R. G. H. Robertson, T. J. Bowles, G. J. Stephenson, D. L. Wark, J. F. Wilkerson and D. A. Knapp, “Limit on Mass from Observation of the β Decay of Molecular Tritium,” Physical Review Letters, Vol. 67, No. 8, 1991, p. 957. doi:10.1103/PhysRevLett.67.957

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.