Fri·Jun 8, 2018Friday·June 8, 2018

1. 01*

   Hunting leptoquarks in monolepton searches

   Saurabh Bansal🇺🇸 · Rodolfo M. Capdevilla🇺🇸 · Antonio Delgado🇺🇸 · Christopher Kolda🇺🇸 · Adam Martin🇺🇸 · Nirmal Raj🇺🇸

   We show that stringent limits on leptoquarks that couple to first-generation quarks and left-handed electrons or muons can be derived from the spectral shape of the charged-current Drell-Yan process ($pp\to {\ell }^{\pm }\nu$) at Run 2 of the LHC. We identify and examine all six leptoquark species that can generate such a monolepton signal, including both scalar and vector leptoquarks, and find cases where the leptoquark exchange interferes constructively, destructively or not at all with the Standard Model signal. When combined with the corresponding leptoquark-mediated neutral-current ($pp\to {\ell }^{+}{\ell }^{-}$) process, we find the most stringent limits obtained to date, outperforming bounds from pair production and atomic parity violation. We show that, with 3000 fb${}^{-1}$ of data, combined measurements of the transverse mass in $pp\to {\ell }^{\pm }\nu$ events and invariant mass in $pp\to {\ell }^{+}{\ell }^{-}$ events can probe masses between 8 TeV and 18 TeV, depending on the species of leptoquark, for electroweak-sized couplings. In light of such robust sensitivities, we strongly encourage the LHC experiments to interpret Drell-Yan (dilepton and monolepton) events in terms of leptoquarks, alongside usual scenarios like $Z^{\prime }$ bosons and contact interactions.

   hep-phPRD(2018)·49 citations
2. 02*

   Mass Calculations of Light Quarkonium, Exotic $J^{PC}=0^{+-}$ Hybrid Mesons from Gaussian Sum-Rules

   J. Ho🇨🇦 · R. Berg🇨🇦 · Wei Chen🇨🇳 · D. Harnett🇨🇦 · T. G. Steele🇨🇦

   We extend previous calculations of leading-order correlation functions of spin-0 and spin-1 light quarkonium hybrids to include QCD condensates of dimensions five and six, with a view to improving the stability of QCD sum-rules analyses in previously unstable channels. Based on these calculations, prior analyses in the literature, and its phenomenological importance, we identify the exotic $J^{PC}=0^{+-}$ channel as the most promising for detailed study. Using Gaussian sum-rules constrained by the Hölder inequality, we calculate masses of light (nonstrange and strange) quarkonium hybrid mesons with $J^{PC}=0^{+-}$. We consider single narrow, single wide, and double narrow resonance models, and find that the double narrow resonance model yields the best agreement between QCD and phenomenology. In both non-strange and strange cases, we find hybrid masses of $2.60$ GeV and $3.57$ GeV.

   hep-phPRD(2018)·27 citations
3. 03*

   Threshold corrections of ${\chi }_{\mathrm{c}}(2P)$ and ${\chi }_{\mathrm{b}}(3P)$ states and $J/\psi \rho$ and $J/\psi \omega$ transitions of the $X(3872)$ in a coupled-channel model

   J. Ferretti🇨🇳 · E. Santopinto🇮🇹

   We calculate the masses of ${\chi }_{\mathrm{c}}(2P)$ and ${\chi }_{\mathrm{b}}(3P)$ states with threshold corrections in a coupled-channel model. Here, the meson quarkonium core is augmented by higher Fock components due to pair-creation effects. According to our results, we interpret the resonances characterized by very small threshold corrections, like ${\chi }_{\mathrm{b}}(3P)$'s, as almost pure quarkonia, and those states characterized by non-negligible threshold corrections, like the $X(3872)$, as quarkonium cores plus meson-meson components. We also study the $J/\psi \rho$ and $J/\psi \omega$ hidden-flavor strong decays of the $X(3872)$. The decays are calculated as the dissociation of one of these components ($D^0{\bar{D}}^{0\ast }$) into a $c\bar{c}$ state ($J/\psi$) plus a light meson ($\rho$ or $\omega$) in a potential model. In particular, our result for the ratio between the $X(3872)\to J/\psi \omega$ and $J/\psi \rho$ widths (0.6) is compatible with the present experimental data ($0.8\pm 0.3$) within the experimental error.

