Wed·Feb 28, 2024Wednesday·February 28, 2024

1. 01*

   Resolving the Ultracollinear Paradox with Effective Field Theory

   Matthew Baumgart🇺🇸 · Panagiotis Christeas🇺🇸

   Naive intuition about scale decoupling breaks down in the presence of fermion masses. Kinematic enhancements can greatly extend the range where one needs to keep a finite mass in calculations to obtain a correct result at even the O(1) level. Treating a light fermion as massive though, leads to a known but somewhat obscure paradox, a seeming leading-order sensitivity to an arbitrarily small mass. We show how a proper formulation in effective field theory not only resolves the physical conundrum, but answers the very practical question of when fermion masses are required. This has important implications for the development of shower Monte Carlo above the weak scale.

   hep-phhep-thnucl-thPRD(2024)·0 citations
2. 02*

   The symmetry approach to quark and lepton masses and mixing

   Gui-Jun Ding🇨🇳 · Jose W.F. Valle🇪🇸

   The Standard Model lacks an organizing principle to describe quark and lepton ``flavours''. Neutrino oscillation experiments show that leptons mix very differently from quarks, adding a major challenge to the flavour puzzle. We briefly sketch the seesaw and the dark-matter-mediated ``scotogenic'' neutrino mass generation approaches. We discuss the limitations of popular neutrino mixing patterns and examine the possibility that they arise from symmetry, giving a bottom-up approach to residual flavour and CP symmetries. We show how such family and/or CP symmetries can yield novel, viable and predictive mixing patterns. Model-independent ways to predict lepton mixing and neutrino mass sum rules are reviewed. We also discuss UV-complete flavour theories in four and more space-time dimensions. As benchmark examples we present an $A_4$ scotogenic construction with trimaximal mixing pattern TM2 and another with $S_4$ flavour symmetry and generalized CP symmetry. Higher-dimensional flavour completions are also briefly discussed, such as 5-D warped flavordynamics with a $T^{\prime }$ symmetry yielding a TM1 mixing pattern, detectable neutrinoless double beta decay rates and a very good global fit of flavour observables. We also mention 6-D orbifolds as a way to fix the structure of the 4-D family symmetry. We give a scotogenic benchmark orbifold model predicting the ``golden'' quark-lepton mass relation, stringent neutrino oscillation parameter regions, and an excellent global flavour fit, including quark observables. Finally, we discuss promising recent progress in tackling the flavor issue through the use of modular symmetries.

   hep-phhep-exPhys.Rept.(2025)·68 citations
3. 03*

   Theoretical Highlights of CP Violation in $B$ Decays

   Eleftheria Malami🇳🇱

   In this presentation, we discuss recent key topics in theoretical analyses of CP violation in benchmarks decays of the $B$ meson. We provide the most updated values of the mixing phases and discuss the importance of including the penguin contributions in their studies. Exploring intriguing patterns in purely tree decays, interesting new methodologies can be developed and applied. New data related to the CP asymmetries of key modes like $B_d^0\to {\pi }^0{K}_S$ and $B_s^0\to K^{+}{K}^{-}$ lead to interesting results. The new $R_{K^{(\ast )}}$ measurement, compatible with the Standard Model, can still allow for electron-muon symmetry violation through new sources of CP violation.

   hep-phhep-exPoS(2024)·3 citations
4. 04*

   Estimation of electric field in intermediate-energy heavy-ion collisions

   Hidetoshi Taya🇯🇵 · Toru Nishimura🇯🇵 · Akira Ohnishi🇯🇵

   We estimate the spacetime profile of the electric field in head-on heavy-ion collisions at intermediate collision energies $\sqrt{s_{\mathrm{NN}}}=\mathcal{O}(3-10\mathrm{GeV})$. Using a hadronic cascade model (JAM; Jet AA Microscopic transport model), we numerically demonstrate that the produced field has strength $eE=\mathcal{O}((30-60\mathrm{MeV}{)}^2)$, which is supercritical to the Schwinger limit of QED and is non-negligibly large compared even to the hadron/QCD scale, and survives for a long time $\tau =\mathcal{O}(10\mathrm{fm}/c)$ due to the baryon stopping. We show that the produced field is nonperturbatively strong in the sense that the nonperturbativity parameters (e.g., the Keldysh parameter) are sufficiently large. This is in contrast to high-energy collisions $\sqrt{s_{\mathrm{NN}}}\gtrsim 100\mathrm{GeV}$, where the field is extremely short-lived and hence is perturbative. Our results imply that the electromagnetic field may have phenomenological impacts on hadronic/QCD processes in intermediate-energy heavy-ion collisions and that heavy-ion collisions can be used as a new tool to explore strong-field physics in the nonperturbative regime.

