Parton Showers vs Dipole Showers Mike Seymour Manchester
- Slides: 7
Parton Showers vs Dipole Showers Mike Seymour Manchester Christmas meeting
This year… • co-Chair of Theoretical Physics Division • co-I for Manchester Grid activities • Chair of Second Year examiners • Chair of STFC Particle Physics Grants Panel (Theory) • Network Project Manager for MCnet • Senior author of Herwig++ • Editor of Computer Physics Communications Mike Seymour Manchester Christmas meeting 2
Parton showers • A Markov chain of 1 2 splittings • Derived in collinear limit any evolution variable • Colour coherence soft limit is correct if evolution variable is θ opening angle Mike Seymour Manchester Christmas meeting 3
Dipole showers • A Markov chain of 2 3 splittings • Valid in large Nc limit and soft limit • With transverse momentum ordering • Can improve to get collinear limit correct Mike Seymour Manchester Christmas meeting 4
Summary • Angular ordered parton shower, and • Transverse momentum ordered dipole shower • Proven to have same emission pattern (in large Nc limit) • Believed to be equally good alternative prescriptions Mike Seymour Manchester Christmas meeting 5
Dokshitzer & Marchesini • “Monte Carlo and large angle gluon radiation”, JHEP 0903: 117, 2009. • Calculated energy loss of primary quark after long evolution ladder x • (sensitive to ‘recoil strategy’) • Compare with DGLAP evolution • “Dipole shower is wrong” – but, they used energy-ordered dipole shower • Nagy & Soper, Skands & Weinzierl – “Dipole shower is fine” Mike Seymour Manchester Christmas meeting 6
Results (with Bryan Webber) • Analytical • Numerical DS Mike Seymour Not consistent with our analytical result! PS Manchester Christmas meeting 7
