arXiv subjects

Stefano Moretti

Publications and source records attributed to Stefano Moretti.

At least 37 records · Page 2Linked to original sources

arXiv2026

Explaining 650 GeV and 95 GeV Anomalies in the 2-Higgs Doublet Model Type-I

We propose an interpretation of a rather significant 650 GeV excess emerged at the Large Hadron Collider (LHC) from CMS Collaboration data in the $γγb\bar b$ final state, accompanied by further clusters at 125(90-100) GeV in the $γγ(b\bar b)$ system, within the 2-Higgs Doublet Model Type-I (2HDM-I) in presence of a softly broken $\mathcal{Z}_{2}$ symmetry. The underlying process that we probe is $gg$-initiated production of a CP-odd (or pseudoscalar) Higgs boson $A$, with mass around 650 GeV, decaying into the Standard Model (SM)-like Higgs state $H$ (decaying into $γγ$) and a $Z$ boson (decaying into $b\bar b$). We configure this theoretical framework so as to also have in the spectrum a light CP-even (or scalar) Higgs state $h$ with mass around 95 GeV, which is included for the purpose of simultaneously explaining additional data anomalies seen in the $b\bar b$, $γγ$ and $τ^+τ^-$ final states while searching for light Higgs states at the Large Electron-Positron (LEP) collider (the first one) and LHC (the last two). By accounting for both experimental and theoretical constraints, our results show that the 2HDM-I can explain all aforementioned anomalies at a significance level of $2.5 σ$.

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arXiv2026

Probing Doubly Charged Higgs Bosons with Three-Body Associated Production at Future $e^+e^-$ Colliders

We study the discovery prospects for a doubly charged Higgs boson $H^{\pm\pm}$ in the 2-Higgs doublet model with type-II seesaw at future $e^+e^-$ colliders. Focusing on the three-body channels $e^+e^- \to H^{\pm\pm}H_1^{\mp}H_1^{\mp}$ and $e^+e^- \to H^{\pm\pm}H_1^{\mp}W^{\mp}$, we scan the model parameter space subject to theoretical consistency as well as current collider, flavor and electroWeak precision observables (EWPOs). We find that these $2\to3$ production modes can exceed the conventional pair-production rate $e^+e^- \to H^{++}H^{--}$, followed by $H^{\pm\pm}\to H_1^{\pm}H_1^{\pm}$ and $H^{\pm}_1W^{\pm}$ decays, over wide regions, particularly above the $H^{\pm\pm}\to H_1^{\pm}H_1^{\pm}$ and $H^{\pm\pm}\to H_1^{\pm}W^{\pm}$ thresholds, reaching cross sections up to ${\cal O}(10^2)$~fb for $\sqrt{s}=500$--$1500$~GeV. A detector-level analysis of the $4\ell + E_T^{\text{miss}}$ signature, including dominant multiboson and top quark backgrounds, shows that discovery sensitivity is achievable for $\sqrt{s}=1000$-$1500$~GeV with integrated luminosities in the few ab$^{-1}$ range, even in the presence of realistic systematic uncertainties.

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arXiv2026

Machine Learning Enhanced Detection of Higgs Chain Decays in Vector Boson Fusion

Over the years, Vector Boson Fusion (VBF) has established itself as one of the most robust production channels for studying the Higgs boson, while also serving as a promising pathway for exploring potential signatures of physics Beyond the Standard Model (BSM) at the Large Hadron Collider (LHC). Following the discovery of a SM-like Higgs boson, new opportunities have arisen to also investigate heavy resonances that decay into SM-like Higgs boson pairs, $hh$, thereby offering valuable insights into the structure of the Higgs sector and the dynamics governing Electro-Weak Symmetry Breaking (EWSB). In this work, we analyze a final state involving, alongside 2 forward/backward light quarks, 4 $b$-quarks emerging from the chain decay $h_2\to h_1h_1\to b\bar b b\bar b$ wherein the heavy CP-even Higgs state $h_2$ is produced in the VBF process $qq\to qqh_2$ and belongs to the Next-to-Minimal Supersymmetric SM (NMSSM). This BSM scenario is used as an illustrative example of the potential of using only low-level calorimeter information enhanced by advanced Deep Learning (DL) methodologies in searching for this channel, which can achieve a statistical significance of approximately $4.5σ$, for an integrated luminosity of 300 fb$^{-1}$ at the CERN machine.

