arXiv subjects

Ian Moult

Publications and source records attributed to Ian Moult.

At least 19 recordsLinked to original sources

arXiv2026

Cutting corners: exciting and magical bounds from the cusp bootstrap

An illuminating probe of the dynamics of a line defect is the global geometry of its worldline. For a conformal line defect in a conformal field theory, sharp corners in the worldline, i.e. cusps, host dynamical degrees of freedom characterized in part by a spectrum of scaling dimensions, called cusp anomalous dimensions. We present various general bounds on cusp anomalous dimensions following from unitarity and cutting-and-gluing consistency of different defect geometries. We first establish, for cusps involving conjugate defects, that level crossings upon varying the cusp angle are forbidden between the lightest singlet cusp and any non-singlet cusp, proving that singlet cusps are the lightest. Then, we study line defects arranged in a rectangular geometry, which are subject to bootstrap constraints reminiscent of the spinless modular bootstrap. We find an analytic ``magic" functional that produces an optimal and universal lower bound on the dimension of a right angle bare cusp in terms of the universal defect Casimir energy between the corresponding defect and its conjugate in flat space.

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arXiv2026

Eye-opening bounds on cusps

We derive new nonperturbative inequalities on the cusp anomalous dimensions of conformal line defects. We impose reflection positivity, locality, and conformal invariance on a pair of cusps forming an ``eye'' geometry, deriving a novel condition on the cusp anomalous dimension which we refer to as conformal concavity. The resulting constraint is much stronger than the known angular concavity, and our derivation applies also to cusps involving distinct line defects. Remarkably, it directly links the smooth and fusion limits, yielding bounds on defect-changing operator dimensions, Casimir energies, and subleading fusion data. We thus uncover a new quantitative bridge between aspects of the local operator data and the fusion rules of line operators in conformal field theories.

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arXiv2026

The EEC-Hedron: Positivity Bounds on Energy Correlators

We study the constraints placed by energy positivity on general unitary quantum field theories. We show that the coefficients in the partial wave expansion of energy-energy correlators all must lie within a bounded region of parameter space, which we call the ``EEC-hedron''. For the particular case of conformal field theories, these positivity constraints on energy correlators lead to bounds on the allowed values of coefficients in the operator product expansion. We demonstrate this approach in the 3d Ising and $O(2)$ CFTs, deriving new bounds on OPE coefficients in both theories.

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arXiv2026

Nonrelativistic Conformal Collider Physics of Multiparticle Point Production

We define detector operators in the nonrelativistic conformal field theory describing fermions at unitarity. We reduce the problem of computing the momentum distribution and correlation between final particles produced by a local source ("point-produced") to the computation of correlation functions involving the detector operators. The general formalism is applied to the point production of three unitary fermions, where we find the momentum and angular distribution of final particles. We discuss a nonrelativistic version of celestial holography, which maps the asymptotic out-state to a quantum wave function in the so-called "oscillator frame."

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arXiv2026

First measurement of the one-point charge correlator in $e^+e^-$ collisions at $\sqrt{s} = 91.2$ GeV with DELPHI Open Data

The chiral structure of the $Z$ couplings imprints a parity-odd flow of electric charge on hadronic $Z$ decays. The related forward-backward asymmetries, a key set of observables in the electroweak precision program, were measured at LEP and SLC using the jet charge. The one-point charge correlator offers a complementary route, measuring the hadronic charge flow directly as a function of polar angle relative to the incoming electron-beam axis, without reference to jets or a reconstructed quark direction, following the formalism developed in a companion paper. We report its first measurement, using $61~\mathrm{pb}^{-1}$ of archival DELPHI Open Data recorded at $\sqrt{s} = 91.2$~GeV in 1994 and 1995. Detector effects are corrected in two stages. The first is derived from fully simulated samples, and the second bounds the residual charge-misreconstruction difference between data and simulation using a measurement in $e^+e^-\to\tau^+\tau^-$ events. The measured charge correlator exhibits the characteristic parity-odd $\sin(2\theta)$ modulation and agrees with the \textsc{PYTHIA}~8.3 prediction. The measurement demonstrates the experimental feasibility of the observable and establishes strategies for controlling associated detector effects, paving the way for a new program of charge-flux measurements, both in archival $e^+e^-$ data and at future colliders.

