共查询到20条相似文献,搜索用时 15 毫秒
1.
Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with
the data recorded by the DELPHI detector at LEP. From measurements of the inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been
used to determine parameters which enter into the extraction of |Vcb| from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are:
and include corrections at order 1/mb3. Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of |Vcb| is obtained:
Received: 26 April 2005, Revised: 16 September 2005, Published online: 16 November 2005 相似文献
2.
Morten L. Laursen Mark A. Samuel Ashok K. Ray 《Zeitschrift fur Physik C Particles and Fields》1980,6(1):3-6
The contribution to the sixth-order muon anomaly from second-order electron vacuum polarization is determined analytically to orderm e/m μ. The result, including the contributions from graphs containing proper and improper fourth-order electron vacuum polarization subgraphs, is $$\begin{gathered} \left( {\frac{\alpha }{\pi }} \right)^3 \left\{ {\frac{2}{9}\log ^2 } \right.\frac{{m_\mu }}{{m_e }} + \left[ {\frac{{31}}{{27}}} \right. + \frac{{\pi ^2 }}{9} - \frac{2}{3}\pi ^2 \log 2 \hfill \\ \left. { + \zeta \left( 3 \right)} \right]\log \frac{{m_\mu }}{{m_e }} + \left[ {\frac{{1075}}{{216}}} \right. - \frac{{25}}{{18}}\pi ^2 + \frac{{5\pi ^2 }}{3}\log 2 \hfill \\ \left. { - 3\zeta \left( 3 \right) + \frac{{11}}{{216}}\pi ^4 - \frac{2}{9}\pi ^2 \log ^2 2 - \frac{1}{9}log^4 2 - \frac{8}{3}a_4 } \right] \hfill \\ + \left[ {\frac{{3199}}{{1080}}\pi ^2 - \frac{{16}}{9}\pi ^2 \log 2 - \frac{{13}}{8}\pi ^3 } \right]\left. {\frac{{m_e }}{{m_\mu }}} \right\} \hfill \\ \end{gathered} $$ . To obtain the total sixth-order contribution toa μ?a e, one must add the light-by-light contribution to the above expression. 相似文献
3.
4.
S. G. Karshenboim 《Physics of Particles and Nuclei Letters》2009,6(6):450-454
Oscillations of neutral meson (K
0-$
\overline {K^0 }
$
\overline {K^0 }
, D
0-$
\overline {D^0 }
$
\overline {D^0 }
, and B
0-$
\overline {B^0 }
$
\overline {B^0 }
are extremely sensitive to the meson and antimeson energies at rest. This energy is determined as mc
2—with the corresponding inertial mass—and as the energy of gravitational interaction. Assuming that the CPT theorem is correct
for inertial masses and estimating the gravitational potential for which the largest contribution originates from the field
of the galaxy center, we obtain the estimate from experimental data on K
0-$
\overline {K^0 }
$
\overline {K^0 }
oscillations:
$
\left| {\left( {\frac{{m_g }}
{{m_i }}} \right)_{K^0 } - \left( {\frac{{m_g }}
{{m_i }}} \right)_{\overline {K^0 } } } \right| \leqslant 8 \times 10^{ - 13} , at C.L. = 90\%
$
\left| {\left( {\frac{{m_g }}
{{m_i }}} \right)_{K^0 } - \left( {\frac{{m_g }}
{{m_i }}} \right)_{\overline {K^0 } } } \right| \leqslant 8 \times 10^{ - 13} , at C.L. = 90\%
相似文献
5.
E. A. Kataeva A. D. Bozhko S. V. Demishev 《Bulletin of the Lebedev Physics Institute》2010,37(11):347-351
The conductivity of carbon films grown by polymethylphenylsiloxane vapor decomposition in stimulated dc discharge plasma was
studied. It is found that the Mott hopping conductivity $
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
$
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
is characteristic of the samples under study in the temperature range of 80–400 K in the electric field E to 5 · 104 V/cm. An analysis of the pre-exponential factor σ
0(T) = σ
00(T
0)T
α allowed the conclusion that the hopping transport is most adequately described in the model with the exponential energy dependence
of the density of localized states for which α = −1/2 and the universal relation ln σ
00 −T
01/4 0 is valid, which is satisfied in the range where the parameter σ
00 varies by eight orders of magnitude. 相似文献
6.
