1) NPE in central UU - Katarina
For the EMC efficiency, suggest to look into related part in Robert's analysis. There is also suggestion to trust the data more than embedding on this matter, if there is no reason not to do so. 
It is suggested to correct the effect of the different collision energy in UU and pp on Raa. 

2) trigger efficiency correction in D-hadron correlation study - Long Ma
It is suggested to consider also tracking and pid efficiency correction.

3) update on Ds meson analysis - Long Zhou
It is suggested to look at the toy MC for cut tuning, also at the toy MC daughter momentum distribution to decide whether to require HFT for all daughters. At low pt, the HFT efficiency drop quickly.
May consider kf vertex for decay vertex fitting, so we have 1 instead of 3 vertices, and the number of parameters related to decay will decrease.
The comparison between 2 analysis need to reach exact agreement with exactly the same cuts. Then we can understand better the difference on width and so on.