Hits selection for time-walk fit.

As an example, hits from run 2209 in the module NS21 are shown.
Module NS21 is a horizontal 3cm-narrow paddle closest to the beam.
Hits are defined as having both PMTs signals after the timing cut.

Event selection criteria:
- A hit in the horizontal module NS21;
- A single hit in the UD (vertical) plane.



Good hits are supposed to line up on the diagonal.
Clearly, there is large background of the unknown origin.
Hits statistics is overwhelmingly in the TOF center
but that is where the signal/background overlapping is.
This turns TWC-fit in "random number generator" depending on
how wide the hit-matching cut is.