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FACTORIZATION IN EXCLUSIVE AND SEMI-INCLUSIVE HEAVY FLAVOR DECAYS AND EFFECTIVE THEORIES FOR MASSLESS PARTICLES

2000; World Scientific; Volume: 15; Issue: 03 Linguagem: Inglês

10.1142/s0217751x00000173

1793-656X

U. Aglietti, Guido Corbò,

Quantum Chromodynamics and Particle Interactions

We prove factorization in the semi-inclusive decay B → D (*) + jet using the Large Energy Effective Theory (LEET). It is also shown that the LEET is unable to consistently describe exclusive processes, such as the decay B → D (*) + π(ρ), and therefore also related properties such as factorization. The reason is an oversimplification of transverse momentum dynamics. We present a variant of the LEET, i.e. a new effective theory for massless particles, the [Formula: see text], which properly takes into account transverse momentum dynamics and is the natural framework to study exclusive nonleptonic decays. The transition from the LEET to the [Formula: see text] is analogous to the replacement of geometrical optics with physical optics, the latter taking into account diffraction to a first approximation. A qualitative argument is presented in favor of factorization in the exclusive nonleptonic decays using the [Formula: see text]. Finally, it is shown that the collinear instability of the LEET disappears when semi-inclusive observables are considered.