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Register a new userHadronization, spin, and lifetimes
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Measurements of lifetimes can be done in two ways. For very short lived particles, the width can be measured. For long lived ones, the lifetime can be directly measured, for example, using a displaced vertex. Practically, the lifetime cannot be extracted for particles with intermediate lifetimes. We show that for such cases information about the lifetime can be extracted for heavy colored particles that can be produced with known polarization. For example, a $t$-like particle with intermediate lifetime hadronizes into a superposition of the lowest two hadronic states, $T^*$ and $T$ (the equivalent of $B^*$ and $B$). Depolarization effects are governed by time scales that are much longer than the hadronization time scale, $lqcd^{-1}$. After a time of order $1/Delta m$, with $Delta m equiv m(T^*)-m(T)$, half of the initial polarization is lost. The polarization is totally lost after a time of order $1/Gamma_{gamma}$, with $Gamma_{gamma}= Gamma(T^*to Tgamma)$. Thus, by comparing the initial and final polarization, we get information on the particles lifetime.
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Models of hadronization of hard jets in QCD are often presented in terms of Feynman-graph structures that can be thought of as effective field theory approximations to dynamical non-perturbative physics in QCD. Such models can be formulated as a kind of multiperipheral model. We obtain general constraints on such models in order for them to be self-consistent, and we relate the constraints to the space-time structure of hadronization. We show that appropriate models can be considered as implementing string-like hadronization. When the models are put in a multiperipheral form, the effective vertices and/or lines must be momentum non-conserving: they take 4-momentum from the external string-like field.
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