Search

We investigate the detection of boosted dark matter in a two component dark matter model with the hidden gauge $U(1)_D$ symmetry. The model introduces heavy and light fermionic dark matter components, where the heavy dark matter annihilation in the Galactic center boosts the light dark matter. Directional direct detection experiments, such as NEWSdm, are suitable for testing the boosted scenario by focusing on signals from the Galactic center. We found that the expected event rate could reach up to O(10) events per year per 5 kg of the detector material., Comment: 4 pages, 8 figures, Contribution to the proceedings of the 29th International Symposium on Particles, Strings and Cosmology (PASCOS 2024)

This study explores a two-component dark matter model in which one component, heavier dark matter, annihilates into a lighter dark matter. The lighter dark matter is expected to generate detectable signals in detectors due to its enhanced momentum, enabling direct detection even for MeV-scale dark matter. We investigate the effectiveness of directional direct detections, especially the nuclear emulsion detector NEWSdm, in verifying these boosted dark matter particles through nuclear recoil. In particular, we focus on light nuclei, such as protons and carbon, as suitable targets for this detection method due to their high sensitivity to MeV-scale dark matter. By modeling the interactions mediated by a dark photon in a hidden U(1)$_D$ gauge symmetry framework, we calculate the expected dark matter flux and scattering rates for various detector configurations. Our results show that nuclear emulsions have the potential to yield distinct, direction-sensitive dark matter signals from the Galactic center, providing a new way to probe low-mass dark matter parameter spaces that evade conventional detection methods., Comment: 17 pages, 10 figures, 3 tables

We propose a model of uniform rate inflation on the brane. The potential is given by a hyperbolic cosine function plus a negative cosmological constant. The equation of motion is solved analytically without using slow-roll approximation. The result is that the inflaton field is rolling at a constant speed. The prediction for cosmological perturbations depends on the field value at the end of inflation. The experimental constraints could be satisfied in the parameter space., Comment: 11 pages, 11 figures

We study a one-loop induced neutrino mass model with an inert isospin triplet scalar field of $Y=0$ and heavier isospin doublet vector-like leptons and singlet Majorana right-handed fermions. In addition to the neutrino mass matrix, We explain sizable scale of muon anomalous magnetic dipole moment $10^{-9}$ by introducing a singly-charged boson $S^\pm$. We show numerical analysis of neutrino oscillation, lepton flavor violations, Z boson decays, and demonstrate our allowed regions in cases of normal and inverted hierarchies. We find the sizable scale of muon anomalous magnetic dipole moment for both cases. Then, we move on to the discussion of dark matter candidates to satisfy the relic density where we have two candidates; fermionic dark matter and bosonic one. And, we classify four cases fermionic dark matter with normal and inverted hierarchies, bosonic one with normal and inverted hierarchies and search for each of the allowed points in the model., Comment: 21 pages, 7 figures, four tables; version accepted for publication in Physics Letters B

We propose a model with two different extra $U(1)$ gauge symmetries; muon minus tauon symmetry $U(1)_{{L_\mu}-L_{\tau}}$ and hidden symmetry $U(1)_H$. Then, we explain muon anomalous magnetic moment, semi-leptonic decays $b\to s\ell\bar\ell$, and dark matter. In particular, we find an intriguing dark matter candidate to be verified by Hyper-Kamiokande and JUNO in the future that request neutrinophilic DM with rather light dark matter mass$\sim{\cal O}(10)$ MeV., Comment: 23 pages, 6 figures, 2 tables

Dark matter with MeV scale mass is difficult to detect with standard direct search detectors. However, they can be searched for by considering the up-scattering of kinetic energies by cosmic rays. Because the dark matter density is higher in the central region of the Galaxy, the up-scattered dark matter will arrive at Earth from the direction of the Galactic center. Once the dark matter is detected, we can expect to recognize this feature by directional direct detection experiments. In this study, we simulate the nuclear recoils of the up-scattered dark matter and quantitatively reveal that a large amount of this type of dark matter is arriving from the direction of the Galactic center. Also, we have shown that the characteristic signatures of the up-scattered dark matter can be verified with more than 5$\sigma$ confidence levels for the assumed target atoms and future upgrades to directional detectors., Comment: 17 pages, 64 figures

We consider an explanation of CDF II W bosom mass anomaly by $Z-Z'$ mixing with $U(1)_R$ gauge symmetry under which right-handed fermions are charged. It is found that $U(1)_R$ is preferred to be leptophobic to accommodate the anomaly while avoiding other experimental constraints. In such a case we require extra charged leptons to cancel quantum anomalies and the SM charged leptons get masses via interactions with the extra ones. These interactions also induce muon $g-2$ and lepton flavor violations. We discuss muon $g-2$, possible flavor constraints, neutrino mass generation via inverse seesaw mechanism, and collider physics regarding $Z'$ production for parameter space explaining the W boson mass anomaly., Comment: 22 pages, 3 figures, 2 tables; version accepted for publication in Physical Review D

