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First direct observation of time-reversal non-invariance in the neutral-kaon system
We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of $\bar{K}^0$ transforming into $K^0$ and $K^0$ into $\bar{K}^0$ as a function of the neutral-kaon eigentime $t$. The comparison is based on the analysis of the neutral-kaon semileptonic...
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Lenguaje: | eng |
Publicado: |
1998
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Materias: | |
Acceso en línea: | https://dx.doi.org/10.1016/S0370-2693(98)01356-2 http://cds.cern.ch/record/368707 |
Sumario: | We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of $\bar{K}^0$ transforming into $K^0$ and $K^0$ into $\bar{K}^0$ as a function of the neutral-kaon eigentime $t$. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at time $t=0$ was tagged by the kaon charge in the reaction $p\bar{p} \rightarrow K^{\pm} \pi^{\mp} K^0(\bar{K}^0)$ at rest, whereas the strangeness of the kaon at the decay time $t=\tau$ was tagged by the lepton charge in the final state. An average decay-rate asymmetry \begin{equation*} \langle^{R(\bar{K}^0_{t=0} \to e^+\pi^-\nu_{t=\tau}) – R(K^0_{t=0} \to e^-\pi^+\bar{\nu}_{t=\tau})}_{R(\bar{K}^0_{t=0} \to e^+\pi^-\nu_{t=\tau}) + R(K^0_{t=0} \to e^-\pi^+\bar{\nu}_{t=\tau})}\rangle = (6.6 \pm 1.3_{stat} \pm 1.0_{syst}) \times 10^{-3} \end{equation*} was measured over the interval $1\tau S \lt \tau \lt 20 \tau S$, thus leading to evidence for time-reversal non-invariance. |
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