931 research outputs found
Analysis of Gamma Radiation from a Radon Source: Indications of a Solar Influence
This article presents an analysis of about 29,000 measurements of gamma
radiation associated with the decay of radon in a sealed container at the
Geological Survey of Israel (GSI) Laboratory in Jerusalem between 28 January
2007 and 10 May 2010. These measurements exhibit strong variations in time of
year and time of day, which may be due in part to environmental influences.
However, time-series analysis reveals a number of periodicities, including two
at approximately 11.2 year and 12.5 year. We have previously
found these oscillations in nuclear-decay data acquired at the Brookhaven
National Laboratory (BNL) and at the Physikalisch-Technische Bundesanstalt
(PTB), and we have suggested that these oscillations are attributable to some
form of solar radiation that has its origin in the deep solar interior. A
curious property of the GSI data is that the annual oscillation is much
stronger in daytime data than in nighttime data, but the opposite is true for
all other oscillations. This may be a systematic effect but, if it is not, this
property should help narrow the theoretical options for the mechanism
responsible for decay-rate variability.Comment: 9 pages, 21 figure
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Observation of a narrow structure in the pp elastic scattering at T{sub kin} = 2.11 GeV
The angular dependences of the pp elastic scattering analyzing power, spin correlation, depolarization transfer were measured in the angular range from 60{degrees} to 97{degrees} CM at 14 energies between 1.96 and 2 .23 GeV. At fixed angles two maxima were observed in the analyzing Power energy dependence, both below and above 2.11 GeV. Furthermore a rapid decrease Of the spin correlation Parameter at 90{degrees} CM occurs around this energy. The observables allow determination of the absolute values of three nonvanishing pp amplitudes at 90{degrees}. The energy dependence of the spin-single amplitude shows a shoulder centered at 2.11 GeV, while the spin-triplet amplitudes are decreasing functions of energy snowing no evidence of structure. All experimental data are listed in tables and their energy dependences are shown in figures
Bitangential interpolation in generalized Schur classes
Bitangential interpolation problems in the class of matrix valued functions
in the generalized Schur class are considered in both the open unit disc and
the open right half plane, including problems in which the solutions is not
assumed to be holomorphic at the interpolation points. Linear fractional
representations of the set of solutions to these problems are presented for
invertible and singular Hermitian Pick matrices. These representations make use
of a description of the ranges of linear fractional transformations with
suitably chosen domains that was developed in a previous paper.Comment: Second version, corrected typos, changed subsection 5.6, 47 page
Transition Form Factor up to within the Factorization Approach
In the paper, we apply the factorization approach to deal with the
transition form factor in the large recoil
regions. The B-meson wave functions and that include the
three-particle Fock states' contributions are adopted to give a consistent PQCD
analysis of the form factor up to . It has been found that
both the wave functions and can give sizable
contributions to the form factor and should be kept for a better understanding
of the meson decays. Then the contributions from different twist structures
of the kaon wavefunction are discussed, including the -breaking
effects. A sizable contribution from the twist-3 wave function is
found, whose model dependence is discussed by taking two group of parameters
that are determined by different distribution amplitude moments obtained in the
literature. It is also shown that and
, which are more
reasonable and consistent with the light-cone sum rule results in the large
recoil regions.Comment: 22 pages and 6 figure
from decays: contour-improved versus fixed-order summation in a new QCD perturbation expansion
We consider the determination of from hadronic decays, by
investigating the contour-improved (CI) and the fixed-order (FO)
renormalization group summations in the frame of a new perturbation expansion
of QCD, which incorporates in a systematic way the available information about
the divergent character of the series. The new expansion functions, which
replace the powers of the coupling, are defined by the analytic continuation in
the Borel complex plane, achieved through an optimal conformal mapping. Using a
physical model recently discussed by Beneke and Jamin, we show that the new
CIPT approaches the true results with great precision when the perturbative
order is increased, while the new FOPT gives a less accurate description in the
regions where the imaginary logarithms present in the expansion of the running
coupling are large. With the new expansions, the discrepancy of 0.024 in
between the standard CI and FO summations is reduced to
only 0.009. From the new CIPT we predict , which practically coincides with the result of the
standard FOPT, but has a more solid theoretical basis
Pinch Technique and the Batalin-Vilkovisky formalism
In this paper we take the first step towards a non-diagrammatic formulation
of the Pinch Technique. In particular we proceed into a systematic
identification of the parts of the one-loop and two-loop Feynman diagrams that
are exchanged during the pinching process in terms of unphysical ghost Green's
functions; the latter appear in the standard Slavnov-Taylor identity satisfied
by the tree-level and one-loop three-gluon vertex. This identification allows
for the consistent generalization of the intrinsic pinch technique to two
loops, through the collective treatment of entire sets of diagrams, instead of
the laborious algebraic manipulation of individual graphs, and sets up the
stage for the generalization of the method to all orders. We show that the task
of comparing the effective Green's functions obtained by the Pinch Technique
with those computed in the background field method Feynman gauge is
significantly facilitated when employing the powerful quantization framework of
Batalin and Vilkovisky. This formalism allows for the derivation of a set of
useful non-linear identities, which express the Background Field Method Green's
functions in terms of the conventional (quantum) ones and auxiliary Green's
functions involving the background source and the gluonic anti-field; these
latter Green's functions are subsequently related by means of a Schwinger-Dyson
type of equation to the ghost Green's functions appearing in the aforementioned
Slavnov-Taylor identity.Comment: 45 pages, uses axodraw; typos corrected, one figure changed, final
version to appear in Phys.Rev.
