Charybdis is designed to simulate the production and decay of black holes
in hadron collider experiments, according to theories with TeV-scale
gravity and extra spatial dimensions. The production of the black
hole is assumed to take place with a basically geometrical cross section.
The decay then takes place via Hawking radiation using the D-dimensional
If you use the code please reference
C.M. Harris, P. Richardson and B.R. Webber, CHARYBDIS: A Black Hole Event Generator, JHEP 0308:033, hep-ph/0307305, 2003;
C.M. Harris, P. Kanti, Hawking radiation from a (4+n)-dimensional black hole: Exact results for the Schwarzschild phase, JHEP 0310:014, hep-ph/0309054, 2003.
The first of these is available here as either postscript or html.
The generator itself only performs the production and decay of the black hole.
It is interfaced, via the Les Houches accord, to either HERWIG or PYTHIA to perform
the parton shower evolution of the partons produced in the decay and their
The most recent version of the code is 1.003, which includes the Yoshino-Rychkov cross section
enhancement factors, an optional new "boiling remnant" model, relabeling of the
hard process as a black hole (in HERWIG only), compatibility with a range of Fortran 77 and 90 compilers,
and changes so that the parameters can be reset in the main HERWIG or PYTHIA program.
As the code is designed to run with
either HERWIG or PYTHIA there are a few things which need to
be set up.
You should have the following code:
- charybdis1003.F the code for the black hole generator;
- dummy.F the dummy routines needed if you are not using PDFLIB;
- mainpythia.f example main program for PYTHIA;
- mainherwig.f example main program for HERWIG;
- charybdis1003.inc include file for the black hole event generator.
In addition to this you will also need a Les Houches accord compliant
version of either HERWIG or PYTHIA with both the dummy Les Houches routines UPINIT and UPEVNT and the dummy PDFLIB subroutines
PDFSET and STRUCTM deleted. For HERWIG the first Les Houches compliant
version is HERWIG6.500,
for PYTHIA you will need a version above 6.220.
In the Les Houches routines the beams are specified as follows:
Square brackets show the default values. In the HERWIG version, they
are overwritten with the values deduced from the HERWIG parameters
PART1,PART2 and PBEAM1,PBEAM2. However in the PYTHIA version they
must be reset explicitly in COMMON/HEPRUP/ if changed.
- IDBMUP(1),IDBMUP(2) PDG codes for the beam particles (only protons
and antiprotons allowed) [2212,2212]
- EBMUP(1),EBMUP(2) energies of the beam particles [7000.,7000.]
The CHARYBDIS parameters available to the user are as follows. Their default
values are set in charybdis1003.F; any of them can be changed in the main
program, as shown in the samples mainpythia.f and mainherwig.f.
- MPLNCK the Planck Mass [1000.]
- MSSDEF shows whose definition of the Planck Mass you are using - see Appendix A of hep-ph/0110127 for a comparison 
- GTSCA sets momentum scale for calling PDFs (.TRUE. is
using the inverse Schwarzschild radius and .FALSE. is using sqrt(s) -
see discussion on p.12 of hep-ph/0106219 but note that the cross sections in this paper were NOT calculated with GTSCA=.TRUE. even though it suggests they were) [F]
- TOTDIM the total number of dimensions (i.e. 4+extra) 
- MINMSS the minimum mass of the black holes to be produced [5000.]
- MAXMSS the maximum mass of the black holes to be produced [14000.]
- NBODY the number of particles produced in the decay of the
black hole remnant 
- TIMVAR time variation of the black hole's Hawking temperature
(.TRUE. is on, .FALSE. is off) [T]
- MSSDEC the type of particles to produce in the decay, 1= only light
SM particles, 2= light SM particles + top W/Z and 3= all SM
- GRYBDY controls the use of the grey-body factors, for GRYBDY=.TRUE.
the correct D-dimensional grey-body factors are used whereas
for GRYBDY=.FALSE. the black-body spectrum is used [T]
- KINCUT Controls the termination of the Schwarzschild phase. For
KINCUT=.TRUE. the Schwarzschild phase terminates when an
emission is selected with energy greater than the black hole
mass whereas for KINCUT=.FALSE. the Schwarzschild phase is
terminated when the mass of the black hole remnant is less
than the Planck mass [F]
- YRCSEC controls whether the Yoshino-Rychkov enhancement factors are
used in computing the cross section (see Phys.Rev.D71:104028,
2005 [hep-th/0503171]) [F]
- THWMAX maximum value of the Hawking temperature (GeV). If a larger
value is generated during decay, it is reset to this [1000.]
- RMBOIL controls whether to use the "boiling remnant" model, in which
the black hole decay continues below the Planck scale, with
temperature limited by THWMAX. (This option is inconsistent
with the use of KINCUT=.TRUE.) [F]
- RMMINM minimum remnant mass. If the "boiling remnant" model is used,
this should be less than MPLNCK, otherwise it is set equal to
MPLNCK if smaller [1000.]
- IBHPRN print out option 0=no printout, 1=errors only,
In the Makefile you must specify which general purpose event
whether or not you want PDFLIB
- GENERATOR = HERWIG for HERWIG
- GENERATOR = PYTHIA for PYTHIA
You must also specify the name of the HERWIG/PYTHIA source and the
location of the PDFLIB library.
- PDFLIB = PDFLIB for PDFLIB
- PDFLIB =
If you extract the code to run it separately then the following
should be taken into account.
- charybdis1003.F will produce the HERWIG version by default when compiled the flag
-DPYTHIA should be added if the PYTHIA version is required.
- dummy.F will by default produce the version for use without PDFLIB the
flag -DPDFLIB should be added if PDFLIB is being used.
In the HERWIG version the black hole entry in the event record has
been assigned the provisional PDG code IDHEP=40 with name 'BlacHole'.
However this has not been implemented in the PYTHIA version.
Chris Harris, Peter Richardson and Bryan Webber
Last modified: Fri Aug 25 13:49:54 BST 2006