arXiv subjects

Stefano Moretti

Publications and source records attributed to Stefano Moretti.

At least 19 recordsLinked to original sources

arXiv2026

Hunting the Unseen: Deep Learning Analysis for Semi-Visible Jet Tagging

Semi-Visible Jets (SVJs) constitute a distinctive collider signature of strongly interacting dark sectors, embedding Dark Matter candidates, wherein jets contain both visible Standard Model objects and invisible dark hadrons, giving rise to correlated jet activity and missing transverse momentum. In this work, we investigate SVJs produced through a heavy Z' mediator and perform an study over a representative set of benchmark scenarios spanning different mediator masses and dark sector parameters in the context of so-called Hidden Valley Models. To characterise the signal, we combine global event kinematics with jet substructure observables, including the primary Lund Jet Plane (LJP), the two-point energy correlation, angularity, and charged hadron multiplicity. These representations are used to train five Deep Learning classifiers for SVJ vs standard jet discrimination: a Vision Transformer operating on LJP images, a JetLOV network based on a hierarchical clustering tree, a Multi-Layer Perceptron using high level observables, and two multimodal networks that combine the image-based or hierarchical representations of the radiation pattern with the high jet-level observables. This enables a direct combination of global kinematics, radiation patterns, and jet clustering structure. We find that global kinematic observables outperform the LJP and hierarchical jet representations, with the latter providing stronger discrimination than LJP images. Combining these complementary representations with global kinematics yields the best overall performance. More broadly, this study shows that unlocking the full discovery potential of SVJs would benefit from going beyond global kinematics to exploit the rich information encoded in their internal structure, providing a benchmark for future searches at the Large Hadron Collider.

hep-ph↗

arXiv2026

Quantum computation of partonic Drell-Yan scattering cross sections and interference effects

We probe the possibilities of efficiently constructing simple Feynman diagrams into quantum devices. More precisely, we study Drell-Yan lepton pair creation at the partonic level of the form q qbar -> gamma/Z -> l- l+. We develop quantum gates that build up the relevant diagrams using simple Feynman rules, such as vertex and propagator gates V and P. We show how the quantum circuit may compute simultaneous amplitudes in the phase space and how to reach the full integrated cross section from the outputs. In addition to this, we also show how the circuit is able to simultaneously isolate the interference effects of the contributing diagrams by a simple basis rotation. The circuit design is made to be general, and thus this work constitutes a step towards the implementation of arbitrary scattering process computations and efficient interference analyses.

hep-ph↗

arXiv2026

Lexicographic Social Ranking on Monotonic Coalitional Rankings

Recent studies on social rankings in coalitional settings have introduced methods that rank individuals by lexicographically comparing vectors of their occurrences across coalitions ordered according to their strength. In this work, we focus on two such solutions: the lexicographical excellence (lex-cel) solution, which disregards coalition size, and the L^(1) solution, which additionally prioritizes smaller coalitions through a double lexicographic comparison. We investigate the combinatorial connections between these two solutions on monotonic coalitional rankings, where equivalence classes are compactly represented through sets of minimal (with respect to set inclusion) coalitions. After introducing general formulas for computing the lex-cel and L^(1) parameter vectors from these minimal coalitions, we also present worst-case running time results. Finally, to further explore the behavior of the two solutions through simulations designed to assess the distance of the rankings they produce, we show that the monotonicity assumption does not lead to actual redundancy in the rankings produced by the two solutions.

cs.GT↗

arXiv2026

When the HL-LHC is blind, LISA is deaf (but not vice versa): 2HDM collider-cosmology synergies

Extensions of the Standard Model scalar sector can render the electroweak phase transition first-order and thereby provide the departure from thermal equilibrium required for electroweak baryogenesis, while at the same time sourcing a stochastic gravitational wave (GW) background in the milli-Hertz range. In this work, we investigate electroweak phase transitions in the CP-conserving type-I two-Higgs-doublet model (2HDM), focusing on the interplay between collider constraints at the HL-LHC and the projected sensitivity of LISA. We compute the expected GW background due to strong first-order electroweak phase transitions and perform extensive Monte Carlo scans over the collider-viable model parameter space. We find that GW signals within reach of LISA arise almost exclusively in regions of parameter space that necessarily predict observable deviations at the HL-LHC, in particular through the $H \to ZZ$ decay channel of the heavy CP-even and neutral Higgs state with $m_H \simeq 180\text{--}250 \, \text{GeV}$. Our results highlight the decisive complementarity between collider and GW probes and show that the largest parts of the 2HDM parameter space relevant for phase transition signals at LISA can already be tested by HL-LHC. A possible future discovery of 2HDM states at the HL-LHC, however, would not allow conclusive statements about LISA being able to find a GW background due to the amount of parameter tuning required for an observable GW signal. In order to evaluate possible caveats of this statement we study the theoretical uncertainties related to the GW predictions in a two-fold approach using both state-of-the-art tools, BSMPT and TransitionListener, and also allow for model realizations in which the electroweak symmetry is not restored in the high-temperature limit, which are the ones combining the loudest GW signals with the weakest collider coverage.

hep-ph↗

arXiv2026

Can $\gamma\gamma$ collisions rival $e^-e^+$ in probing doubly charged Higgs bosons?

