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Gennaro Corcella

Publications and source records attributed to Gennaro Corcella.

At least 19 recordsLinked to original sources
arXiv2026

Top-quark mass interpretation from simulation of top-flavoured mesons

The interpretation of the top quark mass measurements in terms of well-known field theory definitions has been the topic of a long-standing discussion. In this paper we reconsider this issue and simulate fictitious top-flavoured mesons, whose mass can be related to any top mass definition, such as the pole mass, by means of Heavy Quark Effective Theory. We explore final-state observables for top-pair production in $e^+e^-$ and hadron collisions, and relate the top mass in standard $t\bar t$ events to the pole mass extracted from top-meson samples simulated with Pythia 8.3. Our results are in agreement with the expectation of an uncertainty about $200$-$300$ MeV, hence of the order of $\Lambda_{\rm QCD}$.

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arXiv2025

Bounding exotic top decays inclusively at the FCC-ee

Since its discovery, the top quark has never been produced and studied in an environment as clean as that predicted for $e^+e^-$ collisions at future colliders. Details of the top quark's properties, completely unattainable in hadronic collisions, can be analyzed via lepton collisions. New strategies for analyzing the physics of the top quark can, therefore, be developed in such a spectacularly clean environment. Here we focus on the possibility of inclusively measuring exotic excesses in the top decay width by studying the direct production of $t\bar t$ at the FCC-$ee$, thus establishing model-independent limits for rare decays branching fractions of the top quark.

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arXiv2025

Heavy Quark Decays in the Bilepton Model

Given the current absence of new physics signals at the LHC, it is increasingly important to investigate alternative scenarios beyond those commonly explored. In this work, we study a variant of the 331 model that predicts the existence of vector bileptons with electric charge and lepton number +/-2, as well as TeV-scale exotic quarks carrying charges +/- 5/3 and +/- 4/3. Specifically, we focus on the primary production of heavy quarks with charge +/- 5/3, which decay into a bottom quark and a bilepton, followed by the bilepton's decay into same-sign muon pairs. As a case study, we select a benchmark point that complies with current experimental exclusion limits and theoretical expectations for the bilepton mass. Our analysis shows that the resulting signal stands out clearly from Standard Model backgrounds and could be observed at a future 100 TeV hadron collider such as FCC-hh. In contrast, the LHC, even in its high-luminosity phase, lacks the sensitivity required to detect this signal.

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arXiv2024

Top-mass determination from leptonic final states

The top-quark mass is a fundamental parameter of the Standard Model, as it plays a crucial role in the electroweak precision tests, stability of the vacuum and inflation. I review the method and the main results contained in a recent ATLAS analysis which measures the top mass by using the invariant mass of the leptons coming from W and B-hadron decays. The extracted top mass turns out to be the most precise single measurement by ATLAS.

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arXiv2024

Hunting for bileptons at hadron colliders

I review possible signals at hadron colliders of bileptons, namely doubly-charged vectors or scalars with lepton number L=+/- 2, as predicted by a 331 model, based on a SU(3)_c x SU(3)_L x U(1)_X symmetry. In particular, I account for a version of the 331 model, wherein the embedding of the hypercharge is obtained with the addition of 3 exotic quarks and vector bileptons. Furthermore, a sextet of SU(3)_L, necessary to give masses to leptons, yields an extra scalar sector, including a doubly-charged Higgs, i.e. scalar bileptons. As bileptons are mostly produced in pairs at hadron colliders, their main signal is given by two same-sign lepton pairs at high invariant mass. Nevertheless, they can also decay according to non-leptonic modes, such as a TeV-scale heavy quark, charged 4/3 or 5/3, plus a Standard Model quark. I explore both leptonic and non-leptonic decays and the sensitivity to such processes of present and future hadron colliders.

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arXiv2023

The rise and fall of light stops in the LHC top quark sample

We discuss the possibility that light new physics in the top quark sample at the LHC can be found by investigating with greater care well known kinematic distributions, such as the invariant mass $m_{b\ell}$ of the $b$-jet and the charged lepton in fully leptonic $t\bar{t}$ events. We demonstrate that new physics can be probed in the rising part of the already measured $m_{b\ell}$ distribution. To this end we analyze a concrete supersymmetric scenario with light right-handed stop quark, chargino and neutralino. The corresponding spectra are characterized by small mass differences, which make them not yet excluded by current LHC searches and give rise to a specific end-point in the shape of the $m_{b\ell}$ distribution. We argue that this sharp feature is general for models of light new physics that have so far escaped the LHC searches and can offer a precious handle for the implementation of robust searches that exploit, rather than suffer from, soft bottom quarks and leptons. Recasting public data on searches for new physics, we identify candidate models that are not yet excluded. For these models we study the $m_{b\ell}$ distribution and derive the expected signal yields, finding that there is untapped potential for discovery of new physics using the $m_{b\ell}$ distribution.

