We rely on Monte Carlo (MC) simulations to interpret searches for new physics at the Large Hadron Collider (LHC) and elsewhere. These simulations result in noisy and approximate estimators of selection efficiencies and likelihoods. In this context we pioneer an exact-approximate computational method—exact-approximate Markov chain Monte Carlo (MCMC), also known as pseudomarginal MCMC—that returns exact inferences despite noisy simulations. To do so, we introduce an unbiased estimator for a Poisson likelihood. We demonstrate the new estimator and new techniques in examples based on a search for neutralinos and charginos at the LHC using a simplified model. We find attractive performance characteristics—exact inferences are obtained for a similar computational cost to approximate ones from existing methods and inferences are robust with respect to the number of events generated per point. The unbiased estimator uses a Poisson-distributed number of MC events; it is also possible to construct a biased estimator whose bias decays factorially with increasing number of MC events.

Christopher Chang

Benjamin Farmer

Andrew Fowlie

Anders Kvellestad

Exact inference from noisy simulations in collider physics

We examine the sensitivity of the beam normal spin asymmetry in Bhabha scattering to beyond the Standard Model mediators, in the context of the JLab polarized positron program. A key property of this observable is that the Standard Model contribution exhibits a zero crossing at a fixed scattering angle, providing a clean, effectively background-free point for these searches. We consider scalar, vector, and axial vector mediators and present projected bounds, finding that scalar and vector scenarios allow a significant extension of the search ranges beyond existing constraints.

Aleksandr Pustyntsev

Muthubharathi S. Ramasamy

Marc Vanderhaeghen

New physics searches via beam normal spin asymmetry in Bhabha scattering

We present possible strategies for anomaly detection of rare particle decays and exotic hadrons, such as pentaquarks, in low-background environments such as those characteristic of diffractive events and ultraperipheral pp, p-A, or A-A collisions at the CERN Large Hadron Collider (LHC). Our models are trained with toy samples representing the UPC processes measured until now by the ALICE Collaboration. When samples containing rare processes such as J/$\textit{ψ}$ → 4$\textit{π}$ and pentaquark production, where the number of injected pentaquark events is estimated based on current experimentally available upper limits, and those for J/$\textit{ψ}$ → 4$\textit{π}$ are estimated through the branching ratio of the decay channel, are analyzed, the rare processes are flagged as anomalous by the models. This approach demonstrates the applicability of such a technique for searches for new physics in the current and future data sets at collider experiments with high purity, while also allowing for the measurement of upper limits for the production of exotica.

United States

S. Ragoni

B. Kinkaid

J. Seger

C. Anson

D. Tlusty

AI-powered full-data set search for new physics in ultraperipheral and diffractive events

The IceCube Upgrade is an extension of the existing IceCube Neutrino Observatory and will be deployed in the 2025–2026 austral summer. It will significantly improve the sensitivity of the detector to atmospheric neutrino oscillations. The existing 86-string IceCube array contains a dense in-fill known as DeepCore which is optimized to measure neutrinos with energies down to a few GeV. The IceCube Upgrade will consist of seven new densely instrumented strings placed within the DeepCore volume to further enhance the performance in the GeV energy range. The additional strings will feature new optical modules, each containing multiple photomultiplier tubes (PMTs), in contrast to the existing modules that each contain a single PMT. This will more than triple the number of PMT channels with respect to the current IceCube configuration, allowing for improved detection efficiency and reconstruction performance at GeV energies. We describe necessary updates to simulation, event selection, and reconstruction to accommodate the higher data rates observed by the upgraded detector and the addition of multi-PMT modules. We determine the expected sensitivity of the IceCube Upgrade to the atmospheric neutrino oscillation parameters <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>θ</mi></mrow><mrow><mn>23</mn></mrow></msub></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msubsup><mi>m</mi><mn>32</mn><mn>2</mn></msubsup></math>, the appearance of tau neutrinos and the neutrino mass ordering. The IceCube Upgrade will provide neutrino oscillation measurements that are of similar precision to those from accelerator experiments, while providing complementarity by probing higher energies and longer baselines, and with different sources of systematic uncertainties.

