2,788 research outputs found

    Small-Size Resonant Photoacoustic Cell of Inclined Geometry for Gas Detection

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    A photoacoustic cell intended for laser detection of trace gases is represented. The cell is adapted so as to enhance the gas-detection performance and, simultaneously, to reduce the cell size. The cell design provides an efficient cancellation of the window background (a parasite response due to absorption of laser beam in the cell windows) and acoustic isolation from the environment for an acoustic resonance of the cell. The useful photoacoustic response from a detected gas, window background and noise are analyzed in demonstration experiments as functions of the modulation frequency for a prototype cell with the internal volume ~ 0.5 cm^3. The minimal detectable absorption for the prototype is estimated to be ~ 1.2 10^{-8} cm^{-1} W Hz^{-1/2}.Comment: 11 pages, 5 figure

    Local Spectral Density for a Periodically Driven System of Coupled Quantum States with Strong Imperfection in Unperturbed Energies

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    A random matrix theory approach is applied in order to analyze the localization properties of local spectral density for a generic system of coupled quantum states with strong static imperfection in the unperturbed energy levels. The system is excited by an external periodic field, the temporal profile of which is close to monochromatic one. The shape of local spectral density is shown to be well described by the contour obtained from a relevant model of periodically driven two-states system with irreversible losses to an external thermal bath. The shape width and the inverse participation ratio are determined as functions both of the Rabi frequency and of parameters specifying the localization effect for our system in the absence of external field.Comment: 6 pages, 5 figures, submitted to Optics and Spectroscop

    袨袘 协袣小孝袪袝袦袗袥鞋袧袨袦 小袙袨袡小孝袙袝 袗袩袩袪袨袣小袠袦袗笑袠袡 协袪袦袠孝袗鈭捫熜愋斝 协袣小袩袨袧袝袧笑袠袗袥鞋袧蝎啸 肖校袧袣笑袠袡

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    In this article we study the extremal properties of the Hermite鈥揚ad茅 approximations of type I for the exponential system {e位pz}kp=0聽with different arbitrary real and complexes 位0, 位1, 鈥, 位k.聽The theorems proved complement the known results of P. Borwein, F. Wielonsky, K. Driver.袙 褉邪斜芯褌械 懈蟹褍褔邪褞褌褋褟 褝泻褋褌褉械屑邪谢褜薪褘械 褋胁芯泄褋褌胁邪 邪锌锌褉芯泻褋懈屑邪褑懈泄 协褉屑懈褌邪鈥撔熜靶葱 I 褌懈锌邪 写谢褟 褋懈褋褌械屑褘 褝泻褋锌芯薪械薪褌 {e位pz}kp=0 锌褉芯懈蟹胁芯谢褜薪褘屑懈 褉邪蟹谢懈褔薪褘屑懈 写械泄褋褌胁懈褌械谢褜薪褘屑懈 懈 泻芯屑锌谢械泻褋薪褘屑懈 锌芯泻邪蟹邪褌械谢褟屑懈 位0, 位1, 鈥, 位k. 袛芯泻邪蟹邪薪薪褘械 褌械芯褉械屑褘 写芯锌芯谢薪褟褞褌 懈蟹胁械褋褌薪褘械 褉械蟹褍谢褜褌邪褌褘 袩. 袘芯褉胁械泄薪邪, 肖. 袙懈谢芯薪褋泻芯谐芯, K. 袛褉懈胁械褉

    A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project

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    A method to facilitate the consistent inclusion of cross-section measurements based on complex final-states from HERA, TEVATRON and the LHC in proton parton density function (PDF) fits has been developed. This can be used to increase the sensitivity of LHC data to deviations from Standard Model predictions. The method stores perturbative coefficients of NLO QCD calculations of final-state observables measured in hadron colliders in look-up tables. This allows the posteriori inclusion of parton density functions (PDFs), and of the strong coupling, as well as the a posteriori variation of the renormalisation and factorisation scales in cross-section calculations. The main novelties in comparison to original work on the subject are the use of higher-order interpolation, which substantially improves the trade-off between accuracy and memory use, and a CPU and computer memory optimised way to construct and store the look-up table using modern software tools. It is demonstrated that a sufficient accuracy on the cross-section calculation can be achieved with reasonably small look-up table size by using the examples of jet production and electro-weak boson (Z, W) production in proton-proton collisions at a center-of-mass energy of 14 TeV at the LHC. The use of this technique in PDF fitting is demonstrated in a PDF-fit to HERA data and simulated LHC jet cross-sections as well as in a study of the jet cross-section uncertainties at various centre-of-mass energies

