A polarization amplitude A$_{{{\mathit D}_{{J}}}}$ is a parameter that depends on the initial polarization of the ${{\mathit D}_{{J}}}$. For ${{\mathit D}_{{J}}}$ decays the helicity angle, ${{\mathit \theta}_{{H}}}$, distribution varies like 1 + A$_{{{\mathit D}_{{J}}}}$ cos $^2{{\mathit \theta}_{{H}}}$, where ${{\mathit \theta}_{{H}}}$ is the angle in the ${{\mathit D}_{{J}}}$ rest frame between the two pions emitted in the ${{\mathit D}_{{J}}}$ $\rightarrow$ ${{\mathit D}^{*}}{{\mathit \pi}}$ and ${{\mathit D}^{*}}$ $\rightarrow$ ${{\mathit D}}{{\mathit \pi}}$ decays.

VALUE EVTS DOCUMENT ID TECN  COMMENT • • We do not use the following data for averages, fits, limits, etc. • • $4.2$ $\pm1.3$ 60k 1 AAIJ 2013 CC LHCB ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit D}^{*+}}{{\mathit \pi}^{-}}{{\mathit X}}$ 1  Systematic uncertainty not estimated.

References:

AAIJ 2013CC JHEP 1309 145 Study of ${{\mathit D}_{{J}}}$ Meson Decays to ${{\mathit D}^{+}}{{\mathit \pi}^{-}}$, ${{\mathit D}^{0}}{{\mathit \pi}^{+}}$ and ${{\mathit D}^{*+}}{{\mathit \pi}^{-}}$ Final States in ${{\mathit p}}{{\mathit p}}$ Collisions