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arXiv2022

Selected Results in Heavy Quark Fragmentation

I review a few selected topics concerning heavy-quark fragmentation, taking particular care about bottom- and charm-quark production in $e^+e^-$ annihilation and the inclusion of non-perturbative corrections. In particular, I discuss recent developments of calculations carried out in the framework of perturbative fragmentation functions and the perspective to extend them to other processes and higher accuracy. Special attention is paid to the use of an effective strong coupling constant to model hadronization effects.

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arXiv2022

Non-Leptonic Decays of Bileptons

We provide a detailed analysis of the decays of doubly-charged bilepton gauge bosons $Y^{\pm\pm}$, as predicted in models based on a $SU(3)_C\times SU(3)_L\times U(1)_X$ symmetry. In addition to the decay modes into same-sign lepton pairs, which were already investigated in scenarios wherein each branching ratio was about one third, there are, depending on the mass spectrum, possible non-leptonic decays which reduce the leptonic rates. These non-leptonic decays are typically into a light quark (antiquark) and a heavy TeV-scale antiquark (quark), which carries double lepton number and decays via virtual bileptons. We choose two benchmark points to represent the particle spectrum and present a phenomenological analysis of such decays. We find that, while the LHC statistics are too low, even in the high-luminosity phase, they can lead to a visible signal at a future 100 TeV hadron collider (FCC-$hh$). A more exhaustive exploration with a rigorous inclusion of tagging efficiencies, detector simulations and higher-order corrections to the partonic cross section, aiming at assessing the reach of LHC and FCC-$hh$ for bileptons as a function of the model parameters, as well as a recast of four-top searches in terms of the bilepton model, are deferred to future work.

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arXiv2021

Vector-like quarks decaying into singly and doubly charged bosons at LHC

We investigate the production of vector-like quarks with charge $5/3$ at the LHC and their subsequent decays into new singly or doubly charged bosons plus a heavy quark (top or bottom). In particular, we explore final states with same-sign di-leptons (electron or muon pairs), with the leptons coming from the decay of the new bosons and, in the case of production of singly charged bosons, from top quarks as well. These processes are predicted by classes of models based on extensions of the gauge group of the Standard Model, such as the 331 Model, where the electroweak symmetry is described by $SU(3)_L\times U(1)_X$, $X$ being a new abelian charge. For this purpose, a CMS search for vector-like partners with charge 5/3 decaying into $Wt$ is recast to obtain model-independent bounds and projected reaches at future luminosity stages of the LHC. The results are then interpreted as mass bounds for the new particles predicted in the 331 Model and as a constrain on the scale of its spontaneous symmetry breaking. The complete set of model-independent results are provided as recast efficiencies, to allow for reinterpretation in different scenarios.

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arXiv2019

The top-quark mass: challenges in definition and determination

The top-quark mass is a parameter of paramount importance in particle physics, playing a crucial role in the electroweak precision tests and in the stability of the Standard Model vacuum. I will discuss the main strategies to extract the top-quark mass at the LHC and the interpretation of the measurements in terms of well-posed top-mass definitions, taking particular care about renormalon ambiguities, progress in Monte Carlo event generators for top physics and theoretical uncertainties.

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arXiv2018

Exploring Scalar and Vector Bileptons at the LHC

We present an analysis on the production of two same-sign lepton pairs at the LHC, mediated by bileptons in the $SU(3)_c\times SU(3)_L\times U(1)_X$ theory, the so-called 331 model. Compared to other 331 scenarios, in this model the embedding of the hypercharge is obtained with the addition of 3 exotic quarks and doubly-charged vector gauge bosons with lepton numbers $\pm 2$ in the spectrum ($Y^{\pm\pm}$), which can mediate the production of four-lepton final states. Furthermore, a complete description of the model requires the introduction of a Higgs scalar sector, which is a sextet of $SU(3)_L$, necessary in order to correctly account for the lepton masses. As a result of this, new doubly-charged scalar states $H^{\pm\pm}$ are part of the spectrum as well and can in principle compete with the vector bileptons in giving rise to four-lepton final states. We investigate both channels and study several observables at the LHC, for both signal and Standard Model $ZZ$ background. With respect to previous work on vector- and scalar-bilepton production, we use the most updated exclusion limits at the LHC and implement the 331 model in a full Monte Carlo simulation code, capable of being interfaced with any analysis framework. Our result is that the 331 signal can be discriminated from the background with a significance of 6-9 standard deviations, depending on the LHC luminosity, with the vector bileptons dominating over the scalar ones.