   hep-phnucl-exnucl-thPRC(2024)·13 citations
5. 05*

   Direct Detection of Dark Photon Dark Matter with the James Webb Space Telescope

   Haipeng An🇨🇳 · Shuailiang Ge🇨🇳 · Jia Liu🇨🇳 · Zhiyao Lu🇨🇳

   In this study, we propose an investigation into dark photon dark matter (DPDM) within the infrared frequency band, utilizing highly sensitive infrared light detectors commonly integrated into space telescopes, such as the James Webb Space Telescope (JWST). The presence of DPDM induces electron oscillations in both the reflectors and the interior of the detectors. Consequently, these oscillating electrons can emit monochromatic electromagnetic waves with a frequency almost equivalent to the mass of DPDM. By employing the stationary phase approximation, we can demonstrate that when the size of the reflector significantly exceeds the wavelength of the electromagnetic wave, the contribution to the electromagnetic wave field at a given position primarily stems from the surface unit perpendicular to the relative position vector. This simplification results in the reduction of electromagnetic wave calculations to ray optics. Through a careful analysis of photon generation induced by DPDM on the various optical elements of JWST, we find that the contribution of these photons to the detected signal is negligible. Nevertheless, we propose a modified configuration of the JWST mirrors that would enable the DPDM-induced photons to be focused onto the detector. This approach can be applied to future space telescopes during their ground-testing phases. Using the JWST parameters as a representative example, the achievable upper limits on the DPDM-photon mixing constant are $ϵ\sim 10^{-12}-10^{-14}$ in the frequency range $10-500$~THz at the 95\% confidence level. This reveals the strong potential of future space telescopes for DPDM detection during ground testing, with sensitivities exceeding current limits by 1 to 2 orders of magnitude compared with the XENON1T result and the solar cooling bound.

   hep-phastro-ph.COastro-ph.HEhep-exJCAP(2026)·11 citations
6. 06*

   Gluon GTMDs at nonzero skewness and impact parameter dependent parton distributions

   Chentao Tan🇨🇳 · Zhun Lu🇨🇳

   We investigate the leading twist generalized transverse momentum dependent parton distributions (GTMDs) of the unpolarized and longitudinally polarized gluons in the nucleon. We adopt a light-front gluon-triquark model for the nucleon motivated by soft-wall AdS/QCD. The gluon GTMDs are defined through the off-forward gluon-gluon generalized correlator and are expressed as the overlap of light-cone wave functions. The GTMDs can be employed to provide the generalized parton distributions (GPDs) by integrating out the transverse momentum. The Fourier transform of the GPDs encodes the parton distributions in the transverse position space, namely, the impact parameter dependent parton distributions (IPDs). We also calculate the three gluon IPDs corresponding to the GPDs $H^g$, $E^g$ and ${\tilde{H}}^g$, and present their dependence on $x$ and $b_{\perp }$, respectively.

   hep-phEPJC(2024)·9 citations
7. 07*

   Constraining Asymmetric Dark Matter using Colliders and Direct Detection

   Arnab Roy🇦🇺 · Basudeb Dasgupta🇮🇳 · Monoranjan Guchait🇮🇳

   We reappraise the viability of asymmetric dark matter (ADM) realized as a Dirac fermion coupling dominantly to the Standard Model fermions. Treating the interactions of such a DM particle with quarks/leptons in an effective-interactions framework, we derive updated constraints using mono-jet searches from the Large Hadron Collider (LHC) and mono-photon searches at the Large Electron-Positron (LEP) collider. We carefully model the detectors used in these experiments, which is found to have significant impact. The constraint of efficient annihilation of the symmetric part of the ADM, as well as other observational constraints are synthesized to produce a global picture. Consistent with previous work, we find that ADM with mass in the range $1-100$ GeV is strongly constrained, thus ruling out its best motivated mass range. However, we find that leptophilic ADM remains allowed for $\gtrsim 10$ GeV DM, including bounds from colliders, direct detection, and stellar heating. We forecast that the Future Circular Collider for electron-positron collisions (FCC-ee) will improve sensitivity to DM-lepton interactions by almost an order of magnitude.

