SCI and GAL in LEPTO and PYTHIA

The purpose of this page is to collect all the information and source code you need in order to make simulations with LEPTO or PYTHIA using the Soft Colour In teraction (SCI) model [1,4] or the Generalised Area Law (GAL) model [8]. (If you use this code, please cite these papers, and other applicable ones!)

Basically, there are four cases; you can use either LEPTO or PYTHIA, and in these, you can use either SCI or GAL. The choice of program to use depends on what process you want to study - LEPTO simulates DIS in lepton-nucleon scattering, while PYTHIA is a multi-purpose program for hadron-hadron collisions, e+e- collisions, photoproduction in gamma-p and ep, etc. There are three possible versions of PYTHIA (5.7, 6.1 or 6.2), with some small differences, see below.

Below, we collect the source code you need and the parameters you have to set in your programs.

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Source code

LEPTO 6.5.1

SCI and GAL were originally developed as LEPTO routines, and SCI is now part of the standard distribution of LEPTO (version 6.5.1). However, to use GAL you need updated versions of the routines, which also handl e the SCI model (see also the GAL webpage):

• lsci.f
• lepto.f
• lsmall.f
• lweits.f

(where LWEITS is to be changed if you use CTEQ4 or later). LSMALL has been updated to take care of charmonium and bottomonium; see the LEPTO webpage. You may want to include this file also when using the SCI model.

The LEPTO files in a tar.gz archive

PYTHIA 6.2

The routines have been adapted for use as an add-on package to PYTHIA 6.2. (More specifically, the versions of pyevnt.f and pysspa.f below are adapted from Pythia 6.215.) Please note that we have not yet checked if they work with other versions 6.2xx! (Probably not!) You will need the following routines, which handle both the SCI and GAL models:

• Soft Colour Interactions / Generalised Area Law (scigal.f, scicsw.f, sciasw.f)
• Sea Quark Treatment (scisqt.f)
• Hadronisation of small systems (scismall.f)
• Adaption of some PYTHIA (version 6.215) routines to make it work (these have to replace the original PYTHIA routines in the linking step) (pyevnt.f, pysspa.f)

The PYTHIA 6.2 files in a tar.gz archive

OLD VERSIONS: 5.7 and 6.1

These versions of PYTHIA are old and non-standard by now. We still have the code and instructions at this page.

Parameter settings for LEPTO

Below we list the parameters that need to be changed from their default values to give the "best models":

SCI in LEPTO

Run with default settings:

Master switch for Soft Colour Exchanges	LST(34) = 2
String reconnection probability R_0	PARL(7) = 0.50
Master switch for Sea Quark Treatment	LST(35) = 1

GAL in LEPTO

Parameter settings for PYTHIA

Below we list the parameters that need to be changed from their default values to give the "best models". Note! Names of parameters have changed compared to older versions!

You must include the following common block in your program to be able to set parameters and switches:

   COMMON /SCIPAR/MSWI(2),PARSCI(2)
   INTEGER MSWI
   DOUBLE PRECISION PARSCI

SCI in PYTHIA 6.2

GAL in PYTHIA 6.2

Papers about SCI and GAL

(in chronological order)

1. Soft Color Interactions as the Origin of Rapidity Gaps in DIS
   A.Edin, G.Ingelman and J.Rathsman, Aug 1995
   Phys. Lett. B366 (1996) 371
   TSL/ISV-95-0125, DESY-95-163 [ps]
2. Rapidity Gaps in DIS through Soft Color Interactions
   A.Edin, G.Ingelman and J.Rathsman, Jul 1995
   DESY 95-145 [ps]
3. Soft Colour Interactions and the Diffractive Structure Function
   A. Edin, G. Ingelman and J. Rathsman, Feb 1996
   J. Phys. G22 (1996) 943-946
   DESY 96-019 [ps]
4. Unified Description of Rapidity Gaps and Energy Flows in DIS Final States
   A.Edin, G.Ingelman and J.Rathsman, April 1996.
   Z. Phys. C75 (1997) 57-70
   DESY 96-060 [ps]
5. Quarkonium production at the Tevatron through Soft Color Interactions
   A. Edin, G. Ingelman and J. Rathsman
   Phys. Rev. D 56 (1997) 7317-7320
   SLAC-PUB-7506, TSL/ISV-97-0176 [ps]
6. Hadronic J/Psi Production in the soft colour interaction model
   Henrik Lindh, Master thesis
   TSL/ISV-98-0192, [abs, ps]
7. A Generalised Area Law for Hadronic String Reinteractions
   J. Rathsman
   Phys. Lett. B452 (1999) 364
   hep-ph/9812423 [Webpage]
8. Soft Colour Exchanges and the Hadronic Final State
   A. Edin, G. Ingelman, J. Rathsman
   TSL/ISV-99-0215, hep-ph/9912539 [abs, ps]
9. Photoproduction of Quarkonium from Soft Colour Exchanges
   J. Rathsman
   TSL/ISV-99-0219 [abs, ps]
10. Soft Color Interactions and Diffractive Hard Scattering at the Tevatron
    Rikard Enberg, Gunnar Ingelman, Nicusor Tîmneanu
    Phys. Rev. D64 (2001) 114015
    DESY 01-076, hep-ph/0106246 [abs, ps]
11. Soft and hard QCD dynamics in hadroproduction of charmonium
    C. Brenner Mariotto, M.B. Gay Ducati, G. Ingelman
    Eur. Phys. J. C23 (2002) 527-538
    TSL/ISV-2001-0256, Nov. 2001. hep-ph/0111379
12. Diffractive Higgs boson production at the Tevatron and LHC
    Rikard Enberg, Gunnar Ingelman, Andreas Kissavos and Nicusor Tîmneanu
    Phys. Rev. Lett. 89 (2002) 081801
    TSL/ISV-0263, hep-ph/0203267
13. Diffractive Higgs and prompt photons at hadron colliders
    Rikard Enberg, Gunnar Ingelman and Nicusor Tîmneanu
    Phys. Rev. D 67 (2003) 011301
    TSL/ISV-2002-0266, hep-ph/0210408