  The reaction pp -> dpi+eta has been measured at a beam energy of T=2.65 GeV
(p=3.46 GeV/c) using the ANKE spectrometer at COSY-Juelich. The missing mass
distribution of the detected dpi+ pairs exhibits a peak around the eta mass on
top of a strong background of multi-pion pp -> dpi+(n(pi)) events. The
differential cross section d^4(sigma)/d(Omega_d)d(Omega_pi+)d(p_d)d(p_pi+) for
the reaction pp -> dpi+eta has been determined model independently for two
regions of phase space. Employing a dynamical model for the a0+ production
allows one then to deduce a total cross section of sigma(pp -> da0+ ->
dpi+eta)=(1.1 +/- 0.3_(stat) +/- 0.7_(syst)) microbarn for the production of
pi+eta via the scalar a0+(980) resonance and sigma(pp -> dpi+eta) = (3.5 +/-
0.3_(stat) +/- 1.0_(syst)) microbarn for the non-resonant production. Using the
same model as for the interpretation of recent results from ANKE for the
reaction pp -> dK+(bar(K0)), the ratio of the total cross sections is sigma(pp
-> d(K+(bar(K0)))_(L=0))/sigma(pp -> da0+ -> dpi+eta) = 0.029 +/- 0.008_(stat)
+/- 0.009_(syst), which is in agreement with branching ratios in the
literature.
