Mon·Jul 7, 2025Monday·July 7, 2025

1. 01*

   Scattering off unstable states

   Francesco Giacosa🇵🇱 · Vanamali Shastry🇺🇸

   Unstable states that live long enough may appear as in(out)going particles in scattering experiments. Yet, the standard QFT approach strictly applies only to fully stable asymptotic states. This is evident when scattering involving unstable particles develops a $t$-channel singularity at specific angles. We employ a finite-time formalism leading to analytic results without the singularity (even in the infinite-time limit), thus solving the problem at a phenomenological level. In turn, the approach also justifies treating long-lived particles, like weakly decaying pions, as stable during strong interactions.

   hep-phhep-thnucl-thPRD(2026)·0 citations
2. 02*

   Relativistic Axion with Nonrelativistic Momenta: A Robust Bound on Minimal ALP Dark Matter

   Yuma Narita🇯🇵 · Wen Yin🇯🇵

   The axion-like particle (ALP), a pseudo Nambu-Goldstone boson that couples to two photons, has been studied extensively in recent years as a dark matter candidate. For initial field configurations in a minimal ALP model explaining the observed dark matter abundance, we need the potential height to exceed the ALP energy density at redshift $z\approx 5.5\times 10^6$ leading to: $$f_{\varphi }\gtrsim 4\times 10^{13}GeV\left(\frac{10^{-18}eV}{m_{\varphi }}\right),$$ where $m_{\varphi }$ and $f_{\varphi }$ denote the ALP mass and decay constant, respectively. This bound is known for the ALP dark matter dominated by the homogeneous zero-momentum mode, under the requirement that coherent oscillations begin early enough to satisfy the late-forming dark matter constraint. One loop hole to evade this limit may be to introduce a large amount of the non-relativistic modes of the ALP with non-vanishing momenta. Here we show that the same limit remains valid even if nonzero-momentum modes dominate. Interestingly, when $nonrelativistic$ gradient modes prevail, the ALP behaves $relativistic$ radiation rather than matter, if it violates the limit. Moreover, if the typical momentum is sufficiently small, Baumkuchen-like domain walls form, which play an important role in understanding the transition.

   hep-phJHEP(2026)·7 citations
3. 03*

   Improving sensitivity of vectorlike top partner searches with jet substructure

   Anupam Ghosh🇮🇳 · Soumyadip Ghosh🇮🇳 · Soureek Mitra🇮🇳 · Tousik Samui🇮🇳 · Ritesh K. Singh🇮🇳

   Vectorlike quark partners appear in many BSM models and remain an important area of research, as they can offer insights into the electroweak symmetry breaking mechanism. In this work, we have focused on studying the production of a heavy vectorlike top partner in association with a SM top quark via chromomagnetic coupling and the four decay modes of the top partner, namely, $bW$, $tZ$, $th$, and $tg$. The signal has been studied in final states with one fat jet, at least one $b$-tagged jet, one lepton, and missing energy. This study focuses on the extensive use of jet substructure techniques in jets clustered with fixed and dynamically varying radius to deal with events containing differently sized jets. Important kinematic information, along with jet substructure and event shape observables, has been used in a multivariate analysis to extract signal with high significance. A comparative study between fixed and dynamically varying radius clustering of jets is also presented, leading to an improvement in signal sensitivity in the highly boosted scenario.

   hep-phhep-exPRD(2026)·2 citations
4. 04*

   Constraining the CP4-invariant three-Higgs-doublet model via top quark decays

   Duanyang Zhao🇨🇳 · Igor P. Ivanov🇨🇳

   CP4 3HDM is a peculiar three-Higgs-doublet model in which a single symmetry leads to tight constraints on the scalar and Yukawa sectors. In this models, tree-level flavor-changing neutral couplings are unavoidable; however, as previously shown, their contributions to neutral meson oscillations can be suppressed. Here, we explore the remaining quark flavor violating effects, which give rise to the top quark decays to light scalars, including the 125 GeV Higgs boson $h_{SM}$, as well as the magnitude of the $h_{SM}t\bar{t}$ coupling. Utilizing the recently developed scanning procedure, in which observables are used as input, we narrow down the viable options to a unique CP4-invariant Yukawa sector capable of satisfying all meson oscillation and top quark constraints. We present benchmark models that feature neutral or charged Higgs bosons lighter than the top quark, and we look forward to testing them further at the LHC and through flavor physics observables.

