New measurements are presented for charged hadron azimuthal correlations at midrapidity in Au+Au collisions at {radical}(s{sub NN})=62.4 and 200 GeV. They are compared to earlier measurements ...obtained at {radical}(s{sub NN})=130 GeV and in Pb+Pb collisions at {radical}(s{sub NN})=17.2 GeV. Sizeable anisotropies are observed with centrality and transverse momentum (p{sub T}) dependence characteristic of elliptic flow (v{sub 2}). For a broad range of centralities, the observed magnitudes and trends of the differential anisotropy, v{sub 2}(p{sub T}), change very little over the collision energy range {radical}(s{sub NN})=62-200 GeV, indicating saturation of the excitation function for v{sub 2} at these energies. Such a saturation may be indicative of the dominance of a very soft equation of state for {radical}(s{sub NN}){approx}60-200 GeV.
Semi-inclusive triple differential multiplicity distributions of positively charged kaons have been measured over a wide range in rapidity and transverse mass for central collisions of $^{58}$Ni with ...$^{58}$Ni nuclei. The transverse mass ($m_t$) spectra have been studied as a function of rapidity at a beam energy 1.93 AGeV. The $m_t$ distributions of K^+ mesons are well described by a single Boltzmann-type function. The spectral slopes are similar to that of the protons indicating that rescattering plays a significant role in the propagation of the kaon. Multiplicity densities have been obtained as a function of rapidity by extrapolating the Boltzmann-type fits to the measured distributions over the remaining phase space. The total K^+ meson yield has been determined at beam energies of 1.06, 1.45, and 1.93 AGeV, and is presented in comparison to existing data. The low total yield indicates that the K^+ meson can not be explained within a hadro-chemical equilibrium scenario, therefore indicating that the yield does remain sensitive to effects related to its production processes such as the equation of state of nuclear matter and/or modifications to the K^+ dispersion relation.
Charged pion spectra measured in 58Ni-58Ni collisions at 1.06, 1.45 and 1.93 AGeV are interpreted in terms of a thermal model including the decay of Delta resonances. The transverse momentum spectra ...of pions are well reproduced by adding the pions originating from the Delta-resonance decay to the component of thermal pions, deduced from the high transverse momentum part of the pion spectra. About 10 and 18% of the nucleons are excited to Delta states at freeze-out for beam energies of 1 and 2 AGeV, respectively.
J.Phys. G30 (2004) S1201-S1206 The PHENIX experiment at RHIC should be sensitive to decays of the the
anti--pentaquark $\bar{\Theta}^-$ via the K$^-$ $\bar{n}$ channel. Charged
kaons can be ...identified using the standard tracking and time of flight up to a
momentum of 1.5 GeV/c. Anti--neutron candidates are detected via their
annihilation signal in the highly segmented electromagnetic calorimeter
(EMCal). In order to assess the quality of the anti--neutron identification we
reconstruct the $\bar{\Sigma} \to \bar{n}\pi$. As an additional crosscheck the
invariant mass of K$^+$ $\bar{n}$ is reconstructed where no resonance in the
pentaquark mass range is expected. At the present time no enhancement at the
expected pentaquark mass is observed in dAu collisions at $\sqrt{s_{NN}} = 200
GeV.
Nucl.Phys.A698:495-498,2002 The E895 experiment at the AGS measured strange particle production and
collective behavior in Au+Au collisions between 2--8 AGeV. The production of
$\Lambda$ Baryons and ...K$^0$ Mesons as function of energy rises smoothly and
exhibits a nonlinear impact parameter dependence. Neutral and positively
charged Kaons exhibit a strong anti-flow behavior. $\Lambda$ Baryons show a
smaller flow signal than protons.
A systematic study of the elliptic flow in Au+Au collisions at energies from 0.09 to 1.49 AGeV is presented. The experimental information allows us to extract information about the reaction dynamics ...and, by comparison with the IQMD transport model, the Equation of State (EoS) of nuclear matter.
The super Pioneering High Energy Nuclear Interaction eXperiment (sPHENIX) at the Relativistic Heavy Ion Collider (RHIC) will perform high precision measurements of jets and heavy flavor observables ...for a wide selection of nuclear collision systems, elucidating the microscopic nature of strongly interacting matter ranging from nucleons to the strongly coupled quark-gluon plasma. A prototype of the sPHENIX calorimeter system was tested at the Fermilab Test Beam Facility as experiment T-1044 in the spring of 2016. The electromagnetic calorimeter (EMCal) prototype is composed of scintillating fibers embedded in a mixture of tungsten powder and epoxy. The hadronic calorimeter (HCal) prototype is composed of tilted steel plates alternating with plastic scintillator. Results of the test beam reveal the energy resolution for electrons in the EMCal is \(2.8\%\oplus~15.5\%/\sqrt{E}\) and the energy resolution for hadrons in the combined EMCal plus HCal system is \(13.5\%\oplus 64.9\%/\sqrt{E}\). These results demonstrate that the performance of the proposed calorimeter system satisfies the sPHENIX specifications.
The invariant differential cross section for inclusive electron production in \(p + p\) collisions at \(\sqrt{s} = 200\)~GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion ...Collider over the transverse momentum range \(0.4 \le p_T \le 5.0\)~GeV/\(c\) in the central rapidity region (\(|\eta| \le 0.35\)). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, {\it i.e.} charm quarks or, at high \(p_T\), bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined to be \(\sigma_{c\bar{c}} = 0.92 \pm 0.15 {\rm (stat.)} \pm 0.54 {\rm (sys.)}\)~mb.
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