LHCb Software Training: DaVinci

Exercises linked to DaVinci session 3

The purpose of these exercises is to allow you to write a complete though simple selection algorithms for a typical decay: Bs->J/psiPhi. Now that we have the J/psi and the Phi, let's do the Bs using options.

1. Add a Bs maker

Add a MakeResonances instance to your sequence. Let's call it Bs2psiPhi.
Feed the PhysDesktop with your J/psi and Phi candidates.
Define the Decay Descriptor

Bs2JpsiPhi.DecayDescriptor = "B_s0 -> phi(1020) J/psi(1S)";

Define the mass window.

Bs2JpsiPhi.Window = 100 * MeV;

Add a vertex cut for the Bs

Bs2JpsiPhi.MotherFilter.Selections = { "B_s0 : VtxFilterCriterion"};

And configure it

Bs2JpsiPhi.MotherFilter.VtxFilterCriterion.MaxChi2 = 30 ;

With this we are already at the same level as with our C++ code for the J/psi!

You could also cut on the daughters. For instance: Cut on the IP of the kaons in the Phi. Remember how to do that?
Now let's add some plots

Bs2JpsiPhi.HistoProduce=true;
Bs2JpsiPhi.DaughterPlots.Variables={"M","P","Pt","IP"};
Bs2JpsiPhi.MotherPlots.Variables={"M", "P","Pt", "IP"};
Bs2JpsiPhi.DaughterPlotsPath= "Bin" ;
Bs2JpsiPhi.MotherPlotsPath= "Bout" ;

That's all!

2. Run

Run it.

Last modified by Vanya BELYAEV, June 6 2006