18 research outputs found
Effectively cornering new physics at colliders and beyond
No full textThe Standard Model has achieved remarkable success, yet growing empirical and theoretical tensions point to the need for new physics at the TeV scale. As collider experiments enter a precision era, even small deviations from Standard Model predictions can provide crucial clues about the underlying structure of fundamental interactions. This thesis explores these possibilities through both model-dependent studies and the effective field theory approach. Multi-Higgs production is used to probe extended scalar sectors, offering insight into the nature of electroweak symmetry breaking and the dynamics of possible phase transitions. Electroweak-scale triplet models are examined through collider signatures and flavour constraints, presenting a realistic mechanism for radiative neutrino mass generation. In the top-quark sector, momentum-dependent width effects are implemented in a gauge-consistent way, leading to more accurate predictions for SMEFT constraints. To address the challenge of high-multiplicity final states, machine learning techniques, including graph neural networks, are applied to identify hidden correlations and enhance signal sensitivity. Together, these studies sharpen existing bounds and provide complementary strategies to guide future experimental efforts at the High-Luminosity LHC and beyond
BSM patterns in scalar-sector coupling modifiers
No full textWe consider what multiple Higgs interactions may yet reveal about the scalar sector. We estimate the sensitivity of a Feynman topology-templated analysis of weak boson fusion Higgs pair production at present and future colliders — where the signal is a function of the Higgs coupling modifiers κV, κ2V, and κλ. While measurements are statistically limited at the LHC, they are under general perturbative control at present and future colliders, departures from the SM expectation give rise to a significant future potential for BSM discrimination in κ2V. We explore the landscape of BSM models in the space of deviations in κV, κ2V, and κλ, highlighting models that have measurable order-of-magnitude enhancements in either κ2V or κλ, relative to their deviation in the single Higgs coupling κV
A B−anomaly motivated Z′ boson at the energy and precision frontiers
No full textNo abstract available
Impact of new physics on momentum-dependent particle widths and propagators
No full textWe investigate the impact of momentum-dependent particle widths and propagators on gauge and Higgs bosons and the top quark within the Standard Model (SM) and its effective field theory (SMEFT) extensions near thresholds. By incorporating self-energy corrections via Dyson resummation, we quantify deviations from the fixed-width approximation and assess their implications for collider observables. While effects on the Higgs boson are negligible and the � boson shows percent-level deviations in reconstructed transverse mass distributions, the top quark exhibits significant sensitivity near its mass threshold. Future lepton colliders, e.g., electron-positron machines or muon colliders, can offer sensitivity to these effects, enabling constraints on SMEFT Wilson coefficients. We perform a representative case study for the precision frontier available with a staged future muon collider. Our results highlight that momentum dependencies can provide additional sensitivity at precision-era experiments, enhancing the potential for discovering new physics there
Resurrecting the LHC discovery potential in the extended type-II seesaw model
No full textThe juxtaposition of the precision of lepton flavour measurements and the limited energy range of the Large Hadron Collider (LHC) to discover dynamical degrees of freedom linked to the generation of the observed lepton mass patterns naively suggests only a limited relevance of the LHC’s high luminosity phase. This, potentially, extends to future colliders. Using the concrete example of the type-II seesaw model and its effective field theory extension, we show that blind directions create a rich phenomenological interplay of muon precision measurements and electroweak resonance searches at present and future colliders, with testable implications for the HL-LHC phase
Doubling down on down-type diquarks
No full textEffective field theory-based searches for new physics at colliders are relatively insensitive to interactions involving only right-handed down-type quarks. These interactions can hide amongst jet backgrounds at the LHC, and their indirect effects in electroweak and Higgs processes are small. Identifying scenarios in which these interactions dominate, we can naturally pick out just two tree-level mediators, both scalar diquarks. Over the full parameter space of these states, we analyse exotics searches at current and future hadron colliders, Higgs signal strength constraints, and indirect constraints from flavour physics, finding genuine complementarity between the data sets. In particular, while flavour constraints can exclude diquarks in the hundreds of TeV mass range, these can be evaded once a flavour structure is imposed on the couplings, as we illustrate by embedding the diquarks within a composite Higgs model. In combination, however, we show that flavour and collider constraints exclude down-type diquarks to multi-TeV scales, thus narrowing the remaining hiding places for new interactions amongst LHC data
Double and triple Higgs boson production to probe the electroweak phase transition
No full textThe production of three Higgs bosons could be a stretch goal for the LHC and a strategic case for future colliders. In this work, we analyse the phenomenological prospects of (neutral) triple Higgs compared to di-Higgs boson production, for a range of Higgs-sector extensions from a strong first-order electroweak phase transition perspective. In parallel, we include constraints from existing exotics and Higgs boson measurements that further limit the parameter space of such models. Resonance contributions offer large modifications in particular for triple Higgs production, albeit starting from a small SM expectation. With enhancements of order 40 over the SM, however, experimental efforts to obtain limits at the HL-LHC are well motivated and well placed. This is further highlighted by the potential of these processes to inform the investigation of the thermal history of our Universe
Double and triple Higgs boson production to probe the electroweak phase transition
No full textThe production of three Higgs bosons could be a stretch goal for the LHC and a strategic case for future colliders. In this work, we analyse the phenomenological prospects of (neutral) triple Higgs compared to di-Higgs boson production, for a range of Higgs-sector extensions from a strong first-order electroweak phase transition perspective. In parallel, we include constraints from existing exotics and Higgs boson measurements that further limit the parameter space of such models. Resonance contributions offer large modifications in particular for triple Higgs production, albeit starting from a small SM expectation. With enhancements of order 40 over the SM, however, experimental efforts to obtain limits at the HL-LHC are well motivated and well placed. This is further highlighted by the potential of these processes to inform the investigation of the thermal history of our Universe
Equivariant, safe and sensitive — graph networks for new physics
No full textThis study introduces a novel Graph Neural Network (GNN) architecture that leverages infrared and collinear (IRC) safety and equivariance to enhance the analysis of collider data for Beyond the Standard Model (BSM) discoveries. By integrating equivariance in the rapidity-azimuth plane with IRC-safe principles, our model significantly reduces computational overhead while ensuring theoretical consistency in identifying BSM scenarios amidst Quantum Chromodynamics backgrounds. The proposed GNN architecture demonstrates superior performance in tagging semi-visible jets, highlighting its potential as a robust tool for advancing BSM search strategies at high-energy colliders
On the BSM reach of four top production at the LHC
No full textMany scenarios of beyond the Standard Model (BSM) physics give rise to new top-philic interactions that can be probed at proton machines such as the Large Hadron Collider through a variety of production and decay modes. On the one hand, this will enable a detailed determination of the BSM model's parameters when a discovery is made and additional sensitivity in non-dominant production modes can be achieved. On the other hand, the naive narrow width approximation in dominant production modes such as gluon fusion might be inadequate for some BSM parameter regions due to interference effects, effectively making less dominant production modes more relevant in such instances. In this work, we consider both these questions in the context of four top quark final states at the LHC. Firstly, we show that the SM potential can be enhanced through the application of targeted Graph Neural Network techniques that exploit data correlations beyond cut-and-count approaches. Secondly, we show that destructive interference effects that can degrade BSM sensitivity of top-philic states from gluon fusion are largely avoided by turning to four top final states. This achieves considerable exclusion potential for, e.g., the two Higgs doublet model. This further motivates four top final states as sensitive tools for BSM discovery in the near future of the LHC
