# Di-Higgs Production

The recently discovered Higgs boson is the only fundamental scalar in the Standard Model, and thus has the unique property of coupling directly to itself. This self coupling, which we denote $\lambda_3$, is fully determined in the Standard Model, but has yet to be measured directly. A precise measurement of $\lambda_3$ is a crucial window into potential extensions of the Standard Model, and has direct implications for the viability of scenarios such as electroweak baryogenesis and Higgs inflation. Such a measurement is exceedingly difficult at the LHC, but several studies indicate that it could be done at a 100 TeV collider such as the FCC-hh at CERN or the SppC in China.

Our work aims to better understand how precisely $\lambda_3$ could be measured at a higher energy version of the LHC, which could reach energies around 27 TeV. Di-Higgs production, pictured above, is the only process by which we can directly measure the self-coupling. With a focus on the $hh \to b\bar{b}\gamma\gamma$ decay channel, we’ve demonstrated that a $\sim 40\%$ measurement of the self-coupling is possible at an upgraded LHC. In the course of our work, we also discovered that one of the most significant backgrounds, single Higgs production in association with $b$-jets, has been substantially underestimated in previous studies.

##### Samuel Homiller
###### Post-Doctoral Fellow

Post-Doctoral Fellow in the HETG at Harvard University.

## Publications

### Multi-Higgs Production Probes Higgs Flavor

We examine a deep relationship between enhanced couplings of the Higgs to light quarks and the di-Higgs production process at the LHC.

### Higgs Physics at the HL-LHC and HE-LHC

A whitepaper detailing opportunities in Higgs physics at the LHC in the future.

### Measurement of the Triple Higgs Coupling at a HE-LHC

A study of the capabilities of a potential 27 TeV HE-LHC upgrade in measuring the Higgs self-coupling via di-Higgs production.

## Talks

### Measuring the Higgs Trilinear Coupling at an HE-LHC

Measuring the Higgs self-coupling at the LHC has proven to be extremely challenging in the Standard Model, making such a measurement a …

### The Higgs Self-Coupling and Future Colliders

A discussion of prospects for measuring the Higgs self-coupling via di-Higgs production at future hadron colliders.

### Measuring the Higgs Trilinear Coupling at an HE-LHC

Preliminary results contributed to the HL/HE-LHC Yellow Report on prospects for measuring the Higgs self-coupling at a 27-TeV collider.