This is the page for the BRIDGE software. BRIDGE can take an arbitrary model as input (using the same format as MadGraph) and compute the widths (and hence branching ratios) for arbitrary two-body and three-body tree level decays. It can also decay generated events, choosing decay modes randomly according to the branching ratios (or using a set of decay modes that you specify). (We have tested this on MadGraph events; in principle other generators produce similar LHA-formatted output. Let us know if you're trying to use BRIDGE with other programs, and we might be able to help.)
Here is a talk on BRIDGE for the MC4BSM workshop at Princeton, March 23, 2007.
Here is a talk from the Eotvos-Cornell workshop in Budapest, June 2007.
Download the BRIDGE version 2.15 source. (This has been tested on Linux, Mac OS X, and Windows with Cygwin.) To install: untar this within your main MadGraph directory. You will then have a directory MG_ME_V4.y.xx/BRIDGE. Run "make" from within the BRIDGE directory to build. (MadGraph is not strictly required to compile, but the HELAS library is; you will have to edit the makefile to point to the right location if you are not compiling BRIDGE within the MG directory structure.)
Changes:
2.15 More three-body fixes: antigrids.pl corrected, color-flow fixed
(thanks to Renaud Bruneliere and Sezen Sekmen). Also, fixed a problem with
double-counting diagrams for decays like h -> ZZ*
2.14 DGE now deals reasonably with particles that have a decay table
reporting zero width (i.e. they do not decay and the program doesn't get
stuck). Also, better handling of LHE files, especially those generated
with multiple processes in the same file. Thanks again to Brock Tweedie
and Andrey Katz for pointing out the problems.
2.13 Important fixes, especially for anyone
dealing with three-body decays! (July 26, 2009) Fixed a problem
with certain three-body decays with vertices involving a scalar and
vector (which would cause absurd results for, e.g., squark -> Z + quark
+ neutralino in earlier versions). Modified SLHA reading to deal with
whitespace better.
Now DGE deals gracefully with encountering particles not in the stable
list with no decay table: it treats them as stable. Thus, in
particular, running in mode 2 and entering *no* particles in the list
should work by decaying every particle for which a decay table exists.
Also fixed some problems with processing 3-body decay tables in DGE.
Also, antigrids.pl is restored to a Unix format file, rather than DOS,
and treats 3-body tables properly. Thanks to Brock Tweedie and Andrey
Katz for finding numerous problems.
2.12 When running from a MadGraph model directory, BRIDGE now looks for
"helas_couplings.txt" first, then "couplings_check.txt" if that is not
found. This is for compatibility with recent MG changes (to generate the
file, run "make helas_couplings" then "./helas_couplings" in the Model
directory). Also: BRIDGE now
writes a lifetime (c tau for the particular event, in mm) in the "VTIMUP"
column of the LHE file for decayed particles.
2.11 Fixed a mistake in batch mode (thanks to
Rakhi Mahbubani for the
fix), and merged some Vegas problem-catching from the BRIDGE version in
the Four
Generations code of G.Kribs,T.Plehn,M.Spannowsky,T.Tait.
2.10 Fix to allow three body decays like t -> W+ b Z (for heavy enough t) (thanks to Yang Bai)
2.09 improved param card reading
2.08 several bug fixes
2.07 fixed directory structure when working with usrmod (thanks to
Emmanuel Busato, Rakhi Mahbubani, Liantao Wang)
2.06 restored the correct mssminteractions.dat (oops)
2.05 added an option of only calculating three-body decays when there
are no open two-body decays; also, the widths calculated from two-body
decays are used as inputs for propagators in three-body decays if no
width parameter is specified. Also fixed several bugs. Thanks to Johan
Alwall, Can Kilic, and Shufang Su for bug reports and suggestions; thanks
also to the participants in the November 2007 Edinburgh Ultra-Mini
Workshop for suggestions on reorganizing the three-body options.
Note that runBRI and runBRIsusy in 2.05 have a new batch mode command,
[3if2?], which should be 'Y' or 'N' depending on whether or not you
want to calculate 3-body modes of particles that have two-body modes
available.
2.00 added three-body decays, batch mode, numerous minor changes
1.07 fixed a problem where whitespace was being treated differently on
certain Linux releases with older versions of gcc (reported by Jay
Hubisz)
1.06 corrected some vector decays where BRIDGE was reporting, e.g., Z' ->
W+ W+ instead of Z' -> W+ W- (Thanks to Shrihari Gopalakrishna and Neil
Christensen for finding this bug.)
1.05 corrected the "decay
single particle" mode of DGE, which would
inappropriately decay particles with the wrong status (Thanks to Jon
Walsh for pointing this out)
1.04 corrected decays of vectors (V -> VV and V -> VS types); previously
the decay mode wasn't being properly added to the list of decays. (Thanks
to Jay Hubisz for pointing this out)
1.03 some corrections to SLHA input (most importantly, fixing some
couplings of the Z in the MSSM that were incorrect in earlier versions!),
additional minor changes
1.02 fixed problem with DGE in the mode where it decays a particular
particle; intermediate steps were being written out (thanks to Can Kilic
for pointing this out)
1.01 adjusted weighting of output events in case you wish to
make plots combining multiple files that have been decayed in different
ways.
The BRIDGE manual: on the arXiv or locally (PDF).
Request: if you use BRIDGE for any work that you publish, please cite the arXiv version of the BRIDGE manual. Thanks!
Fortran file for Higgs--glue--glue vertex in HELAS, as described in the manual.
BRIDGE was written by Patrick Meade and Matt Reece. Contact us at meade@ias.edu or mreece@princeton.edu if you have comments or questions.