In a study of K + p interactions at 12.7 GeV/ c we have carried out a search for meson resonances having any one of the following properties: (a) a strangeness of S =2, (b) S =1 and isotopic spin of I= 3 2 , or (c) S =1, I= 1 2 and decaying into an antihyperon ( Y ) and a nucleon (N).
From a sample of 2.36 million minimum bias events produced in p p collisions at s =630 GeV in the UA1 experiment and from other published data at the CERN S p p S collider we have estimated the relative production of π ± , π 0 , K ± , K S 0 , Λ, Λ , p and p . We obtain a meson over baryon ratio M B = 6.4 ± 1.1 . From the K S 0 π ± ratio we measure the strangeness suppression factor λ = 0.29 ± 0.02 ± 0.01 which, combining with other available data provides a new world average of 0.29 ± 0.015. Both the K S 0 π ± ratio and the strangeness suppression factor λ as a function of s are investigated, and an extrapolation to the LHC energy is performed.
CONST is strangeness suppression factor, extracted from KS/PI+- ratio (see text).
Measurements of the production inp-BeO collisions of charged baryons and antibaryons with strangeness between −3 and +3 at\(\sqrt s= 21.2GeV\)x=0.48, andpT=600MeV/c are reported. The experimental results can be interpreted within the framework of a simple proton fragmentation-recombination model.
Production of Λ, Λ , and K s 0 has been measured for a wide range of event multiplicity in S+Pb reactions at 200 GeV/c per nucleon. The production of Λ is shown to increase with multiplicity faster than expected from a superposition of p+p collisions. The effect is seen for low multiplicity (below 100 negative particles).
From the measurements of the inclusive production ratios between π - , K - and p̄ at Feynman x = 0 in 360 GeV/ c pp interactions and using the predictions of the Lund fragmentation model, we determine the strangeness and diquark suppression factors and find γ s , l = 0.28 ± 0.03 and γ D , l = 0.063 ± 0.011 .
We present evidence for the existence of two strange J P = 1 − mesons; one at 1410 MeV/c 2 coupling principally to K ∗ (892)π , and the other at 1790 MeV/c 2 couplingto K π , K ∗ π and ϱ K. The data derive from a partial wave analysis of the K 0 π + π − system produced in the reaction K − p → K 0 π + π − n at 11 GeV /c . The production mechanism and quark model assignment of each state are discussed. The state at 1410 MeV/c 2 most naturally understood as the first radial excitation of the K ∗ (892), and the 1790 MeV/c 2 object can be interpreted as the triplet D wave partner to the 3 − K ∗ (1780).
Neutral kaon to negative pion production ratios fromvp and\(\bar vp\) charged current interactions in BEBC are presented and compared with LUND fragmentation model predictions. Good agreement is obtained with a strangeness suppression factor λ=0.203±0.014(stat)±0.010(sys). No evidence is seen for an energy dependence of λ in our kinematic region.
Data on φ -production obtained by the CERN NA49 experiment for central Pb+Pb collisions at 158 GeV/u are presented. Compared with pp interactions the φ -yield shows substantial strangeness enhancement: the φ /π ratio is found to increase by a factor of 2.6 ± 0.6, which is approximately the square of the K/π enhancement.
A search for baryonia with negative and positive strangeness decaying respectively into\(\Lambda+ \bar p + pions\) and\(\bar \Lambda+ p + pions\) has been carried out in a neutron beam with a mean momentum of ≅40 GeV/c in an experiment performed at the Serpukhov accelerator. There is a strong indication of the existence of these baryonia. The following four charge states are observed for negative and positive strangeness: neutral, negative, positive and doubly charged. Their mean mass is 3055±25 MeV/c2 and the width Γ≦36±15 MeV/c2. The data show that the isotopic spin of the baryonia is ≧3/2. The baryonia production cross sections in the acceptable kinematic regionXF≧0.2 andPT≦1 GeV/c times the branching ratios of the observed decays are of the order of 1 μb per nucleon.
A 12 event/μb bubble chamber experiment on K − p interactions at 3.95 GeV/ c yielded 1212 events including systems with strangeness S = −2. Results concerning cascade resonances with masses less than 2000 MeV are reported; in particular a determination of the mass and width of the Ξ o 1530 and an interpretation of the mass region (1700–/) 2000) MeV.
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