Highly-boosted dark matter and cutoff for cosmic-ray neutrino through neutrino portal

We study the cutoff for the cosmic-ray neutrino, set by the scattering with cosmic background neutrinos into dark sector particles through a neutrino portal interaction. We find that a large interaction rate is still viable, when the dark sector particles are mainly coupled to the $\tau-$neutrino, so that the neutrino mean free path can be reduced to be $O(10)~$Mpc over a wide energy range. If stable enough, the dark sector particle, into which most of the cosmic-ray neutrino energy is transferred, can travel across the Universe and reach the earth. The dark sector particle can carry the energy as large as \O({\rm EeV}) if originates from a cosmogenic neutrino.Comment: 6 pages, 7 figures, v2: match the published versio

Charge Quantization and Neutrino Mass from Planck-scale SUSY

We show a possibility for the charge quantization of the standard model (SM) particles. If a global symmetry makes the three copies of a generation and supersymmetry (SUSY) relates the Higgs boson to a lepton, all the charges of the SM particles can be quantized through gauge-anomaly cancellation. In the minimal model realizing the possibility, the gravitino mass around the Planck-scale is needed to generate the SM couplings through (quantum) supergravity. Much below the Planck-scale, the SM is obtained as the effective theory. Interestingly, if the gaugino masses are generated through anomaly mediation, one of the neutrino masses is predicted to be around the neutrino oscillation scales. In an extension of the model, millicharged particles can exist without introducing massless hidden photons.Comment: 17 pages, v2: version appears in PL

Natural Split Mechanism for Sfermions: NN=2 Supersymmetry in Phenomenology

We suggest a natural split mechanism for sfermions based on $N$=2 supersymmetry (SUSY). $N$=2 SUSY protects a sfermion in an $N$=2 multiplet from gaining weight by SUSY breaking. Therefore, if partly $N$=2 SUSY is effectively obtained, a split spectrum can be realized naturally. As an example of the natural split mechanism, we build a gauge-mediated SUSY breaking-like model assuming $N$=2 SUSY is partly broken in a UV theory. The model explains the Higgs boson mass and the muon anomalous magnetic dipole moment within $1~\sigma$ level with a splitting sfermion spectrum. The model has seven light sparticles described by three free parameters and predicts a new chiral multiplet, sb: the $N$=2 partner of the ${\rm U(1)_Y}$ vector multiplet. The bini, the fermion component of the sb, weighs MeVs. We mention the experimental and the cosmological aspects of the model.Comment: 17 pages and 3 figures, Version accepted for publication in PL

An Alternating Direction Algorithm for Matrix Completion with Nonnegative Factors

This paper introduces an algorithm for the nonnegative matrix factorization-and-completion problem, which aims to find nonnegative low-rank matrices X and Y so that the product XY approximates a nonnegative data matrix M whose elements are partially known (to a certain accuracy). This problem aggregates two existing problems: (i) nonnegative matrix factorization where all entries of M are given, and (ii) low-rank matrix completion where nonnegativity is not required. By taking the advantages of both nonnegativity and low-rankness, one can generally obtain superior results than those of just using one of the two properties. We propose to solve the non-convex constrained least-squares problem using an algorithm based on the classic alternating direction augmented Lagrangian method. Preliminary convergence properties of the algorithm and numerical simulation results are presented. Compared to a recent algorithm for nonnegative matrix factorization, the proposed algorithm produces factorizations of similar quality using only about half of the matrix entries. On tasks of recovering incomplete grayscale and hyperspectral images, the proposed algorithm yields overall better qualities than those produced by two recent matrix-completion algorithms that do not exploit nonnegativity