Expanding or filtering array in TTree

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No, “Lb_dtf_PV_key == 0” is meant to compare the values (as it does in TTree::Draw). This is not the same as comparing “Lb_dtf_PV_key == {0,0,0}” (this is never the case, thus the histogram obtained from TTree::Draw should be empty). I think TTree::Draw did something like expanding all arrays at once, maybe similar to the example I have given in my first post:

// entry #1
Lb_TAU              = 0.000282896
Lb_dtflambda_PV_key = 0
Lb_dtflambda_Lambda0_pplus_PE = 17280.6
...
// entry #2
Lb_TAU              = 0.000282896
Lb_dtflambda_PV_key = 1
Lb_dtflambda_Lambda0_pplus_PE = 17242.5
...
// entry #3
Lb_TAU              = 0.000282896
Lb_dtflambda_PV_key = 2
Lb_dtflambda_Lambda0_pplus_PE = 25549.6

Now Lb_dtflambda_PV_key is no longer an array, but a single value. I don’t know what actually is happening in TTree::Draw, but it works as expected. My question is, how do I reproduce this behavior for cloning TTrees?