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Register a new userObservation of $D_{s}^{pm}/D^0$ enhancement in Au+Au collisions at $sqrt{s_{_{rm NN}}}$ = 200 GeV
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We report on the first measurement of charm-strange meson $D_s^{pm}$ production at midrapidity in Au+Au collisions at $sqrt{s_{_{rm NN}}}$ = 200 GeV from the STAR experiment. The yield ratio between strange ($D_{s}^{pm}$) and non-strange ($D^{0}$) open-charm mesons is presented and compared to model calculations. A significant enhancement, relative to a PYTHIA simulation of $p$+$p$ collisions, is observed in the $D_{s}^{pm}/D^0$ yield ratio in Au+Au collisions over a large range of collision centralities. Model calculations incorporating abundant strange-quark production in the quark-gluon plasma (QGP) and coalescence hadronization qualitatively reproduce the data. The transverse-momentum integrated yield ratio of $D_{s}^{pm}/D^0$ at midrapidity is consistent with a prediction from a statistical hadronization model with the parameters constrained by the yields of light and strange hadrons measured at the same collision energy. These results suggest that the coalescence of charm quarks with strange quarks in the QGP plays an important role in $D_{s}^{pm}$ meson production in heavy-ion collisions.
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We report the STAR measurements of dielectron ($e^+e^-$) production at midrapidity ($|y_{ee}|<$1) in Au+Au collisions at $sqrt{s_{rm NN}}$ = 200,GeV. The measurements are evaluated in different invariant mass regions with a focus on 0.30-0.76 ($rho$-like), 0.76-0.80 ($omega$-like), and 0.98-1.05 ($phi$-like) GeV/$c^{2}$. The spectrum in the $omega$-like and $phi$-like regions can be well described by the hadronic cocktail simulation. In the $rho$-like region, however, the vacuum $rho$ spectral function cannot describe the shape of the dielectron excess. In this range, an enhancement of 1.77$pm$0.11(stat.)$pm$0.24(sys.)$pm$0.33(cocktail) is determined with respect to the hadronic cocktail simulation that excludes the $rho$ meson. The excess yield in the $rho$-like region increases with the number of collision participants faster than the $omega$ and $phi$ yields. Theoretical models with broadened $rho$ contributions through interactions with constituents in the hot QCD medium provide a consistent description of the dilepton mass spectra for the measurement presented here and the earlier data at the Super Proton Synchrotron energies.
We report the first measurement of rapidity-odd directed flow ($v_{1}$) for $D^{0}$ and $overline{D^{0}}$ mesons at mid-rapidity ($|y| < 0.8$) in Au+Au collisions at $sqrt{s_{rm NN}}$ = 200,GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10--80% Au+Au collisions, the slope of the $v_{1}$ rapidity dependence ($dv_{1}/dy$), averaged over $D^{0}$ and $overline{D^{0}}$ mesons, is -0.080 $pm$ 0.017 (stat.) $pm$ 0.016 (syst.) for transverse momentum $p_{rm T}$ above 1.5~GeV/$c$. The absolute value of $D^0$-meson $dv_1/dy$ is about 25 times larger than that for charged kaons, with 3.4$sigma$ significance. These data give a unique insight into the initial tilt of the produced matter, and offer constraints on the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.
We report preliminary results of hypertriton observation in heavy-ion collisions at RHIC. We have identified 157 +- 30 candidates in the current sample containing ~10^8 Au+Au events at sqrt{s_{NN}} = 200 GeV. The production rate of hypertriton is close to that of helium 3. No extra penalty factor is observed for hypertriton, in contrast to results observed at the AGS.
We report the first measurement of charmed-hadron ($D^0$) production via the hadronic decay channel ($D^0rightarrow K^- + pi^+$) in Au+Au collisions at $sqrt{s_{_{mathrm{NN}}}}$ = 200,GeV with the STAR experiment. The charm production cross-section per nucleon-nucleon collision at mid-rapidity scales with the number of binary collisions, $N_{bin}$, from $p$+$p$ to central Au+Au collisions. The $D^0$ meson yields in central Au+Au collisions are strongly suppressed compared to those in $p$+$p$ scaled by $N_{bin}$, for transverse momenta $p_{T}>3$ GeV/$c$, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate $p_{T}$ is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.
In this erratum we report changes on the $D^0$ $p_T$ spectra and nuclear modification factor ($R_{AA}$) in Au+Au collisions at $sqrt{s_{_{mathrm{NN}}}}$ = 200 GeV by fixing the errors in the efficiency and selection criteria that affected the Au+Au results. The p+p reference spectrum has changed as well and is updated with new fragmentation parameters.
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