Schur functions and their realizations in the slice hyperholomorphic setting
we start the study of Schur analysis in the quaternionic setting using the
theory of slice hyperholomorphic functions. The novelty of our approach is that
slice hyperholomorphic functions allows to write realizations in terms of a
suitable resolvent, the so called S-resolvent operator and to extend several
results that hold in the complex case to the quaternionic case. We discuss
reproducing kernels, positive definite functions in this setting and we show
how they can be obtained in our setting using the extension operator and the
slice regular product. We define Schur multipliers, and find their co-isometric
realization in terms of the associated de Branges-Rovnyak space
Form Factors in the radiative pion decay
We perform an analysis of the form factors that rule the structure-dependent
amplitude in the radiative pion decay. The resonance contributions to pion -> e
nu_e gamma decays are computed through the proper construction of the vector
and axial-vector form factors by setting the QCD driven asymptotic properties
of the three-point Green functions VVP and VAP, and by demanding the smoothing
of the form factors at high transfer of momentum. A comparison between
theoretical and experimental determinations of the form factors is also carried
out. We also consider and evaluate the role played by a non-standard tensor
form factor. We conclude that, at present and due to the hadronic incertitudes,
the search for New Physics in this process is not feasible.Comment: 14 pages, no figures. Typos corrected. Accepted for publication in
The European Physical Journal
Study of the radiative decay with CMD-2 detector
Using the of data collected with the CMD-2 detector at VEPP-2M
the decay mode , has been
studied. The obtained branching ratio is B(.Comment: 13 pages, 5 figures, LaTex2e, to be published in Phys. Lett.
The Determination of alpha_s from Tau Decays Revisited
We revisit the determination of alpha_s(m_tau) using a fit to inclusive tau
hadronic spectral moments in light of (1) the recent calculation of the
fourth-order perturbative coefficient K_4 in the expansion of the Adler
function, (2) new precision measurements from BABAR of e+e- annihilation cross
sections, which decrease the uncertainty in the separation of vector and
axial-vector spectral functions, and (3) improved results from BABAR and Belle
on tau branching fractions involving kaons. We estimate that the fourth-order
perturbative prediction reduces the theoretical uncertainty, introduced by the
truncation of the series, by 20% with respect to earlier determinations. We
discuss to some detail the perturbative prediction and show that the effect of
the incomplete knowledge of the series is reduced by using the so-called
contour-improved calculation, as opposed to fixed-order perturbation theory
which manifests convergence problems. The corresponding theoretical
uncertainties are studied at the tau and Z mass scales. Nonperturbative
contributions extracted from the most inclusive fit are small, in agreement
with earlier determinations. Systematic effects from quark-hadron duality
violation are estimated with simple models and found to be within the quoted
systematic errors. The fit gives alpha_s(m_tau) = 0.344 +- 0.005 +- 0.007,
where the first error is experimental and the second theoretical. After
evolution to M_Z we obtain alpha_s(M_Z) = 0.1212 +- 0.0005 +- 0.0008 +- 0.0005,
where the errors are respectively experimental, theoretical and due to the
evolution. The result is in agreement with the corresponding NNNLO value
derived from essentially the Z width in the global electroweak fit. The
alpha_s(M_Z) determination from tau decays is the most precise one to date.Comment: 22 pages, 7 figure
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