Update 'B mass model'

B-mass-model.md

@@ -1,10 +1,94 @@
-The B mass fit is performed by the functions defined in [[MassFit.cpp|MassFit.cpp]]. 
+## Introduction
+
+The B mass fit is performed by the functions defined in [[MassFit.cpp|MassFit.cpp]]. In this file, the main function `massFit` is defined. This function is rather complex with many parameters as we tried a lot of mass models. 
+
+The fit model is base on RooFit **TODO**
+
+Before executing any part of the selection code involving the mass fit, it is needed to compile the files with the classes needed for the fit. 
 
 
+## Mass Fit compilation
+ Recompile mass fit
+
+```
+ .L BmassShape/SignalType.cpp+
+ .L BmassShape/SignalPdf.cpp+
+ .L BmassShape/BackgroundType.cpp+
+ .L BmassShape/BackgroundPdf.cpp+
+ .L BmassShape/ParamValues.cpp+
+ .L MassFit.cpp+
+```
+
+## Adding double crystal ball and ExpGauss to RooFit
+
+Standard RooFit does not include a double crystal ball or ExpGaus function used to descibe partialy reconstructed background. Thanks go to Flavio for pointing me to the RooDoubleCB code and helping with the compilation!
+
+### RooDoubleCB compilation
+
+Run `build.C` in `Code/RooFit/RooDoubleCB/`
+
+**TODO** try this out!
+
+### RooExpAndGauss compilation
+
+```
+cd Code/RooFit/RooExpAndGauss/
+make 
+```
+
+**TODO** try this out!
+
+
+## Fit model description
+The fit is defined in the `massFit` function in  [[MassFit.cpp|MassFit.cpp]]. The user can decide
+
+* What year, polarity and Run to fit
+* What sample (data, MC, PHSP, inclusive MC) to fit
+* What selection to fit (stripped, preselected, set cut on MVA response, random subset of a selection, remove multiple candidates)
+* What Q2 range to fit (below Jpsi/Jpsi/rare/all)
+* Whether to constrain of fix the parameters to MC
+* Whether to use LL or DD tracks
+* Wheter to use sWeights or special weights calculated from efficiencis
+* Reduce verbosity/saving 
+* What truth-matching to use
+* Mass range for the yield calculation
+* Apply additional cut on a variable (eg when scanning the B mass fit in different cos(thetak) bins)
+
+
+### Signal
+
+The signal can fully turned off or be described by
+
+* Left-sided Crystal Ball
+* Right-sided Crystal Ball
+* Both-sided Crystal Ball
+* Gaussian
+* Double Gaussian
+
+The fixed/starting parameters are saved in [[ParamValues.cpp|ParamValues.cpp]].
+
+
+
+
+### Background
+
+The signal can fully turned off or be described by 
+
+* Exponential
+* Double Exponential
+* Exponential + ExpGaus
+* One Crystal Ball + single exponential
+
+The fixed/starting parameters are saved in [[ParamValues.cpp|ParamValues.cpp]].
+
+ 
+ ## Source files
 
 
 [[BackgroundPdf Class|BackgroundPdf-Class]]
 
+
+
 [[BackgroundType Class|BackgroundType-Class]]
 
 LinkDef.hpp
@@ -26,16 +110,6 @@ LinkDef.hpp
 
 
 
-## Mass Fit compilation
+
- Recompile mass fit
-
-```
- .L BmassShape/SignalType.cpp+
- .L BmassShape/SignalPdf.cpp+
- .L BmassShape/BackgroundType.cpp+
- .L BmassShape/BackgroundPdf.cpp+
- .L BmassShape/ParamValues.cpp+
- .L MassFit.cpp+
-```