇺🇸

    In extended Higgs models, a discrete symmetry is needed in the quark sector to avoid tree-level flavor-changing neutral currents. However, this is not necessary the case in the lepton sector. We consider a model in which one Higgs couples to quarks and three others couple to the electron, muon and tau, respectively. This four-doublet model is presented with the full scalar potential and the gauge and Yukawa couplings. The constraints from boundedness, perturbativity and oblique parameters are incorporated as well as constraints from meson-antimeson mixing, radiative B-decays and the diphoton Higgs decay rate. We also consider bounds from searches for heavy neutral and charged scalars at the LHC. Since the Standard Model Higgs couplings match predictions very well, we focus on the alignment limit of the model. It is shown that for a wide range of parameters, the lightest additional scalar, pseudoscalar and charged scalar can have substantial decays into electrons and muons (in contrast to the usual leptonic decays into taus). An interesting signature in the neutral sector would be the production, through vector boson fusion, of a pair of scalars, each of which decays into an electron or muon pair.

    hep-phPRD(2023)·5 citations
13. 13*

    Thermal production of cold "hot dark matter" around eV

    Wen Yin🇯🇵

    A very simple production mechanism of feebly interacting dark matter (DM) that rarely annihilates is thermal production, which predicts the DM mass around eV. This has been widely known as the hot DM scenario. Despite there are several observational hints from background lights suggesting a DM in this mass range, the hot DM scenario has been considered strongly in tension with the structure formation of our Universe because the free-streaming length of the DM produced from thermal reactions was thought to be too long. In this paper, I show that the previous conclusions are not always true depending on the reaction for bosonic DM because of the Bose-enhanced reaction at very low momentum. By using the simple $1\leftrightarrow 2$ decay/inverse decay process to produce the DM, I demonstrate that the eV range bosonic DM can be thermally produced $coldly$ from a hot plasma by performing a model-independent analysis applicable to axion, hidden photon, and other bosonic DM candidates. Therefore, the bosonic DM in the eV mass range may still be special and theoretically well-motivated.

    hep-phastro-ph.COhep-exJHEP(2023)·22 citations
14. 14*

    The Tachyonic Higgs and the Inflationary Universe

    Bibhushan Shakya🇩🇪

    The Standard Model Higgs becomes tachyonic at high energy scales according to current measurements. This unstable regime of the Higgs potential can be realized in the early Universe during high scale inflation, potentially with catastrophic consequences. This letter highlights a crucial inherent feature of such configurations that has so far remained ignored: Higgs particle production out of vacuum induced by the rapidly evolving Higgs field, which gets exponentially enhanced due to the tachyonic instability. Such explosive particle production can rapidly drain energy away from the Higgs field, sustaining a significant density of Higgs particles even during inflation, and could initiate a qualitatively different form of preheating in parts of the post-inflationary Universe. Any study of the Higgs field in its tachyonic phase, either during or after inflation, must therefore take this substantial particle energy density into account, which could significantly affect the subsequent evolution of such systems. This could carry important implications for high scale inflation, post-inflationary preheating, observable signals in the cosmic microwave background, gravitational waves, and primordial black holes, as well as deeper concepts ranging from eternal inflation to the metastability of the electroweak vacuum.

    hep-phastro-ph.COhep-th10 citations
15. 15*

    NGC 1068 constraints on neutrino-dark matter scattering

    James M. Cline🇨🇦 · Matteo Puel🇨🇦

    The IceCube collaboration has observed the first steady-state point source of high-energy neutrinos, coming from the active galaxy NGC 1068. If neutrinos interacted strongly enough with dark matter, the emitted neutrinos would have been impeded by the dense spike of dark matter surrounding the supermassive black hole at the galactic center, which powers the emission. We derive a stringent upper limit on the scattering cross section between neutrinos and dark matter based on the observed events and theoretical models of the dark matter spike. The bound can be stronger than that obtained by the single IceCube neutrino event from the blazar TXS 0506+056 for some spike models.

    hep-phastro-ph.COastro-ph.HEJCAP(2023)·55 citations
16. 16*

    A Lighter QCD Axion from Anarchy

    Fatemeh Elahi🇩🇪 · Gilly Elor🇩🇪 · Alexey Kivel🇩🇪 · Julien Laux🇩🇪 · Saereh Najjari🇩🇪 · Felix Yu🇩🇪

    We introduce the Anarchic Axion, a class of axion models which solves the Strong CP problem within current nEDM constraints with a lighter than usual QCD axion, thus populating new parameter space that ongoing and future experiments target. The Anarchic Axion is driven light by a soft breaking of the Peccei-Quinn symmetry, which also predicts a residual neutron electric dipole moment. We introduce a novel measure to quantify the tuning required for large deviations from the usual QCD axion band. In addition to motivating searches for unusually light axions, this work establishes a new target for axion effective field theory.