   hep-phnucl-thPLB(2019)·47 citations
4. 04*

   Proceedings of the first MadAnalysis 5 workshop on LHC recasting in Korea

   Benjamin Fuks · Samuel Bein · Guillaume Chalons · Eric Conte · Taejeong Kim · Seung J. Lee · Dipan Sengupta · Jory Sonneveld · Seohyun Ahn · Seungwon Baek · Jung Chang · Soo-Min Choi and 13 other authors

   We present the activities performed during the first MadAnalysis 5 workshop on LHC recasting that has been organized at High 1 (Gangwon privince, Korea) on August 20-27, 2017. This report includes details on the implementation in the MadAnalysis 5 framework of eight ATLAS and CMS analyses, as well as a description of the corresponding validation and the various issues that have been observed.

   hep-phhep-ex8 citations
5. 05*

   Indirect search for light charged Higgs bosons through the dominant semileptonic decays of top quark $t\to b(\to B/D+X)+H^{+}(\to {\tau }^{+}{\nu }_{\tau })$

   S. Abbaspour🇮🇷 · S. Mohammad Moosavi Nejad🇮🇷 · M. Balali🇮🇷

   In this work we introduce a new channel to indirect search for the light charged Higgs bosons, which are predicted in several extensions of the standard model (SM) such as the two-Higgs-doublet models (2HDMs). We calculate the $\mathcal{O}({\alpha }_s)$ QCD radiative corrections to the energy distribution of bottom- and charmed-flavored hadrons ($B/D$) produced in the dominant decays of the polarized top quark in the 2HDM, i.e. $t(\uparrow )⟶b(\to B/D+\text{jet})+H^{+}(\to {\tau }^{+}{\nu }_{\tau })$. %This analysis is studied in a specific helicity coordinate system where the polarization vector of the top quark is evaluated with respect to the momentum direction of the bottom quark. Generally, the energy distribution of hadrons is governed by the unpolarized rate and the polar and the azimuthal correlation functions which are related to the density matrix elements of the decay $t(\uparrow )\to b{H}^{+}$. In our proposed channel, any deviation of the $B/D$-meson energy spectrum from its corresponding SM predictions can be considered as a signal for the existence of charged Higgs at the LHC. We also calculate, for the first time, the azimuthal correlation rate ${\Gamma }_{\varphi }$ at next-to-leading order which vanishes at the Born level.

   hep-phNPB(2018)·8 citations
6. 06*

   Axionic Electroweak Baryogenesis

   Kwang Sik Jeong🇰🇷 · Tae Hyun Jung🇰🇷 · Chang Sub Shin🇰🇷

   An axion can make the electroweak phase transition strongly first-order as required for electroweak baryogenesis even if it is weakly coupled to the Higgs sector. This is essentially because the axion periodicity naturally allows the structure of phase transition to be insensitive to the axion decay constant that determines the strength of axion interactions. Furthermore, the axion can serve as a CP phase relevant to electroweak baryogenesis if one introduces an effective axion coupling to the top quark Yukawa operator. Then, for $f$ between about TeV and order $10$~TeV, the observed baryon asymmetry can be explained while avoiding current experimental constraints. It will be possible to probe the axion window for baryogenesis in future lepton colliders and beam-dump experiments.

   hep-phPLB(2019)·36 citations
7. 07*

   Numerical Methods and the 4-point 2-loop Higgs amplitudes

   S. P. Jones🇩🇪 · B. Ruijl🇨🇭

   Some of the difficulties faced when calculating multi-loop amplitudes with several mass scales are reviewed. We then focus on one particular difficulty, the evaluation of the Feynman integrals, and introduce the program pySecDec which can be used to numerically compute such integrals. Some of the new features and in particular the sector symmetry finder, which can help to reduce the number of sectors to be numerically integrated after sector decomposition, are described.

