GSI Helmholtzzentrum für Schwerionenforschung
how to convert kinematic variables from lab frame to cm frame in root
Hello everyone, I know the Theta distribution of two body decay reaction in the laboratory frame.I need to convert Theta_lab distribution in to Theta_CM distribution for my analysis. For this , I have searched in the ROOT user guide but unfortunately I could not see any functionality there for that. How to convert different kinematic variables from lab frame to cm frame using root? Is there any functionality available in root for this conversion? Thanks
Re: how to convert kinematic variables from lab frame to cm frame in root
Hello, There are two situations: A) If you do analysis, there is the RhoBooster class which helps transforming the particle candidates between LAB and CM. B) You use TLorentzVector: There is the possibility to boost it with the CM momentum. (see also http://root.cern.ch/root/html534/TLorentzVector.html) Cheers. Ralf
Hi Ajay, just a small remark: I also had to calculate this for lmd fitting. However my function calculates the 4 momentum transfer from the theta angle in the lab frame. You can see it here http://cbmroot.gsi.de//panda_doc/daily/html/classPndLmdDPMAngModel1D.htm l#ab105732897c38a7fa0aaf679dcb2bd11 Maybe this is of some use.. Best regards, Stefan
This means that, if you have a collision along z axis, you can calculate the beta of the center of mass (betacm), and transform one TLV from lab to cm you have just to do: tlv_lab.Boost(0., 0., betacm);
Dear All, Thanks to all of you. I have boosted Lambda and AntiLambda from lab to cm frame using TLorentzVector. I have attached macro here.Please see it once, Am I doing correct ? Please help me. Thanks
No, it is not correct. First of all, you have to calculate the betacm from the initial particles (the target proton at rest and the projectile antiproton), and not from the supposed reconstructed lambdas. Second, if your CM is traveling at betacm, in order to have the coordinates in the CM frame you have to boost them of -betacm.