Measuring of $|V_{ub}|$ in the forthcoming decade

Abstract

I first introduce the importance of measuring V_ub precisely. Then, from a theoretician's point of view, I review (a) past history, (b) present trials, and (c) possible future alternatives on measuring |V_ub| and/or |V_ub/V_cb|. As of my main topic, I introduce a model-independent method, which predicts Γ(B -> X_u l ν) / Γ(B -> X_c l ν) \equiv (γ_u / γ_c) \times | V_{ub} / V_{cb}|^2 \simeq (1.83 \pm 0.28) \times |V_ub / V_cb|^2 and |V_ub/V_cb| \equiv (γ_c / γ_u)^{1/2} \times [{\cal{B}}(B -> X_u l ν)/{\cal{B}}(B -> X_c l ν)]^{1/2} \simeq (0.74 \pm 0.06) \times [{\cal{B}}(B -> X_u l ν)/ {\cal{B}}(B -> X_c l ν)]^{1/2}, based on the heavy quark effective theory. I also explore the possible experimental options to separate B -> X_u l νfrom the dominant B -> X_c l ν: the measurement of inclusive hadronic invariant mass distributions, and the `D - π' (and `K - π') separation conditions. I also clarify the relevant experimental backgrounds.