   hep-phJ.Phys.Conf.Ser.(2018)·0 citations
8. 08*

   Anatomy of the chiral vortical effect

   Ruslan Abramchuk🇷🇺 · Z.V.Khaidukov🇷🇺 · M.A. Zubkov🇮🇱

   We consider the system of relativistic rotating fermions in the presence of rotation. The rotation is set up as an enhancement of the angular momentum. In this approach the angular velocity for the angular momentum plays the same role as the chemical potential for density. We calculate the axial current using the direct solutions of the Dirac equation with the MIT bag boundary conditions. Next, we consider the alternative way of the rotation description, in which the local velocity of the substance multiplied by the chemical potential serves as the effective gauge field. In this approach this is possible to relate the axial current of the chiral vortical effect for the massless fermions to the topological invariant in momentum space, which is robust to the introduction of interactions. We compare the results for the axial current obtained using the two above mentioned approaches.

   hep-phPRD(2018)·29 citations
9. 09*

   Thermodynamic versus kinetic approach to polarization-vorticity coupling

   Wojciech Florkowski🇵🇱 · Avdhesh Kumar🇵🇱 · Radoslaw Ryblewski🇵🇱

   We critically compare thermodynamic and kinetic approaches, that have been recently used to study relations between the spin polarization and fluid vorticity in systems consisting of spin-one-half particles. The thermodynamic approach refers to general properties of global thermal equilibrium with a rigid-like rotation and demonstrates that the spin-polarization and thermal-vorticity tensors are equal. On the other hand, the kinetic approach uses the concept of the Wigner function and its semi-classical expansion. In most of the works done so far, the Wigner functions satisfy kinetic equations with a vanishing collision term. We show that this assumption restricts significantly applicability of such frameworks and, in contrast to many claims found in the literature, does not allow for drawing any conclusions regarding the relation between the thermal-vorticity and spin-polarization tensors, except for the fact that the two should be constant in global equilibrium. We further show how the kinetic-theory equations including spin degrees of freedom can be used to formulate a hydrodynamic framework for particles with spin. We define hydrodynamic equations starting separately from the formulation by de~Groot, van~Leeuwen, and van~Weert and from the canonical formalism. In the former case the energy-momentum tensor is symmetric and the spin tensor is conserved, while in the later case the energy-momentum tensor is not symmetric and the spin tensor is not conserved. Nevertheless, in the two cases the total angular momentum is always conserved. Interestingly, the two approaches are connected by the pseudo-gauge transformation, which we explicitly define.

   hep-phnucl-thPRC(2018)·139 citations
10. 10*

    Solving a Fine-Tuning Problem of the Standard Model through the Introduction of Vector-Like Quarks

    F. J. Botella🇪🇸 · G. C. Branco🇵🇹 · M. Nebot🇵🇹 · M. N. Rebelo🇵🇹 · J. I. Silva-Marcos🇵🇹

    We emphasise that even in the extreme chiral limit where only the top and bottom quarks acquire mass, quark mixing is physically meaningful. This implies that the natural value of $|V_{13}{|}^2+|V_{23}{|}^2$ is of order one, which is to be compared to its experimental value of order $10^{-3}$ . We show how this fine-tuning problem of the Standard Model can be solved through an extension of the Standard Model where vector-like quarks and a complex singlet are introduced, together with a flavour symmetry. The mixings of the light quarks are generated through the mixing of the vector-like quarks with the standard quarks.

    hep-ph2 citations
11. 11*

    A neutrinoless double beta decay master formula from effective field theory

    V. Cirigliano🇺🇸 · W. Dekens🇺🇸 · J. de Vries🇳🇱 · M. L. Graesser🇺🇸 · E. Mereghetti🇺🇸

    We present a master formula describing the neutrinoless-double-beta decay ($0\nu \beta \beta$) rate induced by lepton-number-violating (LNV) operators up to dimension nine in the Standard Model Effective Field Theory. We provide an end-to-end framework connecting the possibly very high LNV scale to the nuclear scale, through a chain of effective field theories. Starting at the electroweak scale, we integrate out the heavy Standard Model degrees of freedom and we match to an $SU(3{)}_c\otimes U(1{)}_{\mathrm{em}}$ effective theory. After evolving the resulting effective Lagrangian to the QCD scale, we use chiral perturbation theory to derive the lepton-number-violating chiral Lagrangian. The chiral Lagrangian is used to derive the two-nucleon $0\nu \beta \beta$ transition operators to leading order in the chiral power counting. Based on renormalization arguments we show that in various cases short-range two-nucleon operators need to be enhanced to leading order. We show that all required nuclear matrix elements can be taken from existing calculations. Our final result is a master formula that describes the $0\nu \beta \beta$ rate in terms of phase-space factors, nuclear matrix elements, hadronic low-energy constants, QCD evolution factors, and high-energy LNV Wilson coefficients, including all the interference terms. Our master formula can be easily matched to any model where LNV originates at energy scales above the electroweak scale. As an explicit example, we match our formula to the minimal left-right-symmetric model in which contributions of operators of different dimension compete, and we discuss the resulting phenomenology.

