31,920 research outputs found
Parity-expanded variational analysis for non-zero momentum
In recent years, the use of variational analysis techniques in lattice QCD
has been demonstrated to be successful in the investigation of the rest-mass
spectrum of many hadrons. However, due to parity-mixing, more care must be
taken for investigations of boosted states to ensure that the projected
correlation functions provided by the variational analysis correspond to the
same states at zero momentum. In this paper we present the Parity-Expanded
Variational Analysis (PEVA) technique, a novel method for ensuring the
successful and consistent isolation of boosted baryons through a parity
expansion of the operator basis used to construct the correlation matrix.Comment: 9 pages, 3 figures, 1 tabl
Probing the proton and its excitations in full QCD
We present a first look at the application of variational techniques for the
extraction of the electromagnetic properties of an excited nucleon system. In
particular, we include preliminary results for charge radii and magnetic
moments of the proton, its first even-parity excitation and the .Comment: 7 pages, 5 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
Transition of in Lattice QCD
With the ongoing experimental interest in exploring the excited hadron
spectrum, evaluations of the matrix elements describing the formation and decay
of such states via radiative processes provide us with an important connection
between theory and experiment. In particular, determinations obtained via the
lattice allow for a direct comparison of QCD-expectation with experimental
observation. Here we present the first light quark determination of the transition form factor from lattice QCD using dynamical
quarks. Using the PACS-CS 2+1 flavour QCD ensembles we are able to obtain
results across a range of masses, to the near physical value of
MeV. An important aspect of our approach is the use of variational methods to
isolate the desired QCD eigenstate. For low-lying states, such techniques
facilitate the removal of excited state contributions. In principle the method
enables one to consider arbitrary eigenstates. We find our results are in
accord with the non-relativistic quark model for heavy masses. In moving
towards the light-quark regime we observe an interesting quark mass dependence,
contrary to the quark model expectation. Comparison of our light-quark result
with experimental determinations highlights a significant discrepancy
suggesting that disconnected sea-quark loop contributions may play a
significant role in fully describing this process.Comment: 9 pages, 5 figures and 1 tabl
Observations of the Biology of \u3ci\u3ePhasgonophora Sulcata\u3c/i\u3e (Hymenoptera: Chalcididae), a Larval Parasitoid of the Twolined Chestnut Borer, \u3ci\u3eAgrilus Bilineatus\u3c/i\u3e (Coleoptera: Buprestidae), in Wisconsin
Phasgorzophora sulcata Westwood was the principal larval parasitoid of Agrilus bilineatus (Weber) during a study conducted in a natural oak-hardwood forest in the Kettle Moraine State Forest, Jefferson County, Wisconsin. Mean percent larval parasitism was 10.5%. Mean A. bilineatus and P. sulcata densities were, respectively, 53.0 and 6.1 adults per square meter of bark. The theoretical developmental threshold temperatures for over- wintering A. bilineatus and P. sulcata larvae were 17.8 and 19.l0C, respectively. The peak flight period of P. sulcata (9 July 1980) occurred ca. 3 weeks after the A. bilineatus peak flight (18 June 1980) at about the time of peak A. bilineatus egg eclosion. The P. sulcata sex ratios (malexfemales) for laboratory-reared and field-captured adults were 1:1.35 and 1:3.22, respectively
Isolating the \Lambda(1405) in Lattice QCD
The negative-parity ground state of the \Lambda{} baryon lies surprisingly
low in mass. At 1405.1 MeV, it lies lower than the negative-parity ground state
nucleon, even though it has a valence strange quark. Using the PACS-CS
(2+1)-flavour full-QCD ensembles available through the ILDG, we employ a
variational analysis using source and sink smearing to isolate this elusive
state. We find three low-lying odd-parity states, and for the first time
reproduce the correct level ordering with respect to the nearby scattering
thresholds.Comment: 4 pages, 7 figure
Extracting Low-Lying Lambda Resonances Using Correlation Matrix Techniques
The lowest-lying negative-parity state of the Lambda is investigated in
(2+1)-flavour full-QCD on the PACS-CS configurations made available through the
ILDG. We show that a variational analysis using multiple source and sink
smearings can extract a state lying lower than that obtained by using a
standard fixed smeared source and sink operator alone.Comment: 3 pages, 1 figure, submitted to the proceedings of T(R)OPICAL QCD II,
Cairns, Australia, 201
Forecasting the Yield Curve for the Euro Region
This paper compares the forecast precision of the Functional Signal plus Noise (FSN), the Dynamic Nelson-Siegel (DL), and a random walk model. The empirical results suggest that both outperform the random walk at short horizons (one-month) and that the the FSN model outperforms the DL at the one-month forecasting horizon. The conclusions provided in this paper are important for policy makers, fixed income portfolio managers, financial institutions and academics.
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