Test of the exponential decay law at short decay times using tau leptons

Abstract

Quantum mechanics predicts an exponential distribution for the decay time of massive particles. However, deviations are expected for decay times shorter than about 10 13 s in models conjecturing the existence of hidden variables. Following a recent proposal, the decay length distribution of 5843 leptons decaying into 3 charged particles was analyzed in search o f s u c h a deviation.The deviation from an exponential distribution with respect to the number of decays present within the exponential form, expressed as the relative w eight of an excess at zero decay length, was measured to be 1.1% 1.4% 3.5% . This result is consistent with zero deviation and leads to an upper limit of 8.5% and a lower limit of 6.3% at the 95% condence level.

Memory effects in spontaneous emission processes

“…[5][6][7][8][9][10][11][12][13][14][15]) may therefore be confronted with our current theoretical and experimental understanding of decaying quantum systems. Concerning experimental studies of deviations from the conventional exponential decay we notice in particular the study of decaying τ -leptons [16], the observed deviations in quantum-mechanical tunneling processes [17] and the power-law behavior of the decay at times-scales larger than twenty lifetimes in dissolved organic materials [18]. In nuclear physics the decay of thorium has also been suggested as a potential target for large-time deviations [19].…”

Full-time nonexponential decay in double-barrier quantum structures

“…The experimental confirmation of the nonexponential behavior has remained elusive over decades. After years of experimental effort, dealing mainly with radioactive atomic nucleus [10], and elementary particles [11], the deviation from the exponential decay law in the short-time limit has been finally reported some years ago for an artificial quantum system [12]. In the framework of an exact single resonance decay model [13], it is illustrated that the deviation at long times depends on the value of the ratio of the resonance energy ε r to the decay width Γ r , i.e., R = ε r /Γ r [14].…”

The Tau Lepton and the Search for New Elementary Particle Physics

“…Alexander et al [32] have examined the distribution of the decay time of individual τ 's to test if the decay distribution is exponential. The τ , being a relatively heavy elementary particle, is a good specimen for such a test.…”