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S. Tanaka

Publications and source records attributed to S. Tanaka.

53 records · Page 3Linked to original sources
arXiv2005

Soliton solutions in an effective action for SU(2) Yang-Mills theory: including effects of higher-derivative term

The Skyrme-Faddeev-Niemi (SFN) model which is an O(3) $σ$ model in three dimensional space upto fourth-order in the first derivative is regarded as a low-energy effective theory of SU(2) Yang-Mills theory. One can show from the Wilsonian renormalization group argument that the effective action of Yang-Mills theory recovers the SFN in the infrared region. However, the thoery contains an additional fourth-order term which destabilizes the soliton solution. In this paper, we derive the second derivative term perturbatively and show that the SFN model with the second derivative term possesses soliton solutions.

hep-ph↗
arXiv2003

Dynamical symmetry breaking under core excitation in graphite: Polarization correlation in soft X-ray recombination emission

A recombination emission spectrum is applied to study the local lattice distortion due to core excitation in graphite. The recombination emission spectrum reveals a long low-energy tail when the C $1s$ electron is excited to the $σ^*$ core exciton state. This indicates a large local lattice distortion around the excited carbon atom within a core hole lifetime ($\sim$10fs). Theoretical calculation based upon an ionic cluster model well reproduces the experiments. The strong polarization correlation between incident and emitted X-rays is conclusive evidence of symmetry breaking in the core exciton state due to coupling with asymmetric vibrational modes.

cond-mat.mtrl-sci↗
arXiv2003

Protein crystallization in confined geometries

We studied the crystallization of a globular protein, lysozyme, in the cubic phase of the lipid monoolein. The solubility of lysozyme in salt solution decreased by a factor of $\sim 4$ when confined in cubic phase. Calculations and Monte Carlo simulations show that this can be explained by the {\it confinement} of lysozyme molecules to the narrow water cells in the cubic phase.

cond-mat.soft↗
arXiv2003

Grazing Eclipsing Dwarf Nova CW Monocerotis: Dwarf Nova-Type Outburst in a Possible Intermediate Polar?

We observed the 2002 October-November outburst of the dwarf nova CW Mon. The outburst showed a clear signature of a premaximum halt, and a more rapid decline after reaching the outburst maximum. On two separate occasions, during the premaximum stage and near the outburst maximum, shallow eclipses were recorded. This finding confirms the previously suggested possibility of the grazing eclipsing nature of this system. The separate occurrence of the eclipses and the premaximum halt can be understood as a result of a combination of two-step ignition of an outburst and the inside-out propagation of the heating wave. We detected a coherent short-period (0.02549 d) signal on two subsequent nights around the optical maximum. This signal was likely present during the maximum phase of the 2000 January outburst. We interpret this signal as a signature of the intermediate polar (IP) type pulses. The rather strange outburst properties, strong and hard X-ray emission, and the low luminosity of the outburst maximum might be understood as consequences of the supposed IP nature. The ratio between the suggested spin period and the orbital period, however, is rather unusual for a system having an orbital period of ~0.176 d.

astro-ph↗
arXiv2002

Scanning Tunneling Spectroscopy on Single Crystal MgB2

We report on the results of scanning tunneling spectroscopy measurements on single crystals of Mg2. Tunneling was performed both parallel and perpendicular to the crystalline c-axis. In the first case, a single superconducting gap (Delta_pi = 2.2 meV) associated with the pi-band is observed. Tunneling parallel to the ab-plane reveals an additional, larger gap (Delta_sigma ~ 7 meV) originating in the highly two-dimensional sigma-band. Vortex imaging in the pi-band was performed with the field and tunnel current parallel to the c-axis. The vortices have a large core size compared to estimates based on Hc2, and show an absence of localized states in the core. Furthermore, superconductivity between the vortices is rapidly suppressed by an applied field. A comparison to specific heat measurements is performed.

cond-mat.supr-con↗
arXiv2002

Vortex Imaging in the pi-Band of Magnesium Diboride

We report scanning tunneling spectroscopy imaging of the vortex lattice in single crystalline MgB2. By tunneling parallel to the c-axis, a single superconducting gap (Delta = 2.2 meV) associated with the pi-band is observed. The vortices in the pi-band have a large core size compared to estimates based on Hc2, and show an absence of localized states in the core. Furthermore, superconductivity between the vortices is rapidly suppressed by an applied field. These results suggest that superconductivity in the pi-band is, at least partially, induced by the intrinsically superconducting sigma-band.

