arXiv subjects

Silvia Ferrario Ravasio

Publications and source records attributed to Silvia Ferrario Ravasio.

At least 19 recordsLinked to original sources

arXiv2026

A Powheg generator for $t$- and $s$-channel single-top production and decay including non-resonant effects

We present a next-to-leading order + parton shower generator for $t$- and $s$-channel single-top production in hadron colliders, for a leptonically-decaying top, including off-shell and non-resonant effects. The generator, publicly available in the POWHEG BOX RES framework, describes the hadro-production of a $b$-jet and a leptonically decaying $W$-boson, accompanied by an additional jet, i.e. $pp\to \ell^{+} ν_{\ell}\, j_b\, j $ and $pp\to \ell^{-} \barν_{\ell}\, j_{\bar{b}}\, j $, where $j_b$ ($j_{\bar{b}}$) is a jet containing a bottom (anti)quark, and $j$ is a generic jet. We also provide an interface to the Pythia parton shower, suited to matching in the presence of decaying resonances such as the top quark. Our matching is designed to combine the advantages of a five-flavour calculation with the description of bottom quark mass effects in final-state jets. We perform a phenomenological study using fiducial cuts and discuss shower effects.

hep-ph↗

arXiv2026

A generalised-$k_t$ jet algorithm for Deep Inelastic Scattering

We introduce an inclusive generalised-$k_t$ jet algorithm for Deep Inelastic Scattering, defined in the Breit frame and implemented in fjcontrib. The family of algorithms is governed by the usual parameter $p$, which controls the transverse-momentum dependence of the algorithm, as well as by a jet radius parameter $R$. The angular-ordered ($p=0$) version of the algorithm was already presented by some of us, and can be used to formulate observables with simple all-order structures. In this article we investigate phenomenological applications of the algorithms related to the identification of the jet associated with the struck quark, and assess their sensitivity to non-perturbative effects, such as hadronisation. We also perform comparisons with the recent Centauro algorithm.

hep-ph↗

arXiv2026

Logarithmically-accurate showers with massive quarks

We formulate PanScales final-state showers that account for quark masses and achieve next-to-leading logarithmic accuracy, while preserving the original accuracy of the showers for observables where the mass of the quarks is irrelevant. We validate the accuracy of the shower algorithms by performing fixed-order tests up to second order in the strong coupling constant, and all-order comparisons to (semi-)analytic resummed calculations for a series of observables, including Lund-tree shapes, non-global energy flows and Lund sub-jet multiplicities. We also include some phenomenological studies using LEP data.

hep-ph↗

arXiv2026

Theory uncertainties of the irreducible background to VBF Higgs production

Higgs boson production through gluon fusion in association with two jets is an irreducible background to Higgs boson production through vector boson fusion, one of the most important channels for analyzing and understanding the Higgs boson properties at the Large Hadron Collider. Despite a range of available simulation tools, precise predictions for the corresponding final states are notoriously hard to achieve. Using state-of-the-art fixed-order calculations as the baseline for a comparison, we perform a detailed study of similarities and differences in existing event generators. We provide consistent setups for the simulations that can be used to obtain identical parametric precision in various programs used by experiments. We find that NLO calculations for the two-jet final state are essential to achieve reliable predictions.

hep-ph↗

arXiv2025

A new suite of Lund-tree observables to resolve jets

We introduce a class of collider observables, named Lund-Tree Shapes (LTS), defined from declustering trees originating from the Lund jet plane representation of the QCD radiation pattern in multi-jet scattering processes. At the differential level, they are continuous global variables akin classical event shapes and $n\to n+1$ jet-resolution parameters, which probe the geometry and hierarchical structure of the radiation in an event. At the integrated, cumulative level, they naturally define $n$ jet rates, providing a jet-multiplicity-based characterisation of multi-jet final states. Their definition applies to scattering processes with any number of resolved jets in the final state, as well as to groomed jets. They are thus usable as resolution variables in the context of higher-order calculations via phase-space slicing, matching fixed-order calculations to parton showers, and testing the logarithmic accuracy of shower algorithms. From a theoretical viewpoint, such observables feature a simple all-order structure and are free of non-global logarithmic corrections. As an initial application, we derive next-to-next-to-leading-logarithmic accurate predictions for processes with two QCD legs at $e e$, $pp$ and $e p$ colliders, and matched predictions to next-to-next-to-leading order for the LHC, discussing aspects of collider phenomenology.