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arXiv2026

Analysis note: one-point charge correlator with DELPHI Open Data

We present the first measurement of the one-point charge correlator, the angular flux of electric charge in hadronic final states, using DELPHI Open Data collected at LEP-1 at $\sqrt{s} = 91.2$~GeV during 1994 and 1995. The data, corrected for detector effects, exhibit a clear $\sin(2\theta)$ modulation, consistent with the parity-violating hadronic charge flow that the chiral structure of the $Z$ couplings imprints on the final state. The measurement demonstrates the experimental feasibility of the observable and establishes strategies for controlling associated detector effects, thereby motivating a new program to measure charge-flux observables. This note documents the experimental details supporting the companion experimental paper and the joint theory--experiment Letter.

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arXiv2026

Observing Macroscopic Consequences of Electroweak Anomalies with Archival DELPHI Data

In this Letter, we emphasize that asymmetries in charge flux produced in the decays of on-shell Z-bosons provide a macroscopic manifestation of electroweak anomalies in the Standard Model (SM). We propose that these can be cleanly observed using charge correlators, providing a new formulation of forward-backward asymmetry measurements that is particularly well suited for precision studies of hadronic decays. Using archival DELPHI data, we perform a first measurement of the one-point charge correlator of electromagnetic charge flux on hadrons, and cleanly observe the macroscopic imprint of the underlying anomaly. Our analysis illustrates the potential of charge correlators as precision electroweak observables, and motivates a renewed effort to resolve longstanding tensions in hadronic asymmetry measurements.

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arXiv2026

Energy Correlators in $V + X$ as a Benchmark Observable for Precision QCD

We propose projected energy correlators measured on the recoiling QCD radiation of a $Z/\gamma$ as a benchmark observable for precision QCD at the LHC. Using the $Z/\gamma$ as a hard scale prevents the need for a jet algorithm, simplifying both the perturbative and non-perturbative corrections. We develop a framework to combine state-of-the-art fixed-order amplitudes, high order resummation, and universal non-perturbative matrix elements. Our approach is based on numerically computed inclusive hard functions, allowing flexibility in the process and the inclusion of realistic experimental cuts. We perform detailed numerical studies of the projected energy correlators at next-to-leading order + next-to-next-to-leading logarithm (NLO+NNLL) to verify the stability of our setup. We present numerical results at NLO+NNLL, which are the first complete matched predictions for energy correlators at the LHC at this order. We discuss the prospects for extensions to higher orders, outlining a path to NNLO calculations of energy correlators at the LHC.

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arXiv2026

Imaging non-hydrodynamic modes with jet wakes

While studies of ultra-relativistic heavy-ion collisions have established that the quark--gluon plasma exhibits hydrodynamic behavior, direct signatures of non-hydrodynamic modes have remained elusive, and no observable is known to be exclusively sensitive to them. Here, we show that the angular structure of the jet wake provides such a probe. In the long-wavelength limit, hydrodynamics contributes only to the lowest angular moments of the detector image of the jet wake, while higher moments directly encode microscopic non-equilibrium dynamics. The jet wake thus serves as a spectroscopic probe of the medium's non-hydrodynamic sector. We develop a general kinetic-theory framework relating the angular moments of the late-time energy flux generated by a jet to the relaxation spectrum of the collision operator. In all models considered, non-hydrodynamic modes leave distinct imprints on the higher angular moments. Our results motivate precision measurements of the higher angular moments of the negative jet wake.

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arXiv2026

Dissecting Parton Showers with Multi-Point Energy Correlators

The last several years have seen tremendous progress in the ability to both compute and measure multi-point correlations in energy flux. The highly differential nature of energy correlators makes them ideal probes of multi-collinear factorization and azimuthal structure within jets. In this paper, we explore the phenomenology of four-point correlators in jet substructure. We identify experimentally realizable projections that probe different factorization channels onto splitting tensors and splitting functions. We perform a detailed phenomenological study using both Herwig and Pythia. By comparing parton shower results with analytic calculations in kinematic limits, we are able to disentangle intrinsic spin correlations from kinematic azimuthal correlations. In experimentally accessible kinematic regions, we find the spin correlations are subdominant, strongly motivating a complete calculation of the four-point correlator in QCD to provide a test of the parton shower results. We also present parameterizations and analysis algorithms that can be used experimentally. Our work sets the stage for the experimental measurement of these observables at the LHC, and their use as probes of the next generation of parton showers.