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arXiv2026

The X17 Existence Hinted at by Nuclear Reactor Neutrinos

We show that by exploiting the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS), neutrino measurements by nuclear reactor experiments appear to corroborate the evidence of the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly. We base our analysis primarily on CONUS+ and Dresden-II data, which, when combined with CEvNS data from COHERENT and neutrino oscillation data from IceCube, single out a unique region of couplings to neutrinos and nuclei.

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arXiv2026

Consistency, unanimity, and the Borda rule in social ranking

The social ranking is a recently proposed framework for evaluating the power of individuals according to the performance ranking of their coalitions. Although its origin can be traced to the classical power indices in simple games, social ranking approaches carry out this evaluation within the ordinal framework of social choice theory. This article introduces the Borda rule into social ranking. Specifically, we focus on two essential properties of the Borda rule--consistency and closeness to unanimity--and investigate the social ranking solutions (SRSs) satisfying these properties. Among several possible definitions of the Borda rule as an SRS, we characterize one of such solutions by (a weak version of) consistency, closeness to unanimity (under the linear and symmetric domain), neutrality (i.e., names of the individuals do not matter), and independence of perfunctory participation (i.e., adding a perfunctory coalition into the worst class of the coalitional ranking does not affect the social ranking). We therefore propose a new Borda-type SRS for evaluating the competence of individuals in coalitional contexts.

econ.TH↗

arXiv2026

Mono-Z' Signatures in the B-L Supersymmetric Standard Model at the LHC

The B-L Supersymmetric Standard Model with Inverse Seesaw (BLSSM-IS) extends the Minimal Supersymmetric Standard Model (MSSM) by incorporating a gauged B-L symmetry, right-handed neutrinos and an additional neutral gauge boson Z'. Searches at the Large Hadron Collider (LHC) constrain the mass of this gauge boson to be as low as only ~ 2.2 TeV in the BLSSM-IS, owing to interference effects with the SM. In this framework, mono-Z' events can arise from the associated production of a Z' boson and a singlet Higgs boson h', where h' subsequently decays into missing energy carried by a pair of the Lightest Supersymmetric Particle (LSP) - either a neutralino or a right-handed sneutrino - which serves as a Dark Matter (DM) candidate. Focusing on leptonic decays of the Z' (electrons and muons), we analyse the kinematic distributions of the final-state leptons and the missing transverse energy in order to extract a signal for this process which is independent of the nature of the BLSSM-IS DM.

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arXiv2026

A quantum algorithm for the n-gluon MHV scattering amplitude

We propose a quantum algorithm for computing the n-gluon maximally helicity violating (MHV) tree-level scattering amplitude. We revisit a newly proposed method for unitarisation of non-unitary operations and present how this implementation can be used to create quantum gates responsible for the color and kinematic factors of the gluon scattering amplitude. As a proof-of-concept, we detail the full conceptual algorithm that yields the squared amplitude and implement the corresponding building blocks on simulated noiseless quantum circuits for n = 4 to analyze its performance. The algorithm is found to perform well with parameter optimizations, suggesting it to be a good candidate for implementing on quantum computers also for higher multiplicities.

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arXiv2026

Interpreting the 650 GeV and 95 GeV Higgs anomalies in the next-to-two-Higgs-doublet model

Recent experimental hints from the Large Hadron Collider (LHC) in di-photon and partially in the $τ^+τ^-$ final states suggest the possible existence of an additional Higgs boson with a mass around 95 GeV. Interestingly, these observations are consistent with earlier results from the Large Electron-Positron (LEP) collider, which pointed to an excess in $b\bar b$ final states within a similar mass range. Additionally, CMS has observed an excess in the $γγb\bar{b}$ final state, indicating a possible resonance near 650 GeV decaying into a pair of SM-like Higgs bosons or into a SM-like Higgs boson accompanied by a lighter scalar with mass near 95 GeV. In this work, we investigate whether these anomalies can be simultaneously explained within the Next-to-2-Higgs-Doublet Model (N2HDM), an extension of the Standard Model (SM) scalar sector featuring two complex Higgs doublets and an additional real singlet. Assuming the existence of a CP-even Higgs state compatible with the 95 GeV excesses (restricted to the $γγ$ and $b\bar b$ channels). Our results show that a heavy CP-even Higgs resonance around 650 GeV, produced predominantly via gluon-gluon fusion and subsequently decaying into a 125 GeV Higgs boson together with another scalar at approximately 95 GeV, can be simultaneously accommodated within both the N2HDM Type-II and Type-Y frameworks in parameter regions that remain consistent with the relevant experimental $2σ$ intervals for the reported excesses, once all theoretical and experimental constraints are imposed. This interpretation leads to distinctive and testable predictions for the ongoing LHC Run~3 and the forthcoming High-Luminosity LHC (HL-LHC) phase, in particular through correlated rates in the $γγb\bar b$, $τ^+τ^- b\bar b$, $b\bar b\,γγ$, and $γγτ^+τ^-$ final states.

