Search for a Higgs Boson decaying to invisible particles with the ATLAS experiment
If dark matter has less than half of the Higgs mass it might be expected that the Higgs boson would decay to dark matter. In run 1 a relatively loose limit on Higgs to invisible yielded extremely dark strong limits in the low mass region. The full run 2 data combined with new experimental techniques should provide a much more stringent limit and much better sensitivity to dark matter. This proposal is to search for the invisible decay of Higgs bosons that recoil against a W or Z boson that decays hadronically. The student will analyse data taken by ATLAS from the years 2015-2018. The student will benefit from the experience the group has of studying H->bb + missing energy. The student will gain an experience of physics analysis and will do shifts also do a service task, likely to be on the silicon upgrade here at Liverpool. The student will join the Liverpool ATLAS Higgs, which has many years experience. They will also work within the ATLAS Higgs->invisible working group which has regular meetings. Higgs to invisible searches are one of the best ways to discovery dark matter at lower masses. They are much more competitive than direct ATLAS searches with the underground dark matter detectors. The analysis will directly lead to a high impact publication.