Lattice investigations of strongly Interacting theories in the Standard Model and beyond.

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The research project of the theoretical particle physics group at theUniversity of Plymouth focuses on key issues of modern particlephysics. Two strands of research are pursued. In the first strand ofresearch, the group takes part in the race to decrease the theoreticaluncertainty on a quantity measured experimentally to an extraordinaryprecision called the anomalous magnetic moment of the muon. Anon-going current experiment that measures the small magnetic moment ofthe muon, a heavier cousin of the electron, aims at reducing furtherthe experimental errors. Our theoretical calculations will allowfurther tests of the theory that describes all phenomena at the levelof fundamental particles, called the Standard Model of particlephysics. A statistically significant larger difference between theexperimental and theoretical results would give strong hints to whatlies beyond the Standard Model and it would be a major discovery. Thetheoretical calculation itself represents a major computational andtheoretical challenge, due to the large number of contributions to themuon anomalous moment, and due to the target high accuracy required tomatch the experimental precision.The second strand of research focuses on exploring theories that canbe used to address the Standard Model's shortcomings. Two maindirections are considered. First, the project will explore the intriguingpossibility that the Higgs boson - discovered in 2012 - could be acomposite particle made of something else. The so called CompositeHiggs models use mechanisms similar to the one that is responsible forthe confinement of the quarks inside a proton. The proton is the simplest example ofa well-known particle, which is not fundamental, but composite. Anotherdirection is to explore and make predictions to test models that couldexplain the 85\% of the matter in the Universe that is not describedby the current theory of the interactions of elementary particles. Over theyears, a lot of experimental evidence has been gathered that support theexistence of the elusive "Dark Matter". Recent observations, notablyof the "Bullet Cluster" which consists of two colliding galaxiessuggest that Dark Matter interacts strongly with itself. Theories thatfeature such a strong interaction share similarities with the theorythat describes the interaction of quarks and lead to the formation ofthe proton as a bound state, and with the theories that are candidatesto feature a composite Higgs boson. The calculations performed willfurther constrain well motivated models and thereforecontribute to answer the question : "What are the fundamentalparticles?" and "What is the nature of dark matter?".