Event Generators for WW Physics
D. Bardin, R. Kleiss, E. Accomando, H. Anlauf, A. Ballestrero, F. A. Berends, E. Boos, F. Caravaglios, D. van Dierendonck, M. Dubinin, V. Edneral, F. C. Erne, J. Fujimoto, V. Ilyin, T. Ishikawa, S. Jadach, T. Kaneko, K. Kato, S. Kawabata, Y. Kurihara, D. Lehner, A. Leike, R. Miquel, G. Montagna, M. Moretti, T. Munehisa, O. Nicrosini, T. Ohl, A. Olchevski, G. J. van Oldenborgh, C. G. Papadopoulos, G. Passarino, D. Perret-Gallix, F. Piccinini, R. Pittau, W. Placzek, A. Pukhov, V. Savrin, M. Schmitt, S. Shichanin, Y. Shimizu, T. Sjostrand, M. Skrzypek, H. Tanaka, Z. Was
TL;DR
Event Generators for WW Physics surveys the landscape of four-fermion Monte Carlo tools used for LEP2 WW studies, comparing diverse algorithms ranging from diagrammatic matrix-element generators to semi-analytic and deterministic codes. The report stresses that a practical LEP2 analysis requires full phase-space event generation with multiple diagrams, gauge-invariant widths, ISR/FSR modeling, and interfaces to hadronization, while also acknowledging that no single ‘Ultimate Monte Carlo’ exists. Through tuned CC03/CC10 and all-4f comparisons, the study demonstrates generally good cross-code agreement within per-mille to percent-level precision for many observables, but reveals non-negligible theoretical uncertainties from higher-order EW corrections, renormalization schemes, and treatment of QED radiation. The findings underscore the importance of standardized inputs, realistic cuts, and continued development (including full one-loop EW corrections) to achieve robust predictions for precision W-boson mass and coupling measurements at LEP2 and beyond. The work also highlights how different coding philosophies yield complementary strengths, guiding experimentalists in choosing appropriate tools and motivating ongoing improvements in four-fermion event generators.
Abstract
The report summarizes the results of the activities of the Working Group on Event Generators for WW Physics at CERN during 1995.