Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userBeam Energy Dependence of Jet-Quenching Effects in Au+Au Collisions at $sqrt{s_{_{ mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV
241
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report measurements of the nuclear modification factor, $R_{ mathrm{CP}}$, for charged hadrons as well as identified $pi^{+(-)}$, $K^{+(-)}$, and $p(overline{p})$ for Au+Au collision energies of $sqrt{s_{_{ mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV. We observe a clear high-$p_{mathrm{T}}$ net suppression in central collisions at 62.4 GeV for charged hadrons which evolves smoothly to a large net enhancement at lower energies. This trend is driven by the evolution of the pion spectra, but is also very similar for the kaon spectra. While the magnitude of the proton $R_{ mathrm{CP}}$ at high $p_{mathrm{T}}$ does depend on collision energy, neither the proton nor the anti-proton $R_{ mathrm{CP}}$ at high $p_{mathrm{T}}$ exhibit net suppression at any energy. A study of how the binary collision scaled high-$p_{mathrm{T}}$ yield evolves with centrality reveals a non-monotonic shape that is consistent with the idea that jet-quenching is increasing faster than the combined phenomena that lead to enhancement.
rate research
Read More
We present STAR measurements of strange hadron ($mathrm{K}^{0}_{mathrm S}$, $Lambda$, $overline{Lambda}$, $Xi^-$, $overline{Xi}^+$, $Omega^-$, $overline{Omega}^+$, and $phi$) production at mid-rapidity ($|y| < 0.5$) in Au+Au collisions at $sqrt{s_{_{mathrm{NN}}}}$ = 7.7 - 39 GeV from the Beam Energy Scan Program at the Relativistic Heavy Ion Collider (RHIC). Transverse momentum spectra, averaged transverse mass, and the overall integrated yields of these strange hadrons are presented versus the centrality and collision energy. Antibaryon-to-baryon ratios ($overline{Lambda}$/$Lambda$, $overline{Xi}^+$/$Xi^-$, $overline{Omega}^+$/$Omega^-$) are presented as well, and used to test a thermal statistical model and to extract the temperature normalized strangeness and baryon chemical potentials at hadronic freeze-out ($mu_{B}/T_{rm ch}$ and $mu_{S}/T_{rm ch}$) in central collisions. Strange baryon-to-pion ratios are compared to various model predictions in central collisions for all energies. The nuclear modification factors ($R_{textrm{CP}}$) and antibaryon-to-meson ratios as a function of transverse momentum are presented for all collision energies. The $mathrm{K}^{0}_{mathrm S}$ $R_{textrm{CP}}$ shows no suppression for $p_{rm T}$ up to 3.5 $mathrm{GeV} / c$ at energies of 7.7 and 11.5 GeV. The $overline{Lambda}$/$mathrm{K}^{0}_{mathrm S}$ ratio also shows baryon-to-meson enhancement at intermediate $p_{rm T}$ ($approx$2.5 $mathrm{GeV} / c$) in central collisions at energies above 19.6 GeV. Both observations suggest that there is likely a change of the underlying strange quark dynamics at collision energies below 19.6 GeV.
We present measurements of 2$^{nd}$ order azimuthal anisotropy ($v_{2}$) at mid-rapidity $(|y|<1.0)$ for light nuclei d, t, $^{3}$He (for $sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and anti-nuclei $bar{rm d}$ ($sqrt{s_{NN}}$ = 200, 62.4, 39, 27, and 19.6 GeV) and $^{3}bar{rm He}$ ($sqrt{s_{NN}}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The $v_{2}$ for these light nuclei produced in heavy-ion collisions is compared with those for p and $bar{rm p}$. We observe mass ordering in nuclei $v_{2}(p_{T})$ at low transverse momenta ($p_{T}<2.0$ GeV/$c$). We also find a centrality dependence of $v_{2}$ for d and $bar{rm d}$. The magnitude of $v_{2}$ for t and $^{3}$He agree within statistical errors. Light-nuclei $v_{2}$ are compared with predictions from a blast wave model. Atomic mass number ($A$) scaling of light-nuclei $v_{2}(p_{T})$ seems to hold for $p_{T}/A < 1.5$ GeV/$c$. Results on light-nuclei $v_{2}$ from a transport-plus-coalescence model are consistent with the experimental measurements.
We report systematic measurements of bulk properties of the system created in Au+Au collisions at $sqrt{s_{mathrm{NN}}}$ = 14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC).The transverse momentum spectra of $pi^{pm}$, $K^{pm}$ and $p(bar{p})$ are studied at mid-rapidity ($|y| < 0.1$) for nine centrality intervals. The centrality, transverse momentum ($p_T$),and pseudorapidity ($eta$) dependence of inclusive charged particle elliptic flow ($v_2$), and rapidity-odd charged particles directed flow ($v_{1}$) results near mid-rapidity are also presented. These measurements are compared with the published results from Au+Au collisions at other energies, and from Pb+Pb collisions at $sqrt{s_{mathrm{NN}}}$ = 2.76 TeV. The results at $sqrt{s_{mathrm{NN}}}$ = 14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. These results are important as the 14.5 GeV energy fills the gap in $mu_B$, which is of the order of 100 MeV,between $sqrt{s_{mathrm{NN}}}$ =11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general.
The inclusive $J/psi$ transverse momentum ($p_{T}$) spectra and nuclear modification factors are reported at midrapidity ($|y|<1.0$) in Au+Au collisions at $sqrt{s_{NN}}=$ 39, 62.4 and 200 GeV taken by the STAR experiment. A suppression of $J/psi$ production, with respect to {color{black}the production in $p+p$ scaled by the number of binary nucleon-nucleon collisions}, is observed in central Au+Au collisions at these three energies. No significant energy dependence of nuclear modification factors is found within uncertainties. The measured nuclear modification factors can be described by model calculations that take into account both suppression of direct $J/psi$ production due to the color screening effect and $J/psi$ regeneration from recombination of uncorrelated charm-anticharm quark pairs.
Measurements of the elliptic flow, $v_{2}$, of identified hadrons ($pi^{pm}$, $K^{pm}$, $K_{s}^{0}$, $p$, $bar{p}$, $phi$, $Lambda$, $bar{Lambda}$, $Xi^{-}$, $bar{Xi}^{+}$, $Omega^{-}$, $bar{Omega}^{+}$) in Au+Au collisions at $sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV are presented. The measurements were done at mid-rapidity using the Time Projection Chamber and the Time-of-Flight detectors of the STAR experiment during the Beam Energy Scan program at RHIC. A significant difference in the $v_{2}$ values for particles and the corresponding anti-particles was observed at all transverse momenta for the first time. The difference increases with decreasing center-of-mass energy, $sqrt{s_{NN}}$ (or increasing baryon chemical potential, $mu_{B}$) and is larger for the baryons as compared to the mesons. This implies that particles and anti-particles are no longer consistent with the universal number-of-constituent quark (NCQ) scaling of $v_{2}$ that was observed at $sqrt{s_{NN}}=$ 200 GeV. However, for the group of particles NCQ scaling at $(m_{T}-m_{0})/n_{q}>$ 0.4 GeV/$c^{2}$ is not violated within $pm$10%. The $v_{2}$ values for $phi$ mesons at 7.7 and 11.5 GeV are approximately two standard deviations from the trend defined by the other hadrons at the highest measured $p_{T}$ values.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
