Measuring the CP-violating parameter γ at Belle II
ABSTRACT :
CP symmetry states that the laws of nature are invariant under the interchange of a particle and an anti-particle. But, CP violation was first observed in the neutral kaon system in 1964. The standard model description of CP violation is due to the imaginary phase of the 3 x 3 CKM matrix. The precise determination of the CP-violating-parameter φ3 (also called γ) is the most promising path to gain a better understanding of CP violation and search for contributions from non-standard model physics. In my talk, I will introduce CP violation and the different methods to determine φ3. The most sensitive way to measure φ3 is the GGSZ method, which uses the distribution over phase space of the products of D decays to multibody self-conjugate final states. I will give a detail description of this method and present some preliminary studies related to performing this measurement at the Belle II experiment. The Belle II detector sits at the interaction point of the asymmetric e+e- collider SuperKEKB at KEK, Japan. The design instantaneous luminosity is 40 times than that of the earlier Belle experiment that collected approximately 1 ab-1 of data at or near a center-of-mass energy corresponding to the Υ(4S) resonance. Belle II started taking the collision data on April 26th, 2018. I will give an overview of SuperKEKB and Belle II, then present the “rediscoveries†of final states related to the determination of φ3 that I have performed with the first data. In addition, I will review some of the service work to the collaboration that I have performed so that I may become an author. The Belle II silicon vertex detector (SVD) is crucial for the precise reconstruction of the vertex position of particles decaying after they have been produced in e+e- collisions. As a part of my service task, I am analyzing beam backgrounds for the SVD detector and also testing and preparing the data-reduction algorithms (skims) for the physics working group that performs the measurement of φ3. I will cover these studies in detail. Finally, I will present my future plans for the GGSZ measurement, rediscoveries, and SVD work.