Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at $\sqrt{s_{NN}} = 200$ GeV

Abstract

Identified mid-rapidity particle spectra of $π^{\pm}$, $K^{\pm}$, and $p(\bar{p})$ from 200 GeV p+p and d+Au collisions are reported. A time-of-flight detector based on multi-gap resistive plate chamber technology is used for particle identification. The particle-species dependence of the Cronin effect is observed to be significantly smaller than that at lower energies. The ratio of the nuclear modification factor ($R_{dAu}$) between protons $(p+\bar{p})$ and charged hadrons ($h$) in the transverse momentum range $1.2<{p_{T}}<3.0$ GeV/c is measured to be $1.19\pm0.05$(stat)$\pm0.03$(syst) in minimum-bias collisions and shows little centrality dependence. The yield ratio of $(p+\bar{p})/h$ in minimum-bias d+Au collisions is found to be a factor of 2 lower than that in Au+Au collisions, indicating that the Cronin effect alone is not enough to account for the relative baryon enhancement observed in heavy ion collisions at RHIC.

Figures (4)

• Figure 1: $1/\beta$ vs. momentum for $\pi^{\pm}$, $K^{\pm}$, and $p(\bar{p})$ from 200 GeV d+Au collisions. Separations between pions and kaons, kaons and protons are achieved up to $p_{T}\simeq1.6$ and $3.0$ GeV/c, respectively. The insert shows $m^{2}=p^{2}(1/\beta^{2}-1)$ for $1.2<p_{T}<1.4$ GeV/c. Clear separation of pions, kaons and protons is seen.
• Figure 2: The invariant yields of $\pi^{+}$ (filled circles), $K^{+}$ (open squares), $p$ (filled triangles) and their anti-particles as a function of $p_{T}$ from d+Au and NSD p+p events at 200 GeV. The rapidity range was $-0.5<y<0.0$ with the direction of the outgoing Au ions as negative rapidity. Errors are statistical.
• Figure 3: The identified particle $R_{dAu}$ for minimum-bias and top 20% d+Au collisions. The filled triangles are for $p+\bar{p}$, the filled circles are for $\pi^{+}+\pi^{-}$ and the open squares are for $K^{+}+K^{-}$. Dashed lines are $R_{dAu}$ of inclusive charged hadrons from stardau. The open triangles and open circles are $R_{CP}$ of $p+\bar{p}$ and $\pi^{0}$ in Au+Au collisions measured by PHENIX phenixpid. Errors are statistical. The gray band represents the normalization uncertainty of 16%.
• Figure 4: Minimum-bias ratios of protons ($p+\bar{p}$) over inclusive charged hadrons ($h$) at $-0.5\!<\!\eta\!<\!0.0$ from $\sqrt{s_{_{NN}}} =200$ GeV p+p (open diamonds), d+Au (filled triangles) and $\sqrt{s_{_{NN}}} =130$ GeV Au+Au phenixpid (asterisks) collisions. Results of $\mathrm{p+\bar{p}}$ collisions at $\sqrt{s_{_{NN}}} = 1.8$ TeV e735 are shown as solid stars. Dashed lines are results of $p/h^{+}$ ratios from $\sqrt{s_{_{NN}}} = 23.8$ GeV p+p (short-dashed lines) and p+W (dot-dashed) collisions cronincronin1979. Errors are statistical.