Yes – positrons are not seen – and this is especially true since a specialized meter which is tuned to detect positrons was used in some of Rossi’s testing - with a sensitivity of picowatts. There was nothing above background.
Mesons are also not possible – since they are not produced by fusion nor by radioactive decay - only as products of very high-energy interactions such as cosmic rays or accelerators. From: David Roberson If electrons were the only particle generated the system would assume a negative charge that continues to increase over time. Most reactions with electrically neutral particles generate an equal number of positive charged particles as negative ones. The fact that there are no 511 keV gammas suggests to me that no positrons are being generated during the process.
