We point out that a non-invertible selection rule can control the flavor violation inherent in lepton portal dark matter, a weakly interacting massive particle candidate that can evade severe constraints from direct detection experiments. We show that ordinary invertible symmetries cannot suppress flavor-violating portal couplings while accommodating the large mixing angles in the PMNS matrix. We then present a simple construction based on the $\textit{ℤ}$ gauging of a $\textit{ℤ}$ symmetry, which realizes one-flavor dominance of the portal couplings consistently with the PMNS mixing matrix. We also discuss possible flavor leakage in a type-I seesaw completion and study experimental probes of the model through lepton observables, especially lepton flavor non-universality in $\textit{Z}$ boson decays.

Japan

Junichiro Kawamura

Taming lepton portal dark matter by a non-invertible selection rule

We construct matrices that shift the scaling dimension of scalar fields for arbitrary de Sitter Feynman diagrams. Acting on a set of master integrals, these weight-shifting matrices shift the scaling dimensions of individual edges of a given diagram by an integer. They can thus be applied to a broader range of problems and are simpler to implement than earlier derivative-based approaches. By introducing a Kronecker product representation of our matrix formulation, we generalise weight-shifting operators beyond four-point functions to arbitrary tree-level diagrams. As an application, we obtain explicit expressions for several massless wavefunction coefficients in four-dimensional de Sitter space, starting from conformally coupled seed functions. Our construction provides a systematic and graph-local approach to generating cosmologically relevant correlators from simpler master integrals.

Germany

Claire Korte

Taiwan

Harry Goodhew

Netherlands

Kamran Vaziri

Nicolas Weiss

Cosmological weight-shifting matrices

The dark photon is a new gauge boson that naturally arises in many beyond-the-Standard-Model scenarios and couples to the electromagnetic current through kinetic mixing. Owing to this feature, it is often considered a portal between the dark and visible sectors and has therefore become the target of numerous experimental searches worldwide. In this work, we propose a search for dark photons based on inverse Compton scattering, $\textit{γe}$ → $\textit{A}$ $\textit{e}$ , to be conducted at electron accelerators. In this setup, photons from a laser source impinge on an accelerated electron beam, producing a dark photon in the final state. We investigate two complementary search strategies based on the resulting missing-energy signature: a single-photon-veto approach and a measurement of the recoil-electron energy spectrum, with angular information considered as an extension of the latter. We derive the projected sensitivity assuming an incident photon energy of about 1 eV and an electron beam energy of 3 GeV. We show that this experimental setup could cover an unexplored region of parameter space and constitute a promising probe of dark sectors in the future.

Brazil

Norway

L. Angel

United Kingdom

G. Casse

Peru

G. Gambini

A. Jesus

Bulgaria

Italy

V. Kozhuharov

A. Machado

Chile

F. Queiroz

E. Segreto

J. Shergold

J. Smirnov

Search for light dark sectors using electron-photon collisions

The $\textit{A}$ flavor symmetry has provided tremendous insight into the flavor structure of the lepton sector of the Standard Model, predicting a very good approximation to neutrino mixing angles called tri-bimaximal mixing (TBM). $\textit{A}$ is spontaneously broken by a scalar called the flavon, and when this happens a number of degenerate vacua can form, resulting in so-called domain walls. These objects are not observed and hence need to be annihilated. This is usually done by explicitly breaking $\textit{A}$ by adding a bias term to the scalar potential. In this paper, we construct a new model invariant under $\textit{A}$ × ℤ which creates cosmologically viable domain walls, lifts the degeneracy of the vacuum giving a natural mechanism for domain walls to annihilate, as well as predicts realistic neutrino mixing angles; all utilizing cross couplings between flavons. The annihilation of the domain walls, with proper choice of wall tension and the consequent bias term, leads to a gravitational wave signal that is potentially detectable in near future gravitational wave experiments, and interestingly intersects with the observed Pulsar Timing Array signal.

United States

Mu-Chun Chen

Harold Matias

Cameron Moffett-Smith

Gravitational waves in an $\textit{A}$ 4 neutrino mass model

We present a novel approach for solving canonical differential equations for Feynman integrals based on an approximation of the integrals with Chebyshev polynomials. By exploiting the analyticity properties of Feynman integrals, the method constructs rapidly converging polynomial approximations along a path, enabling highly efficient numerical evaluation. Moreover, we introduce an adaptive approximation method that dynamically samples to optimise convergence. We implement this framework in double-precision arithmetic and demonstrate its stability across physical phase space using a series of two-loop, five-point examples. Our proof-of-principle implementation proves competitive with state-of-the-art one-fold integral methods, while requiring little to no case-by-case intervention to handle spurious singularities.