We propose a model to explain the W boson mass anomaly reported by the CDFII collaboration that would suggest new physics (NP). We introduce exotic fermions; one isospin doublet vector-like lepton, one isospin singlet singly-charged vector-like lepton, and an isospin doublet inert scalar. The proposed model provides sizable muon anomalous magnetic moment (muon $g-2$) due to no chiral suppression and nonzero mass difference between the real and imaginary parts of neutral inert scalar bosons. The inert scalar mass squared difference and vector-like exotic leptons ($L', E'$ in the main text) affect oblique parameters. Especially, the $T$-parameter shift from zero explains the W boson mass anomaly. We search for the allowed parameter region to explain both muon $g-2$ and W boson mass anomaly at the same time. We also discuss a dark matter (DM) candidate assuming the real part of the inert scalar field to be the one. We find that lighter DM mass is favored to be consistent with experimental constraints., Comment: 21 pages, 7 figures

We propose a radiative seesaw model with a light dark matter candidate (DM) under modular $A_4$ and gauged $U(1)_{B-L}$ symmetries, in which neutrino masses are generated via one-loop level, and we have a bosonic DM candidate $\sim 0.01-50$ GeV. DM is stabilized by nonzero modular weight and a remnant $Z_2$ symmetry of $U(1)_{B-L}$ symmetry. The naturalness of tiny DM mass is indirectly realized by the radiatively induced mass of neutral fermions that interact with our DM candidate. Thus, DM mass does not have to exceed the neutral fermion masses, whose scale is assumed to be 50 GeV. Taking several benchmark points of DM mass in DM analysis, we show the numerical analysis for the neutrino oscillation data in the normal and inverted hierarchy cases and find several features for both cases., Comment: 27 pages, 12 figures, 1 table. arXiv admin note: text overlap with arXiv:2010.03348

We propose a lepton model under modular $A_4$ and gauged $U(1)_R$ symmetries, in which the neutrino masses are induced at one-loop level. Thanks to the modular $A_4$ symmetry, we have several predictions on the lepton sector, especially, on fixed points of $\tau=i,\omega\equiv e^{2\pi i/3},i\times \infty$ each of which has remnant symmetry; $Z_2$ for $\tau=i$ and $Z_3$ for $\tau=\omega, i\infty$. These points are favored by a string theory and phenomenologically interesting., Comment: 19 pages, 6 figures, 1 table

We study neutrino and dark matter based on a gauged $U(1)_R$ symmetry in a framework of radiative seesaw scenario. Identifying dark matter as a bosoninc particle, it interacts with quark and lepton sectors through vector-like heavier quark and leptons, and plays an role in generating neutrino mass matrix together with neutral heavier fermions. We explore several constraints for masses and couplings related to dark matter by computing relic density and direct search, taking the neutrino oscillation, lepton flavor violations, and muon anomalous magnetic moment into account. Finally, we briefly mention semileptonic decays and neutral meson mixings at one-loop box diagrams through dark matter., Comment: 13 pages, 2 figures

Velocity distribution of dark matter is assumed to be isotropic in most cases, however, anisotropy is suggested in some simulations. Directional direct detection of dark matter is a hopeful way to discriminate the anisotropy of dark matter velocity distribution. We simulate the dark matter and target scattering in the directional direct detection, and investigate conditions required to discriminate the anisotropy. If dark matter mass is known, $O(10^3)-O(10^4)$ events are required for the discrimination if the dark matter mass is known by other experiments. We also study the case that the dark matter mass is not known, and in analysis using both the recoil energy and the scattering angle data, both the dark matter mass and the anisotropy can be restricted much better than the analysis only with either of them., Comment: prepared for proceedings of NDM 2020, 6pages, 10 figures

The velocity distribution of dark matter is supposed to be isotropic Maxwell- Boltzmann distribution in most cases, however, its anisotropy is suggested by some simulations. We investigate conditions to give constraints on the anisotropy with directional direct detections., Comment: 3 pages, 10 figures. Prepared for proceedings of TAUP 2019

Velocity distribution of dark matter is supposed to be isotropic Maxwell-Boltzmann distribution in most cases, however, other distribution models including anisotropic one are suggested by simulations. Directional direct detection of dark matter is expected to be a hopeful way to discriminate isotropic distribution from anisotropic one. We investigate the possibility to obtain the anisotropy and WIMP mass by Monte-Carlo simulation supposing the directional detector., Comment: 3pages, 8 figures. Proceedings for PPAP 2019 (2nd workshop on Phenomenology for Particle and Anti-Particle 2019)

