2,448 research outputs found

    Ground state charmed meson spectra for N_f=2+1+1

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    We present a preliminary study of the charmed meson spectra using the electrically neutral subset of the new Budapest-Marseille-Wuppertal N_f=2+1+1 gauge configurations that utilise the 3-HEX smeared clover action. The analysis is performed with a focus on the hyperfine splitting.Comment: 7 pages, 5 figures; presentation given at the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14 - 18 July 2015, Kobe, Japa

    Retroviral Genotoxicity

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    Nucleon axial form factors from two-flavour Lattice QCD

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    We present preliminary results on the axial form factor GA(Q2)G_A(Q^2) and the induced pseudoscalar form factor GP(Q2)G_P(Q^2) of the nucleon. A systematic analysis of the excited-state contributions to form factors is performed on the CLS ensemble `N6' with mπ=340 MeVm_\pi = 340 \ \text{MeV} and lattice spacing a∌0.05 fma \sim 0.05 \ \text{fm}. The relevant three-point functions were computed with source-sink separations ranging from ts∌0.6 fmt_s \sim 0.6 \ \text{fm} to $t_s \sim \ 1.4 \ \text{fm}$. We observe that the form factors suffer from non-trivial excited-state contributions at the source-sink separations available to us. It is noted that naive plateau fits underestimate the excited-state contributions and that the method of summed operator insertions correctly accounts for these effects.Comment: 7 pages, 12 figures; talk presented at Lattice 2014 -- 32nd International Symposium on Lattice Field Theory, 23-28 June, 2014, Columbia University New York, N

    Nucleon electromagnetic form factors in two-flavour QCD

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    We present results for the nucleon electromagnetic form factors, including the momentum transfer dependence and derived quantities (charge radii and magnetic moment). The analysis is performed using O(a) improved Wilson fermions in Nf=2 QCD measured on the CLS ensembles. Particular focus is placed on a systematic evaluation of the influence of excited states in three-point correlation functions, which lead to a biased evaluation, if not accounted for correctly. We argue that the use of summed operator insertions and fit ans\"atze including excited states allow us to suppress and control this effect. We employ a novel method to perform joint chiral and continuum extrapolations, by fitting the form factors directly to the expressions of covariant baryonic chiral effective field theory. The final results for the charge radii and magnetic moment from our lattice calculations include, for the first time, a full error budget. We find that our estimates are compatible with experimental results within their overall uncertainties.Comment: 22 pages, 10 figures, citations modifie

    The high-lying 6^6Li levels at excitation energy around 21 MeV

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    The 3^3H+3^3He cluster structure in 6^6Li was investigated by the 3^3H(α\alpha,3^3H 3^3He)n kinematically complete experiment at the incident energy EαE_\alpha = 67.2 MeV. We have observed two resonances at Ex∗E_x^* = 21.30 and 21.90 MeV which are consistent with the 3^3He(3^3H, Îł\gamma)6^6Li analysis in the Ajzenberg-Selove compilation. Our data are compared with the previous experimental data and the RGM and CSRGM calculations.Comment: 12 pages, 6 figures. Accepted for publication in J. Phys. Soc. Jp

    The Changing Eigenfrequency Continuum during Geomagnetic Storms:Implications for Plasma Mass Dynamics and ULF Wave Coupling

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    Geomagnetic storms are one of the most energetic space weather phenomena. Previous studies have shown that the eigenfrequencies of ultralow frequency (ULF) waves on closed magnetic field lines in the inner magnetosphere decrease during storm times. This change suggests either a reduction in the magnetic field strength and/or an increase in its plasma mass density distribution. We investigate the changes in local eigenfrequencies by applying a superposed multiple‐epoch analysis to cross‐phase spectra from 132 geomagnetic storms. Six ground magnetometer pairs are used to investigate variations from approximately 3 4, the eigenfrequencies decrease by as much as 50% relative to their quiet time values. Both a decrease in magnetic field strength and an increase in plasma mass density, in some locations by more than a factor of 2, are responsible for this reduction. The enhancement of the ring current and an increase in oxygen ion density could explain these observations. At L < 4, the eigenfrequencies increase due to the decrease in plasma mass density caused by plasmaspheric erosion
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