1,720,991 research outputs found
On the Phase Transition of Conformal Field Theories with Holographic Duals
No full textpreprint: ArXiV:hep-th/010723
Some Aspects of the Quantization of p-Forms and Reducible Gauge Theories
No full textThe quantization of thep-form inD dimensions is carried out according to both an extension of the BRST formalism and a method due to A. S. Schwarz. The latter yields a suggestive interpretation of the role of nonphysical fields in the quantization of reducible gauge theories. The introduction of gauge conditions of a different type (namely self-dual) modifies the ghost spectrum but does not affect the partition function
KL→π0γγ decay in the chiral effective lagrangian
No full textIn the framework of chiral perturbation theory we study the one-loop amplitude for KL→π0γγ. We find that it is finite, consistently with the absence of the corresponding counterterms. Our prediction for the branching ratio (6.8·10−7) is below the present experimental upper bound
What does Holographic QCD predict for anomalous (g − 2)μ?
No full textIn this talk we discuss how holographic models of QCD have been applied to the study of the lightby-light contribution to the muon anomalous magnetic moment. After a review of the holographic procedure, we discuss the approach we followed in a previous work, in which, using a certain set of holographic model as a “Theory Space”, we gave our estimate for the π0 exchange diagram. Our result depended also on the value of the quark magnetic susceptibility. Thus, in the last part of the talk, we concentrate on the attempts which have been done in the literature to apply holographic methods to the evaluation of this important order parameter of QCD
Holographic approach to the light-by-light contribution to the muon (g-2)
No full textWe discuss how holographic models of QCD are used to study the the hadronic light-by-light (HLbL) scattering amplitude contribution to the muon anomalous magnetic moment. After a brief description of the various models, we focus on a particular one, introduced by Hirn and Sanz, emphasizing the role it assigns to the pion, and the vector and-axial vector resonances. We review how the parameters of the model are fixed by imposing condition on the low energy and the deep Euclidean limit of two-point correlators of QCD vector and axial vector currents. We then focus on the evaluation of the three-point axial-vector-vector current correlator and the pion anomalous transition form factor to be used in the one-pion exchange HLbL diagram and study its asymptotic properties. Finally, we present preliminary results on the four vector current correlator that defines the Hadronic Light-by-Light tensor. We find that axial-vector resonances play an important rule in recovering the correct asymptotic behaviour predicted by QCD at large Euclidean momenta
Standard Model prediction and new physics tests for D° -> h1+, h2- , l+, l- (h=pi, K; l =e,mu)
No full textMotivated by the recent evidence for direct CP-violation in D0 -> h+h- decays, we provide an exhaustive study of both Cabibbo-favored and Cabibbo-suppressed (singly and doubly) D0 -> h1+h2-l+l- decays. In particular, we study the Dalitz plot for the long-distance contributions in the (m_{ll}^2,m_{hh}^2) parameter space. We find that near-resonant effects, i.e., D0 -> V(h1+h2-)l+l- with V=\rho,K*,\phi, are sizeable and even dominant (over Bremsstrahlung) for the \mu+\mu- decay modes, bringing the branching ratios close to the LHCb reach. We also provide a detailed study of the angular asymmetries for such decays and identify signatures for new physics detection. In particular, new physics signals can be neatly isolated in asymmetries involving the semileptonic operator Q_{10}, where for typical new physics scenarios the effects can be as sizeable as O(1%) for the doubly Cabibbo-suppressed mode
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