4,173 research outputs found

    Exact time correlation functions for N classical Heisenberg spins in the `squashed' equivalent neighbor model

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    We present exact integral representations of the time-dependent spin-spin correlation functions for the classical Heisenberg N-spin `squashed' equivalent neighbor model, in which one spin is coupled via the Heisenberg exchange interaction with strength J1J_1 to the other N-1 spins, each of which is coupled via the Heisenberg exchange coupling with strength J2J_2 to the remaining N-2 spins. At low temperature T we find that the N spins oscillate in four modes, one of which is a central peak for a semi-infinite range of the values of the exchange coupling ratio. For the N=4 case of four spins on a squashed tetrahedron, detailed numerical evaluations of these results are presented. As T→∞T\to\infty, we calculate exactly the long-time asymptotic behavior of the correlation functions for arbitrary N, and compare our results with those obtained for three spins on an isosceles triangle.Comment: 9 pages, 8 figures, submitted to Phys. Rev.

    Module production of the one-arm AFP 3D pixel tracker

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    The ATLAS Forward Proton (AFP) detector is designed to identify events in which one or two protons emerge intact from the LHC collisions. AFP will consist of a tracking detector, to measure the momentum of the protons, and a time of flight system to reduce the background from multiple proton-proton interactions. Following an extensive qualification period, 3D silicon pixel sensors were selected for the AFP tracker. The sensors were produced at CNM (Barcelona) during 2014. The tracker module assembly and quality control was performed at IFAE during 2015. The assembly of the first AFP arm and the following installation in the LHC tunnel took place in February 2016. This paper reviews the fabrication process of the AFP tracker focusing on the pixel modules.Comment: PIXEL 2016 proceedings; Submitted to JINS

    A Very High-beta Optics to be used for an Absolute Luminosity Determination with Forward Detectors in ATLAS

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    The Atlas experiment at the LHC pursues a number of different approaches to obtain an estimate of the absolute luminosity [3]. Measuring elastic scattering at very small angles (3 μrad) represents a different and complimentary approach that will improve the precision of the final luminosity estimate. In this paper we show the required very high-β optics and the detector acceptance studies

    Puroindolines polymorphism and kernel texture in einkorn (Triticum monococcum)

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    BACKGROUND: Patients with severe asthma experience problems in different areas of their health status. Identification of these areas will provide insight in the patients needs and perhaps what determines the burden of disease. The Nijmegen Clinical Screening Instrument (NCSI) was recently developed for use in clinical practice in patients with COPD and provides a detailed picture of the patients' physiological functioning, symptoms, functional impairment, and Quality of Life. Main purpose of this study is to evaluate the use of the NCSI as compared to the Asthma Control Questionnaire (ACQ) and Asthma Quality of Life Questionnaire (AQLQ) in patients with severe asthma. METHODS: The NCSI, AQLQ, and ACQ were measured in 167 patients with severe asthma. Pearson correlations were calculated between NCSI sub-domains and the AQLQ domains and the ACQ. RESULTS: The NCSI measures more aspects of health status as compared to the ACQ and AQLQ in patients with severe asthma. Beside symptoms, subjective impairment, and emotions the NCSI also measures general Quality of Life, health related Quality of Life, satisfaction with relations, fatigue, and behavioural impairment. On all NCSI sub-domains proportions of patients with normal, mild, and severe problems were found. Heterogeneity was found on the number and on the combination of sub-domains on which patients reported severe problems. CONCLUSIONS: The NCSI provides a more detailed picture of the individual patient with severe asthma than the ACQ and AQLQ. The use of the NCSI might allow quick identification of the problem areas and possible factors that impair health status

    Time Correlation Functions of Three Classical Heisenberg Spins on an Isosceles Triangle and on a Chain: Strong Effects of Broken Symmetry

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    At arbitrary temperature TT, we solve for the dynamics of single molecule magnets composed of three classical Heisenberg spins either on a chain with two equal exchange constants J1J_1, or on an isosceles triangle with a third, different exchange constant J2J_2. As T\rightrarrow\infty, the Fourier transforms and long-time asymptotic behaviors of the two-spin time correlation functions are evaluated exactly. The lack of translational symmetry on a chain or an isosceles triangle yields time correlation functions that differ strikingly from those on an equilateral trinagle with J1=J2J_1=J_2. At low TT, the Fourier transforms of the two autocorrelation functions with J1≠J2J_1\ne J_2 show one and four modes, respectively. For a semi-infinite J2/J1J_2/J_1 range, one mode is a central peak. At the origin of this range, this mode has a novel scaling form.Comment: 9 pages, 14 figures, accepted for publication in Phys. Rev.

    Confronting models on cosmic ray interactions with particle physics at LHC energies

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    Inelastic pp collisions are dominated by soft (low momentum transfer) physics where perturbative QCD cannot be fully applied. A deep understanding of both soft and semi-hard processes is crucial for predictions of minimum bias and underlying events of the now coming on line pp Large Hadron Collider (LHC). Moreover, the interaction of cosmic ray particles entering in the atmosphere is extremely sensitive to these soft processes and consequently cannot be formulated from first principles. Because of this, air shower analyses strongly rely on hadronic interaction models, which extrapolate collider data several orders of magnitude. A comparative study of Monte Carlo simulations of pp collisions (at the LHC center-of-mass energy ~ 14 TeV) using the most popular hadronic interaction models for ultrahigh energy cosmic ray (SIBYLL and QGSJET) and for collider physics (the PYTHIA multiparton model) is presented. The most relevant distributions are studied including those observables from diffractive events with the aim of discriminating between the different models.Comment: 8 pages revtex, 8 figures, added reference
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