Abstract
We perform the combined analysis of the double Higgs production via gluon fusion in the $b\bar{b} \gamma\gamma$ and $b\bar{b}\tau^+\tau^-$ decay channels at the High-Luminosity LHC (HL-LHC). To validate our analysis, we reproduce the ATLAS result of the $b\bar{b} \gamma\gamma$ process including all contributions from fakes. For the $b\bar{b}\tau^+\tau^-$ decay channel, we perform the similar analysis to the CMS one. As an improvement, we also perform the multivariate analysis employing the boosted decision tree algorithm. Then, we derive 68% probability contours on anomalous Higgs couplings in the effective field theory (EFT) approach for various analyses. We find that the $b\bar{b}\tau^+\tau^-$ process outperforms the $b\bar{b}\gamma\gamma$ for the measurement of energy-growing operators, while adding the $b\bar{b}\tau^+\tau^-$ process is least beneficial for improving the precision of the Higgs self-coupling (mainly set by the $b\bar{b}\gamma\gamma$ process). We illustrate that the double Higgs production alone can be comparable to the single Higgs process in constraining the modification of the top Yukawa coupling in the positive direction. Focusing on the Higgs self-coupling as a special interest, we derive the precision as a function of various improvable parameters such as tag and mistag rates of tau leptons, heavy flavor jets, photon identification, diphoton mass resolution, and jet energy resolution to take into account future phenomenological studies. As an optimistic benchmark scenario, we illustrate that the 68% and 95% probability intervals of the Higgs self-coupling, $\lambda_3/\lambda_{3}^{SM}$, at the HL-LHC can reach $[0.2,\, 2.3]$ and $[-0.1,\, 3.5] \cup [4.0,\, 6.5]$, respectively, where the correlation among the EFT coefficients is taken into account.
Highlights
The precision measurements of the interactions of the recently discovered Higgs boson [1,2] with the fermions and gauge bosons at the Large Hadron Collider (LHC) indicate that we live in a special theory that stays weakly coupled up to very high energy scales, namely the Standard Model (SM) [3,4,5,6]
We find that the bbτþτ− process outperforms the bbγγ for the measurement of energy-growing operators, while adding the bbτþτ− process is least beneficial for improving the precision of the Higgs self-coupling
We explore three directions to exploit the benefit from the High-Luminosity LHC (HL-LHC): i) we combine two decay channels, bbγγ and bbτþτ−, of the double Higgs production in the effective field theory (EFT) approach, just like combining
Summary
The precision measurements of the interactions of the recently discovered Higgs boson [1,2] with the fermions and gauge bosons at the Large Hadron Collider (LHC) indicate that we live in a special theory that stays weakly coupled up to very high energy scales, namely the Standard Model (SM) [3,4,5,6]. Various decay channels in the single Higgs coupling measurements is beneficial; ii) we apply a multivariate technique employing the boosted decision tree (BDT) algorithm to our analysis as a way to enhance the significance; iii) we parametrize the precision of the Higgs self-coupling as functions of various improvable variables such as tag and mistag rates of tau jets and heavy flavor jets, photon identification efficiency, and invariant mass resolution etc. High-quality invariant mass resolutions of mγγ, mbb , and mττ are incontrovertible ingredients to disentangle a signal from the backgrounds Since those improvements can be made via various independent phenomenological studies, it would be informative to express the precision as a function of those improvable factors to predict our capability in the future. In Appendix A, we provide the detail of our background simulation
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