cond-mat.supr-con↗
arXiv2001

Far-infrared study of the insulator-metal transition in $θ$-(BEDT-TTF)$_2$RbZn(SCN)$_4$

The temperature-dependent infrared properties of $θ$-(BEDT-TTF)$_2$RbZn(SCN)$_4$ were investigated. In the temperatures above the metal-insulator (M-I) transition, the optical conductivity remains finite in the low energy region, but shows no conventional Drude feature typical of metals. Below the M-I transition temperature, the low-energy spectral weight is significantly reduced. An opening of optical gap at about 300 cm$^{-1}$ is observed clearly in the polarization parallel to the donor-stacking direction. Analysis of both the electronic and vibronic spectra suggests a redistribution of charges in ET molecules as temperature decreases across the M-I transition, providing strong support for the charge-ordering state at low temperatures.

cond-mat.str-el↗
arXiv1997

$ψ'$ productions as a test of color-octet mechanism

To test the color-octet model of heavy quarkonium productions, we propose $ψ'$-productions at small-$p_T$ regions in polarized $pp$ collisions for the forthcoming RHIC polarized experiments, whose experimental test at $\sqrt s=50$ GeV might be very promising.

hep-ph↗
arXiv1997

Hard Processes with Spin-Dependent Parton Distributions

To test a possible color-octet contribution of heavy quarkonium productions, we propose $ψ$'-productions for small-$p_T$ regions, where the color-singlet $ψ$' state cannot be produced by the gluon-gluon fusion owing to charge conjugation. We also point out that these processes are very useful to deduce informations of spin-dependent gluon distributions $Δg$.

hep-ph↗
arXiv1996

Moduli Effects on Neutrino Oscillations

We point out the possibility to detect the low-energy signals of moduli in the superstring theory through the neutrino oscillation. The idea is based on the characteristics that the couplings of moduli are different from matter to matter. We estimate the oscillation probability both in the baseline and solar neutrino oscillations. In both cases, when there is at least one modulus of which mass is less than or equal to $10^{-19}$ GeV, the interaction of the modulus significantly changes the conversion probability from one neutrino flavor to another.

hep-ph↗
arXiv1995

Polarized Gluons in the Nucleon

QCD suggests that gluons in the nucleon play an important role in {\it so-called} ``the proton spin problem''. In this talk, the behavior of the polarized gluon distribution in the nucleon is discussed by using the positivity condition of distribution functions together with the unpolarized and polarized experimental data.

hep-ph↗
arXiv1995

Neutrino Oscillations by Interaction with Moduli

We would like to point out the possibility to detect the low-energy signals of moduli in the superstring theory in the neutrino oscillation. The idea is based on the characteristics that the couplings of moduli are different in matter. We estimate the oscillation probability both in the long baseline and in the solar neutrino oscillations and examine the detectable region of the moduli effect.

hep-ph↗
arXiv1995

TWO--SPIN ASYMMETRY OF HEAVY QUARKONIA PRODUCTIONS AT RHIC ENERGY

Hadroproductions of charmonium and bottomonium $χ_J$ in polarized $pp$ collisions at RHIC energies are studied. Two--spin asymmetries $A_{LL}^{χ_J}(pp)$ for these reactions are very good parameters for examining the polarized gluon distributions in a proton.

hep-ph↗
arXiv1994

The Shape of Polarized Gluon Distributions

The recent high precision SMC data on polarized $μp$ scatterings have again confirmed that very little of the proton spin is carried by quarks. To unravel the mystery of the proton spin structure, it is quite important to know the behavior of the polarized gluon distribution. By using the positivity condition of distribution functions together with the unpolarized and polarized experimental data, we restrict the $x$ dependence of the polarized gluon distribution.

hep-ph↗
arXiv1994

A Way to Measure Polarized Gluon Distributions

Effects of the spin-dependent gluon distributions on J/$ψ$ productions in polarized ep and pp collisions are investigated. These productions serve as a very clean probe of the spin-dependent gluon distributions in a proton.

hep-ph↗
arXiv1994

How to probe the spin-dependent gluon distributions

Two-spin asymmetries $A_{LL}^{π^0}$ are calculated for various types of spin-dependent gluon distributions. It is concluded that the E581/704 data on $A_{LL}^{π^0}$ do not necessarily rule out the large gluon polarization but restrict severely the $x$ dependence of its distribution. Moreover, $A_{LL}^{J/ψ}$ are calculated for the forthcoming test of spin-dependent gluon distributions.

hep-ph↗