Progress on the Pythia 8 event generator

Diffraction – 1
Diffraction
Ingelman-Schlein:
Ingelman-Schlein:
Pomeron
Pomeron
as
as
hadron
hadron
with
with
partonic
partonic
content
content
Diffractive Diffractive event event = (Pomeron = (Pomeron flux) flux) × (IPp × (IPp collision) collision)
p
p
Used e.g. in
POMPYT
IP
POMWIG
p
PHOJET
1) σ SD 1) σand SD and σ DD σ DD taken taken from from existing parametrizationor or set by user.
2) Shape 2) f IP/p of(x Pomeron IP , t) ⇒ diffractive distribution mass inside spectrum, a proton, p ⊥ fof IP/p proton (x IP ,t) out.
gives3) diffractive Smooth transition mass spectrum from simple and scattering model low p ⊥ masses of proton.
IPp with
3) Atfull lowpp masses machinery: retainmultiple old framework, interactions, withparton longitudinal showers, string(s). etc.
Above 4) 10 Choice GeVbetween begin smooth 5 Pomeron transition PDFs. to IPp handled with full pp
machinery: 5) Free multiple parameter interactions, σ IPp neededparton fix 〈n showers, interactions
beam 〉 = σ jet
remnants, /σ IPp . . . . .
4) Choice between 5 Pomeron PDFs.
Torbjörn Sjöstrand <strong>Progress</strong> on the Pythia 8 event generator slide 21/46