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Manual for Higgs boson production in association with bottom
quarks in the POWHEG-BOX-V2
The bbH program in the POWHEG-BOX-V2 is an implementation of Higgs boson production in
association with bottom quarks. Details of the calculation are described in Ref. [1]. The code is
applicable for values of the mass and width of the Higgs boson where its decays can be treated
using a narrow-width approximation, and off-shell effects are small. If you use this program,
please quote Refs. [1–4].
Running the program
Download the POWHEG-BOX-V2, following the instructions at the web site
http://powhegbox.mib.infn.it/
and go to the process directory by typing
$ cd POWHEG-BOX-V2/bbH
Running is most conveniently done in a separate directory. Together with the code, we provide
the directory testrun that contains sample input and seed files.
For your runs, generate your own directory, for instance by doing
$ mkdir myruns
The directory must contain the powheg.input file, where parameters for the Higgs boson and
the top quark decays as well as technical parameters are specified, and, for parallel running,
apwgseeds.dat file (see manual-BOX.pdf and Manyseeds.pdf in the POWHEG-BOX-V2/Docs
directory).
Before compiling make sure that:
•lhapdf is installed and lhapdf-config is in the path,
•gfortran,ifort or g77 is in the path, and the appropriate libraries are in the environment
variable LD LIBRARY PATH.
After compiling the executable pwhg main in the bbH directory, enter the myruns directory and
perform all your runs there.
The program can be run in a parallel mode in several consecutive steps by setting
manyseeds 1
in the file powheg.input. With this option, the four steps of grid generation, NLO calculation,
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upper bound generation, and event generation can then be performed in parallel, consecutively,
as described, for instance, in the manual of the VBF Z Z directory in the POWHEG-BOX-V2. Al-
ternatively, all results can be obtained in the serial mode of the program by de-activating the
manyseeds option.
If the default analysis is activated by setting the flag ANALYSIS=default in the Makefile
before compiling the code, after the completion of the NLO calculation for each parallel run a
file pwg-*-NLO.top is generated (where the * denotes the integer identifier of the run). These
files contain histogram information at fixed-order accuracy for an inclusive setup in gnuplot-
friendly format. The default analysis routine can easily be replaced with a personalized one by
the user.
The events that are ultimately generated in Les Houches format can be processed by a generic
Monte-Carlo program. We are providing an interface to PYTHIA 6.4.25. After generating the
exectuable main-PYTHIA-lhef and running it in the directory where the event files are stored,
the program produces an output file pwgPOWHEG+PYTHIA-output.top that contains histograms
at NLO+PS accuracy. The Monte-Carlo parameters can be modified by the user in the file
setup-PYTHIA-lhef.f.
References
[1] B. J¨ager, L. Reina, D. Wackeroth, Higgs boson production in association with b-jets in the
POWHEG BOX, arXiv:1509.05843 [hep-ph].
[2] S. Dawson, C. B. Jackson, L. Reina and D. Wackeroth, Exclusive Higgs boson production
with bottom quarks at hadron colliders, Phys. Rev. D 69 (2004) 074027 [hep-ph/0311067].
[3] S. Dawson, C. B. Jackson, L. Reina and D. Wackeroth, Higgs production in association with
bottom quarks at hadron colliders , Mod. Phys. Lett. A 21 (2006) 89 [hep-ph/0508293].
[4] S. Alioli, P. Nason, C. Oleari and E. Re, A general framework for implementing NLO
calculations in shower Monte Carlo programs: the POWHEG BOX, JHEP 1006 (2010)
043 [arXiv:1002.2581 [hep-ph]].
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