1. More MCFocus Changes Matrix Elements
Maximum intensity searching
Record max weights in a hash table
Numerical problems when P2  m2
Evaluate ||2 in the parent particle’s rest frame
Multiple specified decays provide unexpected benefits
Gets results similar to c-cbar but much faster
Can estimate equivalent number of c-cbar events for normalization
Updating mcfedit
New particle selection layout
More MCFocus options
Edit matrix elements and branching ratios
Read new particle data file and identify & expand “final states”
When will we finish and release it?
What’s left to do?
12/31/2018

2. Storing Max Weights
Some ME’s have a simple (easy calculation) max. value
Like Cos2q
Others do not, and must be sampled many times first
Like
This sampling process takes time, so we ought to save the result
Max weight depends on:
Function (subroutine) Parameters Parent ID Daughter IDs
Function + parameter set is one number
Could have up to 7 daughters
We could store max weights in a 9-dimensional array (sparsely populated)
OR a hash table (much smaller, faster, etc)
Easy to implement, clearly the correct solution
12/31/2018

3. How it Works
RGPHASEME: max weight for OM3P::OMEGA->PI0,PI+,PI+ given as
RGPHASEME: max weight not given. Guessing..
RGPHASEME: max weight of PLN_K::KL->PI+,MU-,NU measured to be E-02
RGPHASEME: max weight of PLN_K::KL->PI+,E-,NU measured to be E-02
RGPHASEME: max weight of PLN_K::K+->PI0,E-,NU measured to be E-02
RGPHASEME: max weight for PVPA::RHO+->PI+,PI0 given as
RGPHASEME: max weight for PVPA::K*+->K0,PI+ given as
RGPHASEME: max weight for PVPA::K*0->K+,PI+ given as
RGPHASEME: max weight of PLN_DS::D0->K+,E-,NU measured to be
RGPHASEME: max weight for PVPA::K*+->K+,PI0 given as
RGPHASEME: max weight of PLN_DS::D+->K0,MU-,NU measured to be
RGPHASEME: max weight for PVPA::PHI->KL,KS given as
RGPHASEME: max weight of PLN_DS::DS+->ETA,MU-,NU measured to be
RGPHASEME: max weight for PVPA::PHI->K+,K+ given as
RGPHASEME: max weight of PLN_K::K+->PI0,MU-,NU measured to be E-02
RGPHASEME: max weight of PLN_DS::D+->K0,E-,NU measured to be
RGPHASEME: max weight for VLN::DS+->PHI,MU-,NU given as
RGPHASEME: max weight for VLN::D0->K*+,E-,NU given as
RGPHASEME: max weight for VLN::D0->K*+,MU-,NU given as
RGPHASEME: max weight for VLN::D+->K*0,MU-,NU given as
...
12/31/2018

4. Numerical Problems in Matrix Elements
Problems when P2  m2
Double precision computation helps a bit, but doesn’t directly address the real problem.
Need to go to another frame
Cos2 should be  1
Precision problems can give arbitrarily large max value.
12/31/2018

5. The Solution
Evaluate all matrix elements in rest frame of the parent particle
Greatly simplifies certain ME’s
Faster, especially for 2-body decays
This requires a new phase space generator which does not boost all the way to the lab frame.
Spin-off from phase, called phasecm
While I was at it, I changed phase to take the parent mass as given from rgmass instead of re-computing from Sqrt(E2-P2).
Also, double precision is used (overkill?)
12/31/2018

6. Multiple Specified Decays
Original purpose was to simulate matrix elements in generic decays, and simplify simulating specific ones
By-products from this, new particle data structure and ability to specify multiple decays, may be the real benefit
K p
black is ccbar in old MC
K 2p
K 3p
red is select decays in new MC 
K K p
p K p
K p
(D*)
red is about 3 times faster for the equivalent charm
K 3p
(D*)
Ks 2K
(D*)
Ks K p
(D*)
12/31/2018

7. c-cbar Common Currency
The new algorithm allows a simple calculation of… Effective c-cbar Pythia events!
Example log file beginning and end:
Specified decay chain
CHARM:
D A.P. = BR TOT =
D+(K-,PI+,PI+)
D+(K*0BAR(K-,PI+),PI+;PVP)
LAMBDAC+ A.P. = BR TOT =
LAMBDAC+(PROTON,K-,PI+)
LAMBDAC+(K*0BAR(K-,PI+),PROTON)
CHARMBAR:
CHARMBAR A.P. =
***************************************************************
Rogue
Final ISEED:
c,cbar Events Pythia generated:
Scaled c,cbar Pythia events: E+07
NGEN:
NACC:
25  faster than c-cbar!
12/31/2018

8. Updating mcfedit
mcfedit must track with MCFocus if it’s going to be useful
Already finished:
Choose matrix elements for vertices
Choose branching ratios for decays
read and write chat files
matrix elements and branching ratios
multi-line decay spec (2 or more)
New options
Match conjugate decay, do matrix elements, use counting rules, Q/diQ supression factor
Better particle selection menus
Read particle2.dat
Still to come:
new particle data browser window
Distinguish final states from decay paths (important!)
expand final states
Macros such as “Do trigger. No, really, I mean it!”
12/31/2018

9. Screen Shots
12/31/2018

10. More Screen Shots
12/31/2018

11. When Can I Release?
Want to add a couple more simple matrix elements for
 -> p0 p+ p-
' -> 3p0
mcfedit should distinguish final states from decay paths
Handle ALIASC and ALIASCB more generally
Write memo and/or WWW documentation
These changes should be released before tuning
Are there any other tests to perform or major missing pieces?
Any Objections? (hint: say “no”)
12/31/2018