   hep-phPRD(2025)·1 citation
5. 05*

   $M1$ Radiative Transition of Light Mesons in the Light-Front Quark Model

   Muhammad Ridwan🇮🇩 · Ahmad Jafar Arifi🇯🇵 · Terry Mart🇮🇩

   We investigate the $M1$ radiative transitions between light vector $\mathcal{V}$ and pseudoscalar $\mathcal{P}$ mesons in the 1S and 2S states in the light-front quark model. To this end, we use the light-front wave functions (LFWFs) obtained from the QCD-motivated effective Hamiltonian that includes smeared spin-spin interactions, where a few harmonic oscillator basis functions were employed as trial wave functions. The results, including their couplings and widths, obtained from LFWFs with different trial wave functions are compared with the available experimental data and other theoretical predictions.

   hep-phnucl-th0 citations
6. 06*

   Constraining the axiverse with reionization

   Ziwen Yin🇨🇳 · Hanyu Cheng🇨🇳 · Eleonora Di Valentino🇬🇧 · Naomi Gendler🇺🇸 · David J. E. Marsh🇬🇧 · Luca Visinelli🇮🇹

   Axions that couple to electromagnetism are produced in the early Universe by, among other channels, freeze-in via the Primakoff process. For sufficiently large axion masses, the same coupling causes the axions to decay into two photons, which subsequently ionize the intergalactic medium. If this decay occurs in the redshift range $20\lesssim z\lesssim 1100$, then the contribution to the cosmic microwave background optical depth ${\tau }_{\mathrm{reio}}$ can lead to a conflict with observations, excluding models with sufficiently strongly coupled, heavy axions and high reheating temperatures, $T_{\mathrm{reh}}$. Using large ensembles of explicit type IIB string theory models with up to $h^{1,1}=100$ axions, we compute the full cosmic reionization history caused by the decays of multiple axions. We compare this to the posterior on the high-$z$ component of ${\tau }_{\mathrm{reio}}$ derived from parametric-independent constraints on the ionization state of the Universe, obtained in a full \textit{Planck} analysis presented in a companion paper. For $h^{1,1}=20,50,100$, we find that approximately 15\%, 15\%, and 10\% of the models in the ensemble prefer $T_{\mathrm{reh}}\lesssim 10^{10}\text{GeV}$ at 95\% CL. We provide a publicly available code at:~\href{https://github.com/ZiwenYin/Reionization-with-multi-axions-decay}{github.com/ZiwenYin/Reionization-with-multi-axions-decay}, which computes the reionization history for arbitrary ensembles of decaying axions. Our analysis opens the door for future large-scale work studying the preference for low-temperature reheating in models with multiple axions.

   hep-phastro-ph.CO17 citations
7. 07*

   Challenging ${\bar{B}}_{(s)}\to D_{(s)}^{(\ast )}$ Form Factors with the Heavy Quark Expansion

