Gravitino/Axino as Decaying Dark Matter and Cosmological Tensions

In supersymmetric axion models, if the gravitino or axino is the lightest SUSY particle (LSP), the other is often the next-to-LSP (NLSP). We investigate the cosmology of such a scenario and point out that the lifetime of the NLSP naturally becomes comparable to the present age of the universe in a viable parameter region. This is a well-motivated example of the so-called decaying dark matter model, which is recently considered as an extension of the $\Lambda$CDM model to relax some cosmological tensions.Comment: 16 pages, 2 figures, Journal versio

Reconstruction of Vector-like Top Partner from Fully Hadronic Final States

We investigate the potential to search for the vector-like top partner in fully hadronic final states at the LHC. An algorithm is developed that kinematically reconstructs the vector-like top. We show that for moderate masses and a large branching fraction into the top quark and Higgs boson, the reconstruction works with good quality.Comment: 15 pages, 6 figures; v2: published version in PR

Higgs mass, muon g-2, and LHC prospects in gauge mediation models with vector-like matters

Recently the ATLAS and CMS collaborations presented preliminary results of Standard Model Higgs searches and reported excesses of events for a Higgs boson at 124-126 GeV. Such a Higgs mass can be naturally realized, simultaneously explaining the muon g-2 anomaly, in gauge-mediated SUSY breaking models with extra vector-like matters. Upper bounds are obtained on the gluino mass, m_{\tilde g}\lesssim 1.2 (1.8) TeV, and on the extra vector-like quark mass, M_{Q'} \lesssim 1.0 (1.8) GeV, in the parameter region where the Higgs boson mass is 124-126 GeV and the muon g-2 is consistent with the experimental value at the 1 sigma (2 sigma) level. The LHC prospects are explored in the parameter region. It is found that some of the regions are already excluded by the LHC, and most of the parameter space is expected to be covered at \sqrt{s} = 14 TeV. A study on the extra vector-like quarks, especially current bounds on their masses and prospects for future searches, is also included.Comment: 28 pages, 10 figure

Predictions for the neutrino parameters in the minimal gauged U(1)Lμ−Lτ_{L_\mu-L_\tau} model

We study the structure of the neutrino mass matrix in the minimal gauged U(1)$_{L_\mu-L_\tau}$ model, where three right-handed neutrinos are added to the Standard Model in order to obtain non-zero masses for active neutrinos. Because of the U(1)$_{L_\mu-L_\tau}$ gauge symmetry, the structure of both Dirac and Majorana mass terms of neutrinos is tightly restricted. In particular, the inverse of the neutrino mass matrix has zeros in the $(\mu,\mu)$ and $(\tau,\tau)$ components, namely, this model offers a symmetric realization of the so-called two-zero-minor structure in the neutrino mass matrix. Due to these constraints, all the CP phases-the Dirac CP phase $\delta$ and the Majorana CP phases $\alpha_2$ and $\alpha_3$-as well as the mass eigenvalues of the light neutrinos $m_i$ are uniquely determined as functions of the neutrino mixing angles $\theta_{12}$, $\theta_{23}$, and $\theta_{13}$, and the squared mass differences $\Delta m_{21}^2$ and $\Delta m_{31}^2$. We find that this model predicts the Dirac CP phase $\delta$ to be $\delta\simeq 1.59\pi$-$1.70\pi$ ($1.54\pi$-$1.78\pi$), the sum of the neutrino masses to be $\sum_{i}m_i \simeq 0.14$-0.22 eV ($0.12$-0.40 eV), and the effective mass for the neutrinoless double beta decay to be $\langle m_{\beta \beta }\rangle \simeq 0.024$-0.055 eV ($0.017$-0.12 eV) at $1\sigma$ ($2\sigma$) level, which are totally consistent with the current experimental limits. These predictions can soon be tested in future neutrino experiments. Implications for leptogenesis are also discussed.Comment: v1: 23 pages, 6 figures. v2: 24 pages, 8 figures, Discussion on leptogenesis adde