arXiv subjects

Massimiliano Procura

Publications and source records attributed to Massimiliano Procura.

At least 19 recordsLinked to original sources

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

Using the $W$ as a Standard Candle to Reach the Top: Calibrating Energy Correlator Based Top Mass Measurements

The top quark mass is a key parameter of the Standard Model, yet measuring it precisely at the Large Hadron Collider (LHC) is challenging. Inspired by the use of standard candles in cosmology, we propose a novel energy correlator-based observable, which directly accesses the dimensionless quantity $m_t$/$m_W$. We perform a Monte Carlo study to demonstrate the feasibility of the top mass extraction from Run 2, 3, and High-Luminosity LHC datasets. Our resulting $m_t$ can be defined in a well-controlled short-distance mass scheme and exhibits remarkably small uncertainties from nonperturbative effects, as well as insensitivity to parton distribution functions, outlining a roadmap for a record precision measurement at the LHC.

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arXiv2025

Improved evaluation of the electroweak contribution to muon $g-2$

A precise evaluation of the electroweak contribution to the anomalous magnetic moment of the muon requires control over all aspects of the Standard Model, ranging from Higgs physics, over multi-loop computations for bosonic and (heavy-)fermion diagrams, to non-perturbative effects in the presence of light quarks. Currently, the dominant uncertainties arise from such hadronic effects in the vector-vector-axial-vector three-point function, an improved understanding of which has recently emerged in the context of hadronic light-by-light scattering. Profiting from these developments as well as new perturbative and non-perturbative input for the charm contribution, we obtain $a_μ^\text{EW}=154.4(4)\times 10^{-11}$.

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arXiv2025

Dispersion relations for the hadronic VVA correlator

We derive two types of dispersion relations for the hadronic vector-vector-axial-vector (VVA) correlator: one in generic three-point kinematics with fixed photon virtualities, the second in the kinematic limit of one soft photon. The VVA correlator enters in the electroweak contribution to the muon anomalous magnetic moment and it also emerges as the leading term in the operator-product expansion for hadronic light-by-light scattering in the limit of two large photon momenta. Previously, this correlator was only described in terms of hadronic models. Our new dispersive treatments are in analogy to the established and the newly proposed dispersive approaches to hadronic light-by-light. The VVA correlator allows us to investigate the relation between the two types of dispersion relations in a simpler example and to elucidate the reshuffling of different hadronic contributions in this comparison. As a byproduct, we reduce the theoretical uncertainties on the first-family VVA contribution to the muon anomalous magnetic moment by combining the dispersive representation with both asymptotic and low-energy constraints.

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arXiv2024

Top Quark Mass Extractions from Energy Correlators: A Feasibility Study

In a recent article, we proposed an energy correlator-based method to achieve a precision top quark mass extraction from jet substructure, using the $W$-boson mass as a standard candle. In this paper, we perform an extensive event generator simulation study of this proposal, testing both its experimental viability, as well as its sensitivity to different subprocesses in the top quark production and decay. On the experimental side, we show that uncertainties in the jet energy scale, constituent energy scale, and tracking efficiency have a minimal effect. On the theoretical side, we find that our observable isolates the perturbative decay of the top quark, while nonperturbative physics, such as the modelling of color reconnection, and underlying event, have a negligible impact on the distribution. We conclude that our proposed measurement is resilient to the experimental and theoretical aspects of the hadron collider environment, with variations in model parameters consistently leading to $\lesssim 100~$MeV shifts in the measured top mass. Our results motivate precision theoretical calculations of the energy correlator on top decays, both analytic and using parton shower generators, and further exploration of the experimental measurement.

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arXiv2023

Precision Top Mass Measurement Using Energy Correlators

Precision top mass measurements at hadron colliders have been notoriously difficult. The fundamental challenge in the current approaches lies in achieving simultaneously high top mass sensitivity and good theoretical control. Inspired by the use of standard candles in cosmology, we overcome this problem by showing that a single energy correlator-based observable can be constructed that reflects the characteristic angular scales associated with both the $W$-boson and top quark. This gives direct access to the dimensionless quantity $m_{t}/m_{W}$, from which $m_{t}$ can be extracted in a well-defined short-distance mass scheme as a function of the well-known $m_{W}$. A Monte-Carlo-based study is performed to demonstrate the properties of our observable and the statistical feasibility of its extraction from the Run 2 and 3 and High-Luminosity LHC data sets. The resulting $m_t$ has remarkably small uncertainties from hadronization effects and is insensitive to the underlying event and parton distribution functions. Our proposed observable provides a road map for a rich program to achieve a top mass determination at the LHC with record precision.

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arXiv2023

A New Paradigm for Precision Top Physics: Weighing the Top with Energy Correlators

Final states in collider experiments are characterized by correlation functions, $\langle E(\vec n_1) \cdots E(\vec n_k) \rangle$, of the energy flow operator $ E(\vec n_i)$. We show that the top quark imprints itself as a peak in the three-point correlator at an angle $ζ\sim m_t^2/p_T^2$, with $m_t$ the top quark mass and $p_T$ its transverse momentum, providing access to one of the most important parameters of the Standard Model in one of the simplest field theoretical observables. Our analysis provides the first step towards a new paradigm for a precise top mass determination that is, for the first time, highly insensitive to soft physics and underlying event contamination whilst remaining directly calculable from the Standard Model Lagrangian.