High-energy $\gamma\gamma$ collisions, realizable as an operational mode of future lepton linear colliders such as the ILC and CLIC, provide a promising environment to probe extended Higgs sectors. We investigate the sensitivity of such colliders to doubly charged Higgs bosons within the 2-Higgs Doublet Model with type-II seesaw (2HDMcT). Focusing on the three-body production channels $\gamma\gamma \to H^{\pm\pm}H_1^{\mp}H_1^{\mp}$ and $\gamma\gamma \to H^{\pm\pm}H_1^{\mp}W^{\mp}$, we perform a parameter space scan consistent with theoretical constraints as well as current collider, flavor, and electroweak precision observables (EWPOs). We show that $\gamma\gamma$ collisions can rival the discovery potential of the conventional $e^+e^-$ mode for probing doubly charged Higgs bosons through a $4\ell+E_T^{miss}$ signature ($\ell=e,\mu$). Despite the reduced effective luminosity resulting from the photon spectrum, the significantly enhanced production cross sections, exceeding those in electron-positron collisions by more than one order of magnitude, compensate for this limitation. By performing a detailed signal-to-background analysis at center-of-mass energies of $\sqrt{s}=830$ and $1245$ GeV, we demonstrate that a discovery significance at the $5\sigma$ level can be achieved for viable benchmark points (BPs).

hep-ph↗

arXiv2026

Probing the Single Production of First-Generation Singlet Vector-like Leptons at Future $e^+e^-$ Colliders

We study the single production of first-generation weak-isosinglet vector-like leptons (VLLs) at future $e^+e^-$ colliders, considering the channels $e^+e^- \to e^{\pm}E^{\mp}$ with $E^{\pm} \to W^{\pm}\nu_e$ and $E^{\pm} \to e^{\pm}Z$. For the heavy VLL masses under consideration, the decay products of the highly boosted $W$ and $Z$ bosons merge into a single fat-jet, providing a powerful handle for signal identification and background suppression. A comprehensive Monte Carlo simulation is carried out at $\sqrt{s}=1$ TeV at the International Linear Collider (ILC) and 1.5 TeV at the Compact Linear Collider (CLIC). The $2\sigma$ exclusion and $5\sigma$ discovery reaches are determined as functions of the integrated luminosity and the mixing parameter $\sin\theta_L$ for representative benchmark masses. Our results show that future $e^+e^-$ colliders can effectively probe the first-generation singlet VLL scenario through these channels. The 1 TeV ILC can probe masses up to 900 GeV, while the 1.5 TeV CLIC extends the reach to 1400 GeV, surpassing existing limits from hadron colliders and complementing constraints from electroweak precision measurements.

hep-ph↗

arXiv2026

Mono-X Signal Characterization from Two-component Dark Matter Using a Convolutional Neural Network

We assess the scope of a Convolutional Neural Network (CNN) in characterizing potential signals of two-component Dark Matter (DM) arising at the Large Hadron Collider (LHC) from mono-jet and mono-Z probes. We show that such a CNN has the ability of not only inferring the presence of two DM particles but also of extracting their mass and spin, the latter being either 0 or 1/2, following detector level analysis. However, such result represents a conceptual proof-of-concept, as we have not entertained a signal-to-background analysis.

hep-ph↗

arXiv2026

Characterisation at the HL-LHC of Long-lived Heavy Neutrinos in Gauge Extensions of the Standard Model

We show how signals of heavy neutrinos with displaced decays can be detected at the Large Hadron Collider in two theoretical setups, both exploiting extended gauge sectors as portals to such new physics, the Left-Right Symmetric Model and $U(1)_{B-L}$. Further, owing to the reduced contamination from backgrounds away from the interaction point, we illustrate how the properties of the heavy neutrinos (mass, width and quantum numbers) can neatly be accessed at the High-Luminosity upgrade of the CERN machine.

hep-ph↗

arXiv2026

Probing the vector-like $X$ quark via the $tW$ channel at future muon-proton colliders

