68 research outputs found
Probing Left-handed Slepton Flavor Mixing at Future Lepton Colliders
It has been argued in the literature that the search for the slepton
oscillation phenomenon can be a powerful probe of intergenerational mixing
between sleptons, once sleptons are found at future colliders. In this article
we estimate possible reach of future lepton colliders in probing left-handed
slepton flavor mixing, especially mixing between the first and third
generations, on which constraints imposed by other processes like are very weak. collider is suitable for this purpose, since it
can produce, if kinematically allowed, sleptons of the first generation via
t-channel, in addition to s-channel. Utilizing e^+e^- \to \tau e + 4jets + \E
signal at linear collider with integrated luminosity L=50 fb^{-1}(500
fb^{-1}) it may be possible to reach mixing angle and mass difference GeV for sneutrinos in the first and third generations at the
statistical significance of 5 \sigma.Comment: 27 pages, 6 figures. A new section added. Conclusion unchanged. To
appear in Phys. Rev.
The SUSY seesaw model and lepton-flavor violation at a future electron-positron linear collider
We study lepton-flavor violating slepton production and decay at a future
e^+e^- linear collider in context with the seesaw mechanism in mSUGRA post-LEP
benchmark scenarios. The present knowledge in the neutrino sector as well as
improved future measurements are taken into account. We calculate the signal
cross-sections \sigma(e^{+/-}e^- -> l_{\beta}^{+/-} l_{\alpha}^-
\tilde{\chi}_b^0 \tilde{\chi}_a^0); l_{\delta}=e, \mu, \tau; \alpha =|= \beta
and estimate the main background processes. Furthermore, we investigate the
correlations of these signals with the corresponding lepton-flavor violating
rare decays l_{\alpha} -> l_{\beta} \gamma. It is shown that these correlations
are relatively weakly affected by uncertainties in the neutrino data, but very
sensitive to the model parameters. Hence, they are particularly suited for
probing the origin of lepton-flavor violation.Comment: 31 pages, 10 figures, version published in Phys. Rev.
A New Parametrization of the Seesaw Mechanism and Applications in Supersymmetric Models
We present a new parametrization of the minimal seesaw model, expressing the
heavy-singlet neutrino Dirac Yukawa couplings and Majorana
masses in terms of effective light-neutrino observables and an
auxiliary Hermitian matrix In the minimal supersymmetric version of the
seesaw model, the latter can be related directly to other low-energy
observables, including processes that violate charged lepton flavour and CP.
This parametrization enables one to respect the stringent constraints on
muon-number violation while studying the possible ranges for other observables
by scanning over the allowed parameter space of the model. Conversely, if any
of the lepton-flavour-violating process is observed, this measurement can be
used directly to constrain and As applications, we
study flavour-violating decays and the electric dipole moments of
leptons in the minimal supersymmetric seesaw model.Comment: Important references adde
Early detection of secondary damage in ipsilateral thalamus after acute infarction at unilateral corona radiata by diffusion tensor imaging and magnetic resonance spectroscopy
<p>Abstract</p> <p>Background</p> <p>Traditional magnetic resonance (MR) imaging can identify abnormal changes in ipsilateral thalamus in patients with unilateral middle cerebral artery (MCA) infarcts. However, it is difficult to demonstrate these early changes quantitatively. Diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy (MRS) are potentially sensitive and quantitative methods of detection in examining changes of tissue microstructure and metabolism. In this study, We used both DTI and MRS to examine possible secondary damage of thalamus in patients with corona radiata infarction.</p> <p>Methods</p> <p>Twelve patients with unilateral corona radiata infarction underwent MR imaging including DTI and MRS at one week (W1), four weeks (W4), and twelve weeks (W12) after onset of stroke. Twelve age-matched controls were imaged. Mean diffusivity (MD), fractional anisotropy (FA), N-acetylaspartate (NAA), choline(Cho), and creatine(Cr) were measured in thalami.</p> <p>Results</p> <p>T1-weighted fluid attenuation inversion recovery (FLAIR), T2-weighted, and T2-FLAIR imaging showed an infarct at unilateral corona radiate but no other lesion in each patient brain. In patients, MD was significantly increased at W12, compared to W1 and W4 (all <it>P</it>< 0.05). NAA was significantly decreased at W4 compared to W1, and at W12 compared to W4 (all <it>P</it>< 0.05) in the ipsilateral thalamus. There was no significant change in FA, Cho, or Cr in the ipsilateral thalamus from W1 to W12. Spearman's rank correlation analysis revealed a significant negative correlation between MD and the peak area of NAA, Cho, and Cr at W1, W4, and W12 and a significant positive correlation of FA with NAA at W1.</p> <p>Conclusions</p> <p>These findings indicate that DTI and MRS can detect the early changes indicating secondary damage in the ipsilateral thalamus after unilateral corona radiata infarction. MRS may reveal the progressive course of damage in the ipsilateral thalamus over time.</p
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