R. Abbasi

M. Ackermann

J. Adams

S.K. Agarwalla

J.A. Aguilar

M. Ahlers

J.M. Alameddine

S. Ali

N.M. Amin

K. Andeen

C. Argüelles

Y. Ashida

S. Athanasiadou

S.N. Axani

R. Babu

X. Bai

J. Baines-Holmes

A. Balagopal V.

S.W. Barwick

S. Bash

V. Basu

R. Bay

J.J. Beatty

J. Becker Tjus

P. Behrens

J. Beise

C. Bellenghi

B. Benkel

S. BenZvi

D. Berley

E. Bernardini

D.Z. Besson

E. Blaufuss

L. Bloom

S. Blot

I. Bodo

F. Bontempo

J.Y. Book Motzkin

C. Boscolo Meneguolo

S. Böser

O. Botner

J. Böttcher

J. Braun

B. Brinson

Z. Brisson-Tsavoussis

R.T. Burley

D. Butterfield

M.A. Campana

K. Carloni

J. Carpio

S. Chattopadhyay

N. Chau

Z. Chen

D. Chirkin

S. Choi

B.A. Clark

A. Coleman

P. Coleman

G.H. Collin

D.A. Coloma Borja

A. Connolly

J.M. Conrad

R. Corley

D.F. Cowen

C. De Clercq

J.J. DeLaunay

D. Delgado

T. Delmeulle

S. Deng

P. Desiati

K.D. de Vries

G. de Wasseige

T. DeYoung

J.C. Díaz-Vélez

S. DiKerby

M. Dittmer

A. Domi

L. Draper

L. Dueser

D. Durnford

K. Dutta

M.A. DuVernois

T. Ehrhardt

L. Eidenschink

A. Eimer

P. Eller

E. Ellinger

D. Elsässer

R. Engel

H. Erpenbeck

W. Esmail

S. Eulig

J. Evans

P.A. Evenson

K.L. Fan

K. Fang

K. Farrag

A.R. Fazely

A. Fedynitch

N. Feigl

Physics potential of the IceCube Upgrade for atmospheric neutrino oscillations

We present a fully automated framework to compute production spin-density matrices for generic collider processes at tree level within M dG 5_ MC@NLO. The method assembles helicity amplitudes into event-by-event production matrices. These are written to the LHE file in a compact form, together with run metadata, enabling direct post-processing of quantum observables. The implementation supports bi- and multipartite qubit and qutrit final states, configurable reference frames, and both polarised and unpolarised initial states. A companion, easy-to-extend library provides analysis routines to determine key quantum-information measures and witnesses. These include purity, concurrence, and entanglement of formation for qubits; Peres-Horodecki tests and negativity; spin-polarisation vectors and correlation matrices; $\textit{D}$-coefficients; and stabiliser-based “magic” measures. As a result, multi-particle quantum correlations can be quantified systematically. We validate the implementation against known results for $$ t\overline{t} $$ and $\textit{VV}$ ($\textit{V}$ = $\textit{W}$ , $\textit{Z}$) production in $\textit{pp}$ and $\textit{e}$ $\textit{e}$ collisions and in heavy-resonance decays. We then consider new applications and study quantum correlations in several LHC final states: $$ t\overline{t}{W}^{\pm } $$ , $\textit{tW}$ vs. $$ t\left(\overline{t}\to {W}^{-}\overline{b}\right) $$ , and $$ t\overline{t}t $$ vs. $$ t\overline{t}t\overline{t} $$ .

Belgium

Valentin Durupt

Italy

Switzerland

Fabio Maltoni

Olivier Mattelaer

Automated computation of spin-density matrices and quantum observables for collider physics

We discuss physics-informed renormalization group flows (PIRGs) for general operators. We show that operator PIRGs provide comprehensive access to all correlation functions of the quantum field theory under investigation. The operator PIRGs can be seen as a completion of the PIRG approach, whose qualitative computational simplification and structural insights are now fully accessible for general applications. The potential of this setup is assessed within a simple analytic example of the zero-dimensional <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ϕ</mi><mn>4</mn></msup></math>-theory, for which the generating functions of the fundamental field are computed within a vertex expansion, using the one- to ten-point functions.

