14:00 BST, Wednesday 9th May
We will use the regular phone bridge,
Thoughts on asymmetry issue:(CR)
- It is not an alignment issue as it seems to move the tail, not the peak
- Is it affected by the fiducial cut? What about a cut at the absorber (i.e. could it be an aperture around there, or some feature of the absorber itself?). Could you make a fiducial cut just on the expected radius at TKD and absorber (forget about the "extra angle" thing). vary the fiducial cut, does the affect change?
- Is it affected by the momentum/TOF selection? Could it be a feature of the TOF detectors (we know there are issues with bad calibrations in certain channels for example). Is it dependent on the TOF bars used in the analysis? Any dependency on TOF12 vs TOF01?
- Is it affected by the initial beam misalignment? We know the beam misalignment in your MC is different to your data. E.g. do you see an affect if you look at only the central portion of your beam at TKU?
I’m not convinced re ruling out alignment. If there is a tilt in our as-built experiment that is not in the MC then I think you can get this effect. I appreciate that the angle is plotted and the mean seems to be central, but, the plateau region is broad and the tails are likely to have a strong effect.
Chris has a good list. I would like also to focus on the empty channel data. Did you make a systematic study of the asymmetry in this data, e.g. by comparing <0 to >0 and/or by making bins left/right and comparing the number of entries. It is conceivable, looking at the plots, that the empty-channel data does not have an asymmetry. In this case, we’d be looking for something that could change in an an absorber change.
I would also look at residuals in position and angle in the empty channel data as a function of position, e.g. compare at each station. A tilt should have the feature that it is correlated (changes) between stations.