We study creation and time evolution of particle number asymmetry with nonequilibrium quantum field theory. We introduce a model of a neutral scalar and a complex scalar and it has CP violating and particle number violating features. Starting with an initial condition specified by density operator, we show how particle number asymmetry can be generated through interaction. We investigate the time evolution of particle number asymmetry of universe using perturbation method., Comment: 5 pages, 2 figures, contributed talk at 1st Workshop on Phenomenology for Particle and Anti-Particle 2018, minor modification

Direct detection of dark matter with directional sensitivity has the potential to discriminate the dark matter velocity distribution. Especially, it will be suitable to discriminate isotropic distribution from anisotropic one. Analyzing data produced with Monte-Carlo simulation, required conditions for the discrimination is estimated. If energy threshold of detector is optimized, $O(10^3-10^4)$ event number is required to discriminate the anisotropy., Comment: proceedings of PPAP2018, 5 pages, 5 figures

Although the velocity distribution of dark matter is assumed to be generally isotropic, some studies have found that $\sim\hspace{-0.1cm}25$\% of the distribution can have anisotropic components. As the directional detection of dark matter is sensitive to both the recoil energy and direction of nuclear recoil, directional information can prove useful in measuring the distribution of dark matter. Using a Monte Carlo simulation based on the modeled directional detection of dark matter, we analyze the differences between isotropic and anisotropic distributions and show that the isotropic case can be rejected at a 90\% confidence level if $O(10^4)$ events can be obtained., Comment: Proceedings of ICNFP 2017. 8 pages, 9 figures

A new mechanism for generating particle number asymmetry (PNA) has been developed. This mechanism is realized with a Lagrangian including a complex scalar field and a neutral scalar field. The complex scalar carries U(1) charge which is associated with the PNA. It is written in terms of the condensation and Green's function, which is obtained with two-particle irreducible (2PI) closed time path (CTP) effective action (EA). In the spatially flat universe with a time-dependent scale factor, the time evolution of the PNA is computed. We start with an initial condition where only the condensation of the neutral scalar is non-zero. The initial condition for the fields is specified by a density operator parameterized by the temperature of the universe. With the above initial conditions, the PNA vanishes at the initial time and later it is generated through the interaction between the complex scalar and the condensation of the neutral scalar. We investigate the case that both the interaction and the expansion rate of the universe are small and include their effects up to the first order of the perturbation. The expanding universe causes the effects of the dilution of the PNA, freezing interaction and the redshift of the particle energy. As for the time dependence of the PNA, we found that PNA oscillates at the early time and it begins to dump at the later time. The period and the amplitude of the oscillation depend on the mass spectrum of the model, the temperature and the expansion rate of the universe., Comment: 59 pages, 10 figures, 3 tables. In version 5, section II and III are modified. One reference is added

Directional detection of dark matter has sensitivity for both recoil energy and direction of nuclear recoil. It opens the way to measure local velocity distribution of dark matter. In this paper, we study possibility to discriminate isotropic distribution and anisotropic one suggested by a N-body simulation with directional detector. Numerical simulation is performed for two cases according to the detectors, one corresponds to angular histogram and the other is energy-angular distribution of the signals. We reveal that the anisotropy of velocity distribution can be discriminated at 90% C.L. with chi-squared test if O($10^4$) signals are obtained., Comment: 19 pages, 34 figures

We introduce a model which may generate particle number asymmetry in an expanding Universe. The model includes CP violating and particle number violating interactions. The model consists of a real scalar field and a complex scalar field. Starting with an initial condition specified by a density matrix, we show how the asymmetry is created through the interaction and how it evolves at later time. We compute the asymmetry using non-equilibrium quantum field theory and as a first test of the model, we study how the asymmetry evolves in the flat limit., Comment: 5 pages 1 figure , Submitted to the proceedings of the conference International workshop for "Strong Field Problems in Quantum Theory" (June 6-11, Tomsk Russia 2016.)

Directional detection of dark matter is the next generation experiment, which is expected to have better back ground rejection efficiency than conventional direct search. Another intriguing possibility of the experiment by means of the directional information is measurement the velocity distribution of dark matter. Especially, it will be potent to figure out whether the velocity distribution is anisotropic. Supposing three distribution models, we discuss the possibility in one of the directional dark matter searches, nuclear emulsion detector., Comment: 6 pages, 6 figures, proceedings of the Interplay between Particle and Astroparticle Physics workshop, 18 -- 22 August, 2014, held at Queen Mary University of London, UK

Direct detection of dark matter with directional sensitivity offers not only measurement of both recoil energy and direction of dark matter, but also a way to understand dark matter distribution in the Galaxy. Maxwell distribution is usually supposed as the distribution near the Earth, however, deviation from that, caused by tidal streams in the Galaxy, has been suggested. We explore the possibility of distinguishing the distribution by direct detection using nuclear emulsions., Comment: 5pages, 11 figures, to appear in the proceedings of CYGNUS 2013 (CNUM: C13-06-10.6)

