The reaction has been studied in accelerators
Summary
Elastic scattering, single-pion and deuteron production have been investigated. The cross-section for elastic scattering is σelastic = (13.5±0.3) mb. The angular distribution has been fitted to dσ/d|t|=(dσ/d|t|)0 e −bt in the region of low values oft. The best fit givesb=(6.7±0.5) (GeV/c)−2 and (dσ/d|t|)0=(91±5) mb(GeV/c)−2. The cross-sections for ppπ0, pnπ+ reactions are respectively (2.6±0.3) mb and (9.7±0.4) mb. These reactions are dominated by the (3/2, 3/2) nucleonpion isobar production and by forward backward collimation of the nucleons. The production rates for the isobarsN∗++1238 ,N∗+1238,N∗+1500 have been estimated, taking into account the experimental peripheral behaviour of the interaction. In the pnπ+ reaction they are (50±2)%; (10±3)%; (4±3)%. In the ppπ+ reaction the production ofN∗++1238 is estimated to be (45±10)%. The dπ+ and dπ+π+π- reaction cross-sections are respectively (0.03±0.01) mb, and (0.04±0.01) mb.
It is behind a paywall:Il Nuovo Cimento A (1971-1996),Volume 49, Issue 3 , pp 479-498
Deuterons are produced and there is enough energy left over to get a few pions in parallel.
So all it needs is enough energy so that the reaction can take place.
The difference with the sun is the numbers available for the interaction. When the average temperature is at the energy where the reaction has a high probability it means a high flux of these interactions will happen spontaneously.