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arXiv2023

Dispersion relations for hadronic light-by-light scattering in triangle kinematics

We present a new strategy for the dispersive evaluation of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon $a_μ$. The new approach directly applies in the kinematic limit relevant for $a_μ$: one of the photons is treated as an external electromagnetic field with vanishing momentum, so that the kinematics corresponds to a triangle. We derive expressions for the relevant single-particle intermediate states, as well as the tensor decompositions of the two-pion sub-processes that appear in addition to those needed in the established dispersive approach. The existing approach is based on a set of dispersion relations for the hadronic light-by-light tensor in four-point kinematics. At present it is not known how to consistently include in this framework resonant intermediate states of spin 2 or larger, due to the appearance of kinematic singularities that can be traced back to the redundancy of the tensor decomposition. We show that our new approach circumvents this problem and enables dispersion relations in the limit of triangle kinematics that are manifestly free from kinematic singularities, paving the way towards a data-driven evaluation of all relevant exclusive hadronic intermediate states.

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arXiv2022

Report of the Topical Group on Top quark physics and heavy flavor production for Snowmass 2021

This report summarizes the work of the Energy Frontier Topical Group on EW Physics: Heavy flavor and top quark physics (EF03) of the 2021 Community Summer Study (Snowmass). It aims to highlight the physics potential of top-quark studies and heavy-flavor production processes (bottom and charm) at the HL-LHC and possible future hadron and lepton colliders and running scenarios.

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arXiv2022

Dark biportals at direct detection

We present a study of the constraining power of low-threshold, high-resolution direct-detection experiments for a biportal simplified dark matter model. In the scenario we consider here, dark matter and Standard Model particles interact through two dark vector mediators $-$ one light and one heavy with respect to the momentum transfer in the experiment. Interference effects at the level of scattering amplitudes can lead to novel marked shape features in the differential recoil spectra, which are best exploited by high-resolution, low-threshold experiments. We identify the region in parameters space for our model where such effects are dominant and show that composite-target experiments with large atomic mass differences are ideal to explore these scenarios. We develop a profile likelihood approach to analyze presently available and future data. Using published results by the CRESST-III experiment and projections of future sensitivities for the COSINUS experiment, we constrain the parameter space in our model, thereby showing the potential of such an analysis on a class of dark matter models which exhibit non-standard features in the recoil spectra.

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arXiv2020

Effects of Longitudinal Short-Distance Constraints on the Hadronic Light-by-Light Contribution to the Muon $g-2$

We present a model-independent method to estimate the effects of short-distance constraints (SDCs) on the hadronic light-by-light contribution to the muon anomalous magnetic moment $a_μ^\text{HLbL}$. The relevant loop integral is evaluated using multi-parameter families of interpolation functions, which satisfy by construction all constraints derived from general principles and smoothly connect the low-energy region with those where either two or all three independent photon virtualities become large. In agreement with other recent model-based analyses, we find that the SDCs and thus the infinite towers of heavy intermediate states that are responsible for saturating them have a rather small effect on $a_μ^\text{HLbL}$. Taking as input the known ground-state pseudoscalar pole contributions, we obtain that the longitudinal SDCs increase $a_μ^\text{HLbL}$ by $(9.1\pm 5.0) \times 10^{-11}$, where the isovector channel is responsible for $(2.6\pm 1.5) \times 10^{-11}$. More precise estimates can be obtained with our method as soon as further accurate, model-independent information about important low-energy contributions from hadronic states with masses up to 1-2 GeV become available.

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arXiv2020

One-loop Angularity Distributions with Recoil using Soft-Collinear Effective Theory

Angularities are event shapes whose sensitivity to the splitting angle of a collinear emission is controlled by a continuous parameter $b$, with $ -1 < b < \infty$. When measured with respect to the thrust axis, this class of QCD observables includes thrust ($b=1$) and jet broadening ($b=0$), the former being insensitive to the recoil of soft against collinear radiation, while the latter being maximally sensitive to it. Presently available analytic results for angularity distributions with $b \neq 0$ can be applied only close to the thrust limit since recoil effects have so far been neglected. As a first step to establish a comprehensive theoretical framework based on Soft-Collinear Effective Theory valid for all recoil-sensitive angularities, we compute for the first time angularity distributions at one-loop order in $α_s$ for all values of $b$ taking into account recoil effects. In the differential cross section, these amount to novel sub-leading singular contributions and/or power corrections, where the former are characterized by fractional powers of the angularity and contribute appreciably close to the peak region, also for $b \gtrsim 0.5$. Our calculations are checked against various limits known in the literature and agree with the numerical output of the Event2 generator.