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arXiv2026

Putting Jet Substructure on Track(s)

One of the main advances in analysis strategies at the Large Hadron Collider (LHC) has been the ability to study the detailed structure of energy flow within high transverse momentum jets, a field referred to as jet substructure. Jet substructure has provided new ways to search for new physics, measure Standard Model parameters, and study the dynamics of the strong nuclear force. To push to the next level of precision, and to make measurements of increasingly subtle correlations, requires exquisite angular resolution achieved through the use of tracking information. In this paper we leverage recent progress in our understanding of factorization theorems and renormalization group techniques to present the first complete calculations of jet substructure observables at the LHC on tracks. We compute projected energy correlators up to four points at next-to-leading collinear logarithmic accuracy, matching the state of the art for jet substructure observables, but extending to tracks. This marks a significant step in enhancing the collider physics program, enabling precise and systematically improvable comparisons between experimental measurements and theoretical calculations, made possible by the exceptional angular resolution of tracking.

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arXiv2026

Les Houches study on inclusive jet production at NNLO+NNLL

Jet production at the LHC is a powerful probe of QCD, making it ideal for precision tests and determinations of QCD parameters such as parton distribution functions and the strong coupling constant. To make the most of the abundant jet production data collected at the LHC, precise calculations are required. While state-of-the-art calculations reach next-to-next-to-leading order (NNLO) QCD accuracy, a critical assessment of the remaining uncertainties arising from non-perturbative effects and missing higher orders remains crucial for correctly interpreting comparisons between theory and data. Scale variation is nearly always used to determine effects from missing higher orders. In this article, we reassess this method in the context of inclusive jet production by performing NNLO QCD calculations supplemented by small-jet-radius resummation through next-to-next-to-leading-logarithmic accuracy (NNLL). We find that NNLL resummation can have an appreciable impact on the scale uncertainty for inclusive jet cross sections, and, for some scale choices, can lead to sizeable shifts of the central cross section. We conclude that scale variations in fixed-order and resummed calculations can drastically underestimate the impact of higher orders for commonly used jet radius parameters, and that missing higher-order estimates obtained via scale variations should be considered unreliable. Our findings add further evidence to the importance of going beyond scale variations in jet and jet substructure calculations.

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arXiv2026

Hydrodynamics and Energy Correlators

We study energy-energy correlators (EECs) in many-body quantum states, focusing on the matter produced in the aftermath of heavy-ion collisions. We analyze the angular structure of EECs in the collinear limit and identify a sequence of dynamical regimes. At the largest angular separations within the small-angle regime, the observable is dominated by disconnected contributions, leading to a classical scaling determined by the collective flow of the medium. We explicitly construct this contribution for hadrons produced from a hydrodynamic medium described by boost-invariant Gubser flow, obtaining the angular dependence of the EEC analytically. We further consider azimuthal perturbations to this flow, illustrating how EECs can be used to probe anisotropies in the initial state. At smaller angular separations, connected contributions become increasingly important. We argue that in this regime the EEC is controlled by collective hydrodynamic modes. The resulting angular behavior is similar to the one identified in the EECs of heavy and large-charge states of conformal field theories. At even smaller angles, this regime is expected to match onto the structure determined by the light-ray operator product expansion, before eventually crossing over to the smallest-angle behavior characteristic of dilute hadronic matter. Altogether, these results provide a unified picture of the angular structure of EECs in many-body QCD states and suggest new observables sensitive to the properties of matter in heavy-ion collisions.

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arXiv2026

Asymptotic charges as detectors and the memory effect in massive QED and perturbative quantum gravity

It has been shown that there are an infinite set of asymptotic symmetries in quantum gravity and QED, and this has been extended to dressed states in some cases. Here we rederive these statements in terms of detectors in order to clarify, confirm, and generalize these results to include external hard gravitons. Using detectors and including the full t dependence in Faddeev-Kulish dressings allows us to correct discrepancies in the literature and make new statements. We show that Faddeev-Kulish dressings correctly encode the memory effect in the 'in' and 'out' scattering Fock spaces. We find a physical contribution to the memory eigenvalues arising from the dressings in both cases.

