4,688 research outputs found

    Explicit generating functional for pions and virtual photons

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    We construct the explicit one-loop functional of chiral perturbation theory for two light flavours, including virtual photons. We stick to contributions where 1 or 2 mesons and at most one photon are running in the loops. With the explicit functional at hand, the evaluation of the relevant Green functions boils down to performing traces over the flavour matrices. For illustration, we work out the pi+ pi- -> pi0 pi0 scattering amplitude at threshold at order p^4, e^2p^2.Comment: 20 pages, 2 figures; version accepted for publication, minor typographical changes, acknowledgments adde

    Isospin violation in epsilon'

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    On the basis of a next-to-leading-order calculation in chiral perturbation theory, the first complete analysis of isospin breaking for direct CP violation in K^0 -> 2 pi decays is performed. We find a destructive interference between three different sources of isospin violation in the CP violation parameter epsilon'. Within the uncertainties of large-N_c estimates for the low-energy constants, the isospin violating correction for epsilon' is below 15 %.Comment: 4 page

    The pionic beta decay in chiral perturbation theory

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    Within the framework of chiral perturbation theory with virtual photons and leptons, we present an updated analysis of the pionic beta decay including all electromagnetic contributions of order e**2 p**2. We discuss the extraction of the Cabibbo-Kobayashi-Maskawa matrix element |Vud| from experimental data. The method employed here is consistent with the analogous treatment of the Kl3 decays and the determination of |Vus|.Comment: 8 pages, 1 figure, latex file, uses EPJC macro

    Radiative corrections to K_{l3} decays

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    We present a complete calculation of the K_{l3} decays K^+ --> pi^0 l^+ nu_l and K^0 --> pi^- l^+ nu_l to O(p^4, (m_d-m_u) p^2, e^2 p^2) in chiral perturbation theory with virtual photons and leptons. We introduce the concept of generalized form factors and kinematical densities in the presence of electromagnetism, and propose a possible treatment of the real photon emission in K^+_{l3} decays. We illustrate our results by applying them to the extraction of the Kobayashi--Maskawa matrix element |V_{us}| from the experimental K^+_{e3} decay parameters.Comment: 13 page

    Analysis of two urban middle schools: factors affecting student achievement

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    Because of increasing student enrollment, a new school was formed in a small low-income Southern California school district. Teachers could choose to transfer to the new school or remain at the existing school. Over five years, quantitative analyses of demographic data showed little differences between the two schools across the years except for a difference in student academic achievement. This mixed-method study examined the demographics and perceptions of academic life at these two middle schools to ascertain an explanation for differences in academic achievement as measured by the same standardized test. Team interviews combined the focus group approach within teams, followed by a teacher survey to seven components of school life and ideas for school reform. Qualitative analyses of in-depth team interviews with 90% of the faculty and individual interviews of four administrators at both schools revealed more similarities than differences within the seven components. They perceived both sites as safe, applying shared discipline plans, functioning well with teachers organized into instructional teams, applying a variety of instructional methods, supporting at-risk students, and expressed concerns regarding parent involvement and the quality of professional development. Differences were noted in teachers\u27 interest or use of the instructional practices of block scheduling and looping at both schools. Teachers desired more input into professional development and a plan that connected such activities to student academic achievement. Teachers and administrators expressed a desire to utilize more strategies to improve parent involvement at each site. The major difference between the two schools was faculty attitude toward administrators\u27 behavior. Almost all teachers shared that they were part of decision-making; but, at the original site, the teachers indicated that administration did not follow-through on their decisions. Nine teachers left this school. At the new school, faculty perceived that administrators were supportive and empowered teachers. Two teachers left this school. Administrators and teachers suggested next steps for their site to be: (a) leadership support and follow-through for teacher decision-making at the original school, (b) shared decision-making for professional development at both schools, (c) utilize more strategies for parent involvement, and (d) implement extra-curricular activities or student intervention program

    Порівняльний гендерний аналіз архетипів у німецькій і українській культурі (Comparative Gender Analysis of Archetypes in the German and in the Ukrainian Cultures)

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    У статті проводиться психологічний аналіз творів ранньої слов´янської та ранньої германської літератури з метою виявлення характерних гендерних архетипів. Будуються гіпотези про співвідношення цих архетипів із загальною динамікою фемінінного і маскулінного елементу в психіці народів. (A psychological analysis of the works of early Slavic and early German literature is presented in order to discover typical gender archetypes. Hypotheses regarding relationships of these archetypes and the general dynamics of feminine and masculine qualities of the mentality of nations are suggested

    Isospin Violation and the Magnetic Moment of the Muon

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    We calculate the leading isospin-violating and electromagnetic corrections for the decay tau -> pi^0 pi nu_tau at low energies. The corrections are small but relevant for the inclusion of tau decay data in the determination of hadronic vacuum polarization especially for the anomalous magnetic moment of the muon. We show that part of the systematic differences between the measured form factors in tau -> pi^0 pi nu_tau and e^+ e^- -> pi^+ pi^- is due to isospin violation .Comment: 12 pages, 2 figures, minor revisions in the text, references added, version to appear in Physics Letters

    A programmable 10 Gigabit injector for the LHCb DAQ and its upgrade

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    The LHCb High Level Trigger and Data Acquisition system selects about 2 kHz of events out of the 1 MHz of events, which have been selected previously by the first-level hardware trigger. The selected events are consolidated into files and then sent to permanent storage for subsequent analysis on the Grid. The goal of the upgrade of the LHCb readout is to lift the limitation to 1 MHz. This means speeding up the DAQ to 40 MHz. Such a DAQ system will certainly employ 10 Gigabit or technologies and might also need new networking protocols: a customized TCP or proprietary solutions. A test module is being presented, which integrates in the existing LHCb infrastructure. It is a 10-Gigabit traffic generator, flexible enough to generate LHCb’s raw data packets using dummy data or simulated data. These data are seen as real data coming from sub-detectors by the DAQ. The implementation is based on an FPGA using 10 Gigabit Ethernet interface. This module is integrated in the experiment control system. The architecture, implementation, and performance results of the solution will be presented

    The IRAM-30m line survey of the Horsehead PDR: I. CF+ as a tracer of C+ and a measure of the Fluorine abundance

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    C+ is a key species in the interstellar medium but its 158 {\mu}m fine structure line cannot be observed from ground-based telescopes. Current models of fluorine chemistry predict that CF+ is the second most important fluorine reservoir, in regions where C+ is abundant. We detected the J = 1-0 and J = 2-1 rotational lines of CF+ with high signal-to-noise ratio towards the PDR and dense core positions in the Horsehead. Using a rotational diagram analysis, we derive a column density of N(CF+) = (1.5 - 2.0) \times 10^12 cm^-2. Because of the simple fluorine chemistry, the CF+ column density is proportional to the fluorine abundance. We thus infer the fluorine gas-phase abundance to be F/H = (0.6 - 1.5) \times 10^-8. Photochemical models indicate that CF+ is found in the layers where C+ is abundant. The emission arises in the UV illuminated skin of the nebula, tracing the outermost cloud layers. Indeed, CF+ and C+ are the only species observed to date in the Horsehead with a double peaked line profile caused by kinematics. We therefore propose that CF+, which is detectable from the ground, can be used as a proxy of the C+ layers.Comment: Accepted to A&A, 4 pages, 4 figures, 2 table
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