23,179 research outputs found

    The Experiment Road to the Heavier Quarks and Other Heavy Objects

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    After a brief history of heavy quarks, I will discuss charm, bottom, and top quarks in turn. For each one, I discuss its first observation, and then what we have learned about production, hadronization, and decays - and what these have taught us about the underlying physics. I will also point out remaining open issues. For this series of lectures, the charm quark will be emphasized. It is the first of the heavy quarks, and its study is where many of the techniques and issues first appeared. Only very brief mention is made of CP violation in the bottom-quark system since that topic is the subject of a separate series of lectures by Gabriel Lopez. As the three quarks are reviewed, a pattern of techniques and lessons emerges. These are identified, and then briefly considered in the context of anticipated physics signals of the future; e.g., for Higgs and SUSY particles.Comment: From three lectures at the "IX Escuela de Particulas y Campos" in Metepec, Mexico - August, 2000. 30 pages, 5 figures Revised version with spelling/grammar corrections and clearer figur

    LHC Symposium 2003: Summary Talk

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    This summary talk reviews the LHC 2003 Symposium, focusing on expectations as we prepare to leap over the current energy frontier into new territory. We may learn from what happened in the two most recent examples of leaping into new energy territory. Quite different scenarios appeared in those two cases. In addition, we review the status of the machine and experiments as reported at the Symposium. Finally, I suggest an attitude which may be most appropriate as we look forward to the opportunities anticipated for the first data from the LHC.Comment: Summary Talk: LHC Symposium, May 1-3, 2003, Fermilab, Batavia, IL US

    Charm Results on CP Violation and Mixing

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    The most recent results on CP violation and mixing in the charm system are reviewed as a guide to the future. While no surprising results are reported so far, charm provides a unique window to physics beyond the Standard Model. The results reported here come from four sources: ALEPH at LEP, E791 and FOCUS/E831 at Fermilab, and CLEO II.V at CESR. Results beyond these sources may be expected as a byproduct of B-motivated experiments.Comment: 17 pages,including 4 figures, Workshop on Physics and Detectors for Daphne, Frascati, Italy, November 16-19, 199

    Toward a language theoretic proof of the four color theorem

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    This paper considers the problem of showing that every pair of binary trees with the same number of leaves parses a common word under a certain simple grammar. We enumerate the common parse words for several infinite families of tree pairs and discuss several ways to reduce the problem of finding a parse word for a pair of trees to that for a smaller pair. The statement that every pair of trees has a common parse word is equivalent to the statement that every planar graph is four-colorable, so the results are a step toward a language theoretic proof of the four color theorem.Comment: 18 pages, many images; final versio

    Reduced purities as measures of decoherence in many-electron systems

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    A hierarchy of measures of decoherence for many-electron systems that is based on the purity and the hierarchy of reduced electronic density matrices is presented. These reduced purities can be used to characterize electronic decoherence in the common case when the many-body electronic density matrix is not known and only reduced information about the electronic subsystem is available. Being defined from reduced electronic quantities, the interpretation of the reduced purities is more intricate than the usual (many-body) purity. This is because the nonidempotency of the rr-body reduced electronic density matrix that is the basis of the reduced purity measures can arise due to decoherence or due to electronic correlations. To guide the interpretation, explicit expressions are provided for the one-body and two-body reduced purities for a general electronic state. Using them, the information content and structure of the one-body and two-body reduced purities is established, and limits on the changes that decoherence can induce are elucidated. The practical use of the reduced purities to understand decoherence dynamics in many-electron systems is exemplified through an analysis of the electronic decoherence dynamics in a model molecular system.Comment: 10 pages, 3 figure

    Quantization of continuum Kac-Moody algebras

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    Continuum Kac-Moody algebras have been recently introduced by the authors and O. Schiffmann. These are Lie algebras governed by a continuum root system, which can be realized as uncountable colimits of Borcherds-Kac-Moody algebras. In this paper, we prove that any continuum Kac-Moody algebra is canonically endowed with a non-degenerate invariant bilinear form. The positive and negative Borel subalgebras form a Manin triple with respect to this pairing, inducing on the continuum Kac-Moody algebra a topological quasi-triangular Lie bialgebra structure. We then construct an explicit quantization, which we refer to as a continuum quantum group, and we show that the latter is similarly realized as an uncountable colimit of Drinfeld-Jimbo quantum groups.Comment: Final version. Minor change