HadronInfo

Why

We can get all information from a track with a few lines. For example, we should write down 4 lines to get the momentum of one electron track

RecMdcKalTrack *mdcTrk = m_track->mdcKalTrack();
RecMdcKalTrack::setPidType(RecMdcKalTrack::electron);
double mass = 0.000511;
HepLorentzVector p4 = mdcTrk->p4(mass);

When we encounter a short-life particle, we must find its decay final tracks, then add all information of them one by one together, sometime a VertexFit is necessary, sometime not. At this case, we have to write down even more than 100 lines code, then debug to make sure the momentum is obtained properly. However, it's both luck and terrible that we have many short-life particle, Lambda, Ks , eta, phi, omega,...

This motevita us to create this package, "Make people access to the short-life particle easyly and reliably and save our life"

How

We find that the detector can only see track and shower, which like two stones building all visable particle. So we create two base class, named TrackInfo and ShowerInfo, A series classes are inherited from them. Here I give one example to show the relationship, PionInfo and KaonInfo are inherited from TrackInfo. Then a template named CombInfo is created to create more classes. It seems like

template <class FirstInfo, class SecondInfo, int pid = 0,
          bool doVertexFit = false>
class CombInfo : public AvailableInfo {
   public:
   ...
   private:
   ...
};

Then we can build all others, for example

typedef CombInfo<ProtonInfo, PionInfo, 3312, 1> LamInfo;
typedef CombInfo<LamInfo, KaonInfo, 3334, 1> OmegamInfo;

the common method

One principle is that all class must pose some methods to providing necessary information of the short-life particles.

• GetName()

The name is important to show our respect to the particles.

• P4()
• Mass() ...

How

usage

Create an instance is very easy. You can create one PionInfo instance from the track,

...
PionInfo pionInfo(aTrack);

Also from a CDCandidate

...
PionInfo pionInfo(pionCandidate);

Nothing

PionInfo pionInfo();

But at this case, you must set the tracks before use it

pionInfo.setTrack(aTrack);
HepLorentzVector p4 = pionInfo.p4();
...

suggestion

• use the glob avariable defined in the header "gHadronInfo.h"

gKs.Feed(aKsCandidate);
aKs.chisq();
aKs.Mass();
aKs.RawMass();
...

• use the TupleSvc Please see the TupleSvc

aKs.Feed(aKsCandidate);
aTupleSvc << aKs;