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arXiv2026

Consistencies in Social Ranking

Ranking individuals based on their performance in different coalitions is a problem emerging in various domains (teams sports, scientific evaluation, argumentation, etc.). Often, for practical reasons, the number of comparable coalitions is limited. Therefore, the foundational principles of ranking solutions must support realistic interpretations in contexts where only certain coalitions can be compared. To address this issue, in this paper we present an axiomatic analysis of solutions for the social ranking problem centered on the notion of consistency. More precisely, we show that an appropriate notion of consistency, which specifies how to combine rankings on individuals across different rankings on coalitions, plays a key role in any axiomatic characterization, representing the true distinguishing feature of each solution. This role is further highlighted by the taxonomy of the complementary axioms used in our characterizations, which boil down to well-studied properties of invariance with respect to the label of players or coalitions, and also with respect to minor changes in a coalitional ranking. By showing the logical independence of the axioms used in each characterization, as well as a rigorous analysis of alternative notions of consistency with respect to the majority of solutions from the literature, this work attempts to provide a first systematic study of the social ranking problem over a variable domain of coalitions.

econ.TH↗

arXiv2026

Searches for Extra Higgs Bosons using $t\bar{t}+$Higgs{$(\to b\bar b)$} Events within 2HDMs: Direct versus Indirect Probes

We study the possibility of establishing the production of additional Higgs states in the process $gg,q\bar q\to t\bar t Φ$, where $Φ$ = $H_{2,3}$, with $H_2$ being CP-even and $H_3$ being CP-odd, at the Large Hadron Collider (LHC), by solely exploiting the kinematic features of the reconstructed $t\bar t$ system. We adopt as reference theoretical framework a generic CP-Conserving 2-Higgs Doublet Model (2HDM), which also accommodate a Standard Model (SM)-like Higgs state $H_1$. We show that the masses $m_{H_{2,3}}$ exhibit clear correlations with the $t\bar{t}$ system properties and could, in principle, be extracted from these. Moreover, the CP properties of the $H_{2,3}$ states can be determined, even when both states are produced simultaneously. We then compare the results produced using this method with those obtained from a full kinematic reconstruction of the $H_{2,3}$ decays in the most studied $b\bar b$ channel (we take $m_{H_{2,3}}< 2m_t$), thus proving the superiority of the approach here proposed. This paves the way to both the discovery and characterization of additional Higgs states produced {\sl inclusively} in association with top-antitop quark pairs, thereby dispensing of the complications intrinsic to the {\sl exclusive} reconstruction of such states from their decay products. We test this by establishing the sensitivity of our approach in the case of a Composite 2HDM (C2HDM), describing the Higges as pseudo-Nambu Goldstone Bosons (pNGBs) and naturally predicting Higgs mass spectra in the range of sensitivity of the described analysis.

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arXiv2026

Probing the pair production of first-generation vector-like leptons at future $e^+e^-$ colliders

This work explores the discovery potential of the first-generation weak isosinglet Vector-Like Leptons (VLLs), denoted by $E^\pm$, via pair production at future electron-positron colliders. Our analysis adopts a comprehensive framework that incorporates beam polarization configurations and leverages detailed detector simulations. We focus on two distinct multilepton signatures: the $2\ell + 2j + \slashed{E}_T$ and $3\ell + 2j + \slashed{E}_T$ final states ($\ell = e, μ$). Both signatures arise from the decay $E^{\pm} \to Z e^{\pm} / W^{\pm} ν_\ell$ and are distinguished by the decay patterns of the associated gauge bosons. By applying optimized selection criteria to both signal and background events, we establish exclusion sensitivities and discovery prospects across the VLL mass spectrum. Our findings demonstrate that, for integrated luminosities of $\SI{25}{fb^{-1}}$, $\SI{90}{fb^{-1}}$ and $\SI{1000}{fb^{-1}}$ at corresponding center-of-mass (c.m.) energies of $\SI{1}{TeV}$, $\SI{1.5}{TeV}$ and $\SI{3}{TeV}$, the accessible mass range extends to approximately $\SI{490}{GeV}$, $\SI{740}{GeV}$ and $\SI{1440}{GeV}$, which represents a substantially improvement over the detection limits of existing hadron collider experiments.

