Runyu Bi


TL;DR: We measure the top quark angular properties w/ ATLAS @CERN.

In the Standard Model (SM), top quark is a member of the weak-isospin doublet, where the other partner is bottom quark. It is by far the heaviest elementry particle discovered in nature, and its lifetime (≃ 5 × 10−25s) is comparatively shorter than the typical hadronization time scale (≃ 3 × 10−24s). It is therefore the only quark that could be considered as a “bare” quark. Due to the V-A structure of the weak interaction occurred in the production of the single top quark, in this channel the top quark will be polarized, along with its decay products. Precision measurements could be performed on the t-channel at LHC.

In our analysis, we will be handling data of center of mass energy of 13TeV, with an integrated luminosity of 139 fb−1, collected by the ATLAS detector. With the advantage of an increased statistics, along with a newly developed analytical model for the differential angular distribution of the top decay, we propose a template fit method to simultaneously measure the polarization of x-y-z axes in the fiducial region. The novelty of performing the measurement in such way consists of: i) this method by nature should give us a higher precision than before; ii) it is also a quantity (P in fiducial region) that has never been measured before. Deviations from SM predictions can give hints of physics beyond the SM.




Graduate Advisor

Joseph Boudreau