Di-electron spectrum at mid-rapidity inp+pcollisions ats=200GeV

Abstract

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 (dN/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.

Dielectron Mass Spectra fromAu+AuCollisions atsNN=200 <

“…1(a). The signal-to-background ratios from p þ p [21], Au þ Au minimum bias, and Au þ Au central collisions at ffiffiffiffiffiffiffi ffi s NN p ¼ 200 GeV are shown in Fig. 1(b).…”

“…We adopted two approaches to reproduce the background that do not originate from pair production: the like-sign pair combinations and the mixed-event technique, for which unlike-sign pairs from different events were used. In the lowmass region, like-sign pairs better reproduce the background spectrum, compared to mixed-event techniques, because the unlike-sign background contains residual correlations (e.g., conversion of photon pairs) [21]. For this reason, the same-event like-sign distribution, corrected for the acceptance differences between like-sign and unlike-sign pairs, was used as the background for M ll < 1 GeV=c 2 .…”

“…In order to disentangle the various sources contributing to the dielectron signal, a hadronic cocktail simulation, performed previously for p þ p collisions [21], was generated for Au þ Au collisions at ffiffiffiffiffiffiffi ffi s NN p ¼ 200 GeV. The simulation included dielectron contributions from decays or Dalitz decays of π 0 , η, η 0 , ω, ϕ, J=ψ, cc, bb, and DrellYan (DY) production.…”

Υ(1S+2S+3S)production ind+Au and

“…A dielectron-spectrum measurement showed σ cc = 0.92 ± 0.10 (stat) ± 0.26 (syst) mb [25]. Measurements of D 0 and D * production gave σ cc = 797 ± 210 (stat) +208 −295 (syst) μb [26].…”

Measurement of electrons from heavy-flavour hadron decays in p-Pb collisions at $\\sqrt{s_{NN}} = 5.02$ TeV using TPC and EMCal detectors with ALICE at LHC

“…5.12, in comparison with the HFE spectrum. The invariant yield of J/ψ and K e3 (K → eπν) decays to electrons where obtained from the cocktail [79,180,181]. The cocktail is a method to calculate the yield of electrons from hadronic decays.…”