    hep-phPRD(2023)·9 citations
17. 17*

    The Higgs Boson and The Fakeon Hypothesis

    Musongela Lubo🇨🇩 · Muanza Steve🇨🇩 · Kikunga Kasenda Ivan🇨🇩 · Mavungu Tsava Christian🇨🇩

    In this paper, we make an attempt to implement the fakeon hypothesis in particle physics. To begin with, we consider a model in which the Higgs boson is the only fakeon. We deduce its interactions with the electroweak gauge bosons. Each such new interaction can be written as a product of two factors. The first one depends, on the electroweak gauge bosons and their derivatives. The second one solely depends, on the physical Higgs and its derivatives. We also study the conserved quantities of different (free) fields in this setting.

    hep-ph1 citation
18. 18*

    Light-quark connected intermediate-window contributions to the muon $g-2$ hadronic vacuum polarization from lattice QCD

    Alexei Bazavov🇺🇸 · Christine Davies🇬🇧 · Carleton DeTar🇺🇸 · Aida X. El-Khadra🇺🇸 · Elvira Gámiz🇪🇸 · Steven Gottlieb🇺🇸 · William I. Jay🇺🇸 · Hwancheol Jeong🇺🇸 · Andreas S. Kronfeld🇺🇸 · Shaun Lahert🇺🇸 · G. Peter Lepage🇺🇸 · Michael Lynch🇺🇸 and 9 other authors

    We present a lattice-QCD calculation of the light-quark connected contribution to window observables associated with the leading-order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{HVP},\mathrm{LO}}$. We employ the MILC Collaboration's isospin-symmetric QCD gauge-field ensembles, which contain four flavors of dynamical highly-improved-staggered quarks with four lattice spacings between $a\approx 0.06$-$0.15$~fm and close-to-physical quark masses. We consider several effective-field-theory-based schemes for finite-volume and other lattice corrections and combine the results via Bayesian model averaging to obtain robust estimates of the associated systematic uncertainties. After unblinding, our final results for the intermediate and ``W2'' windows are $a_{\mu }^{ll,\mathrm{W}}(conn.)=206.6(1.0)\times 10^{-10}$ and $a_{\mu }^{ll,W2}(conn.)=100.7(3.2)\times 10^{-10}$, respectively.

    ↳ hep-lathep-phPRD(2023)·124 citations
19. 19*

    Can Neutrino Self-interactions Save Sterile Neutrino Dark Matter?

    Rui An🇺🇸 · Vera Gluscevic🇺🇸 · Ethan O. Nadler🇺🇸 · Yue Zhang🇨🇦

    Sterile neutrinos only interact with the Standard Model through the neutrino sector, and thus represent a simple dark matter (DM) candidate with many potential astrophysical and cosmological signatures. Recently, sterile neutrinos produced through self-interactions of active neutrinos have received attention as a particle candidate that can yield the entire observed DM relic abundance without violating the most stringent constraints from X-ray observations. We examine consistency of this production mechanism with the abundance of small-scale structure in the universe, as captured by the population of ultra-faint dwarf galaxies orbiting the Milky Way, and derive a lower bound on the sterile-neutrino particle mass of $37$ keV. Combining these results with previous limits from particle physics and astrophysics excludes $100\%$ sterile neutrino DM produced by strong neutrino self-coupling, mediated by a heavy ($\gtrsim 1\mathrm{GeV}$) scalar particle; however, data permits sterile-neutrino DM production via a light mediator.

    ↳ astro-ph.COhep-phApJL(2023)·27 citations
20. 20*

    Ultra-light axions and the $S_8$ tension: joint constraints from the cosmic microwave background and galaxy clustering

    Keir K. Rogers🇨🇦 · Renée Hložek🇨🇦 · Alex Laguë🇨🇦 · Mikhail M. Ivanov🇺🇸 · Oliver H. E. Philcox🇺🇸 · Giovanni Cabass🇺🇸 · Kazuyuki Akitsu🇺🇸 · David J. E. Marsh🇬🇧

