EFFECTS OF PI-NN FORM-FACTOR ON PIONIC CONTRIBUTIONS TO UBAR(X)-DBAR(X) DISTRIBUTION IN THE NUCLEON

Effects of the cutoff parameter in pi-NN and pi-N-DELTA vertices on pionic contributions to uBAR(x)-dBAR(x) in the nucleon and the Gottfried sum rule are investigated. A typical pionic contribution to the deviation from the Gottfried sum rule is found around -0.04 (about 50% of the discrepancy found by the New Muon Collaboration) for the dipole cutoff parameter LAMBDA-2 approximately 1 GeV. This negative contribution is due to an excess of dBAR over uBAR in pi+ and it is (partly) canceled by a positive contribution due to an excess of uBAR over dBAR in an extra pi- in the pi-N-DELTA process. We find that the cancellation is significant especially for the large cutoff (LAMBDA-2 = 1.2-2.0 GeV); thus, the distribution uBAR-dBAR is less sensitive to the cutoff parameter than an SU(3) f-breaking distribution (uBAR + dBAR)/2-sBAR. For the same reason, it is very important to include the pi-N-DELTA process in addition to the pi-NN process. Pionic contributions to uBAR(x)-u(x), d(x)-dBAR(x), and d(x)-u(x) distributions in the nucleon are also discussed. Because pionic contributions produce an asymmetric sea, (u(s) not-equal uBAR(s))pionic and (d(s) not-equal dBAR(s))pionic, we must be careful in discussing valence- and sea-quark distributions in the nucleon.