We explain the ATOMKI anomaly with a very light $\textit{Z}$′ state that features non-anomalous and non-flavour-universal vector and axial-vector couplings to all leptons. This $\textit{Z}$′ comes from a theoretical framework with a spontaneously broken U(1)′ symmetry in addition to the Standard Model gauge group and is compliant with current measurements of the anomalous magnetic moments of the electron and the muon as well as beam dump experiments. The lepton flavour structure of this model allows for $\textit{Z}$′ couplings to all light neutrinos, suggesting the possibility of $\textit{Z}$′-mediated Non-Standard Interactions (NSIs) of neutrinos in matter, so that measurements of the strength parameters of the NSIs can constrain the value of the couplings. We use experimental constraints on NSIs of neutrinos using older TEXONO data and newer IceCube data. The IceCube data, in particular, strongly constrain the flavour universality of the leptonic vector current. The constraints enable us to define the region of parameter space of this theoretical scenario that can be pursued in further phenomenological analyses.

Sweden

Rikard Enberg

United Kingdom

Türkiye

Yaşar Hiçyılmaz

Stefano Moretti

Carlos Heros

Harri Waltari

Constraints on the $\textit{X}$17 boson from IceCube searches for non-standard interactions of neutrinos

We propose a general conjecture for evaluating the multiple-discontinuity integrals that appear in real-time holography using gravitational Schwinger-Keldysh (grSK) geometry. Our conjecture is valid for arbitrary non-derivative interactions with any number of bulk tree-level exchanges. It is also consistent with a unitary exterior EFT at finite temperature with correct causal structure. We present a set of Feynman rules underlying this exterior EFT and illustrate it with the computation of four and five-point functions.

India

R. Loganayagam

Godwin Martin

An exterior EFT for Hawking radiation

Complexity is a fundamental characteristic of states within a quantum system. Its use is however mostly limited to bosonic systems, inhibiting its present applicability to supersymmetric theories. This is also relevant to its application to the AdS/CFT correspondence. To address this limitation, we extend the framework of spread complexity beyond bosonic systems to include fermionic and supercoherent states. This offers a gateway to compute spread complexity analytically for any semiclassical system governed by a Hamiltonian associated with a Lie (super)algebra. This requires extending the Krylov chain to a $\textit{Krylov path}$ in a higher-dimensional lattice. A detailed analysis of supercoherent states within the super Heisenberg-Weyl and OSp(2|1) algebras elucidates distinct contributions from bosonic and fermionic degrees of freedom to the complexity. This generalisation allows us to access the semiclassical regime of the planar limit of the holographic correspondence. We then compute the spread complexity of large charge superstring states on the gravity side, which are equivalent to the dual gauge states. The resulting complexity leads to Krylov paths capturing the geometry in which the string propagates.

Germany

Rathindra Das

Israel

Saskia Demulder

Johanna Erdmenger

Czechia

Christian Northe

Spread complexity for the planar limit of holography

In this paper, we construct the path integral for infinite and semi-infinite scalar worldlines. We show that, at the asymptotic endpoints, on-shell physical states can be generated by inserting vertex operators at infinity. This procedure implements automatically the LSZ reduction, thus leading to a direct worldline representation of scattering amplitudes. To obtain it, we introduce generalized vertex operators, to be viewed as the gluing of entire tree subdiagrams to a given worldline. We demonstrate that the subdiagrams themselves are given, via a recursive relation, by correlation functions on the semi-infinite line. In this sense, the approach we take is fully first-quantized, in that it does not need any field theoretic quantity as input. We envisage that, when suitably extended to gauge theories, it could provide useful insights in addressing current research issues, such as color-kinematics duality.

Roberto Bonezzi

Maria Kallimani

Worldline geometries for scattering amplitudes

Hadronization models used in event generators are physics-inspired functions with many tunable parameters. Since we do not understand hadronization from first principles, there have been multiple proposals to improve the accuracy of hadronization models by utilizing more flexible parametrizations based on neural networks. These recent proposals have focused on the kinematic properties of hadrons, but a full model must also include particle flavor. In this paper, we show how to build a deep learning-based hadronization model that includes both kinematic (continuous) and flavor (discrete) degrees of freedom. Our approach is based on generative adversarial networks and we show the performance within the context of the cluster hadronization model within the herwig event generator.

