1,176 research outputs found
On QCD analysis of stucture function in alternative approach
The alternative approach to QCD analysis of the photon structure function
is presented. It differs from the conventional one by the
presence of the terms which in conventional approach appear in higher orders.
We show that this difference concerns also the photonic parton distribution
functions. In the alternative approach, the complete LO analysis of
can be performed as all required quantities are known. At the
NLO, however, one of the coefficient function is so far not available and thus
only the photonic parton distribution function can be computed and compared to
those of standard approach. We discuss the numerical difference of these
approaches at the LO and the NLO approximation and show that in case of
this difference is non-negligible and may play an important role
in the analysis on photon data of the future experiments.Comment: 25 page
Hypernuclei as chiral solitons
The identification of flavored multiskyrmions with the ground states of known
hypernuclei is successful for several of them, e.g. for isodoublet H(Lambda) -
He(Lambda), A=4, isoscalars He(Lambda) (A=5) and Li(Lambda) (A=7). In other
cases agreement is not so good, but the behaviour of the binding energy with
increasing baryon number is in qualitative agreement with data. Charmed or
beauty hypernuclei within this approach are predicted to be bound stronger than
strange hypernuclei. This conclusion is stable against variation of poorly
known heavy flavor decay constants.Comment: 9 pages, 1 Fig. Presented at the International Workshops on Nuclear
and Particle Physics at 50-Gev PS, NP01 (KEK, Japan, December 2001) and NP02
(Kyoto, Japan, September 2002). Some additions and corrections of numerical
results are mad
On Tamm's problem in the Vavilov-Cherenkov radiation theory
We analyse the well-known Tamm problem treating the charge motion on a finite
space interval with the velocity exceeding light velocity in medium. By
comparing Tamm's formulae with the exact ones we prove that former do not
properly describe Cherenkov radiation terms. We also investigate Tamm's formula
cos(theta)=1/(beta n) defining the position of maximum of the field strengths
Fourier components for the infinite uniform motion of a charge. Numerical
analysis of the Fourier components of field strengths shows that they have a
pronounced maximum at cos(theta)=1/(beta n) only for the charge motion on the
infinitely small interval. As the latter grows, many maxima appear. For the
charge motion on an infinite interval there is infinite number of maxima of the
same amplitude. The quantum analysis of Tamm's formula leads to the same
results.Comment: 28 pages, 8 figures, to be published in J.Phys.D:Appl.Phy
The influence of climatic factors on the course of pregnancy in women of the far north
The article describes the influence of climatic and geographic conditions on the course of pregnancy in women of the Tazovsky district in the far North (Yamalo-Nenets). After analyzing the course of pregnancy on individual cards found that the course of pregnancy has a significant effect on the change in photoperiodicity. In the years of high solar activity, the frequency of complications increases in indigenous and alien residents. In this regard, it is necessary to carry out preventive measures to identify and eliminate complications during pregnancy in all residents of the NorthВ статье рассмотрено влияние климато-географических условий на течение беременности у жительниц Тазовского района Крайнего Севера (ЯНАО). Проанализировав течение беременности по индивидуальным картам установлено, что на течение беременности существенное влияние оказывает изменение фотопериодичности. В годы высокой солнечной активности частота осложнений возрастает у коренных и пришлых жительниц. В связи с этим необходимо проведение профилактических мероприятий по выявлению и устранению осложнений на течение беременности у всех жительниц Север
The influence of climatic factors on the course of pregnancy in women of the far north
The article describes the influence of climatic and geographic conditions on the course of pregnancy in women of the Tazovsky district in the far North (Yamalo-Nenets). After analyzing the course of pregnancy on individual cards found that the course of pregnancy has a significant effect on the change in photoperiodicity. In the years of high solar activity, the frequency of complications increases in indigenous and alien residents. In this regard, it is necessary to carry out preventive measures to identify and eliminate complications during pregnancy in all residents of the NorthВ статье рассмотрено влияние климато-географических условий на течение беременности у жительниц Тазовского района Крайнего Севера (ЯНАО). Проанализировав течение беременности по индивидуальным картам установлено, что на течение беременности существенное влияние оказывает изменение фотопериодичности. В годы высокой солнечной активности частота осложнений возрастает у коренных и пришлых жительниц. В связи с этим необходимо проведение профилактических мероприятий по выявлению и устранению осложнений на течение беременности у всех жительниц Север
Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP
An experimental study of the normalized three-jet rate of b quark events with
respect to light quarks events (light= \ell \equiv u,d,s) has been performed
using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by
the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are
found to agree with theoretical predictions treating mass corrections at
next-to-leading order. Measurements of the b quark mass have also been
performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data
are found to be better described when using the running mass. The measurement
yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12
(theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise
measurement of the b mass derived from a high energy process. When compared to
other b mass determinations by experiments at lower energy scales, this value
agrees with the prediction of Quantum Chromodynamics for the energy evolution
of the running mass. The mass measurement is equivalent to a test of the
flavour independence of the strong coupling constant with an accuracy of 7
permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.
Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance
This paper presents DELPHI measurements and interpretations of
cross-sections, forward-backward asymmetries, and angular distributions, for
the e+e- -> ffbar process for centre-of-mass energies above the Z resonance,
from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are
consistent with the predictions of the Standard Model and are used to study a
variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering
and several models which include physics beyond the Standard Model: the
exchange of Z' bosons, contact interactions between fermions, the exchange of
gravitons in large extra dimensions and the exchange of sneutrino in R-parity
violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.
Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector
Inclusive J/psi production in photon-photon collisions has been observed at
LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X
is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an
integrated luminosity of 617 pb^{-1}, yielding a cross-section of
sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the
event shapes of different types of gamma gamma processes in the PYTHIA program,
we conclude that (74 +/- 22)% of the observed J/psi events are due to
`resolved' photons, the dominant contribution of which is most probably due to
the gluon content of the photon.Comment: 13 pages, 8 figures, Accepted by Phys. Lett.
A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events
Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the
Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy
and momentum constraint methods. The results are expressed as deviations from
the nominal LEP centre-of-mass energy, measured using other techniques. The
results are found to be compatible with the LEP Energy Working Group estimates
for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.
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