   hep-phastro-ph.COhep-exJHEP(2024)·15 citations
8. 08*

   Impact of strong magnetic field, baryon chemical potential, and medium anisotropy on polarization and spin alignment of hadrons

   Bhagyarathi Sahoo🇮🇳 · Captain R. Singh🇮🇳 · Raghunath Sahoo🇮🇳

   The recent observation of global spin polarization of $\Lambda$ ($\bar{\Lambda }$) hyperons and the spin alignment of $\varphi$ and $K^{\ast 0}$ vector mesons create remarkable interest in investigating the particle polarization in the relativistic fluid produced in heavy-ion collisions at GeV/TeV energies. Among other sources of spin polarization phenomena, the Debye mass of a medium plays a crucial role in particle polarization. Any modification brought to the effective mass due to the temperature, strong magnetic field ($eB$), baryonic chemical potential (${\mu }_B$), medium anisotropy ($\xi$), and vorticity, etc., certainly affects the particle spin polarization. In this work, we explore the global hyperon spin polarization and the spin alignment of vector mesons corresponding to the strong magnetic field, baryonic chemical potential, and medium anisotropy. We find that the degree of spin polarization is flavor-dependent for hyperons. Meanwhile, vector meson spin alignment depends on the hadronization mechanisms of initially polarized quarks and anti-quarks. Medium anisotropy significantly changes the degree of spin polarization compared to the magnetic field and baryon chemical potential.

   hep-phhep-exhep-thnucl-ex+1EPJC(2025)·15 citations
9. 09*

   A comparative study of flavour-sensitive observables in hadronic Higgs decays

   Benjamin Campillo Aveleira🇩🇪 · Aude Gehrmann-De Ridder🇨🇭 · Christian T Preuss🇩🇪

   Jet production from hadronic Higgs decays at future lepton colliders will have significantly different phenomenological implications than jet production via off-shell photon and $Z$-boson decays, owing to the fact that Higgs bosons decay to both pairs of quarks and gluons. We compute observables involving flavoured jets in hadronic Higgs decays to three partons at Born level including next-to-leading order corrections in QCD (i.e up to $\mathcal{O}({\alpha }_{\mathrm{S}}^2))$. The calculation is performed in the framework of an effective theory in which the Higgs boson couples directly to gluons and massless $b$-quarks retaining a non-vanishing Yukawa coupling. For the energy of the leading and subleading flavoured jet, the angular separation and the invariant mass of the leading $b$-$\bar{b}$ pair, we contrast the results obtained in both Higgs decay categories and using either of the infrared-safe flavoured jet algorithms flavour-$k_{\mathrm{T}}$ and flavour-dressing.

   hep-phhep-exEPJC(2024)·11 citations
10. 10*

    A case study of sending graph neural networks back to the test bench for applications in high-energy particle physics

    Emanuel Pfeffer🇩🇪 · Michael Waßmer🇩🇪 · Yee-Ying Cung🇩🇪 · Roger Wolf🇩🇪 · Ulrich Husemann🇩🇪

    In high-energy particle collisions, the primary collision products usually decay further resulting in tree-like, hierarchical structures with a priori unknown multiplicity. At the stable-particle level all decay products of a collision form permutation invariant sets of final state objects. The analogy to mathematical graphs gives rise to the idea that graph neural networks (GNNs), which naturally resemble these properties, should be best-suited to address many tasks related to high-energy particle physics. In this paper we describe a benchmark test of a typical GNN against neural networks of the well-established deep fully-connected feed-forward architecture. We aim at performing this comparison maximally unbiased in terms of nodes, hidden layers, or trainable parameters of the neural networks under study. As physics case we use the classification of the final state X produced in association with top quark-antiquark pairs in proton-proton collisions at the Large Hadron Collider at CERN, where X stands for a bottom quark-antiquark pair produced either non-resonantly or through the decay of an intermediately produced Z or Higgs boson.

