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 bb̅ signatures reported in earlier data from the Large Electron-Positron (LEP) collider.

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.

We study the single production of first-generation weak-isosinglet vector-like leptons (VLLs) at future e^+e^- colliders, considering the channels e^+e^- → e^±E^∓ with E^±→ W^±ν_e and E^±→ e^±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 √(s)=1 TeV at the International Linear Collider (ILC) and 1.5 TeV at the Compact Linear Collider (CLIC). The 2σ exclusion and 5σ discovery reaches are determined as functions of the integrated luminosity and the mixing parameter _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.

We show that the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS) at nuclear reactor experiments has significant sensitivity to the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly, wherein electron-positron pairs emerging from a nuclear transition of excited Be-8, He-4 and C-12 nuclei are studied. Such a new state has potentially been identified as a spin-1 object, with axial-vector couplings and a mass around 16.7 MeV, hence, in the kinematic range accessible by the aforementioned experimental settings. Specifically, we fit CONUS+ and Dresden-II data and show that a robust statistical analysis renders these more compatible with the X17 hypothesis, in turn interfering with the Standard Model, than with that of the latter alone. The same stays true when also adding COHERENT data from pi+ decays at rest, singling out two regions of preferred couplings of the X17 to electron and muon neutrinos as well as nuclei.

We study the discovery prospects for a doubly charged Higgs boson Htt in the 2-Higgs doublet model with type-II seesaw at future e+e-colliders. Focusing on the three-body channels e+e--* HttH+1 H+1 and e+e--* HttH+1 W+, we scan the model parameter space subject to theoretical consistency as well as current collider, flavor, and electroweak precision observables. We find that these 2-* 3 production modes can exceed the conventional pair production rate e+e--* H++H--, followed by Htt-* Ht1 Ht1 and Ht1 Wt decays, over wide regions, particularly above the Htt-* Ht1 Ht1 and Htt-* Ht1 Wt thresholds, reaching cross sections up to O(102) fb for ffiffi s p= 500-1500 GeV. A detector-level analysis of the 4l + ET signature, including dominant multiboson and top quark backgrounds, shows that discovery sensitivity is ffiachievable for p s= 1000-1500 GeV with integrated luminosities in the few ab-1 range, even in the presence of realistic systematic uncertainties.

We show that the Aligned 2-Higgs Doublet Model (A2HDM) is a framework able to simultaneously accommodate strong first order electro-weak phase transitions, in turn generating detectable gravitational waves as well as a variety of Higgs boson signals (involving both the Standard Model state and its companions, both neutral and charged) accessible at the Large Hadron Collider (LHC). We map the corresponding expanse of parameter space where such a phenomenology is realised in terms of the relative values of the masses of the discovered Higgs boson and the extended Higgs sector states of this model: two neutral ones (a CP-even and a CP-odd) plus a pair of charged ones. We find that both the Laser Interferometer Space Antenna experiment and High-Luminosity LHC can test such a scenario within their lifetime. This study thus sets the stage for a two-prong complementary approach able to scrutinise the extended Higgs sector of the A2HDM in both its high and low temperature manifestations.

We investigate the discovery potential for the vector-like X-quark (VLX) at future muon–proton (μp) colliders through the process μ^+ p →_μX →_μt 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 √(s)=5.29, 6.48, and 9.16 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 2σ exclusion limit of m_X≃8.3 TeV with g^* = 0.009 for R_L=0.1 at √(s)=9.16 TeV, whereas the FL mode gives the weakest reach because of its smallest branch ratio. These results demonstrate that future μp colliders can offer significant sensitivity to heavy VLX over a broad region of parameter space.

This work explores the discovery potential of the first-generation weak-isosinglet vectorlike leptons, denoted by E+, 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 2l + 2j + /ET and 3l + 2j + /ET final states (l = e, mu). Both signatures arise from the decay E+ -> Ze+/W+nu l 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 vectorlike lepton mass spectrum. Our findings demonstrate that, for integrated luminosities of 25, 90, and 1000 fb-1 at corresponding center-of-mass energies of 1, 1.5, and 3 TeV, the accessible mass range extends to approximately 490, 740, and 1440 GeV, respectively, which represents a substantially improvement over the detection limits of existing hadron collider experiments.

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.

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.

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 gamma gamma and tau & thorn;tau- 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 bb signatures reported in earlier data from the Large Electron-Positron (LEP) collider.

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 → ZZ decay channel of the heavy CP-even and neutral Higgs state with m_H ≃ 180–250 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.

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.

In the framework of effective field theory, we study the anomalous tq̅Z interaction through the process μ^+μ^- → tq̅Z at future muon colliders with √(s)= 3, 10, 14 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 √(s)= 14 TeV with 20 ab^-1, we find that the upper limit on the branching ratio for t→ qZ can reach the order of 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.

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→ h_1h_1→ bb̅ bb̅ wherein the heavy CP-even Higgs state h_2 is produced in the VBF process qq→ 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.

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^±) followed by the decay, H^±, 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 τ decay products are also examined as complementary probes of the spin-0 origin of the τ leptons. The expected discovery sensitivity is evaluated using the Asimov significance for an integrated luminosity of 3 ab^-1 at √(s)=14 TeV. Our results demonstrate that the 2τ + 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.

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 excesses across low- and high-energy experiments. These include the so-called 95 GeV and 650 GeV 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 = hSM) 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.

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→ 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 √(s)=3.46, 5.29, and 6.9 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 2σ exclusion limits and 5σ 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 √(s) at the FCC-eh.

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 bb¯ 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.

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.