300 research outputs found
Higgs boson masses in supersymmetric theories
The Higgs boson mass problem is considered in the next to minimal supersymmetric standard model. The Higgs potential and the renormalization group equations for the gauge, Yukawa and scalar coupling constants are analyzed. The restrictions for the Higgs boson masses are found for the cases of presence and absence of spontaneous CP- violation
Complete gluon bremsstrahlung corrections to the process b -> s l+ l-
In a recent paper, we presented the calculation of the order (alpha_s)
virtual corrections to b->s l+ l- and of those bremsstrahlung terms which are
needed to cancel the infrared divergences. In the present paper we work out the
remaining order(alpha_s) bremsstrahlung corrections to b->s l+ l- which do not
suffer from infrared and collinear singularities. These new contributions turn
out to be small numerically. In addition, we also investigate the impact of the
definition of the charm quark mass on the numerical results.Comment: 20 pages including 11 postscript figure
Complete NNLO QCD Analysis of B -> X_s l^+ l^- and Higher Order Electroweak Effects
We complete the next-to-next-to-leading order QCD calculation of the
branching ratio for B -> X_s l^+ l^- including recent results for the
three-loop anomalous dimension matrix and two-loop matrix elements. These new
contributions modify the branching ratio in the low-q^2 region, BR_ll, by about
+1% and -4%, respectively. We furthermore discuss the appropriate normalization
of the electromagnetic coupling alpha and calculate the dominant higher order
electroweak effects, showing that, due to accidental cancellations, they change
BR_ll by only -1.5% if alpha(mu) is normalized at mu = O(m_b), while they shift
it by about -8.5% if one uses a high scale normalization mu = O(M_W). The
position of the zero of the forward-backward asymmetry, q_0^2, is changed by
around +2%. After introducing a few additional improvements in order to reduce
the theoretical error, we perform a comprehensive study of the uncertainty. We
obtain BR_ll(1 GeV^2 <= q^2 <= 6 GeV^2) = (1.57 +- 0.16) x 10^-6 and q_0^2 =
(3.76 +- 0.33) GeV^2 and note that the part of the uncertainty due to the
b-quark mass can be easily reduced.Comment: 26 pages, 7 figures; v5: corrected normalisation in Eq. (5),
numerical results unchange
CP violation in polarized B-> pi ell+ ell- and B-> rho ell+ ell- decays
We study the decay rate and the CP violating asymmetry of the exclusive B->
pi ell+ ell- and B-> rho ell+ ell- decays in the case where one of the final
leptons is polarized. We calculate the contributions coming from the individual
polarization states in order to identify a so-called wrong sign decay, which is
a decay with a given polarization, whose width and CP asymmetry are smaller as
compared to the unpolarized one. The results are presented for electron and tau
leptons. We observe that in particular decay channels, one can identify a wrong
sign decay which is more sensitive to new physics beyond the Standard Model.Comment: 24 pages, 10 figures; minor errors and misprints corrected,
references added, version to be published in EPJ
Photosensitive bismuth ions in lead tungstate
Electron paramagnetic resonance (EPR) signals of Bi2+ ions have been detected in the EPR spectrum of manganese-, bismuth-, and tin-doped PbWO4 single-crystals irradiated by xenon and mercury lamps at 100 K. The parameters of the Zeeman, hyperfine, and superhyperfine interactions and the localization of Bi2+ ions have been determined. © 2013 Pleiades Publishing, Ltd
Absorption enhancing proximity effects in aperiodic nanowire arrays
Aperiodic Nanowire (NW) arrays have higher absorption than equivalent
periodic arrays, making them of interest for photovoltaic applications. An
inevitable property of aperiodic arrays is the clustering of some NWs into
closer proximity than in the equivalent periodic array. We focus on the modes
of such clusters and show that the reduced symmetry associated with cluster
formation allows external coupling into modes which are dark in periodic
arrays, thus increasing absorption. To exploit such modes fully, arrays must
include tightly clustered NWs that are unlikely to arise from fabrication
variations but must be created intentionally.Comment: Accepted by Optics Expres
Paramagnetic defects in manganese-doped lead tungstate
In manganese-doped PbWO4 crystals, low-intensity signals of triclinic clusters Mn4+-VO and Fe3+-VPb have been revealed in addition to signals of Mn2+ tetragonal centers. The Mn4+-VO cluster is formed by a Mn4+ ion in the W6+ position, which is associated with a vacancy of the nearest neighbor O2-ion, and the Fe3+-VPb cluster consists of a Fe3+ ion substituting for Pb2+ with a local compensation of by a lead vacancy. It has been shown that, in PbWO4: Mn, there is also a small amount of Mn4+ tetragonal centers located in the Pb2+ position with a nonlocal compensation of an excess charge. © 2013 Pleiades Publishing, Ltd
Which role for a European Minister of Economy and Finance in a European Fiscal Union?