    hep-phcs.AIhep-exComput.Softw.Big Sci.(2024)·4 citations
11. 11*

    Ghost-gluon vertex in the presence of the Gribov horizon: General kinematics

    Nahuel Barrios🇺🇾 · Marcelo S. Guimaraes🇧🇷 · Bruno W. Mintz🇧🇷 · Letícia F. Palhares🇧🇷 · Marcela Peláez🇺🇾

    Correlation functions are important probes for the behavior of quantum field theories. Already at tree-level, the Refined Gribov Zwanziger (RGZ) effective action for Yang-Mills theories provides a good approximation for the gluon propagator, as compared to that calculated by nonperturbative methods such as Lattice Field Theory and Dyson-Schwinger Equations. However, the study of higher correlation functions of the RGZ theory is still at its beginning. In this work we evaluate the ghost-antighost-gluon vertex function in Landau gauge at one-loop level, in $d=4$ space-time dimensions for the gauge groups SU(2) and SU(3). More precisely, we extend the analysis conducted in [1] for the soft-gluon limit to an arbitrary kinematic configuration. We introduce renormalization group effects by means of a toy model for the running coupling and investigate the impact of such a model in the ultraviolet tails of our results. We find that RGZ results match fairly closely those from lattice simulations, Schwinger-Dyson equations and the Curci-Ferrari model for three different kinematic configurations. This is compatible with RGZ being a feasible theory for the strong interaction in the infrared regime.

    hep-phhep-lathep-thPRD(2024)·7 citations
12. 12*

    T-odd gluon distribution functions in a spectator model

    Alessandro Bacchetta🇮🇹 · Francesco Giovanni Celiberto🇪🇸 · Marco Radici🇮🇹

    We present a model calculation of T-odd transverse-momentum-dependent distributions of gluons in the nucleon. The model is based on the assumption that a nucleon can emit a gluon, and what remains after the emission is treated as a single spectator particle. This spectator particle is considered to be on-shell, but its mass is allowed to take a continuous range of values, described by a spectral function. The final-state interaction that is necessary to generate T-odd functions is modeled as the exchange of a single gluon between the spectator and the outgoing parton.

    hep-phhep-exnucl-exnucl-thEPJC(2024)·47 citations
13. 13*

    Quasi-Classical Gluon Fields and Low's Soft Theorem at Small $x$

    Ming Li🇺🇸

    In the high energy limit, soft gluons can be approximately described by quasi-classical gluon fields. It is well-known that the gluon field is a pure gauge field on the transverse plane at eikonal order. We derived the complete next-to-eikonal order solutions of the classical Yang-Mills equations for soft gluons in the dense nuclear regime. Utilizing these solutions, it is shown that Low's soft theorem at small x can be obtained by considering off-diagonal matrix elements of quasi-classical chromoelectric field between single gluon states in the dilute regime. We further propose on extending Low's soft theorem at small x to incorporate the effects of gluon saturation in the dense regime.

    hep-phPRL(2024)·14 citations
14. 14*

    Triangle singularity in the $J/\psi \to \varphi {\pi }^{+}{a}_0^{-}({\pi }^{-}\eta ),\varphi {\pi }^{-}{a}_0^{+}({\pi }^{+}\eta )$ decays

    C. W. Xiao🇨🇳 · J. M. Dias🇨🇳 · L. R. Dai🇨🇳 · W. H. Liang🇨🇳 · E. Oset🇪🇸

    We study the $J/\psi \to \varphi {\pi }^{+}{a}_0(980{)}^{-}(a_0^{-}\to {\pi }^{-}\eta )$ decay, evaluating the double mass distribution in terms of the ${\pi }^{-}\eta$ and ${\pi }^{+}{a}_0^{-}$ invariant masses. We show that the ${\pi }^{-}\eta$ mass distribution exhibits the typical cusp structure of the $a_0(980)$ seen in recent high statistics experiments, and the ${\pi }^{+}{a}_0^{-}$ spectrum shows clearly a peak around $M_{\mathrm{inv}}({\pi }^{+}{a}_0^{-})=1420\mathrm{MeV}$, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of $10^{-5}$, which is easily accessible in present laboratories. We also call attention to the fact that the signal obtained is compatible with a bump experimentally observed in the $\eta {\pi }^{+}{\pi }^{-}$ mass distribution in the $J/\psi \to \varphi \eta {\pi }^{+}{\pi }^{-}$ decay and encourage further analysis to extract from there the $\varphi {\pi }^{+}{a}_0^{-}$ and $\varphi {\pi }^{-}{a}_0^{+}$ decay modes.

