Constraining new physics effective interactions via a global fit of electroweak, Drell-Yan, Higgs, top, and flavour observables

Abstract

We present results from a global fit of Standard Model parameters and dimension-6 SMEFT Wilson coefficients that includes electroweak, Drell-Yan, Higgs-boson, top-quark, and flavour observables. Fits obtained by floating individual coefficients are also discussed. The leading-order scale dependence of the SMEFT Wilson coefficients is consistently included in the evolution from the UV scale to the electroweak scale and the low-energy scale of flavour observables. In defining the SMEFT set of active operators we consider both the $U(3)^5$ and the $U(2)^5$ flavour symmetric limits. All fits are obtained within the $\texttt{HEPfit}$ framework and are based on the most recent experimental results and state-of-the-art theoretical predictions for all the observables considered.

Figures (11)

• Figure 1: Results from individual fits in the $U(3)^5$ flavour symmetric SMEFT. For each coefficient $C_i$, the top panel shows the scale of NP allowed by the data at 95% probability (normalized by the square root of the maximum of the 95% HPDI interval for $|C_i|$). The bottom panel shows the width of the 95% probability range divided by two. Both panels show results for the three cases 1) $\Lambda=10$ TeV with RGE, 2) $\Lambda=3$ TeV with RGE, and 3) $\Lambda=1$ TeV with no RGE. Furthermore, in each case we also include results obtained removing the most constraining data set for that particular coefficient (see Table \ref{['tab:u3-ind']}). The color code is as explained in the legend. The horizontal lines indicate the maximum value allowed for each Wilson coefficient in the fit, corresponding to the perturbativity limit $4\pi$ (see Section \ref{['sec:fit-intro']}), for the different values chosen for the NP scale $\Lambda$. The cases in which the $95\%$ HPDI interval touches the prior's edges, indicated in red in Table \ref{['tab:u3-ind']}, are hatched with red diagonal lines. When the posterior distribution of a coefficient is completely flat the $95\%$ HPDI interval is hatched with diagonal white lines.
• Figure 2: Summary of individual lower bounds on the effective NP scale in the $U(3)^5$ flavour symmetric SMEFT, obtained for $\Lambda = 3$ TeV.
• Figure 3: Comparison of individual and marginalised constraints from the global fit with $U(3)^5$ flavour symmetry assumption. The scale of NP has been set to $\Lambda=3$ TeV. The limits shown correspond to the 95% HPDI. Results are presented for both individual and global fits, with and without the RGE effects (the latter also adjusted to a value of $\Lambda=3$ TeV for this comparison), following the colour scheme indicated in the legend.
• Figure 4: Same as Fig. \ref{['fig:full_fit_ind_U3']} for bosonic and two-fermion operators in the $U(2)^5$ symmetric SMEFT (UP basis).
• Figure 5: Same as Figure \ref{['fig:ind_bos_2F']} but for the four-fermion operators that contain at least one leptonic field and one left-handed field.