Automation of orbit determination functions for National Aeronautics and Space Administration (NASA)-supported satellite missions

The Flight Dynamics Facility (FDF) at Goddard Space Flight Center (GSFC) provides spacecraft trajectory determination for a wide variety of National Aeronautics and Space Administration (NASA)-supported satellite missions, using the Tracking Data Relay Satellite System (TDRSS) and Ground Spaceflight and Tracking Data Network (GSTDN). To take advantage of computerized decision making processes that can be used in spacecraft navigation, the Orbit Determination Automation System (ODAS) was designed, developed, and implemented as a prototype system to automate orbit determination (OD) and orbit quality assurance (QA) functions performed by orbit operations. Based on a machine-resident generic schedule and predetermined mission-dependent QA criteria, ODAS autonomously activates an interface with the existing trajectory determination system using a batch least-squares differential correction algorithm to perform the basic OD functions. The computational parameters determined during the OD are processed to make computerized decisions regarding QA, and a controlled recovery process isactivated when the criteria are not satisfied. The complete cycle is autonomous and continuous. ODAS was extensively tested for performance under conditions resembling actual operational conditions and found to be effective and reliable for extended autonomous OD. Details of the system structure and function are discussed, and test results are presented

Ground state properties of heavy alkali halides

We extend previous work on alkali halides by calculations for the heavy-atom species RbF, RbCl, LiBr, NaBr, KBr, RbBr, LiI, NaI, KI, and RbI. Relativistic effects are included by means of energy-consistent pseudopotentials, correlations are treated at the coupled-cluster level. A striking deficiency of the Hartree-Fock approach are lattice constants deviating by up to 7.5 % from experimental values which is reduced to a maximum error of 2.4 % by taking into account electron correlation. Besides, we provide ab-initio data for in-crystal polarizabilities and van der Waals coefficients.Comment: accepted by Phys. Rev.

Ground-state properties of rutile: electron-correlation effects

Electron-correlation effects on cohesive energy, lattice constant and bulk compressibility of rutile are calculated using an ab-initio scheme. A competition between the two groups of partially covalent Ti-O bonds is the reason that the correlation energy does not change linearly with deviations from the equilibrium geometry, but is dominated by quadratic terms instead. As a consequence, the Hartree-Fock lattice constants are close to the experimental ones, while the compressibility is strongly renormalized by electronic correlations.Comment: 1 figure to appear in Phys. Rev.

Electronic structure of the molecule based magnet Cu PM(NO3)2 (H2O)2

We present density functional calculations on the molecule based S=1/2 antiferromagnetic chain compound Cu PM(NO3)2 (H2O)2; PM = pyrimidine. The properties of the ferro- and antiferromagnetic state are investigated at the level of the local density approximation and with the hybrid functional B3LYP. Spin density maps illustrate the exchange path via the pyrimidine molecule which mediates the magnetism in the one-dimensional chain. The computed exchange coupling is antiferromagnetic and in reasonable agreement with the experiment. It is suggested that the antiferromagnetic coupling is due to the possibility of stronger delocalization of the charges on the nitrogen atoms, compared to the ferromagnetic case. In addition, computed isotropic and anisotropic hyperfine interaction parameters are compared with recent NMR experiments

Limits on τ lepton-flavor violating decays into three charged leptons

A search for the neutrinoless, lepton-flavor violating decay of the τ lepton into three charged leptons has been performed using an integrated luminosity of 468  fb^(-1) collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8–3.3)×10^(-8) at 90% confidence level

