Frame-dependence and frame-invariance in polarization measurements (the~quarkonium~example)
Sala P9, IST, Pavilhão de Matemática
Tuesday, June 1st, 2010 at 04:00 PM
We show that the understanding of quarkonium production needs better polarization
measurements, fully taking into account the intrinsic multidimensionality of the problem.
At the same time, we propose a new, frame-invariant formalism, complementing the
multidimensional analysis, that minimizes the dependence of the measurement on the
experimental acceptance, facilitating the comparison with theory, and provides a degree
of control over systematic effects due to acceptance limitations and analysis biases. In
particular, we show that the basic geometry of angular momentum implies the existence of a
frame-invariant identity which formally generalizes the Lam-Tung relation (relevant to
the production of transversely polarized Drell-Yan lepton pairs) to the dilepton decay
distribution of any $J=1$ state, even in the presence of parity-violating effects (decays
of gauge bosons).
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