4,325 research outputs found

    Chiral Symmetry Breaking in Quenched Massive Strong-Coupling QED4_4

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    We present results from a study of subtractive renormalization of the fermion propagator Dyson-Schwinger equation (DSE) in massive strong-coupling quenched QED4_4. Results are compared for three different fermion-photon proper vertex {\it Ans\"{a}tze\/}: bare γμ\gamma^\mu, minimal Ball-Chiu, and Curtis-Pennington. The procedure is straightforward to implement and numerically stable. This is the first study in which this technique is used and it should prove useful in future DSE studies, whenever renormalization is required in numerical work.Comment: REVTEX 3.0, 15 pages plus 7 uuencoded PostScript figure

    Investigation of Thermal Stability Effects of Thick Hydrogenated Amorphous Silicon Precursor Layers for Liquid Phase Crystallized Silicon

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    The thermal stability of thick amp; 8776;4 amp; 8201; amp; 956;m plasma grown hydrogenated amorphous silicon a Si H layers on glass upon application of a rather rapid annealing step is investigated. Such films are of interest as precursor layers for laser liquid phase crystallized silicon solar cells. However, at least half day annealing at T amp; 8776;550 amp; 8201; C is considered to be necessary so far to reduce the hydrogen H content and thus avoid blistering and peeling during the crystallization process due to H. By varying the deposition conditions of a Si H, layers of rather different thermal stability are fabricated. Changes in the surface morphology of these a Si H layers are investigated using scanning electron microscopy and profilometry measurements. Hydrogen effusion, secondary ion mass spectrometry SIMS depth profiling, and Raman spectroscopy measurements are also carried out. In summary, amorphous silicon precursor layers are fabricated that can be heated within 30 amp; 8201;min to a temperature of 550 amp; 8201; C without peeling and major surface morphological changes. Successful laser liquid phase crystallization of such material is demonstrated. The physical nature of a Si H material stability instability upon application of rapid heating is studie

    The Polarised Valence Quark Distribution from semi-inclusive DIS

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    The semi-inclusive difference asymmetry A^{h^{+}-h^{-}} for hadrons of opposite charge has been measured by the COMPASS experiment at CERN. The data were collected in the years 2002-2004 using a 160 GeV polarised muon beam scattered off a large polarised ^6LiD target and cover the range 0.006 < x < 0.7 and 1 < Q^2 < 100 (GeV/c)^2. In leading order QCD (LO) the asymmetry A_d^{h^{+}-h^{-}} measures the valence quark polarisation and provides an evaluation of the first moment of Delta u_v + Delta d_v which is found to be equal to 0.40 +- 0.07 (stat.) +- 0.05 (syst.) over the measured range of x at Q^2 = 10 (GeV/c)^2. When combined with the first moment of g_1^d previously measured on the same data, this result favours a non-symmetric polarisation of light quarks Delta u-bar = - Delta d-bar at a confidence level of two standard deviations, in contrast to the often assumed symmetric scenario Delta u-bar = Delta d-bar = Delta s-bar = Delta s.Comment: 7 pages, 3 figures, COMPASS, revised: details added, author list update

    Spin alignment and violation of the OZI rule in exclusive ω\omega and ϕ\phi production in pp collisions

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    Exclusive production of the isoscalar vector mesons ω\omega and ϕ\phi is measured with a 190 GeV/c/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable xFx_{F} of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xFx_{F} and on the invariant mass MpVM_{p\mathrm{V}} of the system formed by fast proton pfastp_\mathrm{fast} and vector meson VV is discussed in terms of diffractive production of pfastVp_\mathrm{fast}V resonances in competition with central production. The measurement of the spin density matrix element ρ00\rho_{00} of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on xFx_{F} and on MpVM_{p\mathrm{V}} are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to ω\omega production which are absent in the case of the ϕ\phi meson. Removing the low-mass MpVM_{p\mathrm{V}} resonant region, the OZI rule is found to be violated by a factor of eight, independently of xFx_\mathrm{F}.Comment: 23 pages, 13 figures and 5 table

    An overview of the mid-infrared spectro-interferometer MATISSE: science, concept, and current status