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arXiv2020

Effective Field Theory with Two Higgs Doublets

In this article we extend the effective field theory framework describing new physics effects to the case where the underlying low-energy theory is a Two-Higgs-Doublet model. We derive a complete set of independent operators up to dimension six assuming a $Z_2$-invariant CP-conserving Higgs potential. The effects on Higgs and gauge boson masses, mixing angles in the Higgs sector as well as couplings to fermions and gauge bosons are computed. At variance with the case of a single Higgs doublet, we find that pair production of SM-like Higgses, arising through dimension-six operators, is not fixed by fermion-fermion-Higgs couplings and can therefore be sizable.

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arXiv2019

Joint resummation of two angularities at next-to-next-to-leading logarithmic order

Multivariate analyses are emerging as important tools to understand properties of hadronic jets which play a key role in the LHC experimental program. We take a first step towards precise and differential theory predictions by calculating the cross section for $e^+ e^- \to$ 2 jets differential in the angularities $e_α$ and $e_β$. The logarithms of $e_α$ and $e_β$ in the cross section are jointly resummed to next-to-next-to-leading logarithmic accuracy, using the SCET+ framework we developed, and are matched to the next-to-leading order cross section. We perform analytic one-loop calculations that serve as input for our numerical analysis, provide controlled theory uncertainties, and compare our results to Pythia. We also obtain predictions for the cross section differential in the ratio $e_α/e_β$, which cannot be determined from a fixed-order calculation. The effect of nonperturbative corrections is also investigated. Using Event2, we validate the logarithmic structure of the single angularity cross section predicted by factorization theorems at ${\mathcal O}(α_s^2)$, demonstrating that for specific angularities recoil must be taken into account when using the thrust axis, while it can be ignored if these are measured with respect to the winner-take-all axis.

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arXiv2017

Hadronic light-by-light contribution to $(g-2)_μ$: a dispersive approach

After a brief introduction on ongoing experimental and theoretical activities on $(g-2)_μ$, we report on recent progress in approaching the calculation of the hadronic light-by-light contribution with dispersive methods. General properties of the four-point function of the electromagnetic current in QCD, its Lorentz decomposition and dispersive representation are discussed. On this basis a numerical estimate for the pion box contribution and its rescattering corrections is obtained. We conclude with an outlook for this approach to the calculation of hadronic light-by-light.

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arXiv2017

Rescattering effects in the hadronic-light-by-light contribution to the anomalous magnetic moment of the muon

We present a first model-independent calculation of $ππ$ intermediate states in the hadronic-light-by-light (HLbL) contribution to the anomalous magnetic moment of the muon $(g-2)_μ$ that goes beyond the scalar QED pion loop. To this end we combine a recently developed dispersive description of the HLbL tensor with a partial-wave expansion and demonstrate that the known scalar-QED result is recovered after partial-wave resummation. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, $a_μ^{π\text{-box}}=-15.9(2)\times 10^{-11}$. We then construct suitable input for the $γ^*γ^*\toππ$ helicity partial waves based on a pion-pole left-hand cut and show that for the dominant charged-pion contribution this representation is consistent with the two-loop chiral prediction and the COMPASS measurement for the pion polarizability. This allows us to reliably estimate $S$-wave rescattering effects to the full pion box and leads to our final estimate for the sum of these two contributions: $a_μ^{π\text{-box}} + a_{μ,J=0}^{ππ,π\text{-pole LHC}}=-24(1)\times 10^{-11}$.

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arXiv2017

Dispersion relation for hadronic light-by-light scattering: two-pion contributions

In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon $(g-2)_μ$, including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of $γ^*γ^*\toππ$. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, $a_μ^{π\text{-box}}=-15.9(2)\times 10^{-11}$. As an application of the partial-wave formalism, we present a first calculation of $ππ$-rescattering effects in HLbL scattering, with $γ^*γ^*\toππ$ helicity partial waves constructed dispersively using $ππ$ phase shifts derived from the inverse-amplitude method. In this way, the isospin-$0$ part of our calculation can be interpreted as the contribution of the $f_0(500)$ to HLbL scattering in $(g-2)_μ$. We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its $S$-wave rescattering corrections reads $a_μ^{π\text{-box}} + a_{μ,J=0}^{ππ,π\text{-pole LHC}}=-24(1)\times 10^{-11}$.

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arXiv2017

Generalized Fragmentation Functions for Fractal Jet Observables

We introduce a broad class of fractal jet observables that recursively probe the collective properties of hadrons produced in jet fragmentation. To describe these collinear-unsafe observables, we generalize the formalism of fragmentation functions, which are important objects in QCD for calculating cross sections involving identified final-state hadrons. Fragmentation functions are fundamentally nonperturbative, but have a calculable renormalization group evolution. Unlike ordinary fragmentation functions, generalized fragmentation functions exhibit nonlinear evolution, since fractal observables involve correlated subsets of hadrons within a jet. Some special cases of generalized fragmentation functions are reviewed, including jet charge and track functions. We then consider fractal jet observables that are based on hierarchical clustering trees, where the nonlinear evolution equations also exhibit tree-like structure at leading order. We develop a numeric code for performing this evolution and study its phenomenological implications. As an application, we present examples of fractal jet observables that are useful in discriminating quark jets from gluon jets.

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