1,226 research outputs found
Bottonium mass - evaluation using renormalon cancellation
We present a method of calculating the bottonium mass M[Upsilon(1S)] = [2 mb
+ E(b barb)]. The binding energy is separated into the soft and ultrasoft
components E(b barb)=[E(s)+E(us)] by requiring the reproduction of the correct
residue parameter value of the renormalon singularity for the renormalon
cancellation in the sum [2 mb + E(s)]. The Borel resummation is then performed
separately for (2 mb) and E(s), using the infrared safe MSbar mass [bar mb] as
input. E(us) is estimated. Comparing the result with the measured value of
M[Upsilon(1S)], the extracted value of the quark mass is [bar mb](mu=[bar mb])
= 4.241 +- 0.068 GeV (for the central value alphas(MZ)=0.1180). This value of
[bar mb] is close to the earlier values obtained from the QCD spectral sum
rules, but lower than from pQCD evaluations without the renormalon structure
for heavy quarkonia.Comment: 4 pages, uses espcrc2.sty, presented at QCD0
Infrared renormalons and analyticity structure in pQCD
Relation between the infrared renormalons, the Borel resummation
prescriptions, and the analyticity structure of Green functions in perturbative
QCD (pQCD) is investigated. A specific recently suggested Borel resummation
prescription resulted in the Principal Value and an additional power-suppressed
correction that is consistent with the Operator Product Expansion. Arguments
requiring the finiteness of the result for any power coefficient of the leading
infrared renormalon, and the consistency in the case of the absence of that
renormalon, require that this prescription be modified. The apparently most
natural modification leads to the result represented by the Principal Value.
The analytic structure of the amplitude in the complex coupling plane, obtained
in this way, is consistent with that obtained in the literature by other
methods.Comment: 6 pages, revtex4, 1 eps-figure; improved version - the paragraph
containing Eqs.(18) and (19) is new, as well as the next paragraph; the Title
modified; some references added; version to appear in Phys. Rev.
The Importance of Reporting Housing and Husbandry in Rat Research
In 1963, the National Institutes of Health (NIH) first issued guidelines for animal housing and husbandry. The most recent 2010 revision emphasizes animal care âin ways judged to be scientifically, technically, and humanely appropriateâ (National Institutes of Health, 2010, p. XIII). The goal of these guidelines is to ensure humanitarian treatment of animals and to optimize the quality of research. Although these animal care guidelines cover a substantial amount of information regarding animal housing and husbandry, researchers generally do not report all these variables (see Table âTable1).1). The importance of housing and husbandry conditions with respect to standardization across different research laboratories has been debated previously (Crabbe et al., 1999; Van Der Staay and Steckler, 2002; Wahlsten et al., 2003; Wolfer et al., 2004; Van Der Staay, 2006; Richter et al., 2010, 2011). This paper focuses on several animal husbandry and housing issues that are particularly relevant to stress responses in rats, including transportation, handling, cage changing, housing conditions, light levels and the lightâdark cycle. We argue that these key animal housing and husbandry variables should be reported in greater detail in an effort to raise awareness about extraneous experimental variables, especially those that have the potential to interact with the stress response
Energy deposited by neutrons and gamma rays in the cryogenic system of SISSI
International audienc
Potential sources of sexuality in Cenchrus ciliaris L.: Seed fertility, environment and its implication in plant breeding
PosterCenchrus ciliaris L. is an aposporic and pseudogamous apomictic species, and fully sexual plants are very rare or absent. Fertility, which seems to be influenced by environmental factors, is a character of interest for selection of putative maternal sources for hybridizations.Instituto de FisiologĂa y Recursos GenĂ©ticos VegetalesFil: Sanchez, Miguel Alejandro. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Unidad de Estudios Agropecuarios (UDEA); ArgentinaFil: Sanchez, Miguel Alejandro. Instituto Nacional de TecnologĂa Agropecuaria (INTA). Instituto de FisiologĂa y Recursos GenĂ©ticos Vegetales; ArgentinaFil: Bruno, C. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Agropecuarias. EstadĂstica y BiometrĂa; ArgentinaFil: Bruno, C. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Unidad de FitopatologĂa y ModelizaciĂłn AgrĂcola (UFyMA); ArgentinaFil: Grunberg, Karina. Instituto Nacional de TecnologĂa Agropecuaria (INTA). Instituto de FisiologĂa y Recursos GenĂ©ticos Vegetales; ArgentinaFil: Grunberg, Karina.Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Unidad de Estudios Agropecuarios (UDEA); ArgentinaFil: Griffa, Sabrina Mariana. Instituto Nacional de TecnologĂa Agropecuaria (INTA). Instituto de FisiologĂa y Recursos GenĂ©ticos Vegetales; ArgentinaFil: Griffa, Sabrina Mariana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Unidad de Estudios Agropecuarios (UDEA); Argentin
Relating Physical Observables in QCD without Scale-Scheme Ambiguity
We discuss the St\"uckelberg-Peterman extended renormalization group
equations in perturbative QCD, which express the invariance of physical
observables under renormalization-scale and scheme-parameter transformations.
We introduce a universal coupling function that covers all possible choices of
scale and scheme. Any perturbative series in QCD is shown to be equivalent to a
particular point in this function. This function can be computed from a set of
first-order differential equations involving the extended beta functions. We
propose the use of these evolution equations instead of perturbative series for
numerical evaluation of physical observables. This formalism is free of
scale-scheme ambiguity and allows a reliable error analysis of higher-order
corrections. It also provides a precise definition for as the pole in the associated 't Hooft scheme. A concrete application to
is presented.Comment: Plain TEX, 4 figures (available upon request), 22 pages,
DOE/ER/40322-17
Dynamical mass generation by source inversion: Calculating the mass gap of the Gross-Neveu model
We probe the U(N) Gross-Neveu model with a source-term . We
find an expression for the renormalization scheme and scale invariant source
, as a function of the generated mass gap. The expansion of this
function is organized in such a way that all scheme and scale dependence is
reduced to one single parameter d. We get a non-perturbative mass gap as the
solution of . In one loop we find that any physical choice for d
gives good results for high values of N. In two loops we can determine d
self-consistently by the principle of minimal sensitivity and find remarkably
accurate results for N>2.Comment: 13 pages, 3 figures, added referenc
The SISSI project : an intense secondary ion source using superconducting solenoid lenses
International audienceIn order to make a better use of the higher beam intensities soon available at GANIL, a proposal called SISSI was presented in 1989. It consists of a set of two superconducting solenoid lenses of very short focal length (0.6 m). The fist solenoid is used to sharply focus the incoming beam on a fast moving target. The second increases the angular acceptance of the beam line downstream the target for charged reaction products. Calculations show that from a 0.4-mm-diameter beam spot on the target, an acceptance angle of up to 80 mrad will be reached without significant emittance growth due to aberration effects. Technical aspects of that project are presente
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