Switzerland

Samuel Abreu

Portugal

Afonso Guerreiro

Belgium

Ben Page

Chebyshev approximations of Feynman integrals for collider physics

We present a background-independent renormalization framework for one-loop primordial spectra. We apply it to two observables: the scalar-induced tensor spectrum sourced by a minimally coupled spectator field, and the scalar spectrum generated by potential self-interactions. In both cases, the UV part of the loops is isolated and, using the universal WKB behavior of the internal modes, the UV poles are extracted analytically and absorbed into local counterterms without having to specify either the background evolution or the full dynamics of the field running in the loop. This yields finite model-independent expressions for the renormalized spectra amenable to numerical analysis.

Spain

Guillermo Ballesteros

Jesús Egea

Flavio Riccardi

Background-independent one-loop renormalization of tensor and scalar primordial spectra

We propose a new large $\textit{N}$ limit for the thermofield double state which at the extreme ($\textit{N}$ = ∞) limit is dual in the bulk to a back-reacted traversable wormhole, by making use of an operator in the algebra at infinity, an algebra familiar in the literature from the study of quasi-local algebras. We also compute, from a purely algebraic perspective, the effects registered by a left universe observer due to a unitary fluctuation on the right universe of the traversable wormhole, and reproduce a result from an earlier computation by Maldacena, Stanford and Yang [1].

Israel

Eyoab Bahiru

Algebraic traversable wormholes

We describe the Poisson bracket of a Lagrangian field theory expressed in the framework of $\textit{L}$ algebras. If the symplectic structure on phase space is defined following recent work, we show that the Poisson bracket can be computed with the Peierls formula, confirming the well-known result of the covariant phase space formalism. Of particular interest is the Poisson bracket in nonlocal theories. In $\textit{p}$-adic string theory we find that a straightforward construction of the Poisson bracket is obstructed by higher derivative instabilities. We also discuss the inverse relation between the Poisson bracket and symplectic structure in the language of homological algebra, extending some ideas in the mathematical physics literature.

Czechia

Vinícius Bernardes

Theodore Erler

Atakan Fırat

Igor Khavkine

Poisson bracket and $\textit{L}$ $\textit{∞}$ algebras

Using a sequence of effective field theories (EFTs), we calculate the rate for the leptonic decay $$ {B}^{-}\to {\tau}^{-}{\overline{\nu}}_{\tau}\left(\gamma \right) $$ including real and virtual QED corrections, with a cut $\textit{E}$ ≪ Λ imposed on electromagnetic radiation in the $\textit{B}$-meson rest frame. We establish a factorization theorem for the rate and evaluate it at 𝒪($\textit{α}$), resumming the leading logarithmic corrections to all orders in perturbation theory. The large mass $\textit{m}$ allows us to treat the tau lepton as a heavy fermion below $\textit{μ}$ ~ $\textit{m}$ ~ $\textit{m}$ , leading to an EFT construction that is structurally different and noticeably simpler than that for the muon case [1]. In particular, hadron-structure dependent QED corrections can be described in terms of QED-induced $\textit{B}$ → $\textit{τ}$ form factors, which should be calculable on the lattice. Our analysis includes the leading Λ $\textit{/m}$ corrections as well as the leading corrections in $\textit{E}$ $\textit{/}$Λ . We show that contributions of the form Λ $$ {m}_B/{m}_{\tau}^2 $$ , which are naively sizable, cancel among each other. Contrary to the muon channel, structure-dependent corrections involving $\textit{BB}$ $\textit{γ}$ transitions are numerically negligible for the tau case. The remaining logarithmic dependence on $\textit{E}$ is mild. We estimate that the present uncertainty in the calculation of the structure-dependent QED corrections is about 0.5% of the rate. As a byproduct, we present a state-of-the-art prediction for the lepton flavor universality ratio of the tau and muon channels.

Claudia Cornella

Max Ferré

Matthias König

Matthias Neubert

QED Corrections to $$ {B}^{-}\to {\tau}^{-}{\overline{\nu}}_{\tau } $$

A systematic study of chiral effects is presented using an Effective Field Theory framework. By integrating out a massive Dirac fermion at finite temperature in presence of vector and axial background fields, the currents and their anomalies are computed from the path-integral. Chiral effects previously considered separately naturally arise in a unified computation, including new mass corrections. The link between each anomalous transport effect and the anomalies is clearly established, beyond the identification of their coefficients. In particular, we can appreciate how these effects are sourced by the anomalous nature of the theory even in configurations where the anomaly itself vanishes. The consistent and covariant anomalies are both encapsulated in master formulae for the currents which result from a careful treatment of the regularisation. It is finally found that, at finite temperature, the physical currents cannot be inferred simply from the Chern-Simons terms whose divergence reproduce the chiral anomalies.