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    MATISSE is the second-generation mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This new interferometric instrument will allow significant advances by opening new avenues in various fundamental research fields: studying the planet-forming region of disks around young stellar objects, understanding the surface structures and mass loss phenomena affecting evolved stars, and probing the environments of black holes in active galactic nuclei. As a first breakthrough, MATISSE will enlarge the spectral domain of current optical interferometers by offering the L and M bands in addition to the N band. This will open a wide wavelength domain, ranging from 2.8 to 13 um, exploring angular scales as small as 3 mas (L band) / 10 mas (N band). As a second breakthrough, MATISSE will allow mid-infrared imaging - closure-phase aperture-synthesis imaging - with up to four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. Moreover, MATISSE will offer a spectral resolution range from R ~ 30 to R ~ 5000. Here, we present one of the main science objectives, the study of protoplanetary disks, that has driven the instrument design and motivated several VLTI upgrades (GRA4MAT and NAOMI). We introduce the physical concept of MATISSE including a description of the signal on the detectors and an evaluation of the expected performances. We also discuss the current status of the MATISSE instrument, which is entering its testing phase, and the foreseen schedule for the next two years that will lead to the first light at Paranal.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June 2016, 11 pages, 6 Figure

    Multiplicities of charged pions and unidentified charged hadrons from deep-inelastic scattering of muons off an isoscalar target

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    Multiplicities of charged pions and unidentified hadrons produced in deep-inelastic scattering were measured in bins of the Bjorken scaling variable xx, the relative virtual-photon energy yy and the relative hadron energy zz. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and an isoscalar target (6^6LiD). They cover the kinematic domain in the photon virtuality Q2Q^2 > 1(GeV/c)2)^2, 0.004<x<0.40.004 < x < 0.4, 0.2<z<0.850.2 < z < 0.85 and 0.1<y<0.70.1 < y < 0.7. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions

    Adhesive capsulitis and dynamic splinting: a controlled, cohort study

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    <p>Abstract</p> <p>Background</p> <p>Adhesive Capsulitis (AC) affects patient of all ages, and stretching protocols are commonly prescribed for this condition. Dynamic splinting has been shown effective in contracture reduction from pathologies including Trismus to plantar fasciitis. The purpose of this study was to examine the efficacy of dynamic splinting on patients with AC.</p> <p>Methods</p> <p>This controlled, cohort study, was conducted at four physical therapy, sports medicine clinics in Texas and California. Sixty-two patients diagnosed with Stage II Adhesive Capsulitis were grouped by intervention. The intervention categories were as follows: Group I (Control); Group II (Physical Therapy exclusively with standardized protocols); Group III; (Shoulder Dynasplint system exclusively); Group IV (Combined treatment with Shoulder Dynasplint and standardized Physical Therapy). The duration of this study was 90 days for all groups, and the main outcome measures were change in active, external rotation.</p> <p>Results</p> <p>Significant difference was found for all treatment groups (p < 0.001) following a one-way ANOVA. The greatest change with the smallest standard deviation was for the combined treatment group IV, (mean change of 29°).</p> <p>Conclusion</p> <p>The difference for the combined treatment group was attributed to patients' receiving the best PT combined with structured "home therapy" that contributed an additional 90 hours of end-range stretching. This adjunct should be included in the standard of care for adhesive Capsulitis.</p> <p>Trial Registration</p> <p><b>Trial Number</b>: NCT00873158</p

    The Two-Photon Exchange Experiment at DESY

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    We propose a new measurement of the ratio of positron-proton to electron-proton elastic scattering at DESY. The purpose is to determine the contributions beyond single-photon exchange, which are essential for the Quantum Electrodynamic (QED) description of the most fundamental process in hadronic physics. By utilizing a 20 cm long liquid hydrogen target in conjunction with the extracted beam from the DESY synchrotron, we can achieve an average luminosity of 2.12×10352.12\times10^{35} cm2^{-2}\cdots1^{-1}\cdotsr1^{-1} (200\approx200 times the luminosity achieved by OLYMPUS). The proposed TPEX experiment entails a commissioning run at 2 GeV, followed by measurements at 3 GeV, thereby providing new data up to Q2=4.6Q^2=4.6 (GeV/cc)2^2 (twice the range of current measurements). We present and discuss the proposed experimental setup, run plan, and expectations.Comment: 10 pages, 14 figures. arXiv admin note: substantial text overlap with arXiv:2301.0470

    Longitudinal double spin asymmetries in single hadron quasi-real photoproduction at high pTp_T

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    We measured the longitudinal double spin asymmetries ALLA_{LL} for single hadron muo-production off protons and deuterons at photon virtuality Q2Q^2 < 1(GeV/c\it c)2^2 for transverse hadron momenta pTp_T in the range 0.7 GeV/c\it c to 4 GeV/c\it c . They were determined using COMPASS data taken with a polarised muon beam of 160 GeV/c\it c or 200 GeV/c\it c impinging on polarised 6LiD\mathrm{{}^6LiD} or NH3\mathrm{NH_3} targets. The experimental asymmetries are compared to next-to-leading order pQCD calculations, and are sensitive to the gluon polarisation ΔG\Delta G inside the nucleon in the range of the nucleon momentum fraction carried by gluons 0.05<xg<0.20.05 < x_g < 0.2
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