Use of V_{low-k} in a chiral-perturbation-theory description of the $pp\to ppπ^0$ reaction

Abstract

Previously, the near-threhold $pp\to ppπ^0$ reaction was studied with the use of transition operators derived from chiral perturbation theory ($χ$PT) and the nuclear wave functions generated by high-precision phenomenological potentials. A conceptual problem in that approach was that the transition amplitude receives contributions from very high momentum components (above the cutoff scale of $χ$PT) in the nuclear wave functions. In the present work, we avoid this problem by replacing the "bare" phenomenological potentials with V_{low-k}, which is an effective potential derived from a bare potential by integrating out momentum components higher than a specified cutoff scale. The use of V_{low-k} is found to give an enhancement of the $pp\to ppπ^0$ cross sections over the values obtained with bare potentials. Although this enhancement brings the calculated cross sections closer to the experimental values, the incident-energy dependence of the cross section is not well reproduced, a problem that seems to indicate the necessity of including higher chiral order terms than considered in the present work.