    hep-phnucl-exnucl-thJHEP(2018)·187 citations
12. 12*

    Hadronic and New Physics Contributions to $b\to s$ Transitions

    A. Arbey🇫🇷 · T. Hurth🇩🇪 · F. Mahmoudi🇫🇷 · S. Neshatpour🇮🇷

    Assuming the source of the anomalies observed recently in $b\to s$ data to be new physics, there is a priori no reason to believe that - in the effective field theory language - only one type of operator is responsible for the tensions. We thus perform for the first time a global fit where all the Wilson coefficients which can effectively receive new physics contributions are considered, allowing for lepton flavour universality breaking effects as well as contributions from chirality flipped and scalar and pseudoscalar operators, and find the SM pull taking into account all effective parameters. As a result of the full fit to all available $b\to s$ data including all relevant Wilson coefficients, we obtain a total pull of 4.1$\sigma$ with the SM hypothesis assuming 10% error for the power corrections. Moreover, we make a statistical comparison to find whether the most favoured explanation of the anomalies is new physics or underestimated hadronic effects using the most general parameterisation which is fully consistent with the analyticity structure of the amplitudes. This Wilks' test will be a very useful tool to analyse the forthcoming $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ data. Because the significance of the observed tensions in the angular observables in $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ is presently dependent on the theory estimation of the hadronic contributions to these decays, we briefly discuss the various available approaches for taking into account the long-distance hadronic effects and examine how the different estimations of these contributions result in distinct significance of the new physics interpretation of the observed anomalies.

    hep-phPRD(2018)·79 citations
13. 13*

    The Dispirited Case of Gauged $U(1{)}_{B-L}$ Dark Matter

    Miguel Escudero🇪🇸 · Samuel J. Witte🇪🇸 · Nuria Rius🇪🇸

    We explore the constraints and phenomenology of possibly the simplest scenario that could account at the same time for the active neutrino masses and the dark matter in the Universe within a gauged $U(1{)}_{B-L}$ symmetry, namely right-handed neutrino dark matter. We find that null searches from lepton and hadron colliders require dark matter with a mass below 900 GeV to annihilate through a resonance. Additionally, the very strong constraints from high-energy dilepton searches fully exclude the model for $150\text{GeV}<m_{Z^{\prime }}<3\text{TeV}$. We further explore the phenomenology in the high mass region (i.e. masses $\gtrsim \mathcal{O}(1)\text{TeV}$) and highlight theoretical arguments, related to the appearance of a Landau pole or an instability of the scalar potential, disfavoring large portions of this parameter space. Collectively, these considerations illustrate that a minimal extension of the Standard Model via a local $U(1{)}_{B-L}$ symmetry with a viable thermal dark matter candidate is difficult to achieve without fine-tuning. We conclude by discussing possible extensions of the model that relieve tension with collider constraints by reducing the gauge coupling required to produce the correct relic abundance.

    hep-phastro-ph.COJHEP(2018)·55 citations
14. 14*

    Top quark FCNCs in extended Higgs sectors

    Shankha Banerjee🇬🇧 · Mikael Chala🇬🇧 · Michael Spannowsky🇬🇧

    The large number of top quarks produced at the LHC and possible future hadron colliders allows to study rare decays of this particle. In many well motivated models of new physics, for example in non-minimal composite-Higgs models, the existence of scalar singlets can induce new flavor-violating top decays surpassing the Higgs contribution by orders of magnitude. We study the discovery prospects of rare top decays within such models and develop new search strategies to test these interactions in top pair-produced events at the LHC. We demonstrate that scales as large as $10$--$50$ TeV can be probed. Improvements by factors of $\sim 1.5$ and $\sim 3$ can be obtained at $\sqrt{s}=27$ TeV and $\sqrt{s}=100$ TeV colliders.