hep-ph↗

arXiv2025

Logarithmically-accurate and positive-definite NLO shower matching

We present methods to achieve NLL+NLO accurate parton showering for processes with two coloured legs: neutral- and charged-current Drell-Yan, and Higgs production in $pp$ collisions, as well as DIS and $e^+e^-$ to jets. The methods include adaptations of existing approaches, as well as a new NLO matching scheme, ESME, that is positive-definite by construction. Our implementations of the methods within the PanScales framework yield highly competitive NLO event generation speeds. We validate the fixed-order and combined resummation accuracy with tests in the limit of small QCD coupling and briefly touch on phenomenological comparisons to standard NLO results and to Drell-Yan data. The progress reported here is an essential step towards showers with logarithmic accuracy beyond NLL for processes with incoming hadrons.

hep-ph↗

arXiv2025

Higgs production via vector-boson fusion at the LHC

In this article, we summarise the recent experimental measurements and theoretical work on Higgs boson production via vector-boson fusion at the LHC. Along with this, we provide state-of-the-art predictions at fixed order as well as with parton-shower corrections within the Standard Model at 13.6 TeV. The results are presented in the form of multi-differential distributions as well as in the Simplified Template Cross Section bins. All materials and outputs of this study are available on public repositories. Finally, following findings in the literature, recommendations are made to estimate theoretical uncertainties related to parton-shower corrections.

hep-ph↗

arXiv2025

Building Next-to-Next Leading Logarithmic parton showers: the PanScales recipe

Parton showers lie at the core of Shower Monte Carlo event generators, the default theoretical tools used to interpret collider data. In these proceedings, we summarise the strategy of the PanScales collaboration that led to the attainment of the first demonstrably next-to-next-to-leading-logarithmic accurate parton showers.

hep-ph↗

arXiv2025

A new standard for the logarithmic accuracy of parton showers

We report on a major milestone in the construction of logarithmically accurate final-state parton showers, achieving next-to-next-to-leading-logarithmic (NNLL) accuracy for the wide class of observables known as event shapes. The key to this advance lies in the identification of the relation between critical NNLL analytic resummation ingredients and their parton-shower counterparts. Our analytic discussion is supplemented with numerical tests of the logarithmic accuracy of three shower variants for more than a dozen distinct event-shape observables in $Z \to q \bar q$ and Higgs $\to gg$ decays. The NNLL terms are phenomenologically sizeable, as illustrated in comparisons to data.

hep-ph↗

arXiv2024

A Phenomenological Analysis of LHC Neutrino Scattering at NLO Accuracy Matched to Parton Showers

We perform a detailed phenomenological study of high-energy neutrino deep inelastic scattering (DIS) focused on LHC far-forward experiments such as FASER$ν$ and SND@LHC. To this aim, we parametrise the neutrino fluxes reaching these LHC far-forward experiments in terms of `neutrino PDFs' encoding their energy and rapidity dependence by means of the LHAPDF framework. We integrate these neutrino PDFs in the recently developed POWHEG-BOX-RES implementation of neutrino-induced DIS to produce predictions accurate at next-to-leading order (NLO) in the QCD coupling matched to parton showers (PS) with Pythia8. We present NLO+PS predictions for final-state distributions within the acceptance of FASER$ν$ and SND@LHC as well as for two experiments of the proposed Forward Physics Facility (FPF), FASER$ν$2 and FLArE. We quantify the impact of NLO QCD corrections, of the parton showering and hadronisation settings in Pythia8, of the QED shower, and of the incoming neutrino flavour for the description of these observables, and compare our predictions with the GENIE neutrino event generator. Our work demonstrates the relevance of modern higher-order event generators to achieve the key scientific targets of the LHC neutrino experiments.

hep-ph↗

arXiv2024

The ECFA Early-Career Researchers Panel: Report for the year 2023

The European Committee for Future Accelerators (ECFA) Early-Career Researcher (ECR) panel, which represents the interests of the ECR community to ECFA, presents in this document its initiatives and activities in the year 2023. This report summarises the process of the first big turnover in the panel composition at the start of 2023 and reports on the activities of the active working groups - either pursued from before or newly established. The overarching goal of the ECFA-ECR panel is to better understand and support the diverse interests of early-career researchers in the ECFA community and beyond.

physics.acc-ph↗

arXiv2024

Herwig 7.3 Release Note

A new release of the Monte Carlo event generator Herwig (version 7.3) has been launched. This iteration encompasses several enhancements over its predecessor, version 7.2. Noteworthy upgrades include: the implementation of a process-independent electroweak angular-ordered parton shower integrated with QCD and QED radiation; a new recoil scheme for initial-state radiation improving the behaviour of the angular-ordered parton shower; the incorporation of the heavy quark effective theory to refine the hadronization and decay of excited heavy mesons and heavy baryons; a dynamic strategy to regulate the kinematic threshold of cluster splittings within the cluster hadronization model; several improvements to the structure of the cluster hadronization model allowing for refined models; the possibility to extract event-by-event hadronization corrections in a well-defined way; the possibility of using the string model, with a dedicated tune. Additionally, a new tuning of the parton shower and hadronization parameters has been executed. This article discusses the novel features introduced in version 7.3.0.

