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Dear Marco: First: Many thanks to Marco for helping with this work. I only have two comments: 1>The W(theta) function which is the standard formalism for specifying the angular distribution in terms of the initial state magnetic substate population p(mi) is from MiniBooNE technote192 and RS model. In this technote, not only the delta->NPI, the delta->Ngamma's angular distribution was also specified. 2> The magnetic form factor F^V used to calculate the branching ration between delta->Npi and Delta->Ngamma decay was also given by this technote. Actually, difference papers/analysis used difference kind of form factors. In the my old code, I tested 3 of them, you might can see something like this in the old code: *//double fgammaW= 1/(TMath::Power(1+EgammaW*EgammaW/0.706, 2)*(1+EgammaW*EgammaW/3.519)); //double fgammam= 1/(TMath::Power(1+Egammam*Egammam/0.706, 2)*(1+Egammam*Egammam/3.519)); double fgammaW= 1/(TMath::Power(1+EgammaW*EgammaW/0.706, 2)); double fgammam= 1/(TMath::Power(1+Egammam*Egammam/0.706, 2));* 0.706=MV^2 (MV=0.84) given by the paper PhysRevD.71.074003 I remember I changed into a single diple because it was given by a Miniboone note or paper. However, because my old laptop was dead, I can not find the origin of this form factor. I will keep trying in the coming days, but I do not this there is a big difference. I hope these comments are helpful. Regards On Thu, Dec 13, 2018 at 6:50 AM Marco Roda <[log in to unmask]> wrote: > Hi Steve and Libo, (CC main developers) > > I completed the implementation of the Delta decay developed by Libo in a > way that is compatible to the new interface required to allow Pythia 8 > implementation. > > You can see the final code here: > https://github.com/mroda88/Generator/tree/CorrectedHadroRefact > or here > https://github.com/candreop/Generator/tree/HadroRefactorization > > Here are a few question / comments / updates that arises while moving the > code. I will divide them between Angular distribution of the pion and > Evolution of the BR as a function of W. > > -------------------------------------------------------------------- > Angular distribution of pions > -------------------------------------------------------------------- > > 1) the parameters P(3/2) and P(1/2) are not read from xml. Or, to be > precise, one is, the other is by definition 1 - the other. > The value id defaulted to the RS model, namely P(3/2) = 0.75, P(1/2) = > 0.25. > > 2) as a consequence of point 1) the random number that is used to accept > or reject the distribution is tuned as a function of P(1/2) and P(3/2) > > 3) The algorithm calls for an exit in case the value for P(3/2) or P(1/2) > implies a W(theta) distribution which is not always positive. > > > --------------------------------------------------------------------- > Evolution of the Delta BR as a function of the actual mass of the Delta > -------------------------------------------------------------------- > > This piece of code required a major manipulation so I would appreciate, if > you could have a look. > > 1) Previously the code was doing evolution of BR in a single go. > I split it in 2: first it evolves the single decay amplitudes and then if > evaluates the new BR. > In this way the evolution of the pion decay channels can be done according > to the actual pion and nucleon mass involved in the decay. > Very small difference I believe. > > 2) in this process, all the parameters like widths, masses, etc are taken > from the Genie database and they are not hardcoded. > > 3) I noticed a discrepancy between the code and what is in the note > release by Libo, specifically in the definition of R_inv. > I do believe the error is in the note, as what was implemented in the code > is what stated in the MiniBoone tech note and it's also compatible with the > reasoning in the note. > Still I would be happier if you could check. > > 4) That formula anyway disappeared as a consequence of the refactorization > so it's not there anymore. > > 5) Most importantly, I would like you to have a look at the form factor > for the photon we are using. > Both Miniboone Note and Libo's note, report two different scaling > functions for the coupling of the photons with the Delta. > One is a simple dipole, the other is a product of two dipoles. > What I don't understand is why we use a single dipole but then we use the > parameter of one of the other two. > > Comments from everybody are certainly welcome anyway. > > Cheers, > Marco > > -- > > Marco Roda, PhD in Physics > Post Doctorate Research Associate > > University of Liverpool > Department of Physics > Oliver Lodge Laboratory > Liverpool L69 7ZE, UK > > Mail: [log in to unmask] > Office: +44 (0)151 79 43403 > Mobile: +44 (0)745 381 2081 > -- Libo Jiang Cell: (803)-743-6673 ######################################################################## To unsubscribe from the NEUTRINO-MC-CORE list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=NEUTRINO-MC-CORE&A=1