To open root, simply type:
(Declares a 4-Vector named blah0)
blah0.SetPtEtaPhiM(myPt, myEta, myPhi, myMass);
(Sets the values of blah0 as shown)
blah0.SetPxPyPzE(myPx, myPy, myPz, myEnergy);
(Alternate way to blah0)
(Prints the Px of the 4-vector blah0)
Check out this root page
for the full documentation about TLorentzVector
More detailed root stuff
Plotting Histograms in root
There are three steps to plotting a histogram:
1) Declare the histogram before the event loop
TH1D* histogram_name = new TH1D("histogram_name","histogram_name",Nbins,left_edge,right_edge);
where histogram_name is a name you choose, while Nbins, left_edge, right_edge are values (Nbins is an integer, while left_edge and right_edge can value, integer or real).
2) Fill the histogram in the event loop
where fill_value is whatever you want to fill the histogram with in this event.
3) Write out the histogram after the event loop
Now run the job
Opening a histogram file in root
Once you have run the job, there should be a file: QuarkNet_test_RPV2012_Tag.root
(the middle term might be something other than "test" depending on the data file).
To open this file in root:
Some commands to use within root
To quit out of root.
To get a help list of all the "dot" commands in root
To list all the histograms there are to look at
To draw a histogram called histogram_name (if it exists)
You can also do a tab-complete for a command. If you type
then it will list all the things you
can do with that histogram name (for instance: Draw(), Rebin(x), etc).