Create your own analysis

Lets consider example of building simple analysis application. E.g. you want to plot total energy of events with two scintillator hits, and compare $^{100}Mo$ $2\beta\2\nu$ Monte Carlo (mo2b2n component) with the data.

Prepare analysis directory first:

mkdir ana2sc
cd ana2sc
mkdir ana
cd ana
cp $R10SYS/utils/ana10/makefile.user ./makefile
cp $R10SYS/utils/ana10/uloop.cpp .
cp \$R10SYS/utils/ana10/urun.cpp .

Next, you need to code loop function. It is recommended to call slim cut function to ensure you have the same starting condition for every component (to be precise you need to call the most stringent slim cut among all ones used for slimming in this analysis). Loop function for our example would be:

void ana10::Loop(int eventnumber)
{
  // LOOP for analysis events selection. Author V. Vasiliev. 01.2006
  // This function creates histogram, loop through the chain and fills histogram for further displaying/analysis
  //Should be provided by user

  //technical variables 
   Int_t results[20]={0};
   Int_t nbytes = 0;
   Int_t counter = 0;
   Int_t nentries = Int_t(fChain->GetEntries());
   Int_t nb = -1;
   int treenum=-1;
   //------- PUT YOUR CUTS HERE --------------------------------
   Float_t Etot_min=0.2;
   Int_t number_of_scintillators=2;
   //--------End of CUTS----------------------------------------


   //--------------- Set analysis Period -----------------------
   //Set desired run period
   // see ana10/utils.hpp for the defenition of the constants
   SetPeriod(ana::P1,true);
   SetPeriod(ana::P2a,false);
   SetPeriod(ana::P2b,false);

   SetRuns(ana::GOOD_RUN,false);
   SetRuns(ana::OK_RUN,false);
   SetRuns(ana::NOAIR_RUN,false);
   SetRuns(ana::AFTER_EC_RUN,false);
   SetRuns(ana::HV_RUN,false);
   SetRuns(ana::ALL_BUT_BAD_RUN,false);
   SetRuns(ana::STANDARD_RUN,true);
   //--------------END of setting the period--------------------

   //-------- BOOK YOUR HISTOGRAMS HERE-------------------------
   Addh1("etot","Total energy",100,0,4.2);
   //---------End of BOOK---------------------------------------


   if (fChain == 0) return;
   std::cout<<"Number of entries in the chain "<<nentries<<std::endl;
   
   //main selection LOOP, fills booked hystos
   for (Int_t jentry=eventnumber; jentry<nentries;jentry++) {

       Bool_t preselect = false;
       Int_t ientry = LoadTree(jentry);
       Int_t nb = fChain->GetEntry(jentry);

       Int_t i,j,k;
       if (ientry < 0) break;
	results[0]++;

	if(jentry%50000==0) std::cout<<jentry<<" events passed "<<std::endl;

//!!!!!!!!!!!!!ENTER YOUR SELECTION CODE HERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        //It is highly recommended to call correct SLIM selection function 
	if(!Cut(results)) continue;
	
	//check that run is in the runlist 
	//save selected runs duration for normalization of MC later.	
	Int_t iitime;
	Bool_t goodrun=RunList(abs(run),iitime);
	if(!goodrun) continue;
	AddRunTime(abs(run),iitime);

	//Check PMT status. Ignore events w/o LTC correction
	Bool_t goodpms=true;
	for(Int_t k=0;k<Nsc;k++){
	  Int_t pmstat=pmstatus->get(run,Sc[k][1],Sc[k][2],Sc[k][3],Sc[k][4]);
	  goodpms = goodpms && GoodPMStatus(pmstat);
       	}
	if(!goodpms) continue;

	if(Nsc != number_of_scintillators) continue;
	Float_t Etot=0;
	for(Int_t i=0;i<Nsc;i++){
	  Etot+=Sc[i][8]*1000;
	}
	if(Etot<Etot_min) continue;
	results[11]++;

//!!!!!!!!!!!!!!!! CALCULATE EVENT WEIGHT!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        // attach weight to each MC event. 
	Float_t w;
	if(run<0){
	  w= GetEventWeight();// MC
	}else{
	  w=1.; //REAL
	}

//!!!!!!!!!!!!!!FILL HISTOGRAMS HERE!!!!!!!!!!!!!!!!!!!!!

	//Fill histograms for sucessfull events
	Geth1("etot")->Fill(Etot,w);
//!!!!!!!!!!!!!END OF USER SECTION!!!!!!!!!!!!!!!!!!!!!!!

	counter++;

   }
   std::cout<<"number of events:  "<<counter<<std::endl;
   for(Int_t i=0;i<20;i++)
     { 
       if(results[i]) std::cout<<" results for cut "<<i<<" "<<results[i]<<std::endl;
     } 
}

Analysis of loop function structure:

• Selection cut values. We set up minimal total energy (Etot=0.2), and number of scintillators in the event (number_of_scintillator=2). Of cause one can write directly Nsc!=2 instead of Nsc!= number_of_scintillators. But declaring all cuts as variables in the beginning makes it easier later to play with them.
• Selecting analysis period. There are few preset lists of data available to chose from for the analysis. It is done in two steps. First user has to set periods to be analysed (P1 - Phase 1, P2a and P2b are parts of the Phase 2). One or more periods can be set true. Second step is to set the run quality (run status) to be used. STANDARD means agreed run statuses to be used for $2\beta0\nu$ search. See anaRunList.C for all details.

• Book histogram. Note of call Addh1(name, title, nchnls, xmin,xmax) that creates histogram etot. Addh2 has similar parameters. Since loop() is called for each ana10 instance, this call to Addh1 automatically creates etot histogram for each component!
• Loop through events in the tree. We check that event is inside good run, has good PM hits and meet our cuts, and fill etot for good events. Note call to Geth1() to retrieve pointer to histogram. Also note the calculation of the weight for every event, and its usage to fill the histograms. This is part of correct normalisation calculations.
• It useful to fill results array to follow event reduction cut after cut. Since values 1-10 are used in slim cut(), we start from results[11] here.

To compile the program you need to set up following variables in makefile UTILS, URUNC (your copy of urun.cpp), ULOOPC ( your copy of uloop.cpp), SLIMC (slim cut.C).

#******************  USERS SETTINGS**********************
URUNC	    = urun.cpp
ULOOPC	    = uloop.cpp
SLIMC	    = ../slim/cut_2sc.C
#********************************************************

Then run gmake. Make sure there is an ana executable in the directory.