Construction and performance of the PHENIX pad chambers Adcox, K.; Ajitanand, J.; Alexander, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2003, Volume:
497, Issue:
2
Journal Article
Peer reviewed
We present the Pad Chamber detector system in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The three station system provides space points ...along each track in the spectrometer arms at mid-rapidity and covers a total area of
88
m
2
. Its main functions are to provide the track coordinate along the beam and to ensure reliable pattern recognition at very high particle multiplicity. A new concept for two dimensional wire chamber readout via its finely segmented cathode was developed. The full readout system, comprising
172
800
electronic channels, is described together with the challenging design of the chambers. The electronics, mounted on the outer chamber face, together with the chamber itself amounts to 1.2% of a radiation length. Results from cosmic ray tests, showing an average efficiency better than 99.5% for all chambers are presented. The experiences from the full scale operation in the first run are reported.
The flow harmonics upsilon sub(2,3) for charged hadrons are studied for a broad range of centrality selections and beam collision energies in Au + Au (radicalS sub(N)N= 7.7-200 Gev) and Pb + Pb ...(radicalS sub(N)N= 2.76 Tev) collisions. They validate the characteristic signature expected for the system size dependence of viscous damping at each collision energy studied. The extracted viscous coefficients that encode the magnitude of the ratio of shear viscosity to entropy density eta/s are observed to decrease to an apparent minimum as the collision energy is increased from radicalS sub(N)N= 7.7 to approximately 62.4 GeV; thereafter, they show a slow increase with radicalS sub(N)Nup to 2.76 TeV. This pattern of viscous damping provides the first experimental constraint for eta/s in the temperature-baryon chemical potential (T, mu sub(B) plane and could be an initial indication for decay trajectories that lie close to the critical end point in the phase diagram for nuclear matter.
The shear viscosity to entropy ratio (eta/s) is estimated for the hot and dense QCD matter created in Au+Au collisions at BNL Relativistic Heavy Ion Collider (square roots_{NN}=200 GeV). A very low ...value is found; eta/s approximately 0.1, which is close to the conjectured lower bound (1/4pi). It is argued that such a low value is indicative of thermodynamic trajectories for the decaying matter which lie close to the QCD critical end point.
The PHENIX experiment at the BNL Relativistic Heavy Ion Collider has measured second- and third-order Fourier coefficients of the azimuthal distributions of direct photons emitted at midrapidity in ...Au + Au collisions at √ sNN = 200 GeV for various collision centralities. Combining two different analysis techniques, results were obtained in the transverse momentum range of 0.4 < pT < 4.0 GeV/c. At lowpT the second-order coefficients, v2, are similar to the ones observed in hadrons. Third-order coefficients, v3, are nonzero and almost independent of centrality. These new results on v2 and v3, combined with previously published results on yields, are compared to model calculations that provide yields and asymmetries in the same framework. Those models are challenged to explain simultaneously the observed large yield and large azimuthal anisotropies.
We present measurements of bulk properties of the matter produced in Au+Au collisions at $\sqrt{s}$$_ {NN}$= 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons (π±, K±, p, and $\bar{p}$) from ...the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity (| y | < 0.1) results for multiplicity densities dN / dy, average transverse momenta $\langle$pT$\rangle$, and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.
Global polarization of Λ hyperons has been measured to be of the order of a few tenths of a percent in Au+Au collisions at √SNN = 200 GeV, with no significant difference between Λ and Λ¯. These new ...results reveal the collision energy dependence of the global polarization together with the results previously observed √SNN = 7.7 – 62.4 GeV and indicate noticeable vorticity of the medium created in non-central heavy-ion collisions at the highest RHIC collision energy.
The cross section and transverse single-spin asymmetries of μ− and μ+ from open heavy-flavor decays in polarized p+p collisions at s=200 GeV were measured by the PHENIX experiment during 2012 at the ...Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at s=200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (1.4<|y|<2.0) over the transverse momentum range of 1.25<pT<7 GeV/c for the cross section and 1.25<pT<5 GeV/c for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
Inclusive transverse momentum spectra of eta mesons have been measured within p(T)=2-10 GeV/c at midrapidity by the PHENIX experiment in Au+Au collisions at root s(NN) = 200 GeV. In central Au+Au the ...eta yields are significantly suppressed compared to peripheral Au+Au, d+Au, and p+p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi(0). The ratio of eta to pi(0) spectra at high p(T) amounts to 0.40 < R-eta/pi(0)< 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e(+)e(-) collisions.
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