The total neutral energy spectra in the central region of α-α, d-d and p-p interactions at √ssub(NN) = 31 GeV per nucleon pair at the CERN ISR

The spectra in total neutral energy, Esub(TOT)0, have been measured in pp, dd and αα collisions at centre-of-mass energy per nucleon pair, √Ssub(NN), of 31 GeV. The range in Esub(TOT)0 covered was 1 to 19 GeV in pp, 18 to 24 GeV in dd and 1 to 34 GeV in αα interactions. The ratio of the αα to the pp spectra rises monotonically from 7 at Esub(TOT)0=1.5 GeV to 105 at Esub(TOT)0=19 GeV. Since Esub(TOT)0 is the sum over many particles in the detector, it is directly sensitive to multiple nucleon-nucleon collisions in the interactions α particles. The αα spectrum in the range 8<Esub(TOT)0<17 GeV is consistent with being described by a simple model of 4 simultaneous nucleon-nucleon collisions with a cross section about equal to 10% of the observed αα interaction cross section. The spectrum of Esub(TOT)0 above 17 GeV is even flatter than this extreme case where four nucleon pairs are interacting. (orig.)