    hep-phPRD(2024)·7 citations
15. 15*

    Dual chiral density wave induced oscillating Casimir effect

    Daisuke Fujii🇯🇵 · Katsumasa Nakayama🇯🇵 · Kei Suzuki🇯🇵

    The Casimir effect is known to be induced from photon fields confined by a small volume, and also its fermionic counterpart has been predicted in a wide range of quantum systems. Here, we investigate what types of Casimir effects can occur from quark fields in dense and thin quark matter. In particular, in the dual chiral density wave, which is a possible ground state of dense quark matter, we find that the Casimir energy oscillates as a function of the thickness of matter. This oscillating Casimir effect is regarded as an analog of that in Weyl semimetals and is attributed to the Weyl points in the momentum space of quark fields. In addition, we show that an oscillation is also induced from the quark Fermi sea, and the total Casimir energy is composed of multiple oscillations.

    hep-phcond-mat.mes-hallhep-latnucl-th+1PRD(2024)·9 citations
16. 16*

    Cluster Scanning: a novel approach to resonance searches

    Ivan Oleksiyuk🇨🇭 · John Andrew Raine🇨🇭 · Michael Krämer🇩🇪 · Svyatoslav Voloshynovskiy🇨🇭 · Tobias Golling🇨🇭

    We propose a new model-independent method for new physics searches called Cluster Scanning. It uses the k-means algorithm to perform clustering in the space of low-level event or jet observables, and separates potentially anomalous clusters to construct a signal-enriched region. The spectra of a selected observable (e.g. invariant mass) in these two regions are then used to determine whether a resonant signal is present. A pseudo-analysis on the LHC Olympics dataset with a $Z^{\prime }$ resonance shows that Cluster Scanning outperforms the widely used 4-parameter functional background fitting procedures, reducing the number of signal events needed to reach a $3\sigma$ significant access by a factor of 0.61. Emphasis is placed on the speed of the method, which allows the test statistic to be calibrated on synthetic data.

    hep-phhep-exphysics.data-anJHEP(2024)·3 citations
17. 17*

    An Axion Pulsarscope

    Mariia Khelashvili🇺🇸 · Mariangela Lisanti🇺🇸 · Anirudh Prabhu🇺🇸 · Benjamin R. Safdi🇺🇸

    Electromagnetic fields surrounding pulsars may source coherent ultralight axion signals at the known rotational frequencies of the neutron stars, which can be detected by laboratory experiments (e.g., pulsarscopes). As a promising case study, we model axion emission from the well-studied Crab pulsar, which would yield a prominent signal at $f\approx 29.6$ Hz regardless of whether the axion contributes to the dark matter abundance. We estimate the relevant sensitivity of future axion dark matter detection experiments such as DMRadio-GUT, Dark SRF, and CASPEr, assuming different magnetosphere models to bracket the uncertainty in astrophysical modeling. For example, depending on final experimental parameters, the Dark SRF experiment could probe axions with any mass $m_a\ll 10^{-13}$ eV down to $g_{a\gamma \gamma }\sim 3\times 10^{-13}$ GeV${}^{-1}$ with one year of data and assuming the vacuum magnetosphere model. These projected sensitivities may be degraded depending on the extent to which the magnetosphere is screened by charge-filled plasma. The promise of pulsar-sourced axions as a clean target for direct detection experiments motivates dedicated simulations of axion production in pulsar magnetospheres.