    hep-phhep-exEPJC(2018)·43 citations
15. 15*

    A lattice QCD study of pion-nucleon scattering in the Roper channel

    Luka Leskovec🇺🇸 · Christian B. Lang🇦🇹 · M. Padmanath🇩🇪 · Sasa Prelovsek🇸🇮

    We present a lattice QCD study of the puzzling positive-parity nucleon channel, where the Roper resonance $N^{\ast }(1440)$ resides in experiment. The study is based on an ensemble of gauge configurations with $N_f=2+1$ Wilson-clover fermions with a pion mass of $156$ MeV and lattice size $L=2.9$ fm. We use several $qqq$ interpolating fields combined with $N\pi$ and $N\sigma$ two-hadron operators in calculating the energy spectrum in the rest frame. Combining experimental $N\pi$ phase shifts with elastic approximation and the Lüscher formalism suggests in the spectrum an additional energy level near the Roper mass $m_R=1.43$ GeV for our lattice. We do not observe any such additional energy level, which implies that $N\pi$ elastic scattering alone does not render a low-lying Roper resonance. The current status indicates that the $N^{\ast }(1440)$ might arise as dynamically generated resonance from coupling to other channels, most notably the $N\pi \pi$.

    ↳ hep-lathep-phFew Body Syst.(2018)·7 citations
16. 16*

    Two- and three-body interactions in ${\phi }^4$ theory from lattice simulations

    Fernando Romero-López🇪🇸 · Akaki Rusetsky🇩🇪 · Carsten Urbach🇩🇪

    We calculate the one-, two- and three-particle energy levels for different lattice volumes in the complex ${\phi }^4$ theory on the lattice. We argue that the exponentially suppressed finite-volume corrections for the two- and three-particle energy shifts can be reduced significantly by using the single particle mass, which includes the finite-size effects. We show numerically that, for a set of bare parameters, corresponding to the weak repulsive interaction, one can reliably extract the two- and three-particle energy shifts. From those, we extract the scattering length, the effective range and the effective three-body coupling. We show that the parameters, extracted from the two- and three-particle energy shifts, are consistent. Moreover, the effective three-body coupling is significantly different from zero.

    ↳ hep-lathep-phEPJC(2018)·66 citations
17. 17*

    Runaway directions in O'Raifeartaigh models

    Zheng Sun · Xingyue Wei

    R-symmetries, which are needed for supersymmetry (SUSY) breaking in O'Raifeartaigh models, often lead to SUSY runaway directions trough a complexified R-transformation. Non-R symmetries also lead to runaway directions in a similar way. This work investigates the occurrence of runaway directions of both SUSY and SUSY breaking types. We clarify previous issues on fractional charges and genericness, and make a refined statement on conditions for runaway directions related to either R-symmetries or non-R symmetries. We present a generic and anomaly-free model to show the existence of runaway directions related to non-R symmetries. We also comment on the possibility to combine the non-R symmetry case to the R-symmetry case by an R-charge redefinition.

    ↳ hep-thhep-phCommun.Theor.Phys.(2018)·8 citations
18. 18*

    The Eisenhart Lift for Field Theories

    Kieran Finn🇬🇧 · Sotirios Karamitsos🇬🇧 · Apostolos Pilaftsis🇬🇧

    We present the Eisenhart-lift formalism in which the dynamics of a system that evolves under the influence of a conservative force is equivalent to that of a free system embedded in a curved manifold with one additional generalised coordinate. As an illustrative example in Classical Mechanics, we apply this formalism to simple harmonic motion. We extend the Eisenhart lift to homogeneous field theories by adding one new field. Unlike an auxiliary field, this field is fully dynamical and is therefore termed fictitious. We show that the Noether symmetries of a theory with a potential are solutions of the Killing equations in the lifted field space. We generalise this approach to field theories in four and higher spacetime dimensions by virtue of a mixed vielbein that links the field space and spacetime. Possible applications of the extended Eisenhart-lift formalism including the gauge hierarchy problem and the initial conditions problem in inflation are briefly discussed.

