Polarization and entanglement in baryon-antibaryon pair production in electron-positron annihilation
Küçük Resim Yok
Tarih
2019
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Nature Portfolio
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Particles directly produced at electron-positron colliders, such as the J/psi 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 Delta Phi 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 bary-ons, this phase as well as the parameters characterizing the baryon and the antibaryon decays can be determined. Here, we report the measurement of Delta Phi = 42.4 +/- 0.6 +/- 0.5 degrees using Lambda -> p pi(-) and (Lambda) over bar -> (p) over bar pi(+), (n ) over bar pi(0) decays at BESIII. We find a value for the Lambda -> p pi(-) decay parameter of alpha(-) = 0.750 +/- 0.009 +/- 0.004, 17 +/- 3% higher than the current world average, which has been used as input for all Lambda polarization measurements since 1978(5,6). For (Lambda) over bar -> (p) over bar pi(+) we find alpha(+) = -0.758 +/- 0.010 +/- 0.007, giving A(CP) = (alpha(-) + alpha(+))/(alpha(-) - alpha(+)) = -0.006 +/- 0.012 +/- 0.007, a precise direct test of charge-parity symmetry (CP) violation in Lambda decays.
Açıklama
Anahtar Kelimeler
Analyzing Power, Parameter, J/Psi, Decay, Hyperon, Lambda(Lambda)Over-Bar, Observables, E(+)E(-), Lambda
Kaynak
Nature Physics
WoS Q Değeri
Q1
Scopus Q Değeri
Q1
Cilt
15
Sayı
7
