Dear @KillianUB ,
I will repeat the same question. Are you sure the PsdNdRShift from your tree actually contains UShort_t data? Keep in mind that you cannot in general read data of type A into data of type B, and this is true for any programming language and any programming tool (unless of course you or somebody else provided some conversion machinery).
Please, study your dataset schema before going forward with any operation. You have many ways to do this, for example you can TTree::Print or even ask your supervisor about it.
Cheers,
Vincenzo