LEPTOMATCHIG: A program for matching charged Higgs boson production
In order to combine the charged Higgs boson production processes gb->tH+/- (ISUB=161) and gg->tbH+/- (ISUB=401) one must remove double-counting. The Fortran code provided here is the implementation of a double-counting term which should be run together with these two production processes to obtain matched events. Note that in the analysis, the events from the double-counting term must be subtracted (i.e. added with weight -1) from the sum of events from the production processes. Please see the manual for details on the implementation and [1] for the physics background and results.
Files:
- A manual on how to use the code [pdf (145 kB), gzipped ps (60 kB)]
- Source code for the double-counting term [matchig.f (10 kB)]
- An example main program [matchex.f (2.2 kB)] and a larger example, generating an ntuple file with relevant observables (in particular ptbin and ptbout) [run_matching.f (12.3 kB)]
Note that the double-counting term is implemented as an external process to PYTHIA. This means that you might need to remove the (dummy) subroutines UPINIT and UPEVNT from PYTHIA before including the file matchig.f. The present version of the file is adapted to PYTHIA version 6.321 or highe.
The code now gives well matched results with standard PYTHIA v. 6.4 settings, both for virtuality-ordered and pT-ordered showers (PYEVNW and PYEVNT). In the initialization of the external process some optimized parameters are automatically set (MSTP(68)=0 and PARP(67)=1 and MSTP(32)=13).
For older versions of PYTHIA (but note that version 6.226 or higher / 6.314 or higher are needed), please use the older versions of the files, matchig.6.2.f and matchex.6.2.f. Note that in PYTHIA version 6.319-6.320, one must use PYEVNT (not PYEVNW) with MSTP(68)=1 to get the correct behaviour of the gb->tH+/- parton showers. For these older versions of PYTHIA one should always set fixed renormalization and factorisation scales as described in the manual (see also the example program).It you use this code, please cite this webpage and [1].
Questions will be answered by Johan Alwall.
References
- J. Alwall and J. Rathsman
"Improved description of charged Higgs boson production at hadron colliders"
JHEP12(2004)050, hep-ph/0409094
Implementation of gg->tbH+/- in PYTHIA
This page contains a test program and instructions on how to simulate
charged Higgs production through the channel gg(qqbar) -> tbH+/- in PYTHIA. The code for the production channel is now
included in PYTHIA
version 6.223 and up.
IMPORTANT: If you use these processes together
with gb->tH+/-, care has to be taken to avoid
double-counting, see [1] and above.
Please see [2] for a comparison between Herwig and Pythia.
If you use this code, please cite this webpage and [1]. Thanks to J.-L. Kneur for providing the Fortran code for the matrix element [3].
Subprocess numbers of the new processes:
- gg -> tbH+/-: 401
- qqbar -> tbH+/-: 402
Note that in order to get a reliable simulation you might want to increase the value of MSTP(129) (e.g. 1000) (the number of tries to find the maximum cross-section during initialization).
Any questions regarding the implementation will be answered by Johan Alwall.
Source code
References
- J. Alwall and J. Rathsman
"Improved description of charged Higgs boson production at hadron colliders"
JHEP12(2004)050, hep-ph/0409094 - J. Alwall, C. Biscarat, S. Moretti, J. Rathsman and A. Sopczak
"The p pbar -> t b H+/- process at the Tevatron in HERWIG and PYTHIA simulations"
Eur. Phys. J. direct C1 (2004) 005, hep-ph/0312301 - F. Borzumati, J.-L. Kneur, N. Polonsky, Phys Rev. D 60 (1999) 115011