DDecayAlg

DDecayAlg is an algorithm used by BESIII to create NTuple s to be used in charm analysis (e.g. \(D\to K_S^0 h^+h^-\).

It is located in BesExamples of BOSS and mainly uses the DTagTool package to perform tagged analysis of D mesons.

DTagTool

The algorithm starts the DTagTool algorithm

DTagTool dtagTool;

DTagTool has information about tagged decays at BESIII, used at the \(\psi(3770)\to D^0 \bar{D}^0\) decay mode. We can either look at the “single tag” or “stag” which looks at the decay \(D^0(\bar{D}^0) \to f\) where we include both \(D^0\) and \(\bar{D}^0\).

Let’s take the \(K_{S}^{0} \pi^+ \pi^-\) decay, which DTagTool assigns the decay mode "100":

EvtRecDTag * stag = dtagTool.findSTag(100);

This stag object now has the information relating to the candidate decay \(D\to K *S^0 \pi^+ \pi^-\) such as \(\Delta E = E* \text{beam} - E_D\):

deltaE = stag->deltaE();

or the tracks from the event

tracks = stag->tracks();