- Bo Li presented the status of R_b measurement in Z->bb analysis. He showed that the correlation factors for b tagging(c_b -1) is about 3%, similar to LEP/SLD result. However the correlation factors for c tagging (c_c -1) is 10%~90%, significantly higher than LEP result (<10%). More study is needed to understand the c tagging correlation factor. Bo Li mentioned that MC statistics is not enough , he is using 150k full sim MC, Gang mentioned that it is possible to generate 1M fullsim MC.
- Peizhu gave an update on jet energy calibration. He showed that the jet energy scale is closer to truth jet energy scale when he veto ISR events. He also practiced on applying Jet energy scale correction from Z->qq to W->qq events. However, his preliminary in slide 14 showed that W mass after calibration is lower than expected, he will check the potential issue in calibration chain. He also showed the W/Z boson mass after b/c tagging. Zhijun Suggested to try to apply b veto cut (veto events with >=1 b tagged jet) instead of b tagging. B veto cut can be more aggressive ( eg: aggressive cut: veto event with jet B likelihood >0.1, or more robust option: B likelihood>0.3..), Gang suggested that to try b veto and c veto (based on b jet likelihood and c jet likelihood 2D cut ) in next step. The working point can be optimized based on the plot in slide 21.
- PeiXun gave a update on WW threshold scan optimization. Gang suggested to show color map contour plot instead of scatter plot in slide 3-4 for two collision energy point optimization. In slide 11, Peixun showed that YFSWW3 generator has quite large fluctuation in calculation, will check with Fulvio offline to understand more how to use YFSWW3. Zhijun suggested to consider uncertainty on cross section, luminosity, beam energy, energy spread in the optimization.
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