    ↳ physics.class-phgr-qchep-phhep-th+2PRD(2018)·20 citations
19. 19*

    A Systematic Expansion of Running Couplings and Masses

    F.A. Chishtie🇨🇦 · D.G.C. McKeon🇨🇦 · T.N. Sherry🇮🇪

    As an alternative to directly integrating their defining equations to find the running coupling $a(\mu )$ and the running mass $m(\mu )$, we expand these quantities in powers of $\ln \left(\frac{\mu }{{\mu }^{\prime }}\right)$ and their boundary values $a({\mu }^{\prime })$ and $m({\mu }^{\prime })$. Renormalization group summation is used to partially sum these logarithms. We consider this approach using both the $\overline{MS}$ and 't Hooft renormalization schemes. We also show how the couplings and masses in any two mass independent renormalization schemes are related.

    ↳ hep-thhep-phMod.Phys.Lett.A(2019)·6 citations
20. 20*

    Worldline sphaleron for thermal Schwinger pair production

    Oliver Gould🇬🇧 · Arttu Rajantie🇬🇧 · Cheng Xie🇬🇧

    With increasing temperatures, Schwinger pair production changes from a quantum tunnelling to a classical, thermal process, determined by a worldline sphaleron. We show this and calculate the corresponding rate of pair production for both spinor and scalar quantum electrodynamics, including the semiclassical prefactor. For electron-positron pair production from a thermal bath of photons and in the presence of an electric field, the rate we derive is faster than both perturbative photon fusion and the zero temperature Schwinger process. We work to all-orders in the coupling and hence our results are also relevant to the pair production of (strongly coupled) magnetic monopoles in heavy ion collisions.

    ↳ hep-thhep-phPRD(2018)·26 citations
21. 21*

    Scalar perturbations in cosmological $f(R)$ models: the cosmic screening approach

    Ozgur Akarsu🇹🇷 · Ruslan Brilenkov🇦🇹 · Maxim Eingorn🇺🇸 · Valerii Shulga🇨🇳 · Alexander Zhuk🇹🇷

    We investigate cosmological perturbations for nonlinear $f(R)$ models within the cosmic screening approach. Matter is considered both in the form of a set of discrete point-like massive bodies and in the form of a continuous pressureless perfect fluid. We perform full relativistic analysis of the first-order theory of scalar perturbations for arbitrary nonlinear $f(R)$ models and demonstrate that scalar potentials $\Phi (t,\mathbf{r})$ and $\Psi (t,\mathbf{r})$ are determined by a system of only two master equations. Our equations are applicable at all spatial scales as long as the approximation $\delta R/\bar{R}\ll 1$ (which is usually assumed in studies devoted to cosmological perturbations in $f(R)$ models) works.

    ↳ gr-qcastro-ph.COhep-phhep-thEPJC(2018)·9 citations
22. 22*

    Measurements of ZZ production with the ATLAS detector and simulation of loop-induced processes with the HERWIG event generator

    Stefan Richter🇬🇧

    This thesis presents results and method developments in both experimental and theoretical particle physics. The main part shows measurements of ${\ell }^{+}{\ell }^{-}{\ell }^{\prime +}{\ell }^{\prime -}$ production (where $\ell$, ${\ell }^{\prime }$ is either an electron or a muon) in proton-proton collisions at 13 TeV centre-of-mass energy. The collisions were produced by the Large Hadron Collider in 2015 and 2016 and observed with the ATLAS detector. In a phase space sensitive to Z boson pair production, the integrated cross section as well as differential cross sections with respect to twenty-one observables are measured. Ten of these directly measure associated jet activity. The measurements provide an important test of the Standard Model of particle physics. A direct search for effects beyond the Standard Model affecting ZZ production is performed in a generic effective field theory approach. No significant deviations from the Standard Model predictions are observed. Exclusion limits are set on the parameters describing new physics in the effective field theory. In theoretical developments, the automated description of loop-induced processes with the Herwig 7 event generator is presented. These are processes that can only occur via a quantum loop of virtual particles. Preliminary results in leading-order quantum chromodynamics are shown for the production of a Higgs boson, of a pair of Higgs bosons, and of four leptons. The Higgs boson results show that the full loop-induced description can deviate significantly from the common approximation where the mass of the top quark is treated as infinitely large. Thus, including loop effects is crucial to obtaining precise predictions to compare to measurements at the Large Hadron Collider. Developments towards a next-to-leading-order description of arbitrary loop-induced processes are shown.

    ↳ hep-exhep-ph1 citation

* 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.