The concentration of lithium ions in the cathode of lithium ion cells has been obtained by solving the materials balance equation $$\frac{{\partial c}}{{\partial t}} = \varepsilon ^{1/2} D\frac{{\partial ^2 c}}{{\partial x^2 }} + \frac{{aj_n (1--t_ + )}}{\varepsilon }$$ by Laplace transform. On the assumption that the cell is fully discharged when there are zero lithium ions at the current collector of the cathode, the discharge timet d is obtained as $$\tau = \frac{{r^2 }}{{\pi ^2 \varepsilon ^{1/2} }}\ln \left[ {\frac{{\pi ^2 }}{{r^2 }}\left( {\frac{{\varepsilon ^{1/2} }}{J} + \frac{{r^2 }}{6}} \right)} \right]$$ which, when substituted into the equationC=It d /M, whereI is the discharge current andM is the mass of the separator and positive electrode, an analytical expression for the specific capacity of the lithium cell is given as $$C = \frac{{IL_c ^2 }}{{\pi {\rm M}D\varepsilon ^{1/2} }}\ln \left[ {\frac{{\pi ^2 }}{2}\left( {\frac{{FDc_0 \varepsilon ^{3/2} }}{{I(1 - t_ + )L_c }} + \frac{1}{6}} \right)} \right]$$ 相似文献
7.
Using the OPAL detector at LEP, the running of the effective QED coupling α(t) is measured for space-like momentum transfer from the angular distribution of small-angle Bhabha scattering. In an almost
ideal QED framework, with very favourable experimental conditions, we obtain:
where the first error is statistical, the second is the experimental systematic and the third is the theoretical uncertainty.
This agrees with current evaluations of α(t). The null hypothesis that α remains constant within the above interval of -t is excluded with a significance above 5σ. Similarly, our results are inconsistent at the level of 3σ with the hypothesis
that only leptonic loops contribute to the running. This is currently the most significant direct measurement where the running
α(t) is probed differentially within the measured t range.
Received: 2 March 2005, Revised: 30 August 2005, Published online: 3 November 2005 相似文献
8.
D. J. Broadhurst 《Zeitschrift fur Physik C Particles and Fields》1992,54(4):599-606
Using algebraic methods, we find the three-loop relation between the bare and physical couplings of one-flavourD-dimensional QED, in terms of Γ functions and a singleF 32 series, whose expansion nearD=4 is obtained, by wreath-product transformations, to the order required for five-loop calculations. Taking the limitD→4, we find that the \(\overline {MS} \) coupling \(\bar \alpha (\mu )\) satisfies the boundary condition $$\begin{gathered} \frac{{\bar \alpha (m)}}{\pi } = \frac{\alpha }{\pi } + \frac{{15}}{{16}}\frac{{\alpha ^3 }}{{\pi ^3 }} + \left\{ {\frac{{11}}{{96}}\zeta (3) - \frac{1}{3}\pi ^2 \log 2} \right. \hfill \\ \left. { + \frac{{23}}{{72}}\pi ^2 - \frac{{4867}}{{5184}}} \right\}\frac{{\alpha ^4 }}{{\pi ^4 }} + \mathcal{O}(\alpha ^5 ), \hfill \\ \end{gathered} $$ wherem is the physical lepton mass and α is the physical fine structure constant. Combining this new result for the finite part of three-loop on-shell charge renormalization with the recently revised four-loop term in the \(\overline {MS} \) β-function, we obtain $$\begin{gathered} \Lambda _{QED}^{\overline {MS} } \approx \frac{{me^{3\pi /2\alpha } }}{{(3\pi /\alpha )^{9/8} }}\left( {1 - \frac{{175}}{{64}}\frac{\alpha }{\pi } + \left\{ { - \frac{{63}}{{64}}\zeta (3)} \right.} \right. \hfill \\ \left. { + \frac{1}{2}\pi ^2 \log 2 - \frac{{23}}{{48}}\pi ^2 + \frac{{492473}}{{73728}}} \right\}\left. {\frac{{\alpha ^2 }}{{\pi ^2 }}} \right), \hfill \\ \end{gathered} $$ at the four-loop level of one-flavour QED. 相似文献
9.
