Tau neutrino magnetic moments from the Super-Kamiokande and ν\nu e-scattering data

Combined results on $\nu_{\mu}\to \nu_{\tau}$ oscillations and $\nu e$-scattering from the Super-Kamiokande and LAMPF experiments, respectively, limit the Dirac $\nu_{\tau}$ diagonal magnetic moment to $\mu_{\nu_{\tau}} < 1.9\times 10^{-9} \mu_{B}$. For the scheme with 3 Majorana neutrinos the LAMPF results allow the limitation of effective $\nu_{\tau}$ magnetic moment to $\mu_{\nu_{\tau}} < 7.6 \times 10^{-10}\mu_{B}$. The moments in the scheme with additional Majorana light sterile neutrinos as well as experiments on stimulated radiative neutrino conversion are also discussed.Comment: 12 pages, To appear in Phys. Lett.

Standard Model Higgs boson mass from inflation: two loop analysis

We extend the analysis of \cite{Bezrukov:2008ej} of the Standard Model Higgs inflation accounting for two-loop radiative corrections to the effective potential. As was expected, higher loop effects result in some modification of the interval for allowed Higgs masses m_min<m_H<m_max, which somewhat exceeds the region in which the Standard Model can be considered as a viable effective field theory all the way up to the Planck scale. The dependence of the index n_s of scalar perturbations on the Higgs mass is computed in two different renormalization procedures, associated with the Einstein (I) and Jordan (II) frames. In the procedure I the predictions of the spectral index of scalar fluctuations and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to n_s=0.97 and r=0.0034 respectively. In the procedure II the index n_s acquires the visible dependence on the Higgs mass and and goes out of the admitted interval at m_H below m_min. We compare our findings with the results of \cite{DeSimone:2008ei}.Comment: 24 paged, 9 figures. Journal version (typos fixed, expanded discussions

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.

Limits on the magnetic moment of sterile neutrino and two-photon neutrino decay

It is shown that the non-zero transition magnetic moment ($\mu_{tran}$) between the sterile neutrino ($\nu_{s}$) and the muon neutrino ($\nu_{\mu}$) could be effectively searched for via the Primakoff effect, in the process of $\nu_{\mu} Z \to \nu_{s}Z$ conversion in the external Coulomb field of a nucleus $Z$, with the subsequent $\nu_{s}\to \nu_{\mu} + \gamma$ decay. From the recent results of the NOMAD neutrino detector at CERN a model-independent constraint of $\mu_{tran} < (10^{-6} - 10^{-9}) \mu_{B}$ is obtained depending on the value of $\nu_{s}$ mass. For the $m_{s}\sim O(1) GeV$ region these bounds are comparable with the present experimental ones on $\nu_{\mu}$ and $\nu_{e}$ diagonal magnetic moments and are more sensitive than those on $\nu_{\tau}$ magnetic moment. From the same analysis the constraint on $\nu_{\tau}(\nu_{s})\to \nu_{\mu} +\gamma + \gamma$ decay lifetime $\tau > 2\times10^{13} sec/m_{\nu}^{7}(MeV)$ is obtained. The limit is valid for neutrino masses up to $m_{\nu}\sim O(1)GeV$.Comment: 13 pages, LaTex, 2 eps fugures included. 2 references are added. Submitted to Phys. Lett.

de Sitter String Vacua from Supersymmetric D-terms

We propose a new mechanism for obtaining de Sitter vacua in type IIB string theory compactified on (orientifolded) Calabi-Yau manifolds similar to those recently studied by Kachru, Kallosh, Linde and Trivedi (KKLT). dS vacuum appears in KKLT model after uplifting an AdS vacuum by adding an anti-D3-brane, which explicitly breaks supersymmetry. We accomplish the same goal by adding fluxes of gauge fields within the D7-branes, which induce a D-term potential in the effective 4D action. In this way we obtain dS space as a spontaneously broken vacuum from a purely supersymmetric 4D action. We argue that our approach can be directly extended to heterotic string vacua, with the dilaton potential obtained from a combination of gaugino condensation and the D-terms generated by anomalous U(1) gauge groups.Comment: 17 pages, 1 figur

A Quantitative Model of Energy Release and Heating by Time-dependent, Localized Reconnection in a Flare with a Thermal Loop-top X-ray Source

We present a quantitative model of the magnetic energy stored and then released through magnetic reconnection for a flare on 26 Feb 2004. This flare, well observed by RHESSI and TRACE, shows evidence of non-thermal electrons only for a brief, early phase. Throughout the main period of energy release there is a super-hot (T>30 MK) plasma emitting thermal bremsstrahlung atop the flare loops. Our model describes the heating and compression of such a source by localized, transient magnetic reconnection. It is a three-dimensional generalization of the Petschek model whereby Alfven-speed retraction following reconnection drives supersonic inflows parallel to the field lines, which form shocks heating, compressing, and confining a loop-top plasma plug. The confining inflows provide longer life than a freely-expanding or conductively-cooling plasma of similar size and temperature. Superposition of successive transient episodes of localized reconnection across a current sheet produces an apparently persistent, localized source of high-temperature emission. The temperature of the source decreases smoothly on a time scale consistent with observations, far longer than the cooling time of a single plug. Built from a disordered collection of small plugs, the source need not have the coherent jet-like structure predicted by steady-state reconnection models. This new model predicts temperatures and emission measure consistent with the observations of 26 Feb 2004. Furthermore, the total energy released by the flare is found to be roughly consistent with that predicted by the model. Only a small fraction of the energy released appears in the super-hot source at any one time, but roughly a quarter of the flare energy is thermalized by the reconnection shocks over the course of the flare. All energy is presumed to ultimately appear in the lower-temperature T<20 MK, post-flare loops