Heavy quarks, a window into New Physics at ATLAS

The goal of my proposal is fundamental research at the frontier of particle physics and the instrumentation that makes this research possible. I will search for signs of New Physics using the signature of multiple heavy quarks.
Particle Physics, is currently at a cross road. The description of particle interactions is called the Standard Model. From our understanding of this model, new particles and mechanisms are required in order to consistently sustain the theoretical framework at high energies. So far, the Standard Model has been very successful in explaining the existing data from high energy physics experiments, like the ATLAS experiment at the Large Hadron Collider (LHC), but it is not complete. It does not explain the observed dark matter and dark energy, that fill 95% of our universe. Nor does it have a satisfactory answer to why there is more matter than anti-matter in the universe. Lastly, one essential particle, the Higgs boson, has not been found so far.

The LHC at CERN operates at the energy frontier. The LHC collides protons at extremely high energy. The resulting energy density is comparable to the energy density shortly after the Big Bang. The particles produced in this collision will allow to further unravel the fundamental nature of matter and its interactions. Due to the large increase in energy with respect to previous experiments, exciting new discoveries are expected. Among the exhilarating possibilities are candidates for dark matter. This fundamental research will significantly extend the boundaries of our knowledge. The latest measurements at the LHC, have not shown a direct signal of New Physics yet, pointing to a discovery, where the mass scale of new particles is higher than anticipated. At the same time the data indicate a small mass window at low mass, for the missing Higgs Boson.

Heavy new particles are likely to couple to the top quark, the heaviest known elementary particle. The top has a unique signature, as one if its decay products is a so called bottom-quark. For an clean top reconstruction the b-jets need to be identified. This "b-tagging" makes use of the fact, that b-hadrons are long lived and show a clearly displaced secondary vertex. Traditional b-tagging does not determine the charge of b-jets. This is the realm of flavour tagging that distinguishes b and anti-b quarks. The knowledge of the charge of b-jet can considerable reduce combinatorial background. I will make b-physics flavour tagging techniques applicable to New Physics searches.

The ATLAS experiment is one of two general purpose detectors at the LHC. The gigantic apparatus has excellent capabilities to reconstruct the tracks and vertices of particles and measure their momenta and energy with high precision. These properties make the ATLAS detector a great apparatus to test for new physics. The reconstruction of vertices relies on tracking devices. Such a device is essentially a large 80 million channel digital camera, that records the passing of charged particles every 25 nanoseconds. To fully exploit any new discoveries and extend the physics reach for rare processes, an upgrade of the LHC and its detectors is necessary. The ATLAS tracker needs to be upgraded in order to guarantee continuing good tracking performance with increasing intensity of LHC collisions. Continuing good performance of the tracker is very important, as it is a prerequisite for the reconstruction of secondary vertices from b-jets. Therefore I propose to take a leading role in the ATLAS tracker and in particular the pixel upgrade project.

During the course of the fellowship I propose to use events with multiple b-jets collected by ATLAS to search for so far unknown physics phenomena. In addition I will lead research and development on the tracking device upgrade. New tracking devices have a wide range of applications, not only in particle physics, but for example also in medical imaging.