Abstract
We study the process $pp \to Z(\ell^+ \ell^-)h(b\bar b)$ in the Standard Model Effective Field Theory (SMEFT) at high energies using subjet techniques to reconstruct the Higgs boson. We show that at high energies this process probes four directions in the dimension 6 EFT space, namely the operators that contribute to the four contact interactions, $hZ_\mu \bar{f}\gamma^\mu f$, where $f=u_L, u_R,d_L$ and $d_R$. These four directions are, however, already constrained by the $Z$-pole and diboson measurements at LEP. We show that by utilising the energy growth of this process in the SMEFT and the accuracy that can be achieved by using subjet techniques at the High Luminosity LHC, one can obtain bounds on these operators that are an order of magnitude better than existing LEP bounds.
Highlights
Characterizing the properties of the Higgs boson is arguably the most concrete particle physics goal of our time
We show that by utilizing the energy growth of this process in the standard model effective field theory (SMEFT) and the accuracy that can be achieved by using subjet techniques at the High Luminosity LHC, one can obtain bounds on these operators that are an order of magnitude better than existing LEP bounds
For the physically motivated case where the leading effects of new physics can be parametrized by universal operators, the SILH Lagrangian provides a convenient formulation and we show the above directions in this basis in the third row of Table II
Summary
Characterizing the properties of the Higgs boson is arguably the most concrete particle physics goal of our time. Studying the h → bbmode instead of the h → γγ leads to a big enhancement in the rate but the Higgs-strahlung process still remains challenging with an Oð50Þ background-to-signal ratio Relating such a systematics limited result to the extraction of Higgs couplings can be at odds with the implicit assumption of perturbativity of the EFT expansion. As δσ=σSM ≳ 1 signals the breakdown of EFT validity for weakly coupled UV completions [14], a sensitivity to smaller values of δσ=σSM is essential To gain such precision, we need high luminosities (at least 300 fb−1) and advanced boosted Higgs tagging techniques which can reduce the ratio of the number of Zbbto the SM Zhðbb Þ events to an Oð1Þ number as shown earlier in Refs. It allows us to present our results in a combined way with the projections for WZ production in Ref. [20]
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