Track based maximum likelihood ring search algorithm

A track based maximum likelihood algorithm, unbiased to any mass hypothesis, has been developed for the HERA-B RICH to search for deuterons produced in 920 GeV proton–nucleus collisions. Clear signals of deuterons and anti-deuterons have been observed in data recorded by the HERA-B spectrometer. We present the algorithm, discuss its performance and show some preliminary results of an ongoing data analysis.