literature

Upper limit of the muon-neutrino mass and charged pion mass from momentum analysis of a surface muon beam

Dec, 1995
55 pages
Published in:
  • Phys.Rev.D 53 (1996) 6065-6077
Report number:
  • PSI-PR-95-28
Experiments:
  • PSI-CYCLOTRON

Citations per year

1996200320102017202405101520
Abstract: (APS)
We have determined the momentum pμ+ of muons from the decay π+→μ+νμ at rest, by analyzing a surface muon beam in a magnetic spectrometer equipped with a silicon microstrip detector. The result pμ+=(29.79200±0.00011) MeV/c leads to a squared muon-neutrino mass of mνμ2=(−0.016±0.023) MeV2, which corresponds to a "laboratory" upper limit of 0.17 MeV (C.L.=0.9) for the muon-neutrino mass. The cosmological upper limit of the neutrino mass (65 eV), the muon mass, and the new value of pμ+ yield the pion mass mπ+=(139.57022±0.00014) MeV. Alternatively, if one does not use the cosmological upper limit of mνμ, then a combined fit including the new pμ+ value, and the mμ+ and mπ− values from other experiments and the CPT theorem (mπ+=mπ−) leads to mπ±=(139.57037±0.00021) MeV. As a side result, the mean kinetic energy of the pions stopped in the production target, made of isotropic graphite, immediately before their decay is found to be Tπ+―=(0.425±0.016) eV. This is consistent with the hypothesis that the pions are trapped in the potential well of a spherical harmonic oscillator, V(r)=V0+12ksr2, with ks=(1.144±0.088)×1017 eV/cm2.
  • 14.60.Pq
  • 14.60.Ef
  • 14.40.Aq
  • p nucleus: inclusive reaction
  • pi+: hadroproduction
  • hadroproduction: pi+
  • carbon: surface
  • pi+: leptonic decay
  • leptonic decay: pi+
  • at rest