Effects of Relativistic Expansion on the Late-time Supernova Light Curves

The effects of relativistic expansion on the late-time supernova light curves are investigated analytically, and a correction term to the (quasi-)exponential decay is obtained by expanding the observed flux in terms of (\beta), where (\beta) is the maximum velocity of the ejecta divided by the speed of light (c). It is shown that the Doppler effect brightens the light curve owing to the delayed decay of radioactive nuclei as well as to the Lorentz boosting of the photon energies. The leading correction term is quadratic in (\beta), thus being proportional to (E_{\rm k}/(M_{\rm ej} c^2)), where (E_{\rm k}) and (M_{\rm ej}) are the kinetic energy of explosion and the ejecta mass. It is also shown that the correction term evolves as a quadratic function of time since the explosion. The relativistic effect is negligibly small at early phases, but becomes of considerable size at late phases. In particular, for supernove having a very large energy(hypernova) or exploding in a jet-like or whatever non-spherical geometry, (^{56})Ni is likely to be boosted to higher velocities and then we might see an appreciable change in flux. However, the actual size of deviation from the (quasi-)exponential decay will be uncertain, depending on other possible effects such as ionization freeze-out and contributions from other energy sources that power the light curve.Comment: 12 pages including 2 figures, submitted to ApJ

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

Probing minimal SUSY scenarios in the light of muon g−2g-2 and dark matter

We study supersymmetric (SUSY) models in which the muon $g-2$ discrepancy and the dark matter relic abundance are simultaneously explained. The muon $g-2$ discrepancy, or a 3$\sigma$ deviation between the experimental and theoretical results of the muon anomalous magnetic moment, can be resolved by SUSY models, which implies at least three SUSY multiplets have masses of $\mathop{\mathcal{O}}(100)\, \mathrm{GeV}$. In particular, models with the bino, higgsino and slepton having $\mathop{\mathcal{O}}(100)\, \mathrm{GeV}$ masses are not only capable to explain the muon $g-2$ discrepancy but naturally contains the neutralino dark matter with the observed relic abundance. We study constraints and future prospects of such models; in particular, we find that the LHC search for events with two hadronic taus and missing transverse momentum can probe this scenario through chargino/neutralino production. It is shown that almost all the parameter space of the scenario can be probed at the high-luminosity LHC, and a large part can also be tested at the XENON1T experiment as well as at the ILC.Comment: 16 pages, 5 figures; the published versio

Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters

We study the muon anomalous magnetic moment (muon g-2) and the Higgs boson mass in a simple extension of the minimal supersymmetric (SUSY) Standard Model with extra vector-like matters, in the frameworks of gauge mediated SUSY breaking (GMSB) models and gravity mediation (mSUGRA) models. It is shown that the deviation of the muon g-2 and a relatively heavy Higgs boson can be simultaneously explained in large tan-beta region. (i) In GMSB models, the Higgs mass can be more than 135 GeV (130 GeV) in the region where muon g-2 is consistent with the experimental value at the 2 sigma (1 sigma) level, while maintaining the perturbative coupling unification. (ii) In the case of mSUGRA models with universal soft masses, the Higgs mass can be as large as about 130 GeV when muon g-2 is consistent with the experimental value at the 2 sigma level. In both cases, the Higgs mass can be above 140 GeV if the g-2 constraint is not imposed.Comment: 26 pages; 7 figures; corrected typos; minor change

Higgs mass and muon anomalous magnetic moment in the U(1) extended MSSM

We study phenomenological aspects of the MSSM with extra U(1) gauge symmetry. We find that the lightest Higgs boson mass can be increased up to 125 GeV, without introducing a large SUSY scale or large A-terms, in the frameworks of the CMSSM and gauge mediated SUSY breaking (GMSB) models. This scenario can simultaneously explain the discrepancy of the muon anomalous magnetic moment (muon g-2) at the 1 sigma level, in both of the frameworks, U(1)-extended CMSSM/GMSB models. In the CMSSM case, the dark matter abundance can also be explained.Comment: 19 pages, 3 figures; submitted versio

Hypernova Nucleosynthesis and Implications for Cosmic Chemical Evolution

We examine the characteristics of nucleosynthesis in 'hypernovae', i.e., supernovae with very large explosion energies (\gsim 10^{52} ergs). Implications for the cosmic chemical evolution and the abundances in M82 are discussed.Comment: To appear in 'Cosmic Evolution' Conference at IAP, Paris, honoring Jean Audouze and Jim Truran, 13-17 Nov 200

Lepton Flavor Violation and Cosmological Constraints on R-parity Violation

In supersymmetric standard models R-parity violating couplings are severely constrained, since otherwise they would erase the existing baryon asymmetry before the electroweak transition. It is often claimed that this cosmological constraint can be circumvented if the baryon number and one of the lepton flavor numbers are sufficiently conserved in these R-parity violating couplings, because B/3-L_i for each lepton flavor is separately conserved by the sphaleron process. We discuss the effect of lepton flavor violation on the B-L conservation, and show that even tiny slepton mixing angles \theta_{12} \gsim {\cal O}(10^{-4}) and \theta_{23}, \theta_{13}\gsim {\cal O}(10^{-5}) will spoil the separate B/3-L_i conservation. In particular, if lepton flavor violations are observed in experiments such as MEG and B-factories, it will imply that all the R-parity violating couplings must be suppressed to avoid the B-L erasure. We also discuss the implication for the decay of the lightest MSSM particle at the LHC.Comment: 21 pages, 7 figures. v2: minor change

Type Ia Supernovae: Their Origin and Possible Applications in Cosmology

Spectroscopic and photometric evidence indicates that Type Ia supernovae (SNe Ia) are the thermonuclear explosions of accreting white dwarfs. However, the progenitor binary systems and hydrodynamical models for SNe Ia are still controversial. The relatively uniform light curves and spectral evolution of SNe Ia have led to their use as a standard candle for determining cosmological parameters, such as the Hubble constant, the density parameter, and the cosmological constant. Recent progress includes the calibration of the absolute maximum brightness of SNe Ia with the Hubble Space Telescope, the reduction of the dispersion in the Hubble diagram through the use of the relation between the light curve shape and the maximum brightness of SNe Ia, and the discovery of many SNe Ia with high red shifts.Comment: 7 page LaTeX, 5 PostScript figures, to appear in Science, Vol. 276 (1997