Frame-dependence and frame-invariance in polarization measurements (the~quarkonium~example)

Pietro Faccioli


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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