Friederike Ihssen

Jan M. Pawlowski

Physics-informed operator flows and observables

Germany

Stefano Noi

Ramona Gröber

Manoj Mandal

Erratum: Two-loop running effects in Higgs physics in Standard Model Effective Field Theory

Recently, a theoretical framework was set up in Miramontes et al. (Eur Phys J C 85:1055, 2025), which allows for the symmetry-preserving inclusion of full quark-gluon vertices in the description of the meson dynamics. In the present work, we develop a special truncation within this approach, which leads to a tractable set of functional equations that satisfy the fundamental chiral Ward-Takahashi identities. Specifically, in the chiral limit that we consider, this truncation allows us to simplify considerably the quark-gluon Schwinger–Dyson equation, without significant loss of quantitative accuracy. Importantly, this implies a substantial reduction of complexity of the renormalized Bethe–Salpeter equation: it is composed by a pair of one-loop diagrams that contain the full quark-gluon vertex, and a single two-loop diagram that is instrumental for the masslessness of the pion in the chiral limit. A detailed numerical analysis reveals that the incorporation of the aforementioned two-loop diagram is instrumental for the corresponding eigenvalue to reach unity. The key relation between the quark mass function and the pion wave function is shown to be satisfied to within the numerical precision of the loop integrals, which is at the level of about one percent or better. The field-theoretic ingredients required for the extension of this analysis beyond the chiral limit are briefly discussed.

China

M. Ferreira

Spain

A. Miramontes

J. Morgado

J. Papavassiliou

J. Pawlowski

Pion physics with dressed quark-gluon vertices

We investigate the collider signatures of a maximally flavor-violating $ U(1)_{L_\mu-L_\tau} $ model, where a new gauge boson $ Z^\prime $ and scalar triplets induce lepton flavor-changing interactions in the $\textit{μ}$-$\textit{τ}$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $ m_{Z^\prime} $ and the effective parameters $ \tilde{g}/m_{Z^\prime} $ , whereas it remains largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $ m_{Z^\prime} $ , and beam polarization can significantly suppress the Standard Model backgrounds while enhancing new physics contributions. We find that, in the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results show that multi-lepton final states are powerful probes of the $ U(1)_{L\mu - L_\tau} $ framework and can offer valuable guidance for future searches at muon and electron-positron colliders.

Jianing Qin

Fei Huang

Honglei Li

Zhi-Long Han

Jin Sun

Collider probes of four-lepton final states in maximally flavor-violating ${U(1)_{L_\mu-L_\tau}} $ model * Supported by National Natural Science Foundation of China (12505112, 11805081), Shandong Province Natural Science Foundation (ZR2024QA138, ZR2022MA056) and State Key Laboratory of Dark Matter Physics, University of Jinan Disciplinary Cross-Convergence Construction Project 2024 (XKJC- 202404) and Jin Sun is supported by IBS under the project code, (IBS-R018-D1)

We present an application of physics-informed neural networks (PINNs) to the study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>SU</mi><mo stretchy="false">(</mo><msub><mi>N</mi><mi>c</mi></msub><mo stretchy="false">)</mo></math> lattice gauge theories. Our method enables the learning of eigenfunctions and eigenvalues at arbitrary gauge couplings, smoothly moving from the analytically known strong-coupling regime toward weaker couplings. By encoding the Schrödinger equation and the symmetries of the eigenstates directly into the loss function, the network performs an unsupervised exploration of the spectrum. We validate the approach on the single-plaquette U(1) and SU(2) pure-gauge theories, showing that the PINNs successfully reproduce the hierarchy of energy levels and their corresponding wave functions.

Simone Romiti

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>SU</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></mrow></math> lattice gauge theories with physics-informed neural networks