The phenomenon of the diffusion of proton and deuteron in a single crystal of magnesium aluminate spinel was studied by infrared
absorption. The chemical diffusion coefficient of proton was determined by the relaxation time of the absorption intensity
upon the substitution of deuteron with proton. The temperature dependence of the chemical diffusion coefficient of proton
for was expressed as . The chemical diffusion coefficient of proton was found to be independent of the composition of spinel and of the atmosphere.
Paper presented at the 11th Euro Conference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15 2007. 相似文献
10.
For Lax-pair isospectral deformations whose associated spectrum, for given initial data, consists of the disjoint union of a finitely denumerable discrete spectrum (solitons) and a continuous spectrum (continuum), the matrix Riemann–Hilbert problem approach is used to derive the leading-order asymptotics as
of solutions
to the Cauchy problem for the defocusing nonlinear Schrödinger equation (
NLSE),
, with finite-density initial data
11.
12.
P. Abreu et al. 《The European Physical Journal C - Particles and Fields》1999,9(3):367-381
The b[`b]\mbox{b}\bar{\mbox{b}} forward-backward asymmetry has been determined from the average charge flow measured in a sample of 3,500,000 hadronic Z decays collected with the DELPHI detector in 1992–1995. The measurement is performed in an enriched b[`b]\mbox{b}\bar{\mbox{b}} sample selected using an impact parameter tag and results in the following values for the b[`b]\mbox{b}\bar{\mbox{b}} forward-backward asymmetry: $
\begin{gathered}
A_{FB}^{b\bar b} \left( {89.55 GeV} \right) = 0.068 \pm 0.018 \left( {stat.} \right) \pm 0.0013\left( {syst.} \right) \hfill \\
A_{FB}^{b\bar b} \left( {91.26 GeV} \right) = 0.0982 \pm 0.0047 \left( {stat.} \right) \pm 0.0016\left( {syst.} \right) \hfill \\
A_{FB}^{b\bar b} \left( {92.94 GeV} \right) = 0.123 \pm 0.016 \left( {stat.} \right) \pm 0.0027\left( {syst.} \right) \hfill \\
\end{gathered}
$
\begin{gathered}
A_{FB}^{b\bar b} \left( {89.55 GeV} \right) = 0.068 \pm 0.018 \left( {stat.} \right) \pm 0.0013\left( {syst.} \right) \hfill \\
A_{FB}^{b\bar b} \left( {91.26 GeV} \right) = 0.0982 \pm 0.0047 \left( {stat.} \right) \pm 0.0016\left( {syst.} \right) \hfill \\
A_{FB}^{b\bar b} \left( {92.94 GeV} \right) = 0.123 \pm 0.016 \left( {stat.} \right) \pm 0.0027\left( {syst.} \right) \hfill \\
\end{gathered}
The b[`b]\mbox{b}\bar{\mbox{b}} charge separation required for this analysis is directly measured in the b tagged sample, while the other charge separations are obtained from a fragmentation model precisely calibrated to data. The effective weak mixing angle is deduced from the measurement to be: $
sin^2 \theta _{eff}^1 = 0.23186 \pm 0.00083
$
sin^2 \theta _{eff}^1 = 0.23186 \pm 0.00083
相似文献
13.
An algorithm has been proposed to build an estimate of the half-life of a “daughter” nucleus in case, when it is unknown,
which nucleus is its “mother” (“indefinite start time”). For a decay of the “mother” at an instant t we can determine P—a probability of such a decay, if we assume that each “mother”, which has been decayed before t has equal chances to be “mother” of this “daughter”:
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