Final Report Summary - HIGGS@LHC (Search and study of the Higgs bosons at the LHC)
The last six years were extremely rich and exciting for particle physics in general and for Higgs physics in particular. With the historical discovery at the LHC of the Higgs boson in July 2012, crowned by a Nobel Price in fall 2013 to François Englert and Peter Higgs, and the first probe of its fundamental properties, these years witnessed a giant step in the unravelling of the mechanism that breaks the electroweak symmetry and generates the fundamental particle masses. They promoted the Standard Model (SM) as the appropriate theory, up to at least the Fermi energy scale, to describe three of Nature's interactions, the electromagnetic, weak and strong forces. This is particularly true as the production and decay rates of the Higgs state, as measured by the ATLAS and CMS collaborations with the data collected at an energy up to 13 TeV, indicate that its couplings to fermions and gauge bosons are SM-like to a very good approximation.
This result, although extremely important, leads nevertheless to some frustration as the hope of observing from the LHC data some signs of the new physics models that were put forward to address the hierarchy problem, that is deeply rooted in the Brout-Englert-Higgs mechanism with supersymmetric and extra-dimension theories being the most attractive ones, did not yet materialize. There is nevertheless still hope that with the upcoming upgrade of the LHC to a higher luminosity and eventually energy, much larger mass scales than those presently probed could be accessed, which would allow for signs of new physics to be finally detected.
The observation of the Higgs boson, the determination of its basic properties and the study of the implications for the SM and new physics beyond it, were the essential issues addressed by our research project. In particular, we had six main objectives: 1) to perform precise predictions for the Higgs signal at the LHC, 2) to perform precise predictions for the major backgrounds, 3) to develop new search techniques and strategies at the LHC, 4) to develop and improve software tools for Higgs phenomenology, 5) to investigate the phenomenology of new physics scenarios with extended Higgs sectors and 6) to study the connection of Higgs physics with cosmology and flavour physics. All these objectives have been attained either fully or to a large extent.
The main scientific achievements during the grant period can be summarized as follows:
- The members of our team have published more than 160 articles in the most prestigious peer reviewed journals, with a large fraction written by the young researchers financed by the grant. The team members also participated and contributed to a significant number of proceedings of various workshops and conferences important in our field. These publications covered all the subjects that we planed to work on and fulfill the six main objectives of our research plan.
- The grant allowed to finance six post-docs and one PhD student who did an excellent job. They were all granted post-doc or tenure track positions after their stay in Paris. Note that 11 other students, financed by the Paris Universities, started or completed a PhD thesis in the framework of the project. The grant also allowed to strengthen the links between the Paris laboratories.
- The PI and the members of the team participated to important conferences in the field and had several collaborations with scientists at CERN and elsewhere financed by the grant. Some of the ERC funds were used to invite several collaborators and to help organize by our laboratories a few events which are directly related to Higgs physics, such as the yearly conference Higgs-Hunting in Paris.
All in all, we believe that our ERC project was a total success. It helped acquire the most precise knowledge on the Higgs particle, at the crucial time where it was discovered and its basic properties measured by the experimental community. It also greatly helped to search for effects of new physics beyond the SM and to constrain many important scenarios like supersymmetry and extra dimensions.
This result, although extremely important, leads nevertheless to some frustration as the hope of observing from the LHC data some signs of the new physics models that were put forward to address the hierarchy problem, that is deeply rooted in the Brout-Englert-Higgs mechanism with supersymmetric and extra-dimension theories being the most attractive ones, did not yet materialize. There is nevertheless still hope that with the upcoming upgrade of the LHC to a higher luminosity and eventually energy, much larger mass scales than those presently probed could be accessed, which would allow for signs of new physics to be finally detected.
The observation of the Higgs boson, the determination of its basic properties and the study of the implications for the SM and new physics beyond it, were the essential issues addressed by our research project. In particular, we had six main objectives: 1) to perform precise predictions for the Higgs signal at the LHC, 2) to perform precise predictions for the major backgrounds, 3) to develop new search techniques and strategies at the LHC, 4) to develop and improve software tools for Higgs phenomenology, 5) to investigate the phenomenology of new physics scenarios with extended Higgs sectors and 6) to study the connection of Higgs physics with cosmology and flavour physics. All these objectives have been attained either fully or to a large extent.
The main scientific achievements during the grant period can be summarized as follows:
- The members of our team have published more than 160 articles in the most prestigious peer reviewed journals, with a large fraction written by the young researchers financed by the grant. The team members also participated and contributed to a significant number of proceedings of various workshops and conferences important in our field. These publications covered all the subjects that we planed to work on and fulfill the six main objectives of our research plan.
- The grant allowed to finance six post-docs and one PhD student who did an excellent job. They were all granted post-doc or tenure track positions after their stay in Paris. Note that 11 other students, financed by the Paris Universities, started or completed a PhD thesis in the framework of the project. The grant also allowed to strengthen the links between the Paris laboratories.
- The PI and the members of the team participated to important conferences in the field and had several collaborations with scientists at CERN and elsewhere financed by the grant. Some of the ERC funds were used to invite several collaborators and to help organize by our laboratories a few events which are directly related to Higgs physics, such as the yearly conference Higgs-Hunting in Paris.
All in all, we believe that our ERC project was a total success. It helped acquire the most precise knowledge on the Higgs particle, at the crucial time where it was discovered and its basic properties measured by the experimental community. It also greatly helped to search for effects of new physics beyond the SM and to constrain many important scenarios like supersymmetry and extra dimensions.