ROOT macros

There are some basic examples of using the interactive ROOT mode to extract informations from a NuWro output file in the previous section. Usually, what you really want is to have a ROOT macro to do that. This section contains some examples of how to prepare them to work with events generated by NuWro.

You can find ROOT documentation here

Preparing a sample¶

For the examples in this section the following sample was generated:

beam: muon neutrino with energy = 1 GeV
target: Carbon
channels: all CC
no. of events: 1 000 000

using the following command:

nuwro -i numu_1gev_carbon_cc.txt -o numu_1gev_carbon_cc.root

with the following numu_1gev_carbon_cc.txt settings file:

####################
# General settings #
####################

number_of_events = 1000000  // the number of events to generate

#################
# Beam settings #
#################

beam_type = 0       // single-flavor beam
beam_particle = 14  // muon neutrino
beam_energy = 1000  // mono-energetic beam (1000 MeV)

###################
# Target settings #
###################

@target/C.txt  // Carbon

#########################
# Interactions settings #
#########################

dyn_qel_cc = 1  // charged current quasi-elastic
dyn_qel_nc = 0  // neutral current elastic
dyn_res_cc = 1  // charged current resonant pion production
dyn_res_nc = 0  // neutral current resonant pion production
dyn_dis_cc = 1  // charged current deep inelastic scattering
dyn_dis_nc = 0  // neutral current deep inelastic scattering
dyn_coh_cc = 1  // charged current coherent pion production
dyn_coh_nc = 0  // neutral current coherent pion production
dyn_mec_cc = 1  // charged current 2p2
dyn_mec_nc = 0  // neutral current 2p2h

##########################################
# Interactions settings: (quasi-)elastic #
##########################################

qel_cc_axial_mass = 1030  // axial mass [MeV]

###########################################
# Interactions settings: two-body current #
###########################################

mec_kind = 3  // Nieves et al. model

Note

You can see that numu_1gev_carbon_cc.txt does not include all parameters (like e.g. nuwro/data/params.txt settings file example).

For all parameters which were not provided in a settings file NuWro will use default values as described here.

Basic plots¶

Histograms created by Draw¶

In the previous section you can find some basic examples for using the Draw function to make plots, e.g.

tree->Draw("-q2()")

The Draw function can be also used to create ROOT histograms, e.g.

tree->Draw("-q2() >> my_histogram")

will draw the histogram but also save it in TH1F *my_histogram. Pretty handy.

You may want to use Draw to create TH1 objects w/o actually drawing them. Well, just turn graphics off:

tree->Draw("-q2() >> my_histogram", "", "goff");

Having said that, take a look at the following macro (basic_plots.c):

void basic_plots(char *filename)
{
    ///// LOAD FILE AND TTREE /////

    TFile *file = new TFile(filename);
    TTree *tree = (TTree*)file->Get("treeout");

    ///// CREATE HISTOGRAMS /////

    // Q2 distribution
    tree->Draw("-q2() >> q2", "", "goff");
    // Q2 distribution only for QEL events
    tree->Draw("-q2() >> q2_qel_true", "flag.qel", "goff");
    // Q2 distribution for events w/o any pion in the final state
    tree->Draw("-q2() >> q2_qel_like", 
               "fof(211) + fof(111) + fof(-211) == 0",
               "goff");
    // Q2 distribution for non-QEL events w/o any pion in the final state
    tree->Draw("-q2() >> q2_bkg",
               "!flag->qel && fof(211) + fof(111) + fof(-211) == 0",
               "goff");


    ///// HISTOGRAM SETTINGS /////

    q2->SetLineColor(kBlack);
    q2->SetTitle("#nu_{#mu} on Carbon, E_{#nu} = 1 GeV");
    q2->SetXTitle("Q^{2} [MeV^{2}]");

    q2_qel_true->SetLineColor(kBlue);
    q2_qel_like->SetLineColor(kGreen);
    q2_bkg->SetLineColor(kRed);

    ///// SAVE HISTOGRAMS /////

    // first you need a canvas
    TCanvas *c = new TCanvas;

    q2->Draw();
    q2_qel_true->Draw("same"); // "same" -> on the same plot
    q2_qel_like->Draw("same");
    q2_bkg->Draw("same");

    c->Print("numu_1gev_carbon_cc.q2.svg");
}

At the beginning a file is loaded and a right tree is pointed. Get used to it as every of your scripts is going to start like this. Histograms are created using Draw function (as explained above):

Draw("what >> histogram", "[conditions]", "[graphics off]")

Setting up labels, colors etc. are not worth to discuss here - it is not ROOT tutorial after all. Please see ROOT documentation for more informations.

Instead of using default c1 canvas we create our own. Now, every histogram->Draw() call will be put on the canvas. Please note, that if "same" option is not used, current content of the canvas will be overwritten.

Finally, Print function is used to save the plot to SVG file.

Please note, that the main function in the macro has the same name as the macro file. It makes it easy to run the macro directly from the command line:

myroot -b -q 'basic_plots.c("numu_1gev_carbon_cc.root")'

-b stands for batch mode (w/o graphics) and -q is to exit ROOT after job is done.

This call is equivalent to:

$ myroot -b
root [0] .L basic_plots.c 
root [1] basic_plots("numu_1gev_carbon_cc.root")
root [2] .q

The final plot ("numu_1gev_carbon_cc.q2.svg"):

ROOT macros

Preparing a sample¶

Basic plots¶

Histograms created by Draw¶

Histograms created by hand¶