Project Strategy

ROOT
1

Hi,
So I have a very basic understanding of ROOT: how to print an event, open a file, view the branches, things like that. I can also plot one dimensional histograms and write very basic macros. I have a project to do with some ntuple files and I need to determine how each different initial parton distribution function affects the final outcome (different PDF means different outcome). In the file I’ve found some branches and leaves called pdf_1 and pdf_2, which I’ve been playing around with and I’m not sure what I’m doing or what the values I’m getting back mean. My question is how would I go about determining how the parton distribution function affects the outcome of the files I have. Below I’ve copied some of the values I’ve gotten back from the Branch and Leaf I’ve called pdf and pdfLeaf respectively, just some simple things I know how to do.

root [7] pdf->GetListOfLeaves()->Print()
Collection name=‘TObjArray’, class=‘TObjArray’, size=16
OBJ: TLeafElement pdf_1 pdf_1
root [8] TLeaf *pdfLeaf = pdf->GetLeaf(“pdf_1”)
root [10] pdfLeaf->GetLen()
(const Int_t)1
root [14] pdf->Print()
*Br 79 :pdf_1 : Float_t *
*Entries : 99845 : Total Size= 400900 bytes File Size = 3435 *
*Baskets : 13 : Basket Size= 32000 bytes Compression= 116.55 *
…
root [15] pdf->GetEntry(1)
(Int_t)4
root [18] pdfLeaf->Print()
OBJ: TLeafElement pdf_1 pdf_1
root [21] pdfLeaf->GetValue(1)
(const Double_t)4.26805798915929853e+21
root [22] pdf->GetEntry(99000)
(Int_t)4

Again, I’m not completely sure what I’m doing other than just exploring the file and not knowing exactly what I’m finding. Any insight would be very much appreciated. Thank you so much!

cheers,
Zac

2

As I understand your problem is that you do not know really the meaning of pdf_1 and pdf_2 ? right ?
If that’s the case you should ask the person (people) you created this tree …

3

Hi couet,

Thanks for the reply. My problem is that I want to find out where I can find the information within the data file on the parton distribution functions and how I can plot them against something like final momentum or something else interesting.

Cheers,
Zac

4

As I said the internal structure and variables meaning of a TTree depends on its design.
I cannot help you with this. Ask the people who designed this tree.