Property measurements of the Higgs boson: fermionic Higgs couplings and the search for new physics at the LHC

• Applicant: Dr. Jakob Salfeld-Nebgen
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269118925

The discovery of a new elementary particle at the Large Hadron Collider(LHC) of the European Institute for Nuclear Research (CERN) announced on 4. Juli 2012, is one of the most important insights of Particle and High Energy Physics and the key for understanding the origin of mass of elementary particles. All subsequent measurements of the properties of the new particle performed by the CMS and Atlas collaborations are, taking uncertainties into account, in accordance with the ones of the Higgs boson predicted by the Standard Model of particles physics (SM). As a consequence, the Physics Nobelprize in 2013 was given to Peter Higgs and Francois Englert for the theoretical developments of spontaneous symmetry breaking of local gauge symmetries and the associated origin of mass.Whether the new particle observed at the LHC has the exact properties of the Higgs boson prognosticated by the SM or otherwise physics beyond the Standard Model influences its physical properties, is one of the remaining key questions of particle physics. It is in particualr of high interest to determine the charge and parity symmetry (CP) conserving properties of the new particle.The research project aims at answering these questions and shall significantly contribute to the precise determination of the physical properties of the new particle, by analyzing the LHC data to be accumulated in the years 2015 in 2016. More specifically, in this research project the fermionic Higgs couplings shall be measured with unprecedent precision and the results shall subsequently be interpreted in the context of generalized physical models beyond the SM.The decay channel of the Higgs boson into two tau-leptons is most suitable for these considerations and serve as a superb basis to significantly increase the accuracy of the fermionic coupling measurement. This can be achieved by deploying new anaysis methods but also after re-optimizing and adjusting the existing ones to the new experimental conditions at the LHC. Furthermore, a measurement of the CP properties of the fermionic Higgs coupling shall be performed for the first time, for which the decay channel of the Higgs boson into two tau-leptons offers unique possibilities.Finally, the results of these measurements shall be combined with all decay and production mechanism specific Higgs analyses to clarify the identity of the new particle.

• DFG Programme: Research Fellowships
• International Connection: Switzerland
• Host: Professor Dr. Markus Klute