Our understanding that everything in the universe is made from a few fundamental particles and governed by four fundamental forces led to the development of the Standard Model (SM) of particle physics in the 1960s and 1970s. The SM describes the relation between three out of four forces and all known fundamental particles. Through an ever increasing number of observations and theoretical developments, the SM has become a well-established model over the years. However, there are questions for which the SM does not provide answers. One of these important questions is why the universe is matter dominated today when it started with an equal amount of matter and antimatter. A mechanism that allows matter and antimatter to evolve differently with time, is called CP violation. It is one of the key conditions required in the early universe for it to evolve to the matter dominated state which we observe today. However the amount of CP violation predicted in the SM is very small and some new dynamics driving this asymmetry is needed.
CP violation in the SM originates from a single phase in the CKM quark mixing matrix. Due to the unitarity of the matrix, it can be represented as a triangle in the complex plane, with angles α, β and γ. The measurements of CKM unitarity angles β(φ1) and γ(φ3) probe the internal consistency of the SM. The angle βs which is directly related to the CP violating weak phase φs in b → c ̄cs transitions, is very precisely predicted in the SM, therefore deviations from the SM can be interpreted as new physics. Current measurements of φs agree well with the theoretical predictions, however the uncertainty of the world average is still large and allows new physics effects to be at the order of 10%.
The overall objective of the project is to measure CP violation in Bs decays as well as develop tools needed to perform the measurements now and in the future.
