The Cabibbo-Kobayashi-Maskawa matrix element |V ub | is not well determined yet. It can be extracted from both inclusive or exclusive decays, like B → π(ρ)lν l . However, the exclusive determination from B → ρlν l , in particular, suffers from a large model dependence. In this paper, we propose to extract |V ub | from the four-body semileptonic decay B → ππlν l , where the form factors for the pion-pion system are treated in dispersion theory. This is a model-independent approach that takes into account the ππ rescattering effects, as well as the effect of the ρ meson. We demonstrate that both finite-width effects of the ρ meson as well as scalar ππ contributions can be considered completely in this way.

The reactionspp → e + e − and e + e − →pp are analyzed in the near-threshold region. Specific emphasis is put on the role played by the interaction in the initial-or final antinucleon-nucleon (NN) state which is taken into account rigorously. For that purpose a recently publishedNN potential derived within chiral effective field theory and fitted to results of a new partial-wave analysis ofpp scattering data is employed. Our results provide strong support for the conjecture that the pronounced energy dependence of the e + e − ↔pp cross section, seen in pertinent experiments, is primarily due to thepp interaction. Predictions for the proton electromagnetic form factors G E and G M in the timelike region, close to theNN threshold, and for spin-dependent observables are presented. The steep rise of the effective form factor for energies close to thepp threshold is explained solely in terms of thepp interaction. The corresponding experimental information is quantitatively described by our calculation.

We introduce a near-threshold parameterization that is more general than the effective-range expansion up to and including the effective range because it can also handle a near-threshold zero in the D 0D * 0 S-wave. In terms of it we analyze the CDF data on inclusive pp scattering to J/ψπ + π − , and the Belle and BaBar data on B decays to K J/ψπ + π − and K DD * 0 around the D 0D * 0 threshold. It is shown that data can be reproduced with similar quality for X (3872) being a bound and/or a virtual state. We also find that X (3872) might be a higher-order virtual-state pole (double or triplet pole), in the limit in which the small D * 0 width vanishes. Once the latter is restored the corrections to the pole position are non-analytic and much bigger than the D * 0 width itself. The X (3872) compositeness coefficient in D 0D * 0 ranges from nearly 0 up to 1 in the different scenarios.

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We analyze the origin of the structures observed in the reactions e + e − → 3(π + π − ), 2(π + π − π 0 ), ωπ + π − π 0 , and e + e − → 2(π + π − )π 0 around the antiproton-proton (pp) threshold. We calculate the contribution of the two-step process e + e − →N N → multipions to the total reaction amplitude. The amplitude for e + e − →N N is constrained from near-threshold data on the e + e − →pp cross section and the one forN N → multipions can be likewise fixed from available experimental information, for all those 5π and 6π states. The resulting amplitude for e + e − → multipions turns out to be large enough to play a role for the considered e + e − annihilation channels and, in three of the four reactions, even allows us to reproduce the data quantitatively near theN N threshold. The structures seen in the experiments emerges then as a threshold effect due to the opening of theN N channel.