The European Commission has proposed to inaugurate a European Minister of Economy and Finance with the broad purpose of streamlining the complex and fragmented decision-making processes within the European Monetary Union. The Minister would jointly serve as Vice-President of the Commission and President of the Eurogroup, and have the tasks of coordinating budgetary instruments and structural reforms, designing and implementing adequate fiscal policies for the euro area, coordinating the enforcement of the Stability and Growth Pact, among others. This policy report discusses the potential role the Minister could play in the development of the European Fiscal Union. The report lays out the main challenges along the current institutional solutions facing several dimensions of the Fiscal Union, in particular related to fiscal sustainability, macroeconomic shocks, incentives of structural reforms, and the optimum provision of European public goods. The report then discusses whether and to what degree the new European Minister of Economy and Finance can provide appropriate solutions to these challenges for the Fiscal Union
Оценка качества и идентификация отпечатков пальцев путем анализа структурных свойств изображения
The paper addresses the problem of assessing the quality of fingerprint images using spatial analysis methods. The author proposes using the previously developed mathematical model to describe the set of magnitudes of the image gradient. The model is based on the two-parameter Weibull distribution. The author proposes two approaches to assess the quality of fingerprints. The first approach is implemented by the so-called “Full reference method”, which compares the Weibull distribution parameters’ values of statistical estimates. The results of identifying sweat pores using this method are presented. The second approach is called the “No-Reference method” and is used to assess fingerprints’ quality when analyzing and identifying the information content of their individual sections. It is proposed to use an image blur map as a quality characteristic and a statistical estimate of the Weibull distribution shape parameter as a measure of the blur. The shape parameter is estimated at each image point by the combination of magnitudes of the image gradient in the vicinity of the point; in this, the previously developed blur mapping technique is applied. The specific examples illustrate effectiveness of the proposed approaches.Рассмотрена задача оценки качества изображения отпечатков пальцев с применением пространственных методов анализа. Предложено использовать математическую модель, разработанную ранее для описания совокупности магнитуд градиента изображения. Модель основана на двухпараметрическом распределении Вейбулла. Для оценки качества отпечатков пальцев предложены два подхода. Первый реализуется с помощью так называемого метода сравнения с эталоном (Full Reference), когда сравниваются значения статистических оценок параметров распределения Вейбулла. Приведены результаты решения задачи идентификации потовых пор этим методом. Второй подход называется «безэталонным» (No-Reference) и применяется для оценки качества отпечатков при анализе и выделении информативности их отдельных участков. В качестве характеристики качества предлагается использовать карту размытости изображения, а в качестве меры размытости – статистическую оценку параметра формы распределения Вейбулла. Параметр формы оценивается в каждой точке изображения по совокупности магнитуд градиента изображения в окрестности точки, при этом применяется разработанная ранее методика построения карты размытости. Эффективность предложенных подходов иллюстрируется конкретными примерами
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