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arXiv2026

High precision heavy-boson-jet substructure with energy correlators

Energy-correlator-based jet substructure has gained significant attention in recent years. One of the notable applications has been the study of multi-scale jets, where distinct physical scales manifest as features localised in different angular regions of the correlator. In this article, we present the first high-precision study of energy correlators on the simplest multi-scale jets: heavy boson jets. In such systems, the boson mass $M$ introduces an additional scale, generating a sharp peak at angles $\sim M/p_T^{\rm jet}$. We show that this feature can be computed directly by boosting the EEC spectrum measured in $e^+e^- \rightarrow {\rm hadrons}$ at the $Z$ pole. We identify that the peak arises from boosting the well-studied Sudakov factorisation governing the back-to-back limit of the two-point correlator. As a result, the feature is controlled by Sudakov resummation, not a Breit-Wigner-like structure in the $Z$ decay, and is therefore calculable with exceptional precision. We provide predictions at N$^3$LL$'$ accuracy for both $pp$ $Z$-tagged jets and $e^+e^-$ di-$Z$ production, and compare them to Herwig and Pythia simulations, finding close agreement. We also demonstrate that the boosted-$Z$ spectrum can be constructed directly by boosting OPAL measurements at the $Z$ pole. In this light, energy-correlator jet substructure on the hadronic decays of heavy bosons at the LHC provide access to clean, lepton-collider-like measurements across a wide range of effective centre-of-mass energies set by the boson jet transverse momentum.

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arXiv2025

From DGLAP to Sudakov: Precision Predictions for Energy-Energy Correlators

Correlations in the distribution of energy produced in collider experiments provide a snapshot of the microscopic dynamics of QCD, and its evolution from asymptotically free quarks and gluons, to confined hadrons. There has recently been considerable progress in the interpretation and precision calculation of these correlations, using a specific class of observables called energy correlators (EECs). These observables are most cleanly studied in $e^+e^-$ collisions, where they can be measured over their full angular range. Of particular interest are kinematic limits of the correlator, both collinear, and back-to-back, where the correlator exhibits scaling behaviors governed by specific operators in QCD. Resolving these scalings requires measurements with exceptional angular resolution, which can be achieved by performing measurements on tracks (charged particles). In this paper we perform the first calculation of the track-based EEC over its entire kinematic range, achieving a record precision of of NNLL (collinear) + NNLO (fixed order) + NNNNLL (back-to-back) for the track-based EEC, and additionally incorporate the leading non-perturbative corrections and their resummation, including the Collins-Soper kernel computed using lattice QCD. We describe the breadth of physics probed by this observable, and highlight the impact of different components of our factorization theorem on the final distribution. Combined with recent measurements of the track-based EEC with archival LEP data, our calculation initiates the precision study of track-based observables at LEP, which will lead to new insights into the dynamics of QCD, and the precision extraction of its underlying parameters.

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arXiv2025

Energy Correlator Conformal Blocks and Positivity

Correlation functions of energy flow operators (energy-energy correlators) are one of the simplest observables in quantum field theory and gravity, with diverse applications ranging from real world collider physics to constraining the space of consistent theories. In this paper we further develop the conformal block decomposition of energy-energy correlators in conformal field theories (CFTs), focusing on the source-detector operator product expansion (OPE). We compute the general conformal blocks in this channel for traceless symmetric operators of arbitrary spin in the background of a scalar source, considering both parity-even and parity-odd contributions. Motivated by the availability of data from the conformal bootstrap, we analyze the convergence of this source-detector OPE, taking a tensor product of two decoupled CFTs as an elementary example. Finally, we use positivity of energy correlators to derive novel bounds on OPE coefficients involving the stress-energy tensor in generic CFTs, and demonstrate the application of these bounds in the specific example of the 3d Ising CFT, obtaining new constraints for both parity-even and parity-odd operators.

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arXiv2025

Memory Correlators and Ward Identities in the 'in-in' Formalism

The symmetries of asymptotically flat spacetimes impose constraints on observables at infinity. The consequences of this have been extensively explored for S-matrix elements, where soft theorems are known to be equivalent to Ward identities for asymptotic symmetries. However, recently there has been interest in broader classes of asymptotic observables. Here, we consider soft graviton insertions in the 'in-in' formalism. We derive a Ward identity for supertranslations and compute two point functions for the soft charges for 'in-in' correlators. We find that the connected memory correlators are non-trivial in this set up and can be straightforwardly inferred from the average null energy (ANEC) correlators using observations from celestial Conformal Field Theory (cCFT).

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