A measurement of and for small values of t and u at 3 and 4 GeV/c

We have measured with good statistics the differential cross section for p p →π + π − , K + K − around 0°. Our data and previous results show that the s-dependence of dσ/dt has a value compatible with the appropriate baryon exchange. The dip at u≈ −0.15 (GeV/c)2, expected in p p →π − π + according to some models is not observed. Instead, a break in the slope of dσ/du is seen for u≈ −0.30 (GeV/c)2 at 4 GeV/c.