CP Violation, Sneutrino Oscillation and Neutrino Masses in R-parity Violating Supersymmetric Standard Model

In supersymmetric theories, sneutrino--anti-sneutrino mixing can occur with the oscillation time $\sim 0.01$ ps corresponding the atmospheric neutrino mass scale $\sim 0.05$ eV. We explore the possibility of observing sneutrino oscillation phenomena and CP violation when R-parity violation explains the observed neutrino masses and mixing. It is shown for some parameter region in the bilinear model of R-parity violation that the tiny sneutrino mass splitting and time-dependent CP violating asymmetries could be measured in the future experiments if the tau sneutrino is the lightest supersymmetric particle.Comment: 13pp. title changed, new numerical examples added, main conclusions not changed. version to appear in PL

Testing Neutrino Mass Models

The existence of the neutrino masses and mixing would be an important window into the nature of physics beyond the Standard Model, which will be searched for in the forthcoming experiments such as LHC. In this talk, we discuss some examples of neutrino mass models which are testable through the observation of lepton flavor violating processes and/or electric dipole moments correlated with the neutrino mass structure.Comment: 7 pages, Plenary talk at PASCOS 200

Axion Dark Matter with High-Scale Inflation

We show that supersymmetric axion models breaking the PQ symmetry by the interplay of non-renormalizable supersymmetric terms and soft supersymmetry breaking terms provide a natural framework not only for generating the axion scale from soft supersymmetry breaking scale $m_{3/2}$ but also for enhancing it during inflation by factor of order $\sqrt{H_I/m_{3/2}}$ where $H_I \simeq 10^{14}$ GeV according to the recent BICEP2 result. In this scheme, the PQ symmetry can stay broken throughout the whole history of the Universe if the reheat temperature is below $10^{10}$ GeV, or $m_{3/2}$ when the PQ fields couple strongly to thermal (Standard Model) particles. It is also shown that parametric resonance during preheating is not effective enough to induce non-thermal PQ symmetry restoration. As a consequence, axion models with the QCD anomaly $N_{DW}>1$ can be made free from the domain wall problem while the axion isocurvature perturbation is suppressed sufficiently for the axion scale during inflation larger than about M_P (\Omega_a h^2/0.12)^{1/2} ( F_a/10^{12} \mbox{GeV})^{0.6} GeV.Comment: 5 page

Muon g−-2 in two-Higgs-doublet models

Updating various theoretical and experimental constraints on the four different types of two-Higgs-doublet models (2HDMs), we find that only the ``lepton-specific" (or ``type X") 2HDM can explain the present muon g$-$2 anomaly in the parameter region of large $\tan\beta$, a light CP-odd boson, and heavier CP-even and charged bosons which are almost degenerate. The severe constraints on the models come mainly from the consideration of vacuum stability and perturbativity, the electroweak precision data, the $b$-quark observables like $B_S \to \mu\mu$, the precision measurements of the lepton universality as well as the 125 GeV boson property observed at the LHC.Comment: 11 pages, 7 figures, prepared for a review article in Pramana and the proceedings of FCCP2015. arXiv admin note: text overlap with arXiv:1505.0049

R-parity Violation and Neutrino Masses

R-parity violation in the supersymmetric standard model could be the origin of neutrino masses and mixing accounting for the atmospheric and solar neutrino oscillations. More interestingly, this hypothesis may be tested in future colliders by detecting lepton number violating decays of the lightest supersymmetric particle. Here, we present a comprehensive analysis for the determination of sneutrino vacuum expectation values from the one-loop effective scalar potential, and also for the one-loop renormalization of neutrino masses and mixing. Applying our results to theories with gauge mediated supersymmetry breaking, we discuss the effects of the one-loop corrections and how the realistic neutrino mass matrices arise.Comment: 4 pages using ws-p8-50x6-00.cl

Late Leptogenesis from Radiative Soft Terms

We point out that the so-called ``soft leptogenesis'' can occur at TeV scale if the $B$ term is generated through radiative corrections which involve two-loop diagrams with the gaugino exchange. This mechasnism requires the non-trivial CP phase, ${Im}(A m_{1/2}^*)\neq 0$, and can naturally explain the observed baryon asymmetry of the universe associated with the TeV scale seesaw mechanism. Such a low scale leptogenesis would be a promising option in view of the tight upper limit on the reheat temperature avoiding the gravitino problem in supergravity models.Comment: 8 pages, 1 figure include

Dirac Leptogenesis in extended nMSSM

We show that a version of the nearly Minimal Supersymmetric Standard Model (nMSSM), extended only in the singlet sector to include the additional superfields of right-handed neutrinos and very heavy Dirac particles conserving $B-L$, admits a viable scenario for Dirac leptogenesis and naturally small Dirac neutrino masses. The origin of the ($B-L$)-conserving high singlet neutrino scale and the desired supersymmetry breaking terms is associated with dynamical supersymmetry breaking in the hidden sector.Comment: 7 pages, references added, numbering corrected, to be published in JHE

Search for a doubly-charged boson in four lepton final states in type II seesaw

CMS and ATLAS have searched for a doubly-charged boson $H^{\pm\pm}$ which may arise from type II seesaw in the 7 TeV run at the LHC by considering pair or associated production of doubly-charged bosons under the assumption of degenerate triplet scalars. In this work, we consider non-degenerate triplet components with the mass gap $\Delta M \sim 1 - 40$ GeV which leads to enhanced pair-production cross-sections of $H^{\pm\pm}$ added by the gauge decays of the heavier neutral and singly-charged bosons. We reevaluate the constraints in the $\Delta M-M_{H^{++}}$ plane depending on the triplet vacuum expectation value $v_\Delta$ in the type II seesaw model which are much more stringent than the current search limits. We further study the possibility of observing same-sign tetra-lepton signals in the allowed parameter space which can be probed in the future runs of the LHC.Comment: 15 pages, 13 figure