We investigate simplified models in which dark matter particles, taken to be either Dirac or Majorana fermions, couple to quarks via colored mediators. We determine bounds from colliders and direct detection experiments, and show how the interplay of the two leads to a complementary view of this class of dark matter models. Forecasts for future searches in light of the current constraints are presented., Comment: 12 pages, 13 figures (39 images) Fixed erroneous calculation and updated plots

We propose a method for reconstructing the mass of a particle, such as the Higgs boson, decaying into a pair of tau leptons, of which one subsequently undergoes a 3-prong decay. The kinematics is solved using information from the visible decay products, the missing transverse momentum, and the 3-prong tau decay vertex, with the detector resolution taken into account using a likelihood method. The method is shown to give good discrimination between a 125 GeV Higgs boson signal and the dominant backgrounds, such as Z decays to tau tau and W plus jets production. As a result, we find an improvement, compared to existing methods for this channel, in the discovery potential, as well as in measurements of the Higgs boson mass and production cross section times branching ratio., Comment: 19 pages, 8 figures

Some of direct dark matter searches reported not only positive signals but also annual modulation of the signal event. However, the parameter spaces have been excluded by other experiments. Isospin violating dark matter solves the contradiction by supposing different coupling to proton and neutron. We study the possibility to test the favored parameter region by isospin violating dark matter model with the future detector of dark matter using the nuclear emulsion. Since the nuclear emulsion detector has directional sensitivity, the detector is expected to examine whether the annual modulations observed other experiments is caused by dark matter or background signals., Comment: Prepared for the proceedings of the International Workshop on Grand Unified Theories (GUT2012) held at Yukawa Institute for Theoretical Physics, Kyoto, Japan, March 2012

Dark matter signal and its annual modulation of event number are observed by some direct searches in small mass region. However, the regions have been excluded by others. The isospin-violating dark matter is a hopeful candidate to explain the discrepancy. We study the possibility that a future project of dark matter search using nuclear emulsion can reach favored region by the isospin-violating dark matter. Since the detector has the directional sensitivity, it is expected to examine the region including the modulation property., Comment: 15pages, 3figures

In this talk, we will review the signatures of dark matter in two inert triplet models. For the first model with the hypercharge Y=0, the dark matter mass around 5.5 TeV is favored by both the WMAP data and the direct detection. In contrast, for the second model of Y=2, it is excluded by the direct detection experiments although dark matter with its mass around 2.8 TeV is allowed by WMAP., Comment: 8 pages, 3 figures, talk presented at the 2nd International Workshop on Dark Matter, Dark Energy and Matter-Antimatter Asymmetry, Hsinchu, Taiwan, 5-6 Nov 2010

We study the inert triplet models, in which the standard model (SM) is extended to have a new SU(2)L triplet scalar (Y=0 or 2) with an Z2 symmetry. We show that the neutral component of the triplet can be a good dark matter candidate. In particular, for the hypercharge Y=0 triplet model, the WMAP data favors the region where the dark matter mass is around 5.5 TeV, which is also consistent with the direct detection experiments. In contrast, for the Y=2 model, although dark matter with its mass around 2.8 TeV is allowed by WMAP, it is excluded by the direct detection experiments because the spin-independent cross section is enhanced by the Z mediated tree-level scattering process., Comment: 5 pages, 4 figures

We find the novel effect on the decay of a false vacuum in view of quantum field theory, which is induced by a field coupling to the scalar field related to a first-order phase transition. This effect of the environment can never be included in the traditional method using the effective potential, and, in fact, acts as dissipative and fluctuation effects on tunneling phenomena. We show that the decay of the false vacuum is drastically either enhanced or suppressed. It is also clarified what kind of interaction enhance or suppress the tunneling probability., Comment: 4 pages, 3 figures

We study the LHC signature of the minimal supersymmetric standard model with non-universal sfermion masses. In the model, soft masses of gauginos and the 3rd generation of 10 of SU(5) are around the weak scale, while other sfermion soft mass is universal and around a few TeV. Such sfermion mass spectrum is motivated not only from flavor, CP and naturalness constraints but also from E_6 grand unified model with non-Abelian horizontal (flavor) symmetry. The characteristic signature of the model at the LHC is the dominance of the events with 4 b partons in the final state together with high rate of mildly boosted top quark arising from gluino decay. The prominent high p_T jet also arises from squark decay. We show it is possible to find the characteristic signature in the early stage of the LHC. The discrimination of our scenario from some CMSSM model points with similar signature may be possible with large integrated luminosity. The result of sparticle mass measurement using exclusive channel with the help of hemisphere analysis, and inclusive measurement of gluino and squark masses using M_{T2} and M_{T2}^{min} in some representative model points are presented., Comment: 36 pages, 17 figures