Higgs to gamma gamma

In 2012, a Higgs boson-like particle of mass around 125 GeV has been established by the ATLAS and CMS experiments. In this region, the decay to a pair of photons (labelled with the letter gamma in greek) is one of the most sensitive for this search.

After this milestone, in which the team contributed, the search on this topic has moved to the precision area, probing the couplings of the Higgs to various particles, by exploiting the kinematic properties of the various production modes that drives to the Higgs production.

In addition, the team is contributing to the search for the double Higgs production, that is the production of two Higgs bosons in a same protons collision. This kind of process is much more rare as compared to the single production of the Higgs (so-called single Higgs production in this context). For this search, one needs a huge quantity of data, that will be available for the so-called HL-LHC data-taking, that will accumulate around 3000 fb^{-1} of data in the horizon of 2030-2040. But the search has already started and the team contributes to this search, by exploiting the so-called bbgamgam channel, where one of the Higgs boson decays to photons, and the other decays to a pair of b-quarks, thus benefiting from the excellent mass resolution for the photons part, and the high rate for the b quarks pair part.

Two sort of double Higgs production could appear : the non-resonant one (left plot below, with an additional diagram not shown for simplicity), corresponding to the case followed by the Standard Model follows (but non-resonant production could be also be produced by Beyond Standard Model scenarios), and the resonant production (right plot below), which occurs necessary in the context of Beyond Standard Model scenarios. The selection and optimisation for the analysis depends on the scenario studied.

https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2016-15/fig_01b.png         https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2016-15/fig_01c.png

All public ATLAS results in this channel can be found here .

Group members : Marc Escalier (staff), Louis Fayard (staff), Daniel Fournier (staff), Linghua Guo (PhD student) and regularly students in a context of a training period (stage).