We investigate the discovery potential for the vector-like $X$-quark (VLX) at future muon--proton ($\mu p$) colliders through the process $\mu^+ p \to \bar{\nu}_\mu X \to \bar{\nu}_\mu t W^+$. A simplified effective model is adopted in which the production and decay of the VLX are governed by the coupling strength $g^{*}$, the generation-mixing parameter $R_{L}$, and the VLX mass $m_X$. A comprehensive Monte Carlo analysis is performed at $\sqrt{s}=5.29$, $6.48$, and $9.16\ \mathrm{TeV}$, considering four complementary decay channels: the Fully Leptonic (FL), Fully Hadronic (FH), and two Semi-Leptonic (SL1 and SL2) modes. An $80\%$ polarized muon beam together with boosted-object reconstruction based on fat-jet techniques is employed to improve the signal sensitivity. The expected exclusion and discovery reaches are evaluated using the Asimov significance. We find that the sensitivity can be improved substantially with increasing center-of-mass energy and larger values of $R_L$. Among the four channels, the FH mode provides the strongest sensitivity, reaching a $2\sigma$ exclusion limit of $m_X\simeq8.3\ \mathrm{TeV}$ with $g^* = 0.009 $ for $R_L=0.1$ at $\sqrt{s}=9.16\ \mathrm{TeV}$, whereas the FL mode gives the weakest reach because of its smallest branch ratio. These results demonstrate that future $\mu p$ colliders can offer significant sensitivity to heavy VLX over a broad region of parameter space.

hep-ph↗

arXiv2026

Searching for single production of a vector-like $Y$ quark decaying into $bW$ at the FCC-eh

We investigate the exclusion and discovery potential for single production of a vector-like $Y$ quark with electric charge $Q=-4/3$, followed by the decay $Y\to bW$, at the FCC-eh. The $Y$ quark is allowed to couple to both first- and third-generation down-type quarks. The analysis is performed for an electron-beam polarization of $P_e=-80\%$ at $\sqrt{s}=3.46$, $5.29$, and $6.9~\mathrm{TeV}$. Both leptonic and hadronic $W$-boson decay channels are considered. In the hadronic channel, the boosted $W$-boson is reconstructed as a $W$-jet, and kinematic observables are used to suppress the Standard Model (SM) backgrounds. By performing a detailed detector simulations and event analysis, we present the $2\sigma$ exclusion limits and $5\sigma$ discovery reaches in the $g^*$--$m_Y$ plane, where $g^*$ is $Y$ coupling strength to the SM quarks. We find that the hadronic channel can provide stronger exclusion and discovery sensitivities, which are improved with increasing $\sqrt{s}$ at the FCC-eh.

hep-ph↗

arXiv2026

Comparison games and ranking of players

This work addresses the problem of assessing player importance in coalitional settings where the available information concerns the relative strength between pairs of coalitions, rather than the absolute worth of each coalition. We introduce a novel framework that is flexible enough to represent all coalitional pseudo-games and, through the use of coalitional networks, naturally accommodates scenarios with limited or heterogeneous coalition comparisons. Importantly, this framework still enables the computation of semivalues of pseudo-games, such as the Banzhaf and Shapley values, that can be expressed as weighted sums of differences in specific coalition comparisons, thus offering interpretations beyond traditional approaches. Furthermore, for ranking players rather than computing exact numerical attributions, we introduce the concept of a player's score, which simplifies the process of determining rankings based on semivalues, and shifts the perspective from average marginal contribution to average coalitional worth. This turns out to be particularly enlightening for the Banzhaf value.

econ.TH↗

arXiv2026

Soft-Dimuon Signature from Two-Component Scalar Dark Matter at the LHC

We explore the potential of the Large Hadron Collider to probe a two-component scalar dark matter scenario in the opposite-sign dimuon plus missing transverse energy final state, accompanied by a hard jet. The signal features a soft dimuon system with an invariant mass well below $m_Z$. We consider a 3-Higgs Doublet Model with one active and two inert scalar doublets, where a $Z_2 \times Z_2'$ symmetry stabilises the lightest neutral scalar in each inert sector, yielding two scalar DM candidates. The relevant parameter space is mapped in terms of the two DM masses and the mass splittings between each DM candidate and its corresponding next-to-lightest scalar state. We perform a detector-level Monte Carlo analysis and design a dedicated cut-based selection, including a transverse-mass requirement adapted to the signal topology. For a representative benchmark, we obtain $S/B\simeq 9.8%$ and a statistical-only significance of $S/\sqrt{B}=1.35$ at Run 3 with ${\cal L}=300~{\rm fb}^{-1}$, increasing to $S/\sqrt{B}=4.93$ under a statistical-only extrapolation to ${\cal L}=4~{\rm ab}^{-1}$. Before the full selection, the two dark sectors generate a double-bump structure in the dimuon invariant-mass distribution. After the cuts optimised for inclusive sensitivity, however, this feature is not statistically robust enough to establish the two-component origin of the signal. The benchmark is underabundant and is interpreted as a subdominant two-component DM scenario, while the collider analysis remains independent of its cosmological abundance. Although the numerical study is carried out in the I(2+1)HDM, the results are applicable to weakly interacting sectors with similar electroweak associated production and cascade decays, where a heavier state separated from the DM candidate by less than $m_Z$ produces a soft muon pair via an off-shell $Z$ boson.

