Resolving the ultracollinear paradox with effective field theory

Journal Article · Mon Sep 16 00:00:00 UTC 2024 · Physical Review. D.

DOI: https://doi.org/10.1103/PhysRevD.110.056035 · OSTI ID:2474040

Baumgart, Matthew ; Christeas, Panagiotis

Naive intuition about scale decoupling breaks down in the presence of fermion masses. Kinematic enhancements can greatly extend the range where one needs to keep a finite mass in calculations to obtain a correct result at even the $\mathcal{O}\left(1\right)$ level. Treating a light fermion as massive though, leads to a known but somewhat obscure paradox, a seeming leading-order sensitivity to an arbitrarily small mass. We show how a proper formulation in effective field theory not only resolves the physical conundrum but also answers the very practical question of when fermion masses are required. This has important implications for the development of shower Monte Carlo event generators above the weak scale. Published by the American Physical Society 2024

• Research Organization: Arizona State Univ., Tempe, AZ (United States)
• Sponsoring Organization: USDOE Office of Science (SC); USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: SC0019470
• OSTI ID: 2474040
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Journal Issue: 5 Vol. 110; ISSN PRVDAQ; ISSN 2470-0010
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English