Probing the flavour structure of New Physics with Bs mesons at LHCb

One of the most puzzling and so far unexplained features of the Universe is the absence of anti-matter. During the Big Bang matter and anti-matter were generated in equal quantities. However, from measurements of cosmic rays it is known that our galaxy consists mainly of matter. Furthermore, there is no evidence for the intense gamma ray emission that would follow the annihilation of matter and anti-matter in distance galaxies with clouds of antimatter. In the early Universe processes must have existed that distinguished between matter and anti-matter. The Russian physicist Sakharov showed that three conditions have to be fulfilled. One of these is particles and anti-particle should behave differently under the combined operation of charge conjugation (swapping of particle and anti-particle) and parity (left-right mirror symmetry) called CP. In the Standard Model of particle physics CP violation is predicted to occur. All measurements made so far agree with the Standard Model picture. However, the level of CP violation in the Standard Model is much too small to explain the observed dominance of matter in our Universe. One possibility is that New Physics such as Supersymmetry leads to additional sources of CP violation. In order to resolve this puzzle more precise measurements are needed. If discrepancies, compared to the Standard Model picture, are found this will be strong evidence for New Physics and also constrain its form. The Large Hadron Collider, which is starting operation at CERN, will open a new era in physics. The Large Hadron Collider Beauty Experiment (LHCb) is a special purpose experiment running at the LHC. The collaboration consists of around 400 physicists from 52 institutes world-wide. By studying very precisely differences in the rate of decays containing b and anti-b quarks it will provide insight into the phenomenon of CP asymmetries. CP violation in Bs mixing is a fundamental prediction of the Standard Model. The mixing phase, beta_s, is relatively unconstrained. Recently, first measurements of this parameter have been made by CDF and D0. Though the uncertainties are large they favour values much larger than predicted by the Standard Model. LHCb will make precise measurements of this quantity and will either reveal the presence of New Physics or confirm the Standard Model prediction. Uniquely, the experiment is able to make measurements in many decay modes allowing important cross-checks of the consistency of the data and analysis to be made. The main aim of this proposal is the measurement of the Bs mixing phase at LHCb. I will first measure this quantity using the golden mode Bs->J/psi phi. The statistics in this mode are large and it is relatively easy to trigger and reconstruct. It will be an important early measurement for the experiment. Following this, I will measure this quantity in the mode Bs-> J/Psi eta' and also study the channel Bd -> phi phi. These modes are harder to reconstruct and have lower yields and it will take several years to collect a statistically significant sample. One way to increase the yields will be to run the experiment at higher luminosity. LHCb is planning to upgrade the trigger and electronics of the experiment around 2015 in order to run at higher luminosities and to collect even higher statistics. The higher luminosity will result in a busier environment for triggering and reconstruction as well as increasing the radiation damage suffered by the detector. I will contribute to studies of the global detector optimization with the aim of minimizing the amount of material in the detector.