How to measure the helicity of a vector resonance?
by
Prof.Kaoru Hagiwara
→
Asia/Seoul
Description
The helicity of a vector meson can be measured if it decays into three or more hadrons, and if the decay amplitudes have non-factorizable absorbtive parts. As an example, we show how the a1 meson helicity can be measured by studying its 3 pions decay, and show how its accuracy can be tested at the LHC, where high-transverse momentum isolated a1 meson from the cascade W > tau > a1 decays has almost purely left-handed helicity. Once established, the method can be used to study the photon helicity in B > (pi pi pi) gamma and B > (K pi pi) gamma decays, determining the operator
contributing to b > d, gamma and b > s, gamma transitions, respectively.