hep-ph↗

arXiv2026

Probing Anomalous $t{\bar q}Z$ Interactions at Muon Colliders

In the framework of effective field theory, we study the anomalous $t{\bar q}Z$ interaction through the process $\mu^+\mu^- \to t{\bar q}Z$ at future muon colliders with $\sqrt s= 3, 10, 14\,\text{TeV}$. Based on the top quark decay modes involving $W$ and $Z$ bosons, we first divide the signal into six cases. Then, in order to obtain the limits on the corresponding branching ratios, we perform a detector simulation for both signals and Standard Model backgrounds. To enhance the signal significance, we exploit the polarization of the muon beams and employ the fat jet method to reconstruct signals in hadronic final states. For $\sqrt s= 14\,\text{TeV}$ with $20\,\text{ab}^{-1}$, we find that the upper limit on the branching ratio for $t\to qZ$ can reach the order of $\mathcal{O}(10^{-8})$, which exceeds the limits provided by the CMS and ATLAS collaborations by 2 to 3 orders of magnitude. Our study thus demonstrates that TeV-scale muon colliders can provide an efficient and complementary platform for probing rare top quark interactions.

hep-ph↗

arXiv2026

Non-standard decays of vector-like top partners in a $2$-Higgs doublet model at the HL-LHC

Extensions of the Standard Model featuring both an enlarged scalar sector and vector-like fermions arise naturally in a wide class of well-motivated theoretical frameworks. In such scenarios, vector-like Quarks (VLQs) can exhibit non-standard decay modes involving additional Higgs states, giving rise to distinctive collider signatures that remain largely unexplored by existing experimental searches. We investigate the prospects of probing this possibility at the high-luminosity Large Hadron Collider (HL-LHC) through the decay of vector-like top partner ($T$) to charged Higgs ($H^{\pm}$) followed by the decay, $H^\pm\to\tau\nu$, producing a final state containing two tau leptons, two $b$-jets, and missing transverse energy. A model-independent collider analysis is performed using global kinematic observables constructed from visible objects and the missing transverse momentum vector to suppress the dominant backgrounds. Polarization-sensitive observables built from the hadronic $\tau$ decay products are also examined as complementary probes of the spin-$0$ origin of the $\tau$ leptons. The expected discovery sensitivity is evaluated using the Asimov significance for an integrated luminosity of $3$ ab$^{-1}$ at $\sqrt{s}=14$ TeV. Our results demonstrate that the $2\tau\:+\:2b\:+$ missing $E_T$ channel provides a promising and largely orthogonal avenue to search for non-standard VLQ decays in extended Higgs sectors, with discovery-level sensitivity achievable for VLQ masses up to approximately $1.9$ TeV.

hep-ph↗

arXiv2026

The $Z'$-boson of the $B-L$ Supersymmetric Standard Model and its Large Hadron Collider Searches

We discuss how the $Z'$-boson of the $B-L$ Supersymmetric (SUSY) Standard Model (BLSSM) could evade the current lower bound of around 5 TeV on the mass of such a resonance (of sequential nature) from the Large Hadron Collider (LHC) by a significant margin. This happens when the experimental sensitivities are critically impaired as the $Z'$-boson becomes `fat' or develops some leptophobia or possesses an optimally large decay Branching Ratio (BR) to BLSSM-specific states (including the SUSY ones) or when some or all of these are at play simultaneously. We describe how such a $Z'$-boson could acquire there features while still respecting the non-negotiable precision constraints from the LEP and the SLC experiments running at the $Z$-pole as well as those from the multi-purpose experiments at the LHC that search for such a resonance. We explore the interplay of the aforementioned phenomena and identify the regions of the BLSSM parameter space that give rise to the described situation by carrying out a thorough scan of it. We find that $M_{Z'}$ masses as low as 2.24 TeV may still be allowed in the BLSSM under favorable circumstances.

hep-ph↗

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 $4.5\sigma$, for an integrated luminosity of 300 fb$^{-1}$ at the CERN machine.

hep-ph↗

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

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.

hep-ph↗