engleski

Di-electron spectrum at mid-rapidity in p+p collisions at √s=200 GeV

We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e+e− decays, from √s=200 GeV p+p collisions, measured by the large- acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy- flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω→e+e− invariant yields are consistent with previous measurements. The mid-rapidity yields (d N/dy) of φ and J/ψ are extracted through their di-electron decay channels and are consistent with the previous measurements of φ→K+K− and J/ψ→e+e−. Our results suggest a new upper limit of the branching ratio of the η→e+e− of 1.7×10−5 at the 90% confidence level.

Di-electron; mid-rapidity; STAR

STAR Collaboration.