Polarization and entanglement in baryon–antibaryon pair production in electron–positron annihilation

The BESIII Collaboration

Результат исследования: Научные публикации в периодических изданияхписьмо/краткое сообщение

23 Цитирования (Scopus)

Аннотация

Particles directly produced at electron–positron colliders, such as the J/ψ meson, decay with relatively high probability into a baryon–antibaryon pair 1 . For spin-1/2 baryons, the pair can have the same or opposite helicites. A non-vanishing phase ΔΦ between the transition amplitudes to these helicity states results in a transverse polarization of the baryons 2–4 . From the joint angular distribution of the decay products of the baryons, this phase as well as the parameters characterizing the baryon and the antibaryon decays can be determined. Here, we report the measurement of ΔΦ = 42.4 ± 0.6 ± 0.5° using Λ → pπ and Λ¯ → p¯ π + , n¯ π decays at BESIII. We find a value for the Λ → pπ decay parameter of α = 0.750 ± 0.009 ± 0.004, 17 ± 3% higher than the current world average, which has been used as input for all Λ polarization measurements since 1978 5,6 . For Λ¯ → p¯ π + we find α + = −0.758 ± 0.010 ± 0.007, giving A CP = (α + α + )/(α − α + ) = −0.006 ± 0.012 ± 0.007, a precise direct test of charge–parity symmetry (CP) violation in Λ decays.

Язык оригиналаанглийский
Страницы (с-по)631-634
Число страниц4
ЖурналNature Physics
Том15
Номер выпуска7
DOI
СостояниеОпубликовано - 1 июл 2019

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