Charged Meson Rapidity Distributions in central Au+Au Collisions at sqrt(s_nn) = 200 GeV

Abstract

We have measured rapidity densities dN/dy of pions and kaons over a broad rapidity range (-0.1 < y < 3.5) for central Au+Au collisions at sqrt(snn) = 200 GeV. These data have significant implications for the chemistry and dynamics of the dense system that is initially created in the collisions. The full phase-space yields are 1660 +/- 15 +/- 133 (pi+), 1683 +/- 16 +/- 135 (pi-), 286 +/- 5 +/- 23 (K+) and 242 +/- 4 +/- 19 (K-). The systematics of the strange to non--strange meson ratios are found to track the variation of the baryo-chemical potential with rapidity and energy. Landau--Carruthers hydrodynamic is found to describe the bulk transport of the pions in the longitudinal direction.

Figures (4)

• Figure 1: Invariant transverse mass $m_T - m_0$ spectra of $\pi^-$ (a) and $K^-$ (b) from $y\sim 0$ (top) to $y\sim 3.5$ (bottom). Dashed lines are fits to the data, namely a power law in $p_T$ for pions and an exponential in $m_T - m_0$ for kaons. Errors are statistical. Spectra have been rescaled by powers of 10 for clarity.
• Figure 2: Pion and kaon rapidity densities (a) and their mean transverse momentum <p_T>$\left<p_T\right>$ (b) as a function of rapidity. Errors are statistical. The kaon yields were multiplied by 4 for clarity. The dashed lines in (a) are Gaussian fits to the $dN/dy$ distributions (see text).
• Figure 3: Full phase--space $K/\pi$ ratios as a function of $\sqrt{s_{NN}}$ (a) and rapidity systematics at 200$\sqrt{s_{NN}} =\unit[200]{GeV}$ (b). The dashed and dotted lines in (b) are predictions of the statistical model braun. Errors are statistical and systematics in (a), only statistical in (b). AGS data are from kpiAGS1kpiAGS2, SPS data from newna49newna49bkpiSPS1. Data points at 6.3$\sqrt{s_{NN}} =\unit[6.3]{GeV}$ and [7.6]GeV newna49newna49b are preliminary.
• Figure 4: Comparison $dN/dy(\pi)$ and Landau's prediction at 200$\sqrt{s_{NN}} =\unit[200]{GeV}$ (a) and ratio $\sigma_{N(\pi)}/\sigma_{\text{Carrut.}}$ as a function of $\sqrt{s_{NN}} =\unit[]{GeV}$√s_NN $$ (b). Errors are statistical.