2016/04/11 by NA60 Collaboration, R. Arnaldi, K. Banicz +52 · 2 citations
Physics and Astronomy · #Branching fraction #Hadron #High-Energy Particle Collisions Research #Hyperon #Lambda #Meson #Muon #Nuclear physics #Omega #Particle physics #Particle physics theoretical and experimental studies #Physics #Proton #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #hep-ex
paper · pdf · doi:10.1016/j.physletb.2016.04.013
published as Phys.Lett. B757 (2016) 437-444
openalex publication_date 2016/04/11 · openalex created_date 2016/06/24 · arxiv created 2016/08/29 · arxiv updated 2016/08/30 · openalex updated_date 2026/08/05
The NA60 experiment studied low-mass muon pair production in proton–nucleus (p–A) collisions using a 400 GeV proton beam at the CERN SPS. The low-mass dimuon spectrum is well described by the superposition of the two-body and Dalitz decays of the light neutral mesons η , ρ , ω , η ′ and ϕ , and no evidence of in-medium effects is found. A new high-precision measurement of the electromagnetic transition form factors of the η and ω was performed, profiting from a 10 times larger data sample than the peripheral In–In sample previously collected by NA60. Using the pole-parameterisation | F ( M ) | 2 = ( 1 − M 2 / Λ 2 ) − 2 we find Λ η − 2 = 1.934 ± 0.067 (stat.) ±0.050 (syst.) ( GeV / c 2 ) − 2 and Λ ω − 2 = 2.223 ± 0.026 (stat.) ±0.037 (syst.) ( GeV / c 2 ) − 2 . An improved value of the branching ratio of the Dalitz decay ω → μ + μ − π 0 is also obtained, with B R ( ω → μ + μ − π 0 ) = [ 1.41 ± 0.09 (stat.) ± 0.15 (syst.) ] × 10 − 4 . Further results refer to the ρ line shape and a new limit on ρ / ω interference in hadron interactions.