2013/11/25 by Amarjit Soni, Soni, Amarjit
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.1311.6479
openalex publication_date 2013/11/25 · openalex created_date 2022/09/03 · openalex updated_date 2026/07/28
After decades of intensive efforts, lattice methods finally revealed one clear source of the large enhancement of the ratio Re A0/Re A2 \citeRBCUKQCDPRL13, which has been a puzzle in particle physics for about sixty years. Lattice studies of direct K → ππ in the I=2 channel show that in fact this channel clearly suffers from a severe suppression due to a significant cancellation between the two amplitudes for the original, charged current (tree) operator. % [( sαγmu (1 - γ5) uα)( uβγmu(1-gamma5)dβ)], One of these amplitudes goes as N and the other one goes as N2, where N=3 for QCD. For physical pion masses the cancellation between the two contributions towards Re A2 is about 70%. This appreciable cancellation suggests that expectations from large N for QCD may be amenable to receiving significant corrections. The penguin operators seem to make a small contribution to ReA0 at a scale \gsim 1.5 GeV. Possible repercussions of the lattice observation for other decays are briefly discussed.