MASS AND LIFETIME OF UNSTABLE PARTICLES

Journal Article · Sun Jan 01 04:00:00 EST 1961 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.121.350· OSTI ID:4126560

Jacob, R; Sachs, R G

The relationship between the properties of the propagator of an unstable particle and the observation of mass and lifetime is considered. For illustrative purposes a model of a scalar (or pseudoscalar) particle ( theta ) weakly coupled to two pions is treated. The propagator is shown to have a simple pole on the second (unphysical) Riemann sheet and it is assumed, as suggested by Peierls, that this is generally the case. By analysis of a prototype experiment in terms of wave packets, it is shown that the measured mass and lifetime are determined by the real and imaginary parts of the pole, respectively. Nonexponential terms occur in the lifetime curve, as is well known. These are shown to be related to the uncertainty in the time of the production or detection event under normal circumstances. This conclusion is similar to those of Levy and of Schwinger, but more closely related to experimental conditions. In particular it is found that the wave packets introduce a "mass filter" in a somewhat different manner from that suggested by Schwinger. Under special conditions a t/sup -32/ term may occur in the amplitude but would be unimportant in magnitude for, say, the decay of a strange particle. It is noted that such nonexponential decay curves might occur for certain low-energy nuclear processes. Consideration is given to the treatment of two degenerate, unstable particles, such as the neutral K mesons. The general method for handling the problem leads, in the weak-coupling limit. to the same result as the Wigner-Weisskopf method. (auth)

• Research Organization: Univ. of Wisconsin, Madison
• NSA Number: NSA-15-006672
• OSTI ID: 4126560
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 121; ISSN PHRVA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

DECAY
ELEMENTARY PARTICLES
FIELD THEORY
INTERACTIONS
KAONS
LIFETIME
MASS
PARTICLE MODELS
PHYSICS
PIONS
PROPAGATOR
QUANTUM FIELD THEORY
RIEMANN SHEET
STABILITY