40,486 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
The formation of spiral arms and rings in barred galaxies
In this and in a previous paper (Romero-Gomez et al. 2006) we propose a
theory to explain the formation of both spirals and rings in barred galaxies
using a common dynamical framework. It is based on the orbital motion driven by
the unstable equilibrium points of the rotating bar potential. Thus, spirals,
rings and pseudo-rings are related to the invariant manifolds associated to the
periodic orbits around these equilibrium points. We examine the parameter space
of three barred galaxy models and discuss the formation of the different
morphological structures according to the properties of the bar model. We also
study the influence of the shape of the rotation curve in the outer parts, by
making families of models with rising, flat, or falling rotation curves in the
outer parts. The differences between spiral and ringed structures arise from
differences in the dynamical parameters of the host galaxies. The results
presented here will be discussed and compared with observations in a
forthcoming paper.Comment: 16 pages, 13 figures, accepted in A&A. High resolution version
available at http://www.oamp.fr/dynamique/pap/merce.htm
\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
- …