C. Weinheimer, B. Degen, A. Bleile, J. Bonn, L. Bornschein, O. Kazachenko, A. Kovalik and E. Otten, “High Precision Measurement of the Tritium Β Spectrum near Its Endpoint and upper Limit on the Neutrino Mass,” Physics Letters B, Vol. 460, No. 1-2, 1999, pp. 219-226. doi:10.1016/S0370-2693(99)00780-7

has been cited by the following article:

• TITLE: Dirac Hamiltonian with Imaginary Mass and Induced Helicity—Dependence by Indefinite Metric

  AUTHORS: Ulrich D. Jentschura

  KEYWORDS: Neutrinos; Particles; Tachyonos

  JOURNAL NAME: Journal of Modern Physics, Vol.3 No.9, September 24, 2012

  ABSTRACT: It is of general theoretical interest to investigate the properties of superluminal matter wave equations for spin one-half particles. One can either enforce superluminal propagation by an explicit substitution of the real mass term for an imaginary mass, or one can use a matrix representation of the imaginary unit that multiplies the mass term. The latter leads to the tachyonic Dirac equation, while the equation obtained by the substitution m im in the Dirac equation is naturally referred to as the imaginary-mass Dirac equation. Both the tachyonic as well as the imaginary-mass Dirac Hamiltonians commute with the helicity operator. Both Hamiltonians are pseudo-Hermitian and also possess additional modified pseudo-Hermitian properties, leading to constraints on the resonance eigenvalues. Here, by an explicit calculation, we show that specific sum rules over the The spectrum is found to consist of well-defined real energy eigenvalues and complex resonance and anti-resonance energies. In the quantized imaginary-mass Dirac field, one-particle states of right-handed helicity acquire a negative norm (“indefinite metric”) and can be excluded from the physical spectrum by a Gupta-Bleuler type condition.