Strangeness enhancements measured by the NA57 experiment.
The enhancements are defined as the particle yields normalised by the
number of participating nucleons in the collision, and divided
by the observed yield in proton-beryllium collisions. The yields
expected from a simple superposition of nucleon-nucleon collisions would
then lie on a straight line positioned at unity.
Particles having
at least one quark common with the nucleon (that is particles that could
take over at least one quark from the projectile or the target) are shown
on the left. Particles having no quarks in common with the nucleon (in
other words, all the quarks making up these particle must have been produced
in the collision) are shown on the right. Ω particles contain
three strange quarks. (All the particles shown in this picture
are built from "up", "down" and "strange" quarks, with varying numbers
of each quark type in each particle. All matter in everyday nature
is built from "up" and "down" quarks only). Ξ particles contain
two strange quarks, whereas Λ particles contain one strange
quark only.
The error bars shown on the picture are statistical errors, the systematical
errors are indicated by black symbols. The errors presented in the table are
statistical errors only.
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