National Geodetic Satellite Program, Part II: Smithsonian Astrophysical Observatory

A sequence of advances in the determination of geodetic parameters presented by the Smithsonian Astrophysical Observatory are described. A Baker-Nunn photographic system was used in addition to a ruby-laser ranging system to obtain data for refinement of geodetic parameters. A summary of the data employed to: (1) derive coordinates for the locations of various tracking stations; and (2) determine the gravitational potential of the earth, is presented

Centrality dependence of pi(+/-), K-+/-, p, and (p)over-bar production from root(NN)-N-S = 130 GeV Au+Au collisions at RHIC

Identified pi(+/-), K+/-, p, and (p) over bar transverse momentum spectra at midrapidity in root s(NN) = 130 GeV Au + Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. Within errors, all midrapidity particle yields per participant are found to be increasing with the number of participating nucleons. There is an indication that K+/-, p, and (p) over bar yields per participant increase faster than the pi(+/-) yields. In central collisions at high transverse momenta (p(T) greater than or similar to 2 GeV/c), (p) over bar and p yields are comparable to the pi(+/-) yields

Net charge fluctuations in Au+Au interactions root s(NN)=130 GeV

Data from Au+Au interactions at s(NN)=130 GeV, obtained with the PHENIX detector at the Relativistic Heavy-Ion Collider, are used to investigate local net charge fluctuations among particles produced near midrapidity. According to recent suggestions, such fluctuations may carry information from the quark-gluon plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays

Transverse-mass dependence of two-pion correlations in Au+Au collisions at root(NN)-N-S=130 GeV

Two-pion correlations in roots(NN) = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at roots(NN) = 4.1 , 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R-out/R-side) is consistent with unity and independent of k(T)

Event-by-event fluctuations in mean p(T) and mean e(T) in root s(NN)=130 GeV Au+Au collisions

Distributions of event-by-event fluctuations of the mean transverse momentum and mean transverse energy near mid-rapidity have been measured in Au+Au collisions at roots(NN)=130 GeV at the Relativistic Heavy-Ion Collider. By comparing the distributions to what is expected for statistically independent particle emission, the magnitude of nonstatistical fluctuations in mean transverse momentum is determined to be consistent with zero. Also, no significant nonrandom fluctuations in mean transverse energy are observed. By constructing a fluctuation model with two event classes that preserve the mean and variance of the semi-inclusive p(T) or e(T) spectra, we exclude a region of fluctuations in root s(NN)=130 GeV Au+Au collisions

Centrality dependence of charged particle multiplicity in Au-Au collisions at root(S)NN=130 GeV

We present results for the charged-particle multiplicity distribution at midrapidity in Au-Au collisions at roots(NN) = 130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find dN(ch)/d eta (|eta =0) = 622 +/- 1(stat) +/- 41(syst). The results, analyzed as a function of centrality show a steady rise of the particle density per participating nucleon with centrality

Measurement of the midrapidity transverse energy distribution from root(NN)-N-S=130 GeV Au+Au collisions at RHIC

The first measurement of energy produced transverse to the beam direction at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is presented. The midrapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that ⟨ET⟩/⟨Nch⟩ remains relatively constant as a function of centrality. The energy density calculated via Bjorken’s prescription for the 2% most central Au+Au collisions at √sNN=130GeV is at least εBj=4.6 GeV/fm3, which is a factor of 1.6 larger than found at √sNN=17.2 GeV ( Pb+Pb at CERN)

Measurement of single electrons and implications for charm production in Au+Au collisions at root(NN)-N-S=130 GeV

Transverse momentum spectra of electrons from Au+Au collisions at roots(NN) = 130 GeV have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal dN(e)/dy for p(T) \u3e 0.8 GeV/c is 0.025 +/- 0.004(stat) +/- 0.010( syst) in central collisions, and the corresponding charm cross section is 380 +/- 60(stat) +/- 200(syst ) mu b per binary nucleon-nucleon collision

Suppression of hadrons with large transverse momentum in central Au+Au collisions at root s(NN)=130 GeV

Transverse momentum spectra for charged hadrons and for neutral pions in the range 1 Gev/c \u3c P - T \u3c 5 GeV/c have been measured by the PHENIX experiment at RHIC in Au + Au collisions at root S(NN) = 130 GeV. At high p(T) the spectra from peripheral nuclear collisions are consistent with scaling the spectra from p + p collisions by the average number of binary nucleon-nucleon collisions. The spectra from central collisions are significantly suppressed when compared to the binary-scaled p + p expectation, and also when compared to similarly binary-scaled peripheral collisions, indicating a novel nuclear-medium effect in central nuclear collisions at RHIC energies

Centrality dependence of the high (PT) charged hadron suppression in Au+Au collisions at root s(NN)=130 GeV

PHENIX has measured the centrality dependence of charged hadron p(T) spectra from Au + Au collisions at root(s)NN = 130 GeV The truncated mean p(T) decreases with centrality for p(T) \u3e 2 GeV/c, indicating an apparent reduction of the contribution from hard scattering to high p(T) hadron production. For central collisions the yield at high p(T) is shown to be suppressed compared to binary nucleon-nucleon collision scaling of p + p, data. This suppression is monotonically increasing with centrality, but most of the change occurs below 30% centrality, i.e., for collisions with less than similar to 140 participating nucleons. The observed p(T) and centrality dependence is consistent with the particle production predicted by models including hard scattering and subsequent energy loss of the scattered partons in the dense matter created in the collisions