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arXiv2026

Investigating the 95 GeV Higgs Boson Excesses within the I(1+2)HDM

In this work, we explore how the 2-Higgs Doublet Model (2HDM) Type-I, extended by an inert doublet, can provide an explanation for the recently observed excesses at the Large Hadron Collider (LHC) in the $γγ$ and $τ^+ τ^- $ final states. Hence, by imposing theoretical constraints and experimental bounds on the model parameter space, our findings show that a light CP-even Higgs boson, $h$, with a mass around 95 GeV, can account for these anomalies. This result aligns with the excess in $b\bar b$ signatures reported in earlier data from the Large Electron-Positron (LEP) collider.

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arXiv2025

Explaining 95 GeV Anomalies in the 2-Higgs Doublet Model Type-I

We show how the 2-Higgs Doublet Model (2HDM) Type-I can explain some excesses recently seen at the Large Hadron Collider (LHC) in $γγ$ and $τ^+τ^-$ final states in turn matching Large Electron Positron (LEP) data in $b\bar b$ signatures, all anomalies residing around 95 GeV. The explanation to such anomalous data is found in the aforementioned scenario when in inverted mass hierarchy, in two configurations: i) when the lightest CP-even Higgs state is alone capable of reproducing the excesses; ii) when a combination of such a state and the CP-odd Higgs boson is able to do so. To test further this scenario, we present some Benchmark Points (BPs) of it amenable to phenomenological investigation.

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arXiv2025

Boosting probes of CP violation in the top Yukawa coupling with Deep Learning

The precise measurement of the top-Higgs coupling is crucial in particle physics, offering insights into potential new physics Beyond the Standard Model (BSM) carrying {\cal CP} Violation (CPV) effects. In this paper, we explore the {\cal CP} properties of a Higgs boson coupling with a top quark pair, focusing on events where the Higgs state decays into a pair of $b$-quarks and the top-antitop system decays leptonically. The novelty of our analysis resides in the exploitation of two conditional Deep Learning (DL) networks: a Multi-Layer Perceptron (MLP) and a Graph Convolution Network (GCN). These models are trained for selected CPV phase values and then used to interpolate all possible values ranging from $0$ to $π/2$. This enables a comprehensive assessment of sensitivity across all {\cal CP} phase values, thereby streamlining the process as the models are trained only once. Notably, the conditional GCN exhibits superior performance over the conditional MLP, owing to the nature of graph-based Neural Network (NN) structures. Specifically, for Higgs top coupling modifier set to 1, with $\sqrt{s}= 13.6$ TeV and integrated luminosity of $3$ ab$^{-1}$ GCN excludes the {\cal CP} phase larger than $5^\circ$ at $95.4\%$ Confidence Level (C.L). Our Machine Learning (ML) informed findings indicate that assessment of the {\cal CP} properties of the Higgs coupling to the $t\bar t$ pair can be within reach of the High Luminosity Large Hadron Collider (HL-LHC), quantitatively surpassing the sensitivity of more traditional approaches.

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arXiv2025

Explaining Data Anomalies over the NMSSM Parameter Space with Deep Learning Techniques

Motivated by recent results from particle physics analyses, we investigate the Next-to-Minimal Supersymmetric Standard Model (NMSSM) as a framework capable of accommodating a range of current data anomalies across low- and high-energy experiments. These include the so-called 95GeV and 650GeV excesses from Higgs studies, the Electro-Weakino excess from Supersymmetry searches, the latest $(g-2)_μ$ measurements as well as potential deviations from Standard Model (SM) predictions that would appear as a consequence in mono-$H$ (where $H=h_{\rm SM}$) and -$Z$ signatures of Dark Matter. Our analysis demonstrates that viable NMSSM parameter regions exist where all these features can be accommodated at the $2σ$ level while remaining consistent with the most up-to-date theoretical and experimental constraints. To identify such regions, we employ an efficient numerical scanning strategy assisted by deep learning techniques. We further present several benchmark points that realize these scenarios, offering promising directions for future phenomenological studies.

