New data on Delta(++)-baryon production in (p)over-bar-d annihilation at rest

摘要

New experimental results on (p) over bar d annihilation at rest into pions plus a high momentum proton in the final state are discussed. The data sample was collected using the OBELIX spectrometer at the LEAR facility (CERN). The annihilation probabilities, or more precisely the yields (Y) via channels (p) over bar d --> 2 pi(-)pi(+)pi(0)p and (p) over bar d --> 3 pi(-)2 pi(+)pi(0)p with proton momenta p > 400 MeV/c have been measured for the first time: Y = (93.2 +/- 1.6) x 10(-4) and Y = (52.2 +/- 1.4) x 10(-4), respectively. The signal in the invariant mass distribution of the p pi(+) system in the region of the well-known Delta(++) (1232)-isobar is clearly seen in reactions (p) over bar d --> 2 pi(-)pi(+)p, (p) over bar d --> 2 pi(-)pi(+)pi(0)p, (p) over bar d --> 3 pi(-)2 pi(+)p and (p) over bar d --> 3 pi(-)2 pi(+)pi(0)p. The upper limit on reaction (p) over bar (Delta(-)Delta(++)) --> 2 pi(-)pi(+)p in the p (d) over bar annihilation at rest, which could be interpreted as a manifestation of the Delta Delta component of the deuteron, was found to be Y less than or equal to 6.5 x 10(-5) with a 90% confidence level. (C) 1997 Published by Elsevier Science B.V.