Search for low mass Higgs bosons at the LHC with the ATLAS dector – HiggsNet

The search of the Higgs boson is at the heart of the LHC project and one of the most prominent questions in High Energy Physics. Its mass is above 114 GeV/c2, (the LEP limit) and there are numerous experimental and theoretical indirect constraints indicating that the its mass should be below 200 GeV/c2 and probably below 140 GeV/c2, precisely the region where the H to two photons decay mode is the most promising.

This project is to search for the Higgs boson in the two-photon decay mode. The key elements of this search are the following.

- The two photon invariant mass resolution: it is dominated by the energy resolution, but has a non-negligible contribution from the angular resolution on the photon direction.

- Deep understanding of the backgrounds: both of the reducible background (photon-jet and jet-jet backgrounds) and quasi-irreducible background (pair of photons) which cannot be reduced only by particle identification, but will necessitate the use of kinematical discriminating variables.

- Prior to search for the Higgs boson in the di-photon channel, a crucial step is to measure the di-photon and single photon cross sections when the theoretical definition of the cross section itself is all but trivial (in particular due to NLO and fragmentation effects).

- The development of the necessary analysis tools.

The multi-purpose ATLAS experiment, and in particular its Liquid Argon electromagnetic calorimeter was designed and built with these goals in mind. All partners of this project have played a decisive role in the design, construction, integration and commissioning of the ATLAS liquid Argon calorimeter. This project proposes to foster a common effort of these groups in order for them to have leading contribution in the final piece of the chain, that is the search for the Higgs boson in the two photon decay channel and hopefully discover the Higgs boson.

To reach the goals of this project, each partner requests funding for one two-year postdoc. The duration of the project is four years, starting early 2011.