    hep-phastro-ph.COastro-ph.HEPRD(2025)·13 citations
18. 18*

    Flavor-Violating ALPs, Electron g-2, and the Electron-Ion Collider

    Hooman Davoudiasl🇺🇸 · Roman Marcarelli🇺🇸 · Ethan T. Neil🇺🇸

    We revisit the possibility that light axion-like particles (ALPs) with lepton flavor violating couplings could give significant contributions to the electron's anomalous magnetic moment $g_e-2$. Unlike flavor diagonal lepton-ALP couplings, which are exclusively axial, lepton flavor violating couplings can have arbitrary chirality. Focusing on the $e$-$\tau$ ALP coupling, we find that the size of the contribution to $g_e-2$ depends strongly on the chirality of the coupling. A significant part of the parameter space for which such a coupling can explain experimental anomalies in $g_e-2$ can be probed at the Electron-Ion Collider, which is uniquely sensitive to the chirality of the coupling using the polarization of the electron beam.

    hep-phPRD(2024)·15 citations
19. 19*

    GW Backgrounds associated with PBHs

    Guillem Domènech🇩🇪

    PBH formation requires high-density regions in the (random) density field filling the primordial universe. While only the largest (and so rarest) overdensities collapse to form PBHs, the rest cause large anisotropic stresses, which are the source of GWs. We provide an overview of the theoretical aspects of the GW backgrounds associated with PBHs from large primordial fluctuations. We consider GW backgrounds associated with PBH formation, PBH reheating and unresolved PBH binaries. We present several graphical summaries and illustrations for the busy reader.

    ↳ gr-qcastro-ph.COhep-ph19 citations
20. 20*

    Strong CP problem in the quantum rotor

    David Albandea🇪🇸 · Guilherme Catumba🇪🇸 · Alberto Ramos🇪🇸

    Recent studies have claimed that the strong $CP$ problem does not occur in QCD, proposing a new order of limits in volume and topological sectors when studying observables on the lattice. In order to shed light on this issue, we study the effect of the topological $\theta$-term on a simple quantum mechanical rotor that allows a lattice description. The topological susceptibility and the $\theta$-dependence of the energy spectrum are both computed using local lattice correlation functions. The sign problem is overcome by considering Taylor expansions in $\theta$ exploiting automatic differentiation methods for Monte Carlo processes. Our findings confirm the conventional wisdom on the strong $CP$ problem.

    ↳ hep-lathep-phPRD(2024)·24 citations
21. 21*

    Gradient Properties of Perturbative Multiscalar RG Flows to Six Loops

    William H. Pannell🇬🇧 · Andreas Stergiou🇬🇧

    The gradient property of the renormalisation group (RG) flow of multiscalar theories is examined perturbatively in $d=4$ and $d=4-\epsilon$ dimensions. Such theories undergo RG flows in the space of quartic couplings ${\lambda }^I$. Starting at five loops, the relevant vector field that determines the physical RG flow is not the beta function traditionally computed in a minimal subtraction scheme in dimensional regularisation, but a suitable modification of it, the $B$ function. It is found that up to five loops the $B$ vector field is gradient, i.e. $B^I=G^{IJ}\partial A/\partial {\lambda }^J$ with $A$ a scalar and $G_{IJ}$ a rank-two symmetric tensor of the couplings. Up to five loops the beta function is also gradient, but it fails to be so at six loops. The conditions under which the $B$ function (and hence the RG flow) is gradient at six loops are specified, but their verification rests on a separate six-loop computation that remains to be performed.

    ↳ hep-thcond-mat.stat-mechhep-phPLB(2024)·14 citations
22. 22*

    Breakdown of Hawking Evaporation opens new Mass Window for Primordial Black Holes as Dark Matter Candidate

    Valentin Thoss🇩🇪 · Andreas Burkert🇩🇪 · Kazunori Kohri🇯🇵

    The energy injection through Hawking evaporation has been used to put strong constraints on primordial black holes as a dark matter candidate at masses below $10^{17}\mathrm{g}$. However, Hawking's semiclassical approximation breaks down at latest after half-decay. Beyond this point, the evaporation could be significantly suppressed, as was shown in recent work. In this study, we review existing cosmological and astrophysical bounds on primordial black holes, taking this effect into account. We show that the constraints disappear completely for a reasonable range of parameters, which opens a new window below $10^{10}\mathrm{g}$ for light primordial black holes as a dark matter candidate.

    ↳ astro-ph.COastro-ph.HEgr-qchep-ph+1MNRAS(2024)·118 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.