RooFit Code Documentation
class: RooPdf_Bs2JPsiPhi
This is a PDF for use in fitting Bs -> Vector Vector Decays.
It has been written for the Bs -> J/Psi Phi decay to analyse the full three decay angle
distribution. It also implements a mode for analysing just the single transversity angle.
The choice of three or one angle modes is made through the constructor.
The PDF can handle the following ranges
- time: arbitrary t1 to t2 in range [0,inf]
- all angles: full range, no smaller limits allowed
The reference for the three angle distributions is:
Dighe, Dunietz, Fleisher /Eur. Phys. Journal C6 , 647-662 (1999)
The definition of phi_s is such that in the SM it is negative, i.e phi_s = - 2 Chi
The PDF is instantiation is:
!RooPdf_!Bs2JPsiPhi signal (
//These are fixed parameters used only at construction
"name of pdf",
"description",
btype // Sets whether PDF is for B (=1), Bbar (=-1) or Untagged (=0)
//These are RooRealVar parameters which represent the event measurables:
time, // proper time for event decay
ctheta_tr, // transversity angle for event decay
phi_tr, // phi angle for event decay
ctheta_1, // other angle for event decay
// These are the fit parameters
gamma, // average Bs lifetime
dgam, // Bs lifetime difference
Rt, // Fraction of "transverse" or CP -1 final state
Rp, // Fraction of "parallel" CP +1 final state
delta1, // First strong phase (see reference)
delta2, // Second strong phase
delta_ms, // Bs mass difference
phi_s, // CP violating phase
// This is treated as an odd one out for now as it could be a measurable or a fit parameter.
misTagFraction, // Mistag fraction in range [0, 0.5]
) ;
The relation between the Rt and Rp input parameters and the amplitudes is:
AT^2 = Rt
AP^2 = Rp
AO^2 = 1-Rt-Rp
with AT^2 + AP^2 + AO^2 = 0
Example
The PDF plus an example script should be checked out from cvs
cvs checkout Analysis/Bs2Jpsiphi/RooPdf
You will find the .h and .cxx class files for the PDF. These allow you to instantiate a standard RooFit RooAbsPdf
There is an example script to run in root (RooMainExample).