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Collider Physics and QCD Phenomenology Mike Seymour (based at CERN)

Collider Physics and QCD Phenomenology Mike Seymour (based at CERN). HERWIG Monte Carlo event generator Current version ~ frozen (bug fixes and minor new features only) HERWIG++ completely new framework (integrated with PYTHIA7)

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Collider Physics and QCD Phenomenology Mike Seymour (based at CERN)

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  1. Collider Physics and QCD PhenomenologyMike Seymour (based at CERN) • HERWIG Monte Carlo event generator • Current version ~ frozen (bug fixes and minor new features only) • HERWIG++ • completely new framework (integrated with PYTHIA7) • completely new parton shower algorithms (initial-state and final-state) • revised hadronization model • available now for e+e– annihilation and “real soon now” for hadron–hadron • NLO calculations and NLO MCs • Higgs + 2 jets at NLO • Collider phenomenology • W/Z production and mass measurement! Emily Nurse • jet algorithms and top mass measurement! Chris Tevlin • underlying event effects at Tevatron and LHC • Resummation of large logarithms • ‘gaps between jets’ ! Albrecht Kyrieleis and JRF • matching with BFKL • a new source of ‘non-global’ logarithms?

  2. Physics overview Angular ordered parton showers Cluster hadronization model Hadron Emission Reactions With Interfering Gluons

  3. Physics overview Angular ordered parton showers Cluster hadronization model Soft underlying event Current development Parton shower/matrix element matching Hardest emission Multijet matching MC@NLO Multiple scattering model Jimmy HERWIG++ HERWIG – Hadron Emission Reactions With Interfering Gluons

  4. HERWIG++ • Class structure • New parton shower algorithm • Improved cluster fragmentation model • New underlying event model “Jimmy+Ivan” • e+e– version available now • Basic hadronic processes (Drell–Yan, QCD 2!2) “this year” • Full HERWIG functionality “next year” • Work on Fortran HERWIG rapidly ramping down

  5. HERWIG-related phenomenology • Underlying events: HERA ! Tevatron ! LHC ? • Four new models! • W/Z pt distributions and the W mass measurement • Emily Nurse (DØ student)

  6. Tuning HERWIG on W/Z pt distributions E.Nurse, MHS

  7. NLO Jet Calculations • S.Catani, MHS: Nucl.Phys.B485(1997)291; SC, S.Dittmaier, MHS & Z.Trocsanyi NPB627(2002)189 • Subtraction method, based on • Universal (dipole) factorization theorem • Implemented in • EVENT2, DISENT, ORIENT (MHS) • NLOJET++ (Zoltan Nagy) • MCFM (John Campbell and Keith Ellis) • Single framework for NLO implementations of all ‘femtobarn’ processes at Tevatron • Ideal starting point for universal implementation of MC@NLO?

  8. Jet Algorithms • Cone vs cluster algorithm MHS, Z.Phys.C62(1994)127 • Top mass reconstruction as a test case Cluster Cone • Update in progress (Chris Tevlin, ATLAS student)

  9. Resummation of Large Logarithms • Event shape cross sections »sn log2n • Non-global event shapes and non-global logs (Dasgupta and Salam, Phys.Lett.B512(2001)323; JHEP0203(2002)017) • Interjet observables, rapidity gaps (R.B.Appleby and MHS, JHEP0309(2003)056) • Work in progress • More non-global contributions? • Resummation of non-global logs? • Application to exclusive diffractive Higgs production…

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