5,825 research outputs found

    Next-leading BFKL effects in forward-jet production at HERA

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    We show that next-leading logarithmic (NLL) Balitsky-Fadin-Kuraev-Lipatov (BFKL) effects can be tested by the forward-jet cross sections recently measured at HERA. For d\sigma/dx, the NLL corrections are small which confirms the stability of the BFKL description. The triple differential cross section d\sigma/dxdk_T^2dQ^2 is sensitive to NLL effects and opens the way for an experimental test of the full BFKL theoretical framework at NLL accuracy.Comment: 5 pages, 4 figures, NLL-BFKL saddle-point approximation now compared with exact integration, version to appear in PL

    Nonresonant control of multimode molecular wave packets at room temperature

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    Includes bibliographical references (pages 033001-4).We demonstrate the creation and measurement of shaped multimode vibrational wave packets with overtone and combination mode excitation in CCl4. Excitation of wave packets through nonresonant impulsive stimulated Raman scattering allows for coherent control of molecular vibrations without passing through an electronic resonance. This technique is therefore very general and can be implemented in a large class of molecular gases and liquids at STP, which were previously inaccessible because their resonances are in the VUV

    A global analysis of inclusive diffractive cross sections at HERA

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    We describe the most recent data on the diffractive structure functions from the H1 and ZEUS Collaborations at HERA using four models. First, a Pomeron Structure Function (PSF) model, in which the Pomeron is considered as an object with parton distribution functions. Then, the Bartels Ellis Kowalski Wusthoff (BEKW) approach is discussed, assuming the simplest perturbative description of the Pomeron using a two-gluon ladder. A third approach, the Bialas Peschanski (BP) model, based on the dipole formalism is then described. Finally, we discuss the Golec-Biernat-W\"usthoff (GBW) saturation model which takes into account saturation effects. The best description of all avaible measurements can be achieved with either the PSF based model or the BEKW approach. In particular, the BEKW prediction allows to include the highest β\beta measurements, which are dominated by higher twists effects and provide an efficient and compact parametrisation of the diffractive cross section. The two other models also give a good description of cross section measurements at small xx with a small number of parameters. The comparison of all predictions allows us to identify interesting differences in the behaviour of the effective pomeron intercept and in the shape of the longitudinal component of the diffractive structure functions. In this last part, we present some features that can be discriminated by new experimental measurements, completing the HERA program.Comment: 32 pages, 18 figure

    Beable trajectories for revealing quantum control mechanisms

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    The dynamics induced while controlling quantum systems by optimally shaped laser pulses have often been difficult to understand in detail. A method is presented for quantifying the importance of specific sequences of quantum transitions involved in the control process. The method is based on a ``beable'' formulation of quantum mechanics due to John Bell that rigorously maps the quantum evolution onto an ensemble of stochastic trajectories over a classical state space. Detailed mechanism identification is illustrated with a model 7-level system. A general procedure is presented to extract mechanism information directly from closed-loop control experiments. Application to simulated experimental data for the model system proves robust with up to 25% noise.Comment: Latex, 20 pages, 13 figure

    Исторические аспекты общества знания на Западе и в СССР

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    Рецензія на монографію: Осипов Г.В., Кара-Мурза С.Г. Общество знания: История модернизации на Западе и в СССР. — М.: Книжный дом «ЛИБРОКОМ», 2013. — 368 с

    Velocity-selective direct frequency-comb spectroscopy of atomic vapors

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    We present an experimental and theoretical investigation of two-photon direct frequency-comb spectroscopy performed through velocity-selective excitation. In particular, we explore the effect of repetition rate on the 5S1/25D3/2,5/2\textrm{5S}_{1/2}\rightarrow \textrm{5D}_{3/2, 5/2} two-photon transitions excited in a rubidium atomic vapor cell. The transitions occur via step-wise excitation through the 5P1/2,3/2\textrm{5P}_{1/2, 3/2} states by use of the direct output of an optical frequency comb. Experiments were performed with two different frequency combs, one with a repetition rate of 925\approx 925 MHz and one with a repetition rate of 250\approx 250 MHz. The experimental spectra are compared to each other and to a theoretical model.Comment: 10 pages, 7 figure
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