    协袣小孝袪袝袦袗袥鞋袧蝎袝 小袙袨袡小孝袙袗 袗袩袩袪袨袣小袠袦袗笑袠袡 协袪袦袠孝袗鈥撔熜愋斝 协袣小袩袨袧袝袧笑袠袗袥鞋袧蝎啸 肖校袧袣笑袠袡

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    The paper deals with extremal properties of diagonal Hermite-Pad鈥檈 approximants of type I for exponential system {e位pz}kp=0with arbitrary 位0, 位1, 鈥, 位k. Proved theorems complement known results of P. P. Borwein, F. Wielonsky.袙 褉邪斜芯褌械 懈蟹褍褔邪褞褌褋褟 褝泻褋褌褉械屑邪谢褜薪褘械 褋胁芯泄褋褌胁邪 写懈邪谐芯薪邪谢褜薪褘褏 邪锌锌褉芯泻褋懈屑邪褑懈泄 协褉屑懈褌邪鈥撔熜靶葱 I 褌懈锌邪 写谢褟 褋懈褋褌械屑褘 褝泻褋锌芯薪械薪褌 {e位pz}kp=0褋 锌褉芯懈蟹胁芯谢褜薪褘屑懈 褉邪蟹谢懈褔薪褘屑懈 写械泄褋褌胁懈褌械谢褜薪褘屑懈 锌芯泻邪蟹邪褌械谢褟屑懈 位0, 位1, 鈥, 位k. 袛芯泻邪蟹邪薪薪褘械 褌械芯褉械屑褘 写芯锌芯谢薪褟褞褌 懈蟹胁械褋褌薪褘械 褉械蟹褍谢褜褌邪褌褘 袩. 袘芯褉胁械泄薪邪 懈 肖. 袙懈谢芯薪褋泻芯谐芯

    袗小袠袦袩孝袨孝袠效袝小袣袠袝 小袙袨袡小孝袙袗 袦袧袨袚袨效袥袝袧袨袙 协袪袦袠孝袗

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    The article deals with asymptotic properties of diagonal Hermite鈥揚ade鈥檚 approximants of type I for the exponential system {e位 j z}k j 聽= 0 with arbitrary real 位0, 位1, ..., 位k. The proved theorems complement the known results of P. Borwein, F. Wielonsky, and A. P. Starovoitov.袠蟹褍褔邪褞褌褋褟 邪褋懈屑锌褌芯褌懈褔械褋泻懈械 褋胁芯泄褋褌胁邪 写懈邪谐芯薪邪谢褜薪褘褏 邪锌锌褉芯泻褋懈屑邪褑懈泄 协褉屑懈褌邪鈥撔熜靶葱 I 褌懈锌邪 写谢褟 褋懈褋褌械屑褘 褝泻褋锌芯薪械薪褌 {e位 j z}k j 聽= 0 锌褉芯懈蟹胁芯谢褜薪褘屑懈 褉邪蟹谢懈褔薪褘屑懈 写械泄褋褌胁懈褌械谢褜薪褘屑懈 锌芯泻邪蟹邪褌械谢褟屑懈 位0, 位1, ..., 位k. 袛芯泻邪蟹邪薪薪褘械 褌械芯褉械屑褘 写芯锌芯谢薪褟褞褌 懈蟹胁械褋褌薪褘械 褉械蟹褍谢褜褌邪褌褘 袩. 袘芯褉胁械泄薪邪, 肖. 袙懈谢芯薪褋泻芯谐芯 懈 袗. 袩. 小褌邪褉芯胁芯泄褌芯胁邪

    Standalone vertex 铿乶ding in the ATLAS muon spectrometer

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    A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at 鈭歴 = 7 TeV collected with the ATLAS detector at the LHC during 2011

    Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC