On Neutrinos and Fermionic Mass Patterns

Recent data on neutrino mass differences are consistent with a hierarchical neutrino mass structure strikingly similar to what is observed for the other fermionic masses.Comment: 8pages, 2figure

On suppressing the Higgsino-mediated proton decay in SUSY SO(10) GUT's

Using the freedom in SO(10) GUT's one can generalize the existing models without changing the mass spectrum of fermions to obtain a significant suppression of proton decay resulting from the baryon number violating operators of dimension 5. In some limiting cases, their contributions can be made negligible compared to the dimension 6 operators resulting from the heavy gauge bosons exchange.Comment: 19 pages, 3 Postscript figures, 2 mpost figures, rearranged plots, corrected typo

Neutrino mixing and CP violation from Dirac-Majorana bimaximal mixture and quark-lepton unification

We demonstrate that only two ansatz can produce the features of the neutrino mixing angles. The first ansatz comes from the quark-lepton grand unification; $\nu_{Di} = V_{CKM} \nu_{\alpha}$ is satisfied for left-handed neutrinos, where $\nu_{Di}$ are the Dirac mass eigenstates and $\nu_{\alpha}$ are the flavour eigenstates. The second ansatz comes from the assumption; $\nu_{Di} = U_{bimaximal} \nu_{i}$ is satisfied between the Dirac mass eigenstates $\nu_{Di}$ and the light Majorana neutrino mass eigenstates $\nu_{i}$, where $U_{bimaximal}$ is the bimaximal mixing matrix. By these two ansatz, the Maki-Nakagawa-Sakata matrix is given by $U_{MNS} = V_{CKM}^\dagger U_{bimaximal}$. We find that in this model the novel relation $\theta_{sol} + \theta_{13} = \pi/4$ is satisfied, where $\theta_{sol}$ and $\theta_{13}$ are solar and CHOOZ angle respectively. This "Solar-CHOOZ Complementarity" relation indicates that only if the CHOOZ angle $\theta_{13}$ is sizable, the solar angle $\theta_{sol}$ can deviate from the maximal mixing. We also infer the CP violation in neutrino oscillations. The leptonic Dirac CP phase $\delta_{MNS}$ is predicted as $\sin \delta_{MNS} \simeq A \lambda^2 \eta$, where $A, \lambda, \eta$ are the CKM parameters in Wolfenstein parametrization. Furthermore, we remark that the ratio of the Jarlskog CP violation factor for quarks and leptons is important, because the large uncertainty on $\eta$ is cancelled out in the ratio, $R_J \equiv J_{CKM}/J_{MNS} \simeq 4\sqrt{2} A \lambda^3 \simeq 5 \times 10^{-2}$.Comment: 9 pages, no figures; v2 references added, v3 references adde

Radiative Generation of the LMA Solution from Small Solar Neutrino Mixing at the GUT Scale

We show that in see-saw models with small or even vanishing lepton mixing angle $\theta_{12}$, maximal $\theta_{23}$, zero $\theta_{13}$ and zero CP phases at the GUT scale, the currently favored LMA solution of the solar neutrino problem can be obtained in a rather natural way by Renormalization Group effects. We find that most of the running takes place in the energy ranges above and between the see-saw scales, unless the charged lepton Yukawa couplings are large, which would correspond to a large $\tan \beta$ in the Minimal Supersymmetric Standard Model (MSSM). The Renormalization Group evolution of the solar mixing angle $\theta_{12}$ is generically larger than the evolution of $\theta_{13}$ and $\theta_{23}$. A large enhancement occurs for an inverted mass hierarchy and for a regular mass hierarchy with $|m_2 - m_1| \ll |m_2 + m_1|$. We present numerical examples of the evolution of the lepton mixing angles in the Standard Model and the MSSM, in which the current best-fit values of the LMA mixing angles are produced with vanishing solar mixing angle $\theta_{12}$ at the GUT scale.Comment: 10 pages, 6 figures; reference added, minor changes in the text; results unchanged; final version to appear in JHE

Neutrino Masses and Lepton-flavor-violating τ\tau Decays in the Supersymmetric Left-right Model

In the supersymmetric left-right model, the light neutrino masses are given by the Type-II seesaw mechanism. A duality property about this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino mass matrix. In this paper, We work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model. The stability of the Type-II seesaw scenario is briefly discussed. We also study the lepton-flavor-violating processes ($\tau\to \mu\gamma$ and $\tau\to e\gamma$) by using the reconstructed Higgs triplet Yukawa couplings

Flavour structure and proton decay in 6D orbifold GUTs

We study proton decay in a supersymmetric {\sf SO(10)} gauge theory in six dimensions compactified on an orbifold. The dimension-5 proton decay operators are forbidden by R-symmetry, whereas the dimension-6 operators are enhanced due to the presence of KK towers. Three sequential quark-lepton families are localised at the three orbifold fixed points, where {\sf SO(10)} is broken to its three GUT subgroups. The physical quarks and leptons are mixtures of these brane states and additional bulk zero modes. This leads to a characteristic pattern of branching ratios in proton decay, in particular the suppression of the p\to \m^+K^0 mode.Comment: 20 pages, 1 figur

Jeugdhulp en sport: : Samen voor een beter toekomstperspectief van kwetsbare jeugd

Ongeveer een op de tien mensen krijgt tijdens hun jeugd een vorm van jeugdhulp. Deze jongeren hebben te maken met een of meerdere uitdagingen die een gezonde toekomst in de weg staan. Denk bijvoorbeeld aan leer- of gedragsproblemen, een instabiele gezinssituatie of sociale druk van vrienden om het verkeerde pad op te gaan.Beleidsmakers en jeugdhulporganisaties proberen op verschillende manieren de ongelijkheid in toekomstperspectieven tussen jongeren te verkleinen. Steeds vaker denken zij daarbij aan de sportvereniging als een plek waar de genoemde sociaal kwetsbare jongeren zich positief kunnen ontwikkelen. Hoewel bekend is dat voor jeugd sportdeelname samenhangt met verschillende positieve uitkomsten (zie kader 1), is het onduidelijk of dit ook geldt voor kwetsbare jongeren. Wat betekent sportdeelname voor het toekomstperspectief van kwetsbare jongeren? Hoe geef je vorm aan een sportomgeving die kan bijdragen aan positieve sportervaringen? En wat is nodig voor een succesvolle samenwerking tussen jeugdhulporganisaties en sportverenigingen? Die vragen beantwoorden we in deze samenvatting van de bevindingen van vier jaar onderzoek naar jeugdhulp en sport

Global fits to neutrino oscillation data

I summarize the determination of neutrino oscillation parameters within the three-flavor framework from world neutrino oscillation data with date of May 2006, including the first results from the MINOS long-baseline experiment. It is illustrated how the determination of the leading "solar" and "atmospheric" parameters, as well as the bound on $\theta_{13}$ emerge from an interplay of various complementary data sets. Furthermore, I discuss possible implications of sub-leading three-flavor effects in present atmospheric neutrino data induced by $\Delta m^2_{21}$ and $\theta_{13}$ for the bound on $\theta_{13}$ and non-maximal values of $\theta_{23}$, emphasizing, however, that these effects are not statistically significant at present. Finally, in view of the upcoming MiniBooNE results I briefly comment on the problem to reconcile the LSND signal.Comment: 5 pages, 5 figures, talk presented at the SNOW2006 workshop, Stockholm, 2-6 May 200