arXiv subjects

Marion O. A. Thomas

Publications and source records attributed to Marion O. A. Thomas.

5 recordsLinked to original sources

arXiv2026

Descoped and Upscoped FCC-ee Running Scenarios in the SMEFT

We present projections for the sensitivity to new physics of descoped and upscoped FCC-ee scenarios in the framework of the Standard Model Effective Field Theory (SMEFT). Starting from the baseline FCC-ee programme, we analyse the subsequent impact of, first, removing the top-quark run, then reducing the beam power from 50 MW to 30 MW, and finally removing two interaction points (IPs), in all cases propagating the resulting loss in top-quark mass precision through increased parametric uncertainties. We also analyse the possibility of a staged top-quark run, where the top-quark run is partially restored in case funding becomes available only at a later stage. Motivated by the trade-off between beam power and operational costs, we also consider two upscoped scenarios, either through a uniform increase in luminosity across all energy runs, or through a luminosity enhancement targeting exclusively the top-quark run. We explore the sensitivity and limitations of each scenario and highlight in particular the complementarity between the FCC-ee projections and the (HL)-LHC measurements. By comparing the physics impact of the different running scenarios with the FCC-ee baseline, we show explicitly the importance of the top-quark run, indicating that a substantial fraction of the FCC-ee physics potential depends on it.

hep-ph↗

arXiv2026

New Physics Reach through Precision at Future Colliders: a Multi-Pronged Approach

We present projections for the sensitivity of future high-energy colliders to new physics through precision measurements of the Standard Model (SM) interactions, focusing on near-term electron-positron facilities: FCC-ee, LEP3, and the Linear Collider Facility. We interpret these projections in three complementary frameworks: Higgs coupling modifiers, effective Higgs and electroweak couplings, and global SMEFT fits. The SMEFT analysis includes renormalisation-group evolution, linear/quadratic contributions, and NLO corrections to EFT cross sections where available. By matching the EFT to UV-complete models, we also quantify the sensitivity of future colliders to representative benchmark scenarios, including composite Higgs models and single-particle SM extensions. In parallel, we release an updated version of the open-source SMEFiT framework, enabling the results presented here to be fully reproduced, extended, and customised.

hep-ph↗

arXiv2024

Diboson production in the SMEFT from gluon fusion

Precision measurements of diboson production at the LHC is an important probe of the limits of the Standard Model. The gluon-fusion channel of this process offers a connection between the Higgs and top sectors. We study in a systematic way gluon-induced diboson production in the Standard Model Effective Field Theory. We compute the amplitudes of double Higgs, double $Z/W$ and associated $ZH$ production at one loop and with up to one insertion of a dimension-6 operator. We study their high-energy limit and identify to which operators each channel could be most sensitive. To illustrate the relevance of these processes, we perform a phenomenological study of associated $ZH$ production. We show that for some top operators the gluon-induced channel can offer competitive sensitivity to constraints obtained from top quark production processes.

hep-ph↗

arXiv2024

CP violation in loop-induced diboson production

We consider the impact of CP-violating Higgs and top interactions on diboson production from gluon fusion within the Standard Model Effective Field Theory framework. We systematically study differential distributions for double Higgs, double $W$ and $Z$ production and compare their features to those obtained from CP-conserving interactions. For electroweak gauge boson production, we explore the impact of the new interactions on the angular distributions of the leptonic decay products and the associated gauge boson polarisation fractions both inclusively and differentially with the transverse momentum of the gauge boson.

hep-ph↗

arXiv2024

Mapping the SMEFT at High-Energy Colliders: from LEP and the (HL-)LHC to the FCC-ee

We present SMEFiT3.0, an updated global SMEFT analysis of Higgs, top quark, and diboson production data from the LHC complemented by electroweak precision observables (EWPOs) from LEP and SLD. We consider recent inclusive and differential measurements from the LHC Run II, alongside with a novel implementation of the EWPOs based on independent calculations of the relevant EFT contributions. We estimate the impact of HL-LHC measurements on the SMEFT parameter space when added on top of SMEFiT3.0, through dedicated projections extrapolating from Run II data. We quantify the significant constraints that measurements from two proposed high-energy circular $e^+e^-$ colliders, the FCC-ee and the CEPC, would impose on both the SMEFT parameter space and on representative UV-complete models. Our analysis considers projections for the FCC-ee and the CEPC based on the latest running scenarios and includes $Z$-pole EWPOs, fermion-pair, Higgs, diboson, and top quark production, using optimal observables for both the $W^+W^-$ and the $t\bar{t}$ channels. The framework presented in this work may be extended to other future colliders and running scenarios, providing timely input to ongoing studies towards future high-energy particle physics facilities.

hep-ph↗