   Marzia Bordone🇨🇭 · Nico Gubernari🇬🇧 · Martin Jung🇮🇹 · Danny van Dyk🇬🇧

   Recent publications by three lattice QCD collaborations have provided an unprecedented wealth of theoretical predictions for the ${\bar{B}}_q\to D_q^{(\ast )}$ form factors, for spectator flavours $q=u/d$ and $q=s$. We analyse these predictions within the framework of the heavy-quark expansion (HQE) to order ${\alpha }_s$, $1/m_b$, and $1/m_c^2$. For the first time, our analysis imposes unitarity bounds for all of the ${\bar{B}}_q^{(\ast )}\to D_q^{(\ast )}$ form factors; this includes newly identified tensor form factors arising in ${\bar{B}}_q^{\ast }\to D_q^{(\ast )}$. This enables us to treat all form factors in the same fashion. At the level of our present analysis, the inclusion of the tensor bounds is not yet constraining the HQE parameter space. We find the lattice QCD results to be well compatible with each other in a joint HQE fit as well as with QCD sum rule estimates that were used in previous HQE analyses. This is in contrast to the strong variability of the posterior predictions, in particular of the form factors ratios $R_0$ and $R_2$. Using the posterior distributions of our HQE analysis, we provide predictions for angular observables and LFU ratios in the ${\bar{B}}_q\to D_q^{(\ast )}{\ell }^{-}\bar{\nu }$ decays.

   hep-phhep-latJHEP(2025)·11 citations
8. 08*

   Rotational susceptibility of a hot and dense hadronic matter

   Bhagyarathi Sahoo🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇲🇽 · Raghunath Sahoo🇮🇳

   We study the effect of global rotation on rotational susceptibilities (${\chi }_{\omega }^{(1)}$, ${\chi }_{\omega }^2$, etc.), which quantify how much the system responds to small angular velocities, in a hadron resonance gas produced by ultra-relativistic heavy ion collisions. The higher-order rotational susceptibilities and their ratios are estimated in the presence and absence of baryon chemical potential (${\mu }_{\mathrm{B}}$) in the system. The effect of particle spin ($s$) and system size ($R$) on the first- and second-order rotational susceptibility is explored. To consider a more realistic scenario, the effect of interactions between hadrons is taken into account by considering van der Waals-like interactions, which include both attractive and repulsive interactions. To validate our results, a comparison with the ideal HRG as a baseline and a 3-flavour NJL model is shown. A nuclear liquid-gas phase transition, which is the characteristic feature of the van der Waals hadron resonance gas model, absent in an ideal hadron gas model, is probed via global rotation.

   hep-phhep-exhep-thnucl-ex+1EPJA(2026)·2 citations
9. 09*

   Postsphaleron darkogenesis

   Sudhakantha Girmohanta🇨🇳 · Yuichiro Nakai🇨🇳 · Zhihao Zhang🇨🇳

   A supercooled phase transition in a nearly conformal dark sector can provide a natural setting for darkogenesis via its out-of-equilibrium dynamics, where a particle-antiparticle number asymmetry in the dark sector can be reprocessed into the visible sector, yielding the observed baryon asymmetry and an asymmetric dark matter. We consider a scenario where the number asymmetry is generated from the decay of a mother particle produced via parametric resonance during the phase transition induced due to its coupling to the dilaton associated with spontaneous breaking of scale invariance. It is shown that the correct baryon asymmetry and dark matter abundance can be realized for a dark phase transition at $\mathcal{O}(1)\mathrm{GeV}$, which can also explain the nano-Hz gravitational wave signal reported by pulsar timing array experiments. The scenario will be tested further in neutron-antineutron oscillation experiments.

   hep-phastro-ph.COhep-exhep-thPRD(2025)·5 citations
10. 10*

    Dark bubble cosmology and the equivalence principle

    Ivano Basile🇩🇪 · Alessandro Borys🇮🇹 · Joaquin Masias🇩🇪

    The main goal of string phenomenology is to find realistic models of particle physics and cosmology within string theory. Dark bubble cosmology is an alternative to string compactifications, where our universe lives on a bubble expanding in a higher-dimensional spacetime. This construction is inherently non-supersymmetric and can yield a four-dimensional realistic cosmology, where radiation behaves as expected due to its coupling to higher-dimensional fields. We study the coupling of the electroweak and strong sectors to the induced braneworld gravity via the same mechanism. While the electroweak sector is unaffected, the gravitational and inertial masses of the proton differ significantly, severely violating measurements of the equivalence principle.

    hep-phhep-thPRD(2026)·5 citations
11. 11*

    Generalised Non-Linear Electrodynamics: classical picture and effective mass generation

    Abedennour Dib🇫🇷 · José A. Helayël-Neto🇧🇷 · Alessandro D.A.M. Spallicci🇫🇷

    Starting from a generic Lagrangian, we discuss the number of propagating degrees of freedom in the framework of generalised non-linear electrodynamics when a photon-background split is applied. We start by stating results obtained in a previous paper, before modifying the action to an equivalent form. Within this new formulation, we highlight the presence of an effective mass and consider the mechanical reduction of the model to ensure the positivity of said mass. We then study the constraint algebra of the model and show that we shift from a model with two first-class to two second-class constraints, which implies the propagation of an additional degree of freedom. We also show that the Hamiltonian is bound from below and thus does not suffer from Ostrogradski-type instabilities. We conclude by deriving the propagator for the model, and discussing the potential link between the nature of this additional polarisation and the mechanism behind the effective mass generation in this class of models.

    hep-phEPJC(2026)·1 citation
12. 12*

    Evolving Dark Sector and the Dark Dimension Scenario

    Alek Bedroya🇺🇸 · Georges Obied🇬🇧 · Cumrun Vafa🇺🇸 · David H. Wu🇺🇸

    String theory naturally leads to the expectation that dark energy is not stable, and may be evolving as captured by the Swampland de Sitter conjectures. Moreover, motivated by the distance conjecture, a unification of dark sector has been proposed, where the smallness of dark energy leads to one extra dimension of micron size with dark matter being the Kaluza--Klein graviton excitations in this extra dimension. We consider the natural possibility that the radius of the dark dimension varies as the energy decreases, leading to the variation of the dark matter mass. This correlates the variation of the dark energy with the variation of the dark matter mass as they depend on the variations of a scalar field $\varphi$ controlling the radius of the extra dimension. A simple realization of this idea for small range of $\varphi$ is adequately captured by choosing a potential which is locally of the form $V=V_0\exp (-c\varphi )$ and dark matter mass $m_{\mathrm{DM}}=m_0\exp (-c^{\prime }\varphi )$ as was proposed in Agrawal et al. (2019). We find excellent agreement with recent experimental data from DESI DR2 combined with SN measurements (from DES, Union3 or Pantheon+) and reproduces the same significance as CPL parametrization with the added benefit of providing a natural explanation for the apparent phantom behavior ($w<-1$) reported by DESI and DES based on a physical model. DESI and SN datasets independently favor non-zero values of $c^{\prime }$ and $c$, respectively, both lying within the expected $\mathcal{O}(1)$ range suggested by the Swampland criteria. Moreover, our best fit value $c^{\prime }\simeq 0.05\pm 0.01$ is remarkably consistent with the experimental upper bound of $c^{\prime }\lesssim 0.2$ demanded by the lack of detection of fifth force in the dark sector.

    ↳ astro-ph.COgr-qchep-phhep-th66 citations
13. 13*

    An Open System Approach to Gravity

    Santiago Agüí Salcedo🇬🇧 · Thomas Colas🇬🇧 · Lennard Dufner🇬🇧 · Enrico Pajer🇬🇧

    Several major open problems in cosmology, including the nature of inflation, dark matter, and dark energy, share a common structure: they involve spacetime-filling media with unknown microphysics, and can be probed so far only through their gravitational effects. This observation motivates a systematic open-system approach to cosmology, in which gravity evolves in the presence of a generic, unobservable environment. In this work, we develop a general framework for open gravitational dynamics based on general relativity and the Schwinger-Keldysh formalism, carefully addressing the nontrivial constraints imposed by diffeomorphism invariance. At the quantum level, our path integral formulation computes the gravitational density matrix in perturbation theory around a semi-classical spacetime. As illustrative applications, we study inflation and the propagation of gravitational waves in classical regimes where environmental interactions are non-negligible. In the inflationary context, our framework reproduces the known Open Effective Field Theory of Inflation in the decoupling limit and extends it to include gravitational interactions. For gravitational waves, we derive the most general conservative and dissipative corrections to propagation. Remarkably, we find that the leading-order gravitational birefringence is dissipative in nature, whereas conservative birefringence appears only at higher derivative order, opposite to the electromagnetic case. Our results pave the way to modeling dissipative effects in the late universe.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2026)·35 citations
14. 14*

