1,705 research outputs found

    The Role of Higher Twist in Determining Polarized Parton Densities from DIS data

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    Different methods to extract the polarized parton densities from the world polarized DIS data are considered. The higher twist corrections hN(x)/Q2h^N(x)/Q^2 to the spin dependent proton and neutron g1g_1 structure functions are found to be non-negligible and important in the QCD analysis of the present experimental data. Their role in determining the polarized parton densities in the framework of the different approaches is discussed.Comment: To appear in the Proceedings of the Spin2004 Symposium, Trieste, 11-16 Oct 200

    Set Systems Containing Many Maximal Chains

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    The purpose of this short problem paper is to raise an extremal question on set systems which seems to be natural and appealing. Our question is: which set systems of a given size maximise the number of (n+1)(n+1)-element chains in the power set P({1,2,…,n})\mathcal{P}(\{1,2,\dots,n\})? We will show that for each fixed α>0\alpha>0 there is a family of α2n\alpha 2^n sets containing (α+o(1))n!(\alpha+o(1))n! such chains, and that this is asymptotically best possible. For smaller set systems we are unable to answer the question. We conjecture that a `tower of cubes' construction is extremal. We finish by mentioning briefly a connection to an extremal problem on posets and a variant of our question for the grid graph.Comment: 5 page

    Narrative Health Communication and Behavior Change: The Influence of Exemplars in the News on Intention to Quit Smoking.

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    This study investigated psychological mechanisms underlying the effect of narrative health communication on behavioral intention. Specifically, the study examined how exemplification in news about successful smoking cessation affects recipients\u27 narrative engagement, thereby changing their intention to quit smoking. Nationally representative samples of U.S. adult smokers participated in 2 experiments. The results from the 2 experiments consistently showed that smokers reading a news article with an exemplar experienced greater narrative engagement compared to those reading an article without an exemplar. Those who reported more engagement were in turn more likely to report greater smoking cessation intentions

    Can the polarization of the strange quarks in the proton be positive ?

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    Recently, the HERMES Collaboration at DESY, using a leading order QCD analysis of their data on semi-inclusive deep inelastic production of charged hadrons, reported a marginally positive polarization for the strange quarks in the proton. We argue that a non-negative polarization is almost impossible.Comment: 6 pages, latex, minor changes in the discussion after Eq. (9
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