arXiv subjects

Daniel Gillies

Publications and source records attributed to Daniel Gillies.

3 recordsLinked to original sources

arXiv2026

Anomalous triple gauge couplings in the light of dimension-8 operators in $W^+W^-$

We compare the size of dimension-8 effects on $W^+W^-$ production at the LHC arising from the $q\bar q$ and $\gamma\gamma$ initial states. In particular, we consider bosonic operators, which contribute to the anomalous triple and quadruple gauge couplings. The relevant dimension-6 and dimension-8 operators are matched to the anomalous triple gauge couplings that contribute to the $q\bar q$ channel, allowing for the resummation of large logarithmic contributions arising in the presence of a jet-veto through the program MCFM-RE. For the $\gamma\gamma$ channel, which receives contributions from both triple and quadruple gauge couplings, such resummation can be performed through the program MadGraph, by simply setting the factorisation scale to the jet-veto scale. We find that, when neglecting fermionic dimension-8 operators, the $\gamma\gamma$ channel has a dominant bosonic dimension-8 contribution and this channel can be used to understand the range of validity of the Effective Field Theory. With this in mind, and carefully considering theoretical and experimental uncertainties, we provide constraints on higher dimensional operators using current and future data.

hep-ph↗

arXiv2026

Probing EFT breakdown in the tails of $W^+ W^-$ observables

In this letter, we test clipping effective field theory (EFT) simulations as a method of ensuring EFT validity. The procedure imposes that, at the level of the simulation, the invariant mass of a $W^+W^-$ pair $M_{WW}$ is less than the new physics scale $\Lambda$. We compare this to two other methods, comparison bin by bin of dimension-6 and dimension-8 squared contributions and implementing a cut on data. We find that setting $M_{WW} < \Lambda$ is not strict enough to ensure that the hierarchy of EFT operators is respected for dimension-6 and dimension-8 contributions. We also show that, even when using a stricter cut on $M_{WW}$, due to different correlations between $M_{WW}$ and $M_{e\mu}$ at different EFT orders, the bins in $M_{e\mu}$ (the invariant mass of the leptons originating from $W$ decays) used in an EFT fit may not truly be in the regime of EFT validity when performing a dimension-6 fit with $M_{WW} < \Lambda$. We also explore the correlations of three transverse mass observables: $M_{T1}, M_{T2}$ and $M_{T3}$, finding that $M_{T1}$ and $M_{T3}$ follow the $M_{WW}$ distribution more closely than $M_{e\mu}$. We present sensitivity studies using both the $M_{T3}$ distribution and $M_{e\mu}$ distribution. We test implementing an experimental cut on $M_{T3}$ in place of clipping the EFT simulation at $M_{WW} < \Lambda$. We finally comment that adding $M_{WW} < \Lambda$ cuts only to the EFT simulation could be interpreted as modifying the SMEFT expansion by a form factor and could therefore impact the model independence of EFT fits under this procedure.

hep-ph↗

arXiv2024

Dimension-8 operators in $W^+W^-$ production via gluon fusion

We investigate the impact of dimension-8 operators on $W^+W^-$ production at the LHC for the incoming gluon-gluon channel. To this end, we have identified all dimension-8 CP-even operators contributing to the process in question, and computed the corresponding tree-level helicity amplitudes for fully-leptonic decays of the $W$ bosons. These are implemented in the program MCFM-RE, which automatically incorporates the effect of a jet-veto to reduce the otherwise overwhelming $t\bar t$ background. We find that, unless we break the hierarchy of the effective field theory (EFT), the interference of the dimension-8 operators with the Standard Model is negligible across the considered distributions. This justifies including the square of dimension-6 operators when performing EFT fits with this channel. We then present new constraints on CP-even and CP-odd dimension-6 operators within the EFT regime. Lastly, we postulate a scenario in which the hierarchy of the EFT is broken, justified by the strong constraints on dimension-6 operators from existing on-shell Higgs data. In this scenario, we discuss the constraints that can be reasonably set on CP-even dimension-8 operators with current and future data. We remark that the effect of the jet-veto on the ability to constrain new physics in the $W^+W^-$ channel is quite dramatic and must be properly taken into account.

hep-ph↗