United States

Jay Chan

Xiangyang Ju

Poland

Adam Kania

Benjamin Nachman

Vishnu Sangli

Andrzej Siodmok

Integrating particle flavor into deep learning models for hadronization

In quantum mechanics, the measurable quantities of a given theory are predicted by performing a weighted sum over possibilities. We show how to arrange the possibilities into bundles such that the associated subsums can be viewed as well-defined theories on their own right. These bundles are submanifolds of possibilities which we call possifolds. We collect and prove some basic facts about possifolds. Especially, we show that possifolds are ensembles of what in a certain broadly defined sense that we explain can be regarded as soliton excitations (soliton-possifold correspondence). We provide an outlook on some applications. Among other things, we illustrate the use of the developed framework for the example of the Lieb-Liniger model. It describes nonrelativistic bosons with an attractive interaction. We derive a dual theory describing the lowest-lying energy excitation modes. While the standard Bogoliubov-approximation breaks down at the critical point, our derived summation prescription stays regular. In the Bogoliubov-limit we observe the summation to possess an enhanced symmetry at this point while the summation cannot be ignored there. We finally provide a glimpse on the restrictions black hole physics implies in this context for the gravitational path integral.

Artem Averin

Framework for the quantum mechanical sum of possibilities and meaning for field theory and gravity

In the absence of impurities and boundary effects, first order phase transitions are initiated by the nucleation of critical bubbles. In thermally driven transitions many systems can remain metastable for an extended time, possibly tens of orders of magnitude longer than typical microscopic timescales. In standard Markov chain Monte Carlo simulations of these systems the probability of critical bubbles can be too suppressed for the transition to happen in any practical simulation time. The computation can be accelerated by using modified sampling methods, for example multicanonical or Wang-Landau sampling. However, even using these methods, there remains a condensation barrier which dramatically reduces the efficiency at large volumes. We present a novel sampling method, the method of expanded ensembles, which very effectively circumvents the condensation barrier and enables efficient simulations at large volumes.

Finland

Jaakko Hällfors

Kari Rummukainen

Expanded ensemble method for bubble nucleation

Mirror matter from the dark hidden sector with the same particle content and gauge interactions as in the standard model is still an interesting candidate for dark matter. Several experiments on the search for positronium and neutron oscillations into their mirror partner have been conducted recently. In this work, we consider the transitions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>K</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>−</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mi>m</mi></mrow><mrow><mn>0</mn></mrow></msubsup></mrow></math> of a neutral kaon into a hidden mirror kaon. It is shown that their probability can be probed with the sensitivity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>P</mi><mo stretchy="false">(</mo><msup><mrow><mi>K</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>−</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mi>m</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo stretchy="false">)</mo><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>7</mn></mrow></msup></mrow></math> from the search for missing-energy events in the NA64 experiment at the CERN SPS with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><msup><mn>10</mn><mn>11</mn></msup></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>+</mo></msup></math> on target. This would result in a limit on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mn>0</mn></msup><mo>−</mo><msubsup><mi>K</mi><mi>m</mi><mn>0</mn></msubsup></math> mixing parameter much stronger than the similar bound estimated from the cosmological considerations.

Russia

Chile

JINR

S.N. Gninenko

N.V. Krasnikov

Search for a mirror hidden sector with neutral kaons at NA64

Distillation is a quark-smearing method for the construction of a broad class of hadron operators useful in lattice QCD computations and defined via a projection operator into a vector space of smooth gauge-covariant fields. A new orthonormal basis for this space is constructed which builds in locality. This basis is useful for the construction of stochastic methods to estimate the correlation functions computed in Monte Carlo calculations relevant for hadronic physics.

Spain

Nicolas Lang

Robert G. Edwards

Ireland

Michael J. Peardon

Optimizing stochastic algorithms for hadron correlation function computations in lattice QCD using a localized distillation basis

A key search mode for axionlike particles (ALPs) that couple to charm quarks is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>a</mi></math>. Here we calculate the form factor that allows the rate of this process to be determined using lattice QCD for the first time. Our calculations use the relativistic highly improved staggered quark (HISQ) action for the valence charm quarks on gluon field configurations generated by the MILC collaboration that include <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>u</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>s</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi></math> HISQ quarks in the sea at four values of the lattice spacing and both unphysical and physical sea quark masses. We determine the form factor as a function of ALP mass with an uncertainty of less than 2% across our full range of ALP masses from zero up to 95% of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> mass. This represents a substantial improvement in accuracy of the theoretical picture of this decay compared to the previously used tree-level and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msub><mi>α</mi><mi>s</mi></msub><mo stretchy="false">)</mo></math> perturbation theory. We use our form factor to determine constraints on ALP masses and couplings to charm quarks and photons in several different scenarios using recent experimental data from BESIII. Our calculation paves the way for further lattice QCD input on new physics constraints from radiative decays.

Brian Colquhoun

Christine T.H. Davies

G. Peter Lepage

Sophie Renner

Constraints on axionlike particles using lattice QCD calculations of the rate for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>a</mi></math>