    Deep Learning and Model Independence

    Martin King🇩🇪

    The lack of evidence in favor of any new physics models means that the search for new physics beyond the Standard Model (BSM) is wide open, with no direction clearly more promising than any other. This marks a turn towards what can be called `model-independent' methods-strategies that reduce the influence of modelling assumptions by performing minimally-biased precision measurements, using effective field theories, or using Deep Learning methods (DL). In this paper, I present the novel and promising uses of DL as a primary tool in high energy physics research, highlighting the use of autoencoder networks and unsupervised learning methods. I advocate for the importance and usefulness of the concept of model independence and propose a definition that recognizes that independence of models is not absolute, but comes in degrees.

    ↳ physics.hist-phhep-ph0 citations
15. 15*

    Entanglement features in scattering mediated by heavy particles

    Chon Man Sou🇨🇳 · Yi Wang🇨🇳 · Xingkai Zhang🇨🇳

    The amount of information propagated by an intermediate heavy particle exhibits characteristic features in inelastic scatterings with $n\ge 3$ final particles. As the total energy increases, the entanglement entropy, between its decay products and other final particles, exhibits a universal sharp dip, suppressed by its small decay rate. This indicates an entanglement suppression from a low-energy effective theory to a channel dominated by an on-shell heavy particle. As demonstrations of these entanglement features, we study concrete models of $2\to 3$ and $2\to 4$ scatterings, which shed light on the entanglement structure beyond the area law derived for $2\to 2$ scattering. In practice, these features may be probed by suitably marginalizing the phase-space distribution of final particles.

    ↳ hep-thhep-phquant-phJHEP(2025)·12 citations
16. 16*

    Experiment and the Pursuit of Ugly Models

    Martin King🇩🇪

    Scientists do not merely choose to accept fully formed theories, they also have to decide which models to work on before they are fully developed and tested. Since decisive empirical evidence in favour of a model will not yet have been gathered, other criteria must play determining roles. I examine the case of modern high-energy physics where the experimental context that once favoured the pursuit of beautiful, simple, and general theories now favours the pursuit of models that are ad hoc, narrow in scope, and complex; in short, ugly models. The lack of new discoveries since the Higgs boson, together with the lack of a new higher energy collider, has left searches for new physics conceptually and empirically wide open. Physicists must make use of the experiment at hand while also creatively exploring alternatives that have not yet been explored. This encourages the pursuit of models that have at least one of two key features: i) they take radically novel approaches, or ii) are easily testable. I present four cases, neutralino dark matter, the relaxion, repulsive gravity, and models of lepton flavour universality violation, and show that even if they do not exhibit traditional epistemic virtues, they are nonetheless pursuitworthy. I argue that experimental context strongly determines pursuitworthiness and I lay out the conditions under which experiment encourages the pursuit of ugly models.

    ↳ physics.hist-phhep-phEur.J.Phil.Sci.(2025)·1 citation
17. 17*

    Do Anomalies Break Momentum Routing Invariance?

    A. R. Vieira🇧🇷

    The diagrammatic computation of the chiral anomaly is associated with momentum-routing invariance breaking. This happens because the momentum routing in the internal lines of a loop diagram is chosen such that the gauge Ward identities hold and the chiral Ward identity is broken by the finite term measured in the pion decay into two photons. Since the latter is observable, it seems that there is a preferred momentum routing set by experiments. However, it is shown in this work that the chiral anomaly is momentum-routing invariant. This idea is specially important for situations in which there are no experiments yet to decide on the momentum routing, like in supersymmetric theories and in frameworks with CPT and Lorentz violation. Therefore, we resort to momentum-routing invariance to find out what symmetry is broken in a nonminimal CPT- and Lorentz-violating version of quantum electrodynamics.

    ↳ hep-thhep-ph0 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.