A testable scenario of WIMPZILLA with Dark Radiation

As the electromagnetic gauge symmetry makes the electron stable, a new abelian gauge symmetry may be responsible for the stability of superheavy dark matter. The gauge boson associated with the new gauge symmetry naturally plays the role of dark radiation and contributes to the effective number of `neutrino species', which has been recently measured by Planck. We estimate the contribution of dark radiation from the radiative decay of a scalar particle induced by the WIMPZILLA in the loop. The scalar particle may affect the invisible decay of the Higgs boson by the Higgs portal type coupling.Comment: 4 pages, 3 figure

East Asian Liberalization and the Challenge from China

macroeconomics, East Asian Liberalization, China

The Global Financial Crisis: Decoupling of East Asia—Myth or Reality?

The “decoupling” of East Asia from its economic interactions—both in trade and finance—with the rest of the world refers to the phenomenon of a weakening of the impact of demand and supply shocks emanating from the advanced countries on the region’s economic performance since the early 1990s. Available empirical evidence, including the faster recovery of East Asia from the 2008 global economic crisis, does not appear to lend credence to the decoupling thesis. However, with increases in income throughout the region and the three free trade agreements of the People’s Republic of China, Japan, and Korea with the Association of Southeast Asian Nations (which have entered into force), East Asia will witness a continuing expansion in intra-regional trade, much of which will consist of horizontal intra-industry trade. At the same time, if East Asia succeeds in instituting an efficient capital control regime and in strengthening the Chiang Mai Initiative Multilateralization, it will be able to cope better with the volatility of capital flows to the region. Together these developments will then help speed up economic integration among ASEAN+3 member states to build a region that is more self-contained than it has been.global economic crisis; decoupling east asia; free trade agreements; intra-regional trade; chiang mai initiative multilateralization

Some aspects of chemical non-equilibrium in high speed high temperature flows

Imperial Users onl

Bounds on dark matter interpretation of Fermi-LAT GeV excess

Annihilation of light dark matter of $m_{\rm DM} \approx (10-40)$ GeV into the Standard Model fermions has been suggested as a possible origin of the gamma-ray excess at GeV energies in the Fermi-LAT data. In this paper, we examine possible model-independent signatures of such dark matter models in other experiments such as AMS-02, colliders, and cosmic microwave background (CMB) measurements. We point out that first generation of fermion final states is disfavored by the existing experimental data. Currently AMS-02 positron measurements provide stringent bounds on cross sections of dark matter annihilation into leptonic final states, and $e^+e^-$ final state is in severe tension with this constraint, if not ruled out. The $e^+e^-$ channel will be complementarily verified in an early stage of ILC and future CMB measurements. Light quark final states ($q\bar q$) are relatively strongly constrained by the LHC and dark matter direct detection experiments even though these bounds are model-dependent. Dark matter signals from annihilations into $q\bar{q}$ channels would be constrained by AMS-02 antiproton data which will be released in very near future. In optimistic case, diffuse radio emission from nearby galaxy (clusters) and the galactic center might provide another hint or limit on dark matter annihilation.Comment: 20 pages, 3 figures; figures and text updated, discussion improved, references added; updated to match published version in NP

An alternative interpretation for cosmic ray peaks

We propose an alternative mechanism based upon dark matter (DM) interpretation for anomalous peak signatures in cosmic ray measurements, assuming an extended dark sector with two DM species. This is contrasted with previous effort to explain various line-like cosmic-ray excesses in the context of DM models where the relevant DM candidate directly annihilates into Standard Model (SM) particles. The heavier DM is assumed to annihilate to an on-shell intermediate state. As the simplest choice, it decays directly into the lighter DM along with an unstable particle which in turn decays to a pair of SM states corresponding to the interesting cosmic anomaly. We show that a sharp continuum energy peak can be readily generated under the proposed DM scenario, depending on dark sector particle mass spectra. Remarkably, such a peak is robustly identified as half the mass of the unstable particle. Furthermore, other underlying mass parameters are analytically related to the shape of energy spectrum. We apply this idea to the two well-known line excesses in the cosmic photon spectrum: 130 GeV gamma-ray line and 3.5 keV X-ray line. Each observed peak spectrum is well-reproduced by theoretical expectation predicated upon our suggested mechanism, and moreover, our resulting best fits provide rather improved chi-square values.Comment: 9 pages, 3 figure

Hidden-sector-assisted 125 GeV Higgs boson

In order to significantly raise the mass of the supersymmetry Higgs boson, we consider a radiative correction to it by heavy (\sim 1 TeV) hidden sector fields, which communicate with the Higgs through relatively heavy "messengers" (300-500 GeV). The messenger fields (S, \bar{S}) are coupled to the Higgs ("y_HSH_uH_d," y_H\lesssim 0.7) and also to hidden sector fields with a Yukawa coupling of order unity. The hidden sector fields are assumed to be large representations of a hidden gauge group, and so their scalar partner masses can be heavier than other typical soft scalars in the visible sector. Even with a relatively small y_H (\sim 0.2) or tan\beta\sim 10 but without top-stop's considerable contributions, the radiative correction by such hidden sector fields can be enhanced enough to yield the 125 GeV Higgs mass.Comment: 5 pages, 3 eps figure

Electrical Investigation of the Oblique Hanle Effect in Ferromagnet/Oxide/Semiconductor Contacts

We have investigated the electrical Hanle effect with magnetic fields applied at an oblique angle ({\theta}) to the spin direction (the oblique Hanle effect, OHE) in CoFe/MgO/semiconductor (SC) contacts by employing a three-terminal measurement scheme. The electrical oblique Hanle signals obtained in CoFe/MgO/Si and CoFe/MgO/Ge contacts show clearly different line shapes depending on the spin lifetime of the host SC. Notably, at moderate magnetic fields, the asymptotic values of the oblique Hanle signals (in both contacts) are consistently reduced by a factor of cos^2({\theta}) irrespective of the bias current and temperature. These results are in good agreement with predictions of the spin precession and relaxation model for the electrical oblique Hanle effect. At high magnetic fields where the magnetization of CoFe is significantly tilted from the film plane to the magnetic field direction, we find that the observed angular dependence of voltage signals in the CoFe/MgO/Si and CoFe/MgO/Ge contacts are well explained by the OHE, considering the misalignment angle between the external magnetic field and the magnetization of CoFe.Comment: 19 pages, 8 figure