Changes in the annihilation delay time distribution of stopped antiprotons in helium gas, due to contaminants. II

A different type of analysis was performed to study the effect of contaminants on the temporal distribution of delayed annihilations of antiprotons stopped in helium gas, with respect to some first results published in Ableevet. al. (Nuovo Cimento A,107 (1994) 1325). A more objective criterion was established to single out aslow part in the total delayed component, in order to deduce from this, for each case, the mean value of the product (vσ − − ) c,l of the quenching cross-section and the mean velocity of contaminant molecules, and the fraction of the slow componentη c, l . The fractionη c, l was found to be amazingly stable for each impurity, independent of the concentration: around 79% of the total delayed component for all the atomic impurities (Ar, Ne, Xe) and 64% for the molecular ones (H2, N2

Exotic trapping of antiprotons in 4He: dependence on pressure

The behaviour of the «delayed» component of the time distribution of the annihilation of p ¯ at rest in4He is experimentally studied at various pressures of the gas target, in the range 3000 to 5 mbar at room temperatur