Charged antiparticle to particle ratios near midrapidity in $p+p$ collisions at $\sqrt{s_{NN}}=200\text{GeV}$

The ratios of the yields of primary charged antiparticles to particles have been obtained for pions, kaons, and protons near midrapidity for $p+p$ collisions at $\sqrt{s_{NN}}=200\text{GeV}$. Ratios of $\langle {\pi }^{-}/{\pi }^{+}\rangle =1.000\pm 0.012$ (stat.) $\pm 0.019$ (syst.), $\langle K^{-}/K^{+}\rangle =0.93\pm 0.05$ (stat.) $\pm 0.03$ (syst.), and $\langle \overline{p}/p\rangle =0.85\pm 0.04$ (stat.) $\pm 0.03$ (syst.) have been measured. The reported values represent the ratio of the yields averaged over the rapidity range of $0.1<y_{\pi }<1.3$ and $0<y_{K,p}<0.8$, and for transverse momenta of $0.1<p_T^{\pi ,K}<1.0\text{GeV}/c$ and $0.3<p_T^p<1.0\text{GeV}/c$. Within the uncertainties, all three ratios are consistent with the values measured in $d+\mathrm{Au}$ collisions at the same energy. The data are compared to results from other collision systems and energies.

Figure 1

Particle ratios as a function of centrality for each species for the $p+p$, $d+\mathrm{Au}$, and $12\%$ most central $\mathrm{Au}+\mathrm{Au}$ collision systems at $\sqrt{s_{NN}}=200\text{GeV}$. The brackets represent the total systematic error. The value of $\langle \nu \rangle$ has been shifted by $+0.15$ for the measured $\langle K^{-}/K^{+}\rangle$ ratios for clarity.

Figure 2

Antiproton to proton ratio near midrapidity as a function of $\sqrt{s_{NN}}$ for $p+p$ collisions (open symbols) and central heavy ion collisions (filled symbols). The error bars represent the statistical and systematic errors in the measurements added in quadrature.