The STAR collaboration at RHIC reports measurements of the inclusive yield of non-photonic electrons, which arise dominantly from semi-leptonic decays of heavy flavor mesons, over a broad range of transverse momenta ($1.2 < \pt < 10$ \gevc) in \pp, \dAu, and \AuAu collisions at \sqrtsNN = 200 GeV. The non-photonic electron yield exhibits unexpectedly large suppression in central \AuAu collisions at high \pt, suggesting substantial heavy quark energy loss at RHIC. The centrality and \pt dependences of the suppression provide constraints on theoretical models of suppression.
Non photonic electron yield in P+P collisions versus PT To obtain a differential cross-section in mb/(GeV2), multiply listed data by 30 Note that, in addition to the statistical and systematical errors, there is a normalization error on the value, given in the second column.
Non photonic electron yield in P+P collisions versus $p_{T}$. To obtain a differential cross-section in mb/(GeV$^2$), multiply listed data by 30.
Non photonic electron yield in minimum bias D+AU collisions versus PT To obtain a differential cross-section in mb/(GeV2), multiply listed data by 30 Note that, in addition to the statistical and systematical errors, there is a normalization error on the value, given in the second column.
Mid-rapidity open charm spectra from direct reconstruction of $D^{0}$($\bar{D^0}$)$\to K^{\mp}\pi^{\pm}$ in d+Au collisions and indirect electron/positron measurements via charm semileptonic decays in p+p and d+Au collisions at \srt = 200 GeV are reported. The $D^{0}$($\bar{D^0}$) spectrum covers a transverse momentum ($p_T$) range of 0.1 $<p_T<$ 3 \GeVc whereas the electron spectra cover a range of 1 $<p_T<$ 4 GeV/$c$. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at mid-rapidity for open charm production from d+Au collisions at RHIC is $d\sigma^{NN}_{c\bar{c}}/dy$=0.30$\pm$0.04 (stat.)$\pm$0.09(syst.) mb. The results are compared to theoretical calculations. Implications for charmoniumm results in A+A collisions are discussed.
Inclusive electrons yield versus transverse momentum in D+AU collisions Data points at PT = 2.2, 2.7 and 3.5 GeV/c was obtained using only the TPC (Time Projection Chamber) and cover a pseudo-rapidity range of -1<eta<1, while other points were obtained using both a prototypeTime-of-Flight System and the TPC and cover a pseudo-rapidity range of -1<eta<0.
Inclusive electrons yield versus transverse momentum in P+P collisions.
D0 yield versus transverse momentum in D+AU collisions.
We report the STAR measurement of Phi meson production in Au+Au and p+p collisions at sqrt (s)=200 GeV. Using the event mixing technique, the Phi spectra and yields are obtained at mid-rapidity for five centrality bins in Au+Au collisions and for non-singly-diffractive p+p collisions. It is found that the Phi transverse momentum distributions from Au+Au collisions are better fitted with a single-exponential while the p+p spectrum is better described by a double-exponential distribution. The measured nuclear modification factors indicate that Phi production in central Au+Au collisions is suppressed relative to peripheral collisions when scaled by the number of binary collisions. The systematics of <pt> versus centrality and the constant Phi/K- ratio versus beam species, centrality, and collision energy rule out kaon coalescence as the dominant mechanism for Phi production.
Transverse mass distributions for $\phi$ meson from Au+Au (circles) and p+p (squares) collisions at 200 GeV. For clarity, some Au+Au distributions for different centralities are scaled by factors. The top 5% data are obtained from the central trigger data set. All other distributions are obtained from the minimum-bias data set. Dashed lines represent the exponential fits to the distributions and the dotted-dashed line is the result of a double-exponential fit to the distribution from p+p collisions. Error bars are statistical errors only. (x500), (x30), etc. in plot refers to the scaling of data for clearer visual results.
Results of $\phi$ meson inverse slope parameter, $<p_T>$, and dN/dy from NSD p+p and Au+Au collisions at RHIC. All values are for |y| < 0.5. Systematic uncertainties: for Au, 11% on both dN/dy and $<p_T>$. For p+p, 15% on dN/dy and 5% on $<p_T>$.
$R_{CP}$ (a): The ratio of central (top 5%) over peripheral (60-80%) ($R_{CP}$) normalized by $<N_{bin}>$. The ratios for the $\Lambda$ and $K_S^0$, shown by dotted-dashed and dashed lines, are taken from [13]; $R_{AA}$ (b) and (c) are the ratios of central Au + Au (top 5%) to p + p and peripheral Au + Au (60-80%) to p + p, respectively. The values of $R_{AA}$ for charged hadrons are shown as open circles [25]. The width of the gray bands represent the uncertainties in the estimation of $<N_{bin}>$ summed in quadrature with the normalization uncertainties of the spectra. Errors on the $\phi$ data points are the statistical plus 15% systematic errors. Overall normalization errors from binary scaling are listed in the header of each column.
The analyzing power AN in inclusive π0 production has been measured with use of the new 185-GeV/c Fermilab polarized proton beam. We obtain the value AN=0.10±0.03 for π0's in the kinematic region 0.2<xF<0.8 and 0.3<pT<1.2 GeV/c. In certain models of particle production this suggests that the spin of the proton is carried by its valence quarks.
No description provided.
No description provided.
Individual polarisation measurements.
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