Analysis of the D^+ → K^-π^+e^+ν_e decay channel

Using 347.5  fb^(-1) of data recorded by the BABAR detector at the PEP-II electron-positron collider, 244×10^3 signal events for the D^+ → K^-π^+e^+ν_e decay channel are analyzed. This decay mode is dominated by the K̅ ^*(892)^0 contribution. We determine the K̅ ^*(892)^0 parameters: m_(K^*(892)^0)=(895.4±0.2±0.2)  MeV/c^2, Γ_(K^*(892)^0)=(46.5±0.3±0.2)  MeV/c^2, and the Blatt-Weisskopf parameter r_(BW) =2.1±0.5±0.5  (GeV/c)^-1, where the first uncertainty comes from statistics and the second from systematic uncertainties. We also measure the parameters defining the corresponding hadronic form factors at q^2 = 0 (r_V = ^(V(0))/_(A1(0)) = 1.463 ± 0.017 ± 0.031, r_2 = _(A1(0)) ^(A2(0))= 0.801±0.020±0.020) and the value of the axial-vector pole mass parametrizing the q^2 variation of A_1 and A_2: m_A=(2.63±0.10±0.13)  GeV/c^2. The S-wave fraction is equal to (5.79±0.16±0.15)%. Other signal components correspond to fractions below 1%. Using the D^+ → K^-π^+π^+ channel as a normalization, we measure the D^+ semileptonic branching fraction: B(D^+ → K^-π^+e^+ν_e)=(4.00±0.03±0.04±0.09)×10^(-2), where the third uncertainty comes from external inputs. We then obtain the value of the hadronic form factor A_1 at q^2=0: A_1(0)=0.6200±0.0056±0.0065±0.0071. Fixing the P-wave parameters, we measure the phase of the S wave for several values of the Kπ mass. These results confirm those obtained with Kπ production at small momentum transfer in fixed target experiments

Measurement of the γγ^*→η_c transition form factor

We study the reaction e^+e^-→e^+e^-η_c, η_c→K_SK^±π^∓ and obtain η_c mass and width values 2982.2±0.4±1.6  MeV/c^2 and 31.7±1.2±0.8  MeV, respectively. We find Γ(η_c→γγ)B(ηc→KK π)=0.374±0.009±0.031  keV, and measure the γγ^*→η_c transition form factor in the momentum transfer range from 2 to 50  GeV^2. The analysis is based on 469  fb^(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e^+e^- center-of-mass energies near 10.6 GeV

Observation of η_c(1S) and η_c(2S) decays to K^+K^-π^+π^-π^0 in two-photon interactions

We study the processes γγ→K_S^0K^±π^∓ and γγ→K^+K^-π^+π-π^0 using a data sample of 519.2fb^(-1) recorded by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at center-of-mass energies near the Υ(nS) (n=2, 3, 4) resonances. We observe the η_c(1S), χ_(c0)(1P) and η_c(2S) resonances produced in two-photon interactions and decaying to K^+K^-π^+π^-π^0, with significances of 18.1, 5.4 and 5.3 standard deviations (including systematic errors), respectively, and report 4.0σ evidence of the χ_(c2)(1P) decay to this final state. We measure the η_c(2S) mass and width in K_S^0K^±π^∓ decays, and obtain the values m(η_c(2S))=3638.5±1.5±0.8  MeV/c^2 and Γ(η_c(2S))=13.4±4.6±3.2  MeV, where the first uncertainty is statistical and the second is systematic. We measure the two-photon width times branching fraction for the reported resonance signals, and search for the χ_(c2)(2P) resonance, but no significant signal is observed

Evidence for the decay X(3872)→J/ψω

We present a study of the decays B^(0,+)→J/ψπ^+π^-π^0K^(0,+), using 467×10^6 BB[overbar] pairs recorded with the BABAR detector. We present evidence for the decay mode X(3872)→J/ψω, with product branching fractions B(B^+→X(3872)K^+)×B(X(3872)→J/ψω)=[0.6±0.2(stat)±0.1(syst)]×10^(-5), and B(B^0→X(3872)K^0)×B(X(3872)→J/ψω)=[0.6±0.3(stat)±0.1(syst)]×10^(-5). A detailed study of the π^+π^-π^0 mass distribution from X(3872) decay favors a negative-parity assignment