154 research outputs found
Theory of rare kaon decays
We review some recent theoretical results on rare kaon decays. Particular
attention is devoted to find Standard Model tests. This is theoretically easy
in , while a careful study of the long distance
contributions is needed for , and Comment: 11 pages Latex file, no figures;Invited plenary talk at the 3rd
International Conference on B Physics and CP Violation (BCONF99), Taipei,
Taiwan, 3-7 Dec 199
Recent developments in rare kaon decays
We discuss issues in rare and radiative kaon decays. The interest is to
extract useful short-distance information and uncover underlying dynamics. We
emphasize channels where either we can understand non-perturbative aspects of
QCD or there is a chance to test the Standard Model.Comment: Invited minireview for Modern Physics Letters A (MPLA), 15 pages, 9
figures, usepackages epsf,colo
Standard Model prediction and new physics tests for D0 -> h+h-l+l- (h=\pi,K; l=e,\mu)
Motivated 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 modes.Comment: 19 pages, 5 figures. v2 (journal version) contains the new subsection
III.B, where the potential size of new physics effects is discussed. Tables
and figures slightly changed to match the journal version. Typos corrected
and references added. Conclusions unchange
Antisymmetric tensors in holographic approaches to QCD
We study real (massive) antisymmetric tensors of rank two in holographic
models of QCD based on the gauge/string duality. Our aim is to understand in
detail how the AdS/CFT correspondence describes correlators with tensor
currents in QCD. To this end we study a set of bootstrapped correlators with
spin-1 vector and tensor currents, imposing matching to QCD at the partonic
level. We show that a consistent description of this set of correlators yields
a very predictive picture. For instance, it imposes strong constraints on
infrared boundary conditions and precludes the introduction of dilatonic
backgrounds as a mechanism to achieve linear confinement. Additionally,
correlators with tensor currents turn out to be especially sensitive to chiral
symmetry breaking, thus offering an ideal testing ground for genuine QCD
effects. Several phenomenological consequences are explored, such as the
nontrivial interplay between states and conventional vector
mesons.Comment: 15 pages, 2 figures. Minor changes to match the journal versio
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