2,058 research outputs found
Determination of the strange quark mass from Cabibbo-suppressed tau decays with resummed perturbation theory in an effective scheme
We present an analysis of the m_s^2-corrections to Cabibbo-suppressed tau
lepton decays employing contour improved resummation within an effective scheme
which is an essential new feature as compared to previous analyses. The whole
perturbative QCD dynamics of the tau-system is described by the beta-function
of the effective coupling constant and by two gamma-functions for the effective
mass parameters of the strange quark in different spin channels. We analyze the
stability of our results with regard to high-order terms in the perturbative
expansion of the renormalization group functions. A numerical value for the
strange quark mass in the MS scheme is extracted m_s(M_\tau)=130\pm 27_{exp}\pm
9_{th} MeV. After running to the scale 1 GeV this translates into m_s(1
GeV)=176 \pm 37_{exp}\pm 13_{th} MeV.Comment: 32 pages, latex, 4 postscript figures, revised version to appear in
European Physical Journal C, discussion of the choice of the moments added,
some errors correcte
Asymptotic structure of perturbative series for lepton decay observables: corrections
In a previous paper we performed an analysis of asymptotic structure of
perturbation theory series for semileptonic -lepton decays in massless
limit. We extend our analysis to the Cabibbo suppressed decay
modes of the lepton. In particular we address the problem of
corrections to theoretical formulas. The properties of the asymptotic behavior
of the finite order perturbation theory series for the coefficient functions of
the corrections are studied.Comment: 25 page
Studies on the use of radioisotopes for the control of the red palm weevil, Rhynchophorus ferrugineus F., by the sterile insect technique
Mechanism of the fluxional behaviour in (1–5-η-cycloheptadienyl)-(1–5-η-cycloheptatrienyl)iron
Evidence for a 1.2-shift mechanism of the 1-5-η-cycloheptatrienyl moiety with respect to the central iron atom of the title compound is presented together with absolute assignments of the ^(13)C n.m.r. chemical shifts of the C_(7)H_(7) ring. A low-temperature rocking motion of both rings can be frozen out at -70 °C
Keck Imaging of Binary L Dwarfs
We present Keck near-infrared imaging of three binary L dwarf systems, all of
which are likely to be sub-stellar. Two are lithium dwarfs, and a third
exhibits an L7 spectral type, making it the coolest binary known to date. All
have component flux ratios near 1 and projected physical separations between 5
and 10 AU, assuming distances of 18 to 26 pc from recent measurements of
trigonometric parallax. These surprisingly similar binaries represent the sole
detections of companions in ten L dwarf systems which were analyzed in the
preliminary phase of a much larger dual-epoch imaging survey. The detection
rate prompts us to speculate that binary companions to L dwarfs are common,
that similar-mass systems predominate, and that their distribution peaks at
radial distances in accord both with M dwarf binaries and with the radial
location of Jovian planets in our own solar system. To fully establish these
conjectures against doubts raised by biases inherent in this small preliminary
survey, however, will require quantitative analysis of a larger volume-limited
sample which has been observed with high resolution and dynamic range.Comment: LaTex manuscript in 13 pages, 3 postscript figures, Accepted for
publication in the Letters of the Astrophysical Journal; Postscript pre-print
version available at: http://www.hep.upenn.edu/PORG/papers/koerner99a.p
- …