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arXiv2018

Fragmentation Uncertainties in Hadronic Observables for Top-quark Mass Measurements

We study the Monte Carlo uncertainties due to modeling of hadronization and showering in the extraction of the top-quark mass from observables that use exclusive hadronic final states in top decays, such as $t \rightarrow \text{anything+J/}ψ$ or $t\rightarrow \text{anything}+(B\rightarrow \text{charged tracks})$, where $B$ is a $B$-hadron. To this end, we investigate the sensitivity of the top-quark mass, determined by means of a few observables already proposed in the literature as well as some new proposals, to the relevant parameters of event generators, such as HERWIG 6 and PYTHIA 8. We find that constraining those parameters at $\mathcal{O}(1\%-10\%)$ is required to avoid a Monte Carlo uncertainty on $m_t$ greater than 500 MeV. For the sake of achieving the needed accuracy on such parameters, we examine the sensitivity of the top-quark mass measured from spectral features, such as peaks, endpoints and distributions of $E_{B}$, $m_{B\ell}$, and some $m_{T2}$-like variables. We find that restricting oneself to regions sufficiently close to the endpoints enables one to substantially decrease the dependence on the Monte Carlo parameters, but at the price of inflating significantly the statistical uncertainties. To ameliorate this situation we study how well the data on top-quark production and decay at the LHC can be utilized to constrain the showering and hadronization variables. We find that a global exploration of several calibration observables, sensitive to the Monte Carlo parameters but very mildly to $m_{t}$, can offer useful constraints on the parameters, as long as such quantities are measured with a 1% precision.

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arXiv2018

Loopholes in $Z^\prime$ searches at the LHC: exploring supersymmetric and leptophobic scenarios

Searching for heavy vector bosons $Z^\prime$, predicted in models inspired by Grand Unification Theories, is among the challenging objectives of the LHC. The ATLAS and CMS collaborations have looked for $Z^\prime$ bosons assuming that they can decay only into Standard Model channels, and have set exclusion limits by investigating dilepton, dijet and to a smaller extent top-antitop final states. In this work we explore possible loopholes in these $Z^\prime$ searches by studying supersymmetric as well as leptophobic scenarios. We demonstrate the existence of realizations in which the $Z^\prime$ boson automatically evades the typical bounds derived from the analyses of the Drell-Yan invariant-mass spectrum. Dileptonic final states can in contrast only originate from supersymmetric $Z^\prime$ decays and are thus accompanied by additional effects. This feature is analyzed in the context of judiciously chosen benchmark configurations, for which visible signals could be expected in future LHC data with a $4σ-7σ$ significance. Our results should hence motivate an extension of the current $Z^\prime$ search program to account for supersymmetric and leptophobic models.

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arXiv2017

Supersymmetric signals in Z' decays

I present a scenario wherein heavy neutral vector bosons Z', predicted by GUT-inspired U(1)' models, decay into supersymmetric final states, besides the Standard Model channels investigated at the LHC. It is found that accounting for such decays lowers the exclusion limits on the Z' mass at 13 TeV by about 200-300 GeV.

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arXiv2017

Non-standard heavy vectors at the LHC

Heavy vector-boson hunting is one of the major analyses undertaken by the experiments carried out at the LHC. I will explore two scenarios which have not been investigated yet by the experimental collaborations. The first scenario consists in searching for Z' bosons, predicted by U(1)' GUT-inspired models, by studying its supersymmetric decays, leading to resonant final states with charged leptons and missing energy. Afterwards, I shall discuss the 331 model and the production of doubly-charged vector bileptons, yielding events with two same-sign lepton pairs at the LHC.

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arXiv2017

Bilepton Signatures at the LHC

We discuss the main signatures of the Bilepton Model at the Large Hadron Collider, focusing on its gauge boson sector. The model is characterised by five additional gauge bosons, four charged and one neutral, beyond those of the Standard Model, plus three exotic quarks. The latter turn into ordinary quarks with the emission of bilepton doublets $(Y^{++},Y^{+})$ and $(Y^{--},Y^{-})$ of lepton number $L=-2$ and $L=+2$ respectively, with the doubly-charged bileptons decaying into same-sign lepton pairs. We perform a phenomenological analysis investigating processes with two doubly-charged bileptons and two jets at the LHC and find that, setting suitable cuts on pseudorapidities and transverse momenta of final-states jets and leptons, the model yields a visible signal and the main Standard Model backgrounds can be suppressed. Compared to previous studies, our investigation is based on a full Monte Carlo implementation of the model and accounts for parton showers, hadronization and an actual jet-clustering algorithm for both signal and Standard Model background, thus providing an optimal framework for an actual experimental search.

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