44,836 research outputs found
Effects of Sfermion Mixing induced by RGE Running in the Minimal Flavor Violating CMSSM
Within the Constrained Minimal Supersymmetric Standard Model (CMSSM) with
Minimal Flavor Violation (MFV) for scalar quarks we study the effects of
intergenerational squark mixing on -physics observables, electroweak
precision observables (EWPO) and the Higgs boson mass predictions. Squark
mixing is generated through the Renormalization Group Equations (RGE) running
from the GUT scale to the electroweak scale due to presence of non diagonal
Yukawa matrices in the RGE's, e.g. due to the CKM matrix. We find that the
-Physics observables as well as the Higgs mass predictions do not receive
sizable corrections. On the other hand, the EWPO such as the boson mass can
receive corrections by far exceeding the current experimental precision. These
contributions can place new upper bounds on the CMSSM parameter space. We
extend our analysis to the CMSSM extended with a mechanism to explain neutrino
masses (CMSSM-seesaw I), which induces flavor violation in the scalar lepton
sector. Effects from slepton mixing on the analyzed observables are in general
smaller than from squark mixing, but can reach the level of the current
experimenal uncertainty for the EWPO
\phi K^{+}K^{-} production in electron-positron annihilation
In this work we study the e^{+}e^{-}\to\phi K^{+}K^{-} reaction. The leading
order electromagnetic contributions to this process involve the \gamma*\phi\
K^{+}K^{-} vertex function with a highly virtual photon. We calculate this
function at low energies using R\chi PT supplemented with the anomalous term
for the VV'P interactions. Tree level contributions involve the kaon form
factors and the K*K transition form factors. We improve this result, valid for
low photon virtualities, replacing the lowest order terms in the kaon form
factors and K*K transition form factors by the form factors as obtained in
U\chi PT in the former case and the ones extracted from recent data on
e^{+}e^{-}\to KK* in the latter case. We calculate rescattering effects which
involve meson-meson amplitudes. The corresponding result is improved using the
unitarized meson-meson amplitudes containing the scalar poles instead of the
lowest order terms. Using the BABAR value for BR(X\to \phi f_{0})\Gamma (X\to
e^{+} e^{-}), we calculate the contribution from intermediate X(2175). A good
description of data is obtained in the case of destructive interference between
this contribution and the previous ones, but more accurate data on the
isovector K*K transition form factor is required in order to exclude
contributions from an intermediate isovector resonance to e^{+}e^{-}\to \phi\
K^{+}K^{-} around 2.2 GeV.Comment: 21 pages, 17 figures. Revised version to appear in Phys. Rev. D.
Contributions of intermediate X(2175) included. Extraction of form factors
update
Pion-to-vacuum vector and axial vector amplitudes and weak decays of pions in a magnetic field
We propose a model-independent parametrization for the one-pion-to-vacuum
matrix elements of the vector and axial vector hadronic currents in the
presence of an external uniform magnetic field. It is shown that, in general,
these hadronic matrix elements can be written in terms of several gauge
covariant Lorentz structures and form factors. Within this framework we obtain
a general expression for the weak decay and discuss
the corresponding limits of strong and weak external magnetic fields.Comment: 33 page
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