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arXiv2025

Probing Standard Model-like di-Higgs Production at Photon-Photon Colliders in the I(1+2)HDM Type-I

In this paper, pair production of Standard Model (SM)-like Higgs bosons, $hh$, is studied through $γγ$ scattering at future electron-positron colliders, in the framework of the Inert Doublet Model with two Active Doublets, i.e., the I(1+2)HDM for short. The relevance of the process $γγ\to hh$ for such a Beyond the SM (BSM) scenario stems from the fact that it is a one-loop process at lowest order, wherein inert charged states $χ^\pm$ contribute alongside with $W^\pm$, $H^\pm$ and heavy fermions (primarily, bottom and top quarks), crucially, at the same perturbative order. {Given that $χ^\pm/H^\pm$ masses and $hS^+S^-$ ($S^\pm=χ^\pm, H^\pm$) couplings are very mildly constrained,} there exist regions of the parameter space of the I(1+2)HDM where the former can be rather light and the latter rather large. After imposing up-to-date theoretical and experimental constraints on the I(1+2)HDM, it is found that the production rates of such process at future $γγ$ machines can be enhanced up to a factor of $\approx$ $50$ with respect to the SM, significantly exceeding typical yields of conventional 2-Higgs Doublet Models (2HDMs). Further, thanks to the level of control that one can attain at such facilities on the photon kinematics, leading to excellent invariant mass resolution of the incoming photon pairs, we show how it is possible to extract from this process the value of the $χ^\pm$ mass (along that of the active $H^\pm$ states) with high precision, whichever the decays of the $hh$ pair, both with and without beam polarization.

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arXiv2025

Could the 650 GeV Excess be a Pseudoscalar of a 3-Higgs Doublet Model?

In this study, we propose the interpretation of a 650 GeV excess observed at the Large Hadron Collider (LHC) by the CMS Collaboration in terms of the production of a CP-odd (or pseudoscalar) Higgs boson A, with mass around 650 GeV, decaying into the Standard Model (SM)-like Higgs state $h_{125}$ (in turn decaying into $γγ$) and a Z boson (in turn decaying into $b\bar b$), within a 3-Higgs Doublet Model (3HDM) featuring two active and one inert doublet, known as the I(1+2)HDM. This theoretical structure features a spectrum with both the SM-like Higgs boson (with a 125 GeV mass) and a lighter CP-even (or scalar) Higgs state with mass around 95 GeV, $h_{95}$, which is present in this scenario for the purpose of simultaneously explaining anomalies seen in the $b\bar b$, $γγ$ and $τ^+τ^-$ final states in searches for additional light Higgs states at the Large Electron-Positron (LEP) collider and LHC itself. It should be noted that, in the I(1+2)HDM, the inert sector presents loop-induced enhancements to the $h_{95} \to γγ$ width via inert charged Higgs states, providing a viable mechanism to explain, in particular, the observed (and most significant) di-photon excess at 95 GeV. Taking into account both experimental and theoretical constraints, our results can not only explain the aforementioned anomalies (possibly, aside from the $τ^+τ^-$, which is the most marginal one) but also predict, as collateral signals, resonant production of the same CP-odd scalar A followed by the decays: (i) $A \to h_{95} \, Z$, leading to the same $γγb \bar{b}$ final state displaying the original 650 GeV anomaly and (ii) $A\to t\bar t$, leading to a well-known and studied signature.

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arXiv2025

Hunting the elusive $X17$ in CE$ν$NS at the ESS

The so-called $X17$ particle has been proposed in order to explain a very significant resonant behaviour (in both the angular separation and invariant mass) of $e^+e^-$ pairs produced during a nuclear transition of excited $^8$Be, $^4$He and $^{12}$C nuclei. Fits to the corresponding data point, as most probable explanation, to a spin-1 object, which is protophobic and has a mass of approximately 16.7 MeV, which then makes the $X17$ potentially observable in Coherent Elastic neutrino ($ν$) Nucleus Scattering (CE$ν$NS) at the European Spallation Source (ESS). By adopting as theoretical framework a minimal extension of the Standard Model (SM) with a generic $U(1)'$ gauge group mixing with the hypercharge one of the latter, which can naturally accommodate the $X17$ state compliant with all available measurements from a variety of experiments, we predict that CE$ν$NS at the ESS will constitute an effective means to probe this hypothesis, even after allowing for the inevitable systematics associated to the performance of the planned detectors therein.

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