Martin Grunewald

“Heavy Particle Physics with the CMS Experiment at the LHC”

Martin Grunewald was born 1962 in Hagen, Germany. He obtained a German "Physikdiplom" in 1988, an MSc and PhD in Physics at the California Institute of Technology, and a Habilitation at Humboldt University Berlin.

The granted project is entitled: "Heavy Particle Physics with the CMS Experiment at the LHC". The Large Hadron Collider (LHC), a world-wide unique project in fundamental physics, recently started operations at the European Laboratory for Particle Physics, CERN, Geneva, Switzerland.  This particle accelerator collides protons at a centre-of-mass energy of up to 14 TeV, which is a factor seven higher than before, and with orders of magnitude higher intensity.  The particle collisions are measured with the CMS detector, built and operated by the international CMS collaboration involving some 30 
nations, 150 institutes and more than 2000 scientists and engineers, among them a new group from Ghent university funded by FWO.

The specific interest of this proposal lies in the measurement of the properties of heavy particles, most notably the top quark, the heaviest fermion known today, and the Higgs boson, a particle required by theory to solve the problem of mass generation (c.f. P.Higgs and two Belgians, F.Englert and R. Brout) but not yet seen in experiment. The production and decay of top quarks at LHC energies, never attained before, will be studied, allowing to make precision measurement of top-quark properties, in particular its mass. The foundations for these measurements need to be established for the CMS detector, including (i) identification of leptons, photons and jets, appearing in the decay of top quarks and Higgs bosons, (ii) reconstruction and energy calibration of jets for best possible resolution, (iii) missing energy reconstruction to identify neutrinos, and (iv) trigger and selection algorithms to select only the interesting signal events involving heavy-particle production among the overwhelming rate of background events.  These areas also underpin the measurements of the properties of the Higgs boson once it is found.  Also for this particle, the measurement of its mass, besides its lifetime and the 
rates for each decay mode, are of crucial importance in particle physics.  Within its theoretical framework, mathematical relations between the masses of the heavy particles occur, such that the measurement of all heavy-particle masses tests the theoretical 
foundation and our understanding of nature at a level never possible before, allowing us to discriminate between more or less complicated hypothetical extensions of our theoretical model with implications for astrophysics and cosmology.