Add a new DecFile for Lb->JpsipK decay, using a new XLL event model

Dear experts,

We would like to add a new decay file for Lb-> JpsipK decay mode where XLL is used to enhance the yields with m(pK) around L*(1520) region. This will benefit the amplitude analysis of this decay mode.

Here is the message to be put in the release note:

! 2019-03-19 - Mengzhen Wang (MR !254)
   Add 1 new decfiles
   + 15144059 : Lb_JpsipK,mm=XLL2,DecProdCut.dec

The decfile has been tested locally, and examed using the decparser.sh script. No warning message is presented, and the full log information is:

Opening logfile </afs/cern.ch/work/m/mengzhen/cmtuser/GaussDev_v49r12/Gen/DecFiles/cmt/decparser/decparse.log> and loading colours DONE
Starting the decfile check
Opening decfile............................................. DONE
Checking for Unix EOF....................................... DONE
Now parsing: EventType...................................... DONE
Eventtype found: 15144059
Now parsing: Descriptor..................................... DONE
Now parsing: NickName....................................... DONE
Now parsing: Cuts........................................... DONE
Now parsing: CPUTime........................................ DONE
Now parsing: Documentation.................................. DONE
Now parsing: PhysicsWG...................................... DONE
Now parsing: Tested......................................... DONE
Now parsing: Responsible.................................... DONE
Now parsing: Email.......................................... DONE
Now parsing: Date........................................... DONE
End of header.
Found decay: Lambda_b0sig
Found decay: MyJ/psi
File parsed successfully.
Checking for CPU time field................................. DONE
Checking general flag....................................... DONE
Checking selection flag..................................... DONE
Unfolding decay............................................. DONE
Checking the decay flag..................................... DONE
Checking charm and lepton flag.............................. DONE
Checking track flag......................................... DONE
Checking neutrals flag...................................... DONE
Getting The Interwebs....................................... DONE
Checking the extra and user for duplicity and funky stuff... DONE
Eventtype constructed: 1514405X
Checking nickname........................................... DONE
Checking the Physics WG..................................... DONE
Building descriptor......................................... DONE
Checking descriptor......................................... DONE
Lambda_b0sig [(1.0, ['K-', 'MyJ/psi', 'p+'])]
MyJ/psi [(1.0, ['mu+', 'mu-'])]
Main decay chain:
['MyJ/psi', 'p+', 'K-']
['p+', 'K-', 'mu+', 'mu-']
Decfile check complete.