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I study an aspect of chiral perturbation theory (\chi PT) which enables oneto ``bridge'' different reactions. That is, an operator fixed in one of thereactions can then be used to predict the other. For this purpose, I calculatethe partial wave amplitude for the p-wave pion production (pp\to pn\pi^+) usingthe pion production operator from the lowest and the next nonvanishing orders.The operator includes a contact operator whose coupling has been fixed using amatrix element of a low-energy weak process (pp\to de^+\nu_e). I find that thisoperator does not reproduce the partial wave amplitude extracted fromexperimental data, showing that the bridging over the reactions withsignificantly different kinematics is not necessarily successful. I study thedependence of the amplitude on the various inputs such as the NN potential, the\pi N\Delta coupling, and the cutoff. I argue the importance of a higher ordercalculation. In order to gain an insight into a higher order calculation, I adda higher order counter term to the operator used above, and fit the couplingsto both the low-energy weak process and the pion production. The energydependence of the partial wave amplitude for the pion production is describedby the operator consistently with the data. However, I find a result whichtells us to be careful about the convergence of the chiral expansion for thepp\to pn\pi^+ reaction.

Bridging over p-wave pi-production and weak processes in few-nucleon systems with chiral perturbation theory