Metastable π Junction between an s±-Wave and an s-Wave Superconductor

We examine a contact between a superconductor whose order parameter changes sign across the Brillioun zone, and an ordinary, uniform-sign superconductor. Within a Ginzburg-Landau-type model, we find that if the barrier between the two superconductors is not too high, the frustration of the Josephson coupling between different portions of the Fermi surface across the contact can lead to surprising consequences. These include time-reversal symmetry breaking at the interface and unusual energy-phase relations with multiple local minima. We propose this mechanism as a possible explanation for the half-integer flux quantum transitions in composite niobium-iron pnictide superconducting loops, which were discovered in recent experiments [C.-T. Chen et al., Nature Phys. 6, 260 (2010).]

Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology

We analyze the impact of a measurement, or of an improved bound, on theta_{13} for the determination of the effective neutrino mass in neutrino-less double beta decay and cosmology. In particular, we discuss how an improved limit on (or a specific value of) theta_{13} can influence the determination of the neutrino mass spectrum via neutrino-less double beta decay. We also discuss the interplay with improved cosmological neutrino mass searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR

Heavy Quark Physics From Lattice QCD

We review the application of lattice QCD to the phenomenology of b- and c-quarks. After a short discussion of the lattice techniques used to evaluate hadronic matrix elements and the corresponding systematic uncertainties, we summarise results for leptonic decay constants, B--Bbar mixing, semileptonic and rare radiative decays. A discussion of the determination of heavy quark effective theory parameters is followed by an explanation of the difficulty in applying lattice methods to exclusive nonleptonic decays.Comment: 52 pages LaTeX with 10 eps files. Requires: hfsprocl.sty (included) plus axodraw.sty, rotating.sty and array.sty. To appear in Heavy Flavours (2nd edition) edited by A J Buras and M Lindner (World Scientific, Singapore). Revised version corrects typo in axis labelling of Fig 1

Neutrino Masses and Absence of Flavor Changing Interactions in the 2HDM from Gauge Principles

We propose several Two Higgs Doublet Models with the addition of an Abelian gauge group which free the usual framework from flavor changing neutral interactions and explain neutrino masses through the seesaw mechanism. We discuss the kinetic and mass-mixing gripping phenomenology which encompass several constraints coming from atomic parity violation, the muon anomalous magnetic moment, rare meson decays, Higgs physics, LEP precision data, neutrino-electron scattering, low energy accelerators and LHC probes.Comment: 54 pages, 10 figure

Soft L_e-L_mu-L_tau flavour symmetry breaking and sterile neutrino keV Dark Matter

We discuss how a $L_e-L_\mu-L_\tau$ flavour symmetry that is softly broken leads to keV sterile neutrinos, which are a prime candidate for Warm Dark Matter. This is to our knowledge the first model where flavour symmetries are applied simultaneously to active and sterile neutrinos explaining at the same time active neutrino properties and this peculiar Dark Matter scenario. The essential point is that different scales of the symmetry breaking and the symmetry preserving entries in the mass matrix lead to one right-handed neutrino which is nearly massless compared to the other two. Furthermore, we naturally predict vanishing $\theta_{13}$ and maximal $\theta_{23}$, while the correct value of $\theta_{12}$ must come from the mixing of the charged leptons. We can furthermore predict an exact mass spectrum for the light neutrinos, which will be testable in the very near future.Comment: 14 page

Microscopic and Macroscopic Effects in the Decoherence of Neutrino Oscillations

We present a generic structure (the layer structure) for decoherence effectsin neutrino oscillations, which includes decoherence from quantum mechanicaland classical uncertainties. The calculation is done by combining the conceptof open quantum system and quantum field theory, forming a structure composedof phase spaces from microscopic to macroscopic level. Having information lossat different levels, quantum mechanical uncertainties parameterize decoherenceby an intrinsic mass eigenstate separation effect, while decoherence forclassical uncertainties is typically dominated by a statistical averagingeffect. With the help of the layer structure, we classify the former as statedecoherence (SD) and the latter as phase decoherence (PD), then furtherconclude that both SD and PD result from phase wash-out effects of differentphase structures on different layers. Such effects admit for simple numericalcalculations of decoherence for a given width and shape of uncertainties. Whileour structure is generic, so are the uncertainties, nonetheless, a few notableones are: the wavepacket size of the external particles, the effectiveinteraction volume at production and detection, the energy reconstruction modeland the neutrino production profile. Furthermore, we estimate the experimentalsensitivities for SD and PD parameterized by the uncertainty parameters, forreactor neutrinos and decay-at-rest neutrinos, using a traditional ratemeasuring method and a novel phase measuring method.<br

Implications of a matter-antimatter mass asymmetry in Penning-trap experiments

The Standard Model (SM) of particle physics, being a local, unitary andLorentz-invariant quantum field theory, remains symmetric under the combinedaction of Charge, Parity, and Time Reversal (CPT) symmetry. This automaticallyimplies that fundamental properties of particles and antiparticles should beequal in magnitude. These fundamental tenets of the CPT principle have been putto stringent tests in recent Penning-trap experiments, where thematter-antimatter mass asymmetry has been measured. In light of these recentadvances, we compare the bounds arising on CPT invariance from kaon systemswith those from Penning-trap experiments. Using a simple yet powerful argumentof mass decomposition of hadrons, we show that bounds on quark-antiquark massdifferences from kaon oscillations are way beyond the reach of Penning-trapexperiments. We discuss possible reformulations of our understanding of the SMin the case of a discovery of CPT violation by these precision experiments. Wefind that in most cases, these extensions are quite exotic, and requiresignificant fine-tuning to preserve micro-causality.<br