HERWIRI 1.02

HERWIRI 1.02 is one aspect of the HERWIRI Project to incorporate various sets of infrared improvements into a parton shower generator for hadronic physics. HERWIRI 1.02 incorporates IR-improved DGLAP-CS kernels in the HERWIG6.5 event generator.

The program is available here as a 532 kB gzip'ed tar file herwiri1.02.tar.gz. The file readme.txt contains instructions. gzip'ed tar file. Relevant documentation includes:

Main references:

1. G.Corcella, I.G.Knowles, G.Marchesini, S.Moretti, K.Odagiri, P.Richardson, M.H.Seymour and B.R.Webber, JHEP 0101 (2001) 010
2. G.Marchesini, B.R.Webber, G.Abbiendi, I.G.Knowles, M.H.Seymour, and L.Stanco, Computer Physics Communications 67 (1992) 465.
3. B. F. L. Ward, IR-Improved DGLAP Theory: Kernels, Parton Distributions, Reduced Cross Sections, Annals Phys. 323, 2147-2171 (2008).

For more infomation, visit the official HERWIG information page: http://hepwww.rl.ac.uk/theory/seymour/herwig/ .

HERWIRI 1.02 is written in fortran 77, and has been compiled with gfortran under linux (suse10.2, fedora 6,10, and others). A Makefile is provided. The main program has the same form as described in the HERWIG manual. An example hwmain.f) is provided in the package. Instructions for compiling and running the program are included in the readme.txt file.

In the example, the user routine HWRAP calculates the rapidity distribution of the Z boson. A sample run is shown in sample.dat and a sample of the rapidity output is shown in output.dat. This rapidity distribution is obtained with the cuts 40 GeV/c² < M_ll < 140 GeV/c², p_T^l > 20 GeV/c, and |η^l| < 2.0.

Functions modified in HERWIG:

HWBRAN

HWBSUD

HWBSU1

HWBSU2

HWBSUG

HWSGQQ

HWIGIN

New functions:

IRNF	Computes the number of active flavours based on Q.
IREI	Computes the exponential integral Ei(x) for x > 0.
IRQQBAR	Newton-Raphson method to solve an algebraic equation of the form F(x) = 0.