Diffractive heavy pseudoscalar-meson productions by weak neutral currents

A first theoretical study for neutrino-induced diffractive productions of heavy pseudoscalar-mesons, \eta_c and \eta_b, off a nucleon is performed based on factorization formalism in QCD. We evaluate the forward diffractive production cross section in perturbative QCD in terms of the light-cone wave functions of Z boson and \eta_{c,b} mesons, and the gluon distribution of the nucleon. The diffractive production of \eta_c is governed by the axial vector coupling of the longitudinally polarized Z boson to Q\bar{Q} pair, and the resulting \eta_c production cross section is larger than the J/\psi one by one order of magnitude. The bottomonium \eta_b production, which shows up for higher beam energy, is also discussed.Comment: 5 pages with 3 embedded figures. Talk presented at the 15th International Spin Physics Symposium, Spin 2002, Brookhaven National Laboratory, September 9-14, 200

Conductance of a helical edge liquid coupled to a magnetic impurity

Transport in an ideal two-dimensional quantum spin Hall device is dominated by the counterpropagating edge states of electrons with opposite spins, giving the universal value of the conductance, $2e^2/h$. We study the effect on the conductance of a magnetic impurity, which can backscatter an electron from one edge state to the other. In the case of isotropic Kondo exchange we find that the correction to the electrical conductance caused by such an impurity vanishes in the dc limit, while the thermal conductance does acquire a finite correction due to the spin-flip backscattering.Comment: 5 pages, 2 figure

Single-cycle THz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3

Using the tilted-pulse-intensity-front scheme, we generate single-cycle terahertz (THz) pulses by optical rectification of femtosecond laser pulses in LiNbO3. In the THz generation setup, the condition that the image of the grating coincides with the tilted-optical-pulse front is fulfilled to obtain optimal THz beam characteristics and pump-to-THz conversion efficiency. The designed focusing geometry enables tight focus of the collimated THz beam with a spot size close to the diffraction limit, and the maximum THz electric field of 1.2 MV/cm is obtained

The Long Term Temperature Variation in the Lunar Subsurface

Introduction: Lunar surface heat flow values were measured directly during the Apollo missions. These experiments were carried out on Apollo 15 and 17 for about six years between July 7, 1971 and September 30, 1977. The heat flow values derived from these two measurement sites were 21 mW/m2 and 14 mW/m2 respectively [1]. Langseth et al. concluded the repre-sentative global lunar heat flow to be around 18 mW/m2 based on approximately the first 3 years of data until the end of the 1974 (see Figure 1). Recently, Saito et al. (2006) succeeded in archiving the heat flow data from March 1 1976 until September 30th 1977 [2]. These data are very useful for identify-ing this very long-term variation because we could extend the period of data almost by a factor of two (from 3 years to 6 years) compared to the data ar-chived previously. Because an anomaly had occurred on April 28th, 1976 on the Apollo 15 experiment, the data of Apollo 15 could not be expanded. Therefore, the data obtained by Apollo 17 were used for long term analysis

Vibrationally resolved partial cross sections and asymmetry parameters for carbon K-shell photoionization of the CO_2 molecule

We have measured the vibrationally resolved partial cross sections \sigma_{v_1^{\prime}} and asymmetry parameters \beta_{v_1^{\prime}} for C K-shell photoionization of the CO2 molecule in the Σu shape resonance region above the C K-shell ionization threshold. The positions of both the maxima of \sigma_{v_1^{\prime}} and the minima of \beta_{v_1^{\prime}} move towards the C K-shell threshold with increasing symmetric stretching vibrational excitation v'1 in the C 1s single-hole state. Calculations employing the relaxed-core Hartree–Fock approach reproduce the observed vibrational effects

On the origin of magnetoresistance in Sr2_2FeMoO6_6

We report detailed magnetization ($M$) and magnetoresistance ($MR$) studies on a series of Sr$_2$FeMoO$_6$ samples with independent control on anti-site defect and grain boundary densities. These results, exhibiting a switching-like behavior of $MR$ with $M$, establish that the $MR$ is controlled by the magnetic polarization of grain boundary regions, rather than of the grains within a resonant tunnelling mechanism.Comment: 4 pages, 4 figure