A Higgs boson like particle of mass circa 125 GeV has been established by the ATLAS and CMS experiments. Clear evidence has been found of its decay into the gamma gamma, ZZ and WW channels, which are all bosons. Having evidence of its decay into fermion pairs, in particular tautau and bb, is now essential to assess its compatibility to the standard model.
All ATLAS public Higgs results are available on this page, with the latest Higgs to tau-tau conference note. The figure below illustrates for one subsample the difficulty of the channel: the Higgs to tau tau signal (in red), is very close in mass to the much more abundant Z to tau tau background.
A PhD thesis (Dimitris Varouchas supervised by David Rousseau) on the topic was defended in 2009 (so at the beginning of data taking), but the ATLAS LAL group has just restarted recently to work on the Higgs to tau tau channel (lep-had) sub channel. The group has so far been involved in the development and maintenance of MissingMassCalculator (MMC) the sophisticated algorithm to compute on an event by event basis a best estimate of the tau-tau mass, future contributions are foreseen in multi-variate analysis, and tau and missing ET developments closely related to the analysis.
The group members quoted above are also participating to a collaboration with KEK and University of Tsukuba on the improvment of the tau id applied to the Higgs to tau tau measurement. This collaboration has been developed in the frame of the French Japanese Particle Physics Laboratory (FJPPL) which is a virtual laboratory supported both by KEK and IN2P3.
Group members : Mhamad Ayoub (PhD student), Michel Jaffré (staff) and Faten Hariri (PhD student), Clara Nellist (postdoc), Pierre Petroff (staff), Luc Poggioli (staff), Tasneem Rashid (PhD student), David Rousseau (staff)