PYTHIA 6.4 Physics and Manual

there is every reason to cite them. A reasonable selection would vary as a function of thephysics you are studying. The criterion for which to pick should be simple: imagine thata Monte Carlo implementation had not been available. Would you then have cited a givenpaper on the grounds of its physics contents alone? If so, do not punish the extra effortof turning these ideas into publicly available software. (Monte Carlo manuals are goodfor nothing in the eyes of many theorists, so often only the acceptance of ‘mainstream’publications counts.) Here follows a list of some main areas where the Pythia programscontain original research:Fragmentation/Hadronization:• The string fragmentation model [And83, And98].• The string effect [And80].• Baryon production (diquark/popcorn) [And82, And85, Edé97].• Fragmentation of systems with string junctions [Sjö03].• Small-mass string fragmentation [Nor98].• Fragmentation of multiparton systems [Sjö84].• Colour rearrangement [Sjö94a] and Bose-Einstein effects [Lön95].• Fragmentation effects on α s determinations [Sjö84a].Parton Showers:• Initial-state parton showers (Q 2 -ordering) [Sjö85, Miu99].• Final-state parton showers (Q 2 -ordering) [Ben87a, Nor01].• Initial-state parton showers (p 2 ⊥-ordering) [Sjö04a].• Final-state parton showers (p 2 ⊥-ordering) [Sjö04a].• Photon radiation from quarks [Sjö92c]DIS and photon physics:• Deeply Inelastic Scattering [And81a, Ben88].• Photoproduction [Sch93a], γγ [Sch94a] and γ ∗ p/γ ∗ γ/γ ∗ γ ∗ [Fri00] physics.• Parton distributions of the photon [Sch95, Sch96].Beyond the Standard Model physics:• Supersymmetry [Amb96, Mre99a], with R-parity violation [Ska01, Sjö03].• Technicolor [Lan02a].• Extra dimensions [Bij01]• Z ′ models [Lyn00]Other topics:• Colour flow in hard scatterings [Ben84].• Elastic and diffractive cross sections [Sch94].• Minijets, underlying event, and minimum-bias (multiple parton–parton interactions)[Sjö87a, Sjö04, Sjö04a].• Rapidity gaps [Dok92].• Jet clustering in k ⊥ [Sjö83].In addition to a physics survey, the current report also contains a complete manualfor the program. Such manuals have always been updated and distributed jointly withthe programs, but have grown in size with time. A word of warning may therefore be inplace. The program description is fairly lengthy, and certainly could not be absorbed inone sitting. This is not even necessary, since all switches and parameters are providedwith sensible default values, based on our best understanding (of the physics, and of what6