    We search for ultra-light axions as dark matter (DM) and dark energy particle candidates, for axion masses $10^{-32}\mathrm{eV}\le m_{\mathrm{a}}\le 10^{-24}\mathrm{eV}$, by a joint analysis of cosmic microwave background (CMB) and galaxy clustering data -- and consider if axions can resolve the tension in inferred values of the matter clustering parameter $S_8$. We give legacy constraints from Planck 2018 CMB data, improving 2015 limits on the axion density ${\Omega }_{\mathrm{a}}{h}^2$ by up to a factor of three; CMB data from the Atacama Cosmology Telescope and the South Pole Telescope marginally weaken Planck bounds at $m_{\mathrm{a}}=10^{-25}\mathrm{eV}$, owing to lower (and theoretically-consistent) gravitational lensing signals. We jointly infer, from Planck CMB and full-shape galaxy power spectrum and bispectrum data from the Baryon Oscillation Spectroscopic Survey (BOSS), that axions are, today, $<10\%$ of the DM for $m_{\mathrm{a}}\le 10^{-26}\mathrm{eV}$ and $<1\%$ for $10^{-30}\mathrm{eV}\le m_{\mathrm{a}}\le 10^{-28}\mathrm{eV}$. BOSS data strengthen limits, in particular at higher $m_{\mathrm{a}}$ by probing high-wavenumber modes ($k<0.4h{\mathrm{Mpc}}^{-1}$). BOSS alone finds a preference for axions at $2.7\sigma$, for $m_{\mathrm{a}}=10^{-26}\mathrm{eV}$, but Planck disfavours this result. Nonetheless, axions in a window $10^{-28}\mathrm{eV}\le m_{\mathrm{a}}\le 10^{-25}\mathrm{eV}$ can improve consistency between CMB and galaxy clustering data, e.g., reducing the $S_8$ discrepancy from $2.7\sigma$ to $1.6\sigma$, since these axions suppress structure growth at the $8h^{-1}\mathrm{Mpc}$ scales to which $S_8$ is sensitive. We expect improved constraints with upcoming high-resolution CMB and galaxy lensing and future galaxy clustering data, where we will further assess if axions can restore cosmic concordance.

    ↳ astro-ph.COhep-phJCAP(2023)·119 citations
21. 21*

    Cosmic bounce and phantom-like equation of state from tunnelling

    Jean Alexandre🇬🇧 · Silvia Pla🇬🇧

    We allow a scalar field on a flat FLRW background metric to tunnel between two degenerate vacua. The resulting true vacuum state then violates the Null Energy Condition, and the corresponding homogeneous fluid induces a bounce, after which it has a phantom-like equation of state and asymptotically leads to a de Sitter phase. The mechanism presented here requires no exotic matter or modified gravity, it is purely generated by quantum fluctuations and is valid for a generic double well potential.

    ↳ hep-thgr-qchep-phJHEP(2023)·8 citations
22. 22*

    An update of Euclidean windows of the hadronic vacuum polarization

    T. Blum🇺🇸 · P. A. Boyle🇺🇸 · M. Bruno🇮🇹 · D. Giusti🇩🇪 · V. Gülpers🇬🇧 · R. C. Hill🇬🇧 · T. Izubuchi🇺🇸 · Y.-C. Jang🇺🇸 · L. Jin🇺🇸 · C. Jung🇺🇸 · A. Jüttner🇬🇧 · C. Kelly🇺🇸 and 5 other authors

    We compute the standard Euclidean window of the hadronic vacuum polarization using multiple independent blinded analyses. We improve the continuum and infinite-volume extrapolations of the dominant quark-connected light-quark isospin-symmetric contribution and address additional sub-leading systematic effects from sea-charm quarks and residual chiral-symmetry breaking from first principles. We find $a_{\mu }^{\mathrm{W}}=235.56(65)(50)\times 10^{-10}$, which is in $3.8\sigma$ tension with the recently published dispersive result of Colangelo et al., $a_{\mu }^{\mathrm{W}}=229.4(1.4)\times 10^{-10}$, and in agreement with other recent lattice determinations. We also provide a result for the standard short-distance window. The results reported here are unchanged compared to our presentation at the Edinburgh workshop of the g-2 Theory Initiative in 2022.

    ↳ hep-lathep-phPRD(2023)·199 citations
23. 23*

    Fermion soliton stars

    L. Del Grosso🇮🇹 · G. Franciolini🇮🇹 · P. Pani🇮🇹 · A. Urbano🇮🇹

    A real scalar field coupled to a fermion via a Yukawa term can evade no-go theorems preventing solitonic solutions. For the first time, we study this model within General Relativity without approximations, finding static and spherically symmetric solutions that describe fermion soliton stars. The Yukawa coupling provides an effective mass for the fermion, which is key to the existence of self-gravitating relativistic solutions. We systematically study this novel family of solutions and present their mass-radius diagram and maximum compactness, which is close to (but smaller than) that of the corresponding Schwarzschild photon sphere. Finally, we discuss the ranges of the parameters of the fundamental theory in which the latter might have interesting astrophysical implications, including compact (sub)solar and supermassive fermion soliton stars for a standard gas of degenerate neutrons and electrons, respectively.

    ↳ gr-qcastro-ph.COhep-phPRD(2023)·55 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.