72,986 research outputs found

    Open heavy-flavour production in pp and Pb-Pb collisions at the LHC, measured with ALICE at central rapidity

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    The ALICE experiment studies nucleus-nucleus collisions at the LHC in order to investigate the properties of QCD matter at extreme energy densities. The measurement of open charm and open beauty production allows to investigate the interaction of heavy quarks with the hot and dense medium formed in high-energy nucleus-nucleus collisions. In particular, in-medium energy loss is predicted to be different for gluons, light quarks and heavy quarks and to depend on the medium energy density and size. ALICE has measured open heavy-flavour particle production at central rapidity in several decay channels in Pb-Pb and pp collisions at sqrt{s_NN} = 2.76 TeV and sqrt{s} = 2.76, 7 TeV respectively. The results obtained from the reconstruction of D meson decays at central rapidity and from electrons from heavy-flavour hadron decay will be presented.Comment: Proceedings of the International Conference "Primordial QCD Matter in LHC Era -Implication of QCD results on the early universe", El Cairo, 4th-8th December 201

    On the compatibility between cup products, the Alekseev--Torossian connection and the Kashiwara--Vergne conjecture

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    For a finite-dimensional Lie algebra g\mathfrak g over a field K⊃C\mathbb K\supset \mathbb C, we deduce from the compatibility between cup products Kontsevich (2003, Section 8) and from the main result of Shoikhet (2001) an alternative way of re-writing Kontsevich product ⋆\star on S(g)\mathrm S(\mathfrak g) by means of the Alekseev--Torossian flat connection (Alekseev and Torossian, 2010). We deduce a similar formula directly from the Kashiwara--Vergne conjecture (Kashiwara and Vergne, 1978).Comment: 8 pages, 1 figure; notation changed; corrected many other misprints recently noticed; comments are very welcome

    The explicit equivalence between the standard and the logarithmic star product for Lie algebras

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    The purpose of this short note is to establish an explicit equivalence between the two star products ⋆\star and ⋆log⁡\star_{\log} on the symmetric algebra S(g)\mathrm S(\mathfrak g) of a finite-dimensional Lie algebra g\mathfrak g over a field K⊃C\mathbb K\supset\mathbb C of characteristic 0 associated with the standard angular propagator and the logarithmic one: the differential operator of infinite order with constant coefficients realizing the equivalence is related to the incarnation of the Grothendieck-Teichm\"uller group considered by Kontsevich.Comment: 2 figures; corrected and completed the formulation of Theorem 3.7. Comments are very welcome
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