Event decay problem using TGenPhaseSpace

Newbie
1

hi ,
can anyone help me with this problem,
To develop an algorithm to generate a D0 meson of mass 1864.84±0.17 MeV assuming an exponential pT distribution and flat pseudo-rapidity distribution between -1 to 1. Allow the particle to decay to pi+ pi-. Generate 10^7 events, with each event containing D0 distributed with poison distribution of mean 4.

to make it simple: generate random events with 4D^o on an avg decaying into pi+pi- following poison distribution .
I’ve uploaded my code ,it doesn’t work properly.

Thanks in advance.

ChargedKStar8.C (9.0 KB)

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ROOT Version: 5
Platform: Not Provided
Compiler: Not Provided

2

Hi
The code seems not doing what you describe.
You need for each event generate a Poisson number with mean 4, using gRandom->Poisson(4), loop on this number and generate a D0 vector using:

  • pT from an exponential distribution : pt = gRandom->Exp(mean). What is the mean value ?
  • eta = gRandom->Uniform(-1,1)
  • phi = gRandom->>Uniform(-TMath::Pi()I,TMath::Pi())
  • mass = 1…86484 (fixed)

Then you create a LorentxVector with these generated values:

TLorentzVector D0;
D0..SetPtEtaPhiM(pt,eta,phi,mass);

and afterwards you generate the decaying particle using as in your code:

TGenPhaseSpace event; 
event.SetDecay(D0,2,masses4);
weight= event.Generate();

Lorenzo

3

hi Lorenzo,
thanks, it really helped a lot.
can you tell me how to get the charge of the decay daughters?

cheers
Ajalotra

4

Hi,

You will have to deal with the charge separately. TGenPhaseSpace is only kinematics and it does not deal with charges of mother and daughter particles.

Lorenzo

5

~thank you

Ajalotra

6

Hi Lorenzo,

(a) can we find Experimental mass resolution with this?
(b) If the momentum resolution of electrons is 3%, find out the invariant mass distribution of D0?

how do we do this?
can you help.

Regards
Ajalotra

7

Hi,
Sorry for my late answer. Your question is not clear and I don’t see the relation with TGenPhaseSpace. This seems to me not a ROOT question but a physics analysis question that you should ask your supervisor or your colleagues.

Kind regards

Lorenzo