#22 How many charged higgses can there be?

The Standard Model (SM) of particle physics predicted the existence of the Higgs boson, discovered at LHC in 2012. Since then its properties have been extensively studied, and no new particles have been discovered, despite numerous searches. If other particles exist, they are either very heavy or have very week interactions.

Charged Higgs (elementary spin 0 particles with electric charge) are predicted in many Beyond the Standard Model (BSM) theories, and have been extensively looked for at the LHC. But despite no direct hints for their existence, such particles could have sizeable contributions to the decay of the Higgs boson into two photons, one of the decay channels of the Higgs best measured at the LHC.

In this work the students will compute the contributions of charged scalars stemming from gauge singlets, and use the best LHC results for h → γγ decay widths to answer the following questions: how light could a charged scalar be to have avoided detection so far? How many charged scalars could there be without spoiling LHC observations, and what would their masses be? Could such charged scalars be observed and discovered anytime  soon?

Requirements: good dominion of numerical skills (Python or Matlab, for instance). Minimum 3rd year students, so that at least they have knowledge of Quantum Mechanics – but 2nd year students will be able to understand and follow the project. Master students would get the most of it.