hep-ph↗

arXiv2024

An event generator for neutrino-induced Deep Inelastic Scattering and applications to neutrino astronomy

We extend the recently presented, fully exclusive, next-to-leading-order accurate event generator for the simulation of massless neutral- and charged-current deep inelastic scattering (DIS) to the case of incoming neutrinos. The generator can be used to study neutrino-nucleon interactions at (ultra) high energies, and is relevant for a range of fixed-target collider experiments and large-volume neutrino detectors, investigating atmospheric and astrophysical neutrinos. The matching with multi-purpose event generators such as PYTHIA 8 is performed with the POWHEG method, and accounts for parton showering and non-perturbative effects such as hadronization. This makes it possible to investigate higher-order perturbative corrections to realistic observables, such as the distribution of charged particles. To illustrate the capabilities of the code we provide predictions for several differential distributions in fixed-target collisions for neutrino energies up to 1 PeV.

hep-ph↗

arXiv2024

Ad interim recommendations for the Higgs boson production cross sections at $\sqrt{s} = 13.6$ TeV

This note documents predictions for the inclusive production cross sections of the Standard Model Higgs boson at the Large Hadron Collider at a centre of mass energy of 13.6 TeV. The predictions here are based on simple extrapolations of previously documented predictions published in the CERN Yellow Report "Deciphering the Nature of the Higgs Sector". The predictions documented in this note should serve as a reference while a more complete and update-to-date derivation of cross section predictions is in progress.

hep-ph↗

arXiv2024

Next-to-leading-logarithmic PanScales showers for Deep Inelastic Scattering and Vector Boson Fusion

We introduce the first family of parton showers that achieve next-to-leading logarithmic (NLL) accuracy for processes involving a $t$-channel exchange of a colour-singlet, and embed them in the PanScales framework. These showers are applicable to processes such as deep inelastic scattering (DIS), vector boson fusion (VBF), and vector boson scattering (VBS). We extensively test and verify the NLL accuracy of the new showers at both fixed order and all orders across a wide range of observables. We also introduce a generalisation of the Cambridge-Aachen jet algorithm and formulate new DIS observables that exhibit a simple resummation structure. The NLL showers are compared to a standard transverse-momentum ordered dipole shower, serving as a proxy for the current state-of-the-art leading-logarithmic showers available in public codes. Depending on the observable, we find discrepancies at NLL of the order of $15\%$. We also present some exploratory phenomenological results for Higgs production in VBF. This work enables, for the first time, to resum simultaneously global and non-global observables for the VBF process at NLL accuracy.

hep-ph↗

arXiv2024

A POWHEG generator for deep inelastic scattering

We present a new event generator for the simulation of both neutral- and charged-current deep inelastic scattering (DIS) at next-to-leading order in QCD matched to parton showers using the POWHEG method. Our implementation builds on the existing POWHEG BOX framework originally designed for hadron-hadron collisions, supplemented by considerable extensions to account for the genuinely different kinematics inherent to lepton-hadron collisions. In particular, we present new momentum mappings that conserve the special kinematics found in DIS, which we use to modify the POWHEG BOX implementation of the Frixione-Kunszt-Signer subtraction mechanism. We compare our predictions to fixed-order and resummed predictions, as well as to data from the HERA ep collider. Finally we study a few representative distributions for the upcoming Electron Ion Collider.

hep-ph↗

arXiv2023

Introduction to the PanScales framework, version 0.1

In this article, we document version 0.1 of the PanScales code for parton shower simulations. With the help of a few examples, we discuss basic usage of the code, including tests of logarithmic accuracy of parton showers. We expose some of the numerical techniques underlying the logarithmic tests and include a description of how users can implement their own showers within the framework. Some of the simpler logarithmic tests can be performed in a few minutes on a modern laptop. As an early step towards phenomenology, we also outline some aspects of a preliminary interface to Pythia, for access to its hard matrix elements and its hadronisation modules.

hep-ph↗

arXiv2023

Parton showering with higher-logarithmic accuracy for soft emissions

The accuracy of parton-shower simulations is often a limiting factor in the interpretation of data from high-energy colliders. We present the first formulation of parton showers with accuracy one order beyond state-of-the-art next-to-leading logarithms, for classes of observable that are dominantly sensitive to low-energy (soft) emissions, specifically non-global observables and subjet multiplicities. This represents a major step towards general next-to-next-to-leading logarithmic accuracy for parton showers.

hep-ph↗