1999/04/25 by J. Thompson, Julia A. Thompson, Thompson, Julia A.
Engineering · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #Superconducting Materials and Applications #hep-ex
paper · pdf · doi:10.48550/arxiv.hep-ex/9904026
5 pages, sprocl.sty, psfig.tex, 4 embedded figures. Presented at WIN '99 in Capetown, South Africa, January 1999
arxiv created 1999/04/25 · openalex publication_date 1999/04/25 · arxiv updated 2009/11/30 · openalex created_date 2024/04/11 · openalex updated_date 2026/07/28
Preliminary values for the K+ -> pi+ mu+ mu- branching ratio and form factor are reported, based on 400 events, a factor of 2 more in total events and 100 times the present world sample of fully reconstructed events. The results are consistent with previous results on the pi+ e+ e- mode. However, the relatively large slope of the form factor in q2, lambda = 0.182+/-0.01+/-0.007, required to fit the pi+ e+ e- data and to give consistency between the pi+ e+ e- and pi+ mu+ mu- branching ratios, is larger than expected in simple models of the decays. The K+ -> pi+ mu+ mu- branching ratio we find, (9.23 +/- 0.6 stat +/- 0.58 syst)x10-8, is the most precise measurement of this mode and is approximately 3.2 sigma larger than the previous measurement. These pi+ l+ l- results are inconsistent with O(p4) Chiral Perturbation Theory but compatible with O(p6). Systematic studies for both modes are still in progress.