Results 1 - 10 of 437470
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[en] We present the non-forward quark matrix elements of operators with one and two covariant derivatives needed for the renormalisation of the first and second moments of generalised parton distributions in one-loop lattice perturbation theory using clover fermions. For some representations of the hypercubic group commonly used in simulations we define the sets of possible mixing operators and compute the one-loop mixing matrices of renormalisation factors. Tadpole improvement is applied to the results and some numerical examples are presented
[en] We show that a fourth family of quarks with mt(prime) in the range of (400-600) GeV provides a rather simple explanation for the several indications of new physics that have been observed involving CP asymmetries of the b-quark. The built-in hierarchy of the 4 x 4 mixing matrix is such that the t(prime) readily provides a needed perturbation (∼15%) to sin2β as measured in B → ψ Ks and simultaneously is the dominant source of CP asymmetry in Bs → ψφ. The correlation between CP asymmetries in Bs → ψφ and Bd → φKs suggests m(prime)t ∼ (400-600) GeV. Such heavy masses point to the tantalizing possibility that the 4th family plays an important role in the electroweak symmetry breaking.
[en] Gaining insight into ensembles of magnetic configurations which could originate the confining string tension between quarks, constitutes a major concern in current lattice investigations. This interest also applies to a different approach, where gauge models with spontaneous symmetry breaking are constructed to describe the confining string as a smooth vortex solution. In this article, we initially show how to incorporate non-Abelian information into an ensemble of monopoles in 4D, characterized by phenomenological parameters. Next, using some recent techniques developed for polymers, we are able to relate the coloured ensemble with a non-Abelian gauge model. This could offer an interesting perspective in discussing some of the different approaches for describing confinement. (paper)
[en] Quark-antiquark bound states are examined in the long-range strong-coupling limit with the Wilson minimal-area law assumed as input. Matrix element relations are established which in the effective theory obtain dynamical equations resembling the confining part of the relativistic flux-tube model. (author)