Endpoint behavior of high-energy scattering cross sections

In high-energy processes near the endpoint, there emerge new contributions associated with spectator interactions. Away from the endpoint region, these new contributions are suppressed compared to the leading contribution, but the leading contribution becomes suppressed as we approach the endpoint and the new contributions become comparable. We present how the new contributions scale as we reach the endpoint and show that they are comparable to the suppressed leading contributions in deep-inelastic scattering by employing a power counting analysis. The hadronic tensor in deep-inelastic scattering is shown to factorize including the spectator interactions, and it can be expressed in terms of the lightcone distribution amplitudes of initial hadrons. We also consider the contribution of the spectator contributions in Drell-Yan processes. Here the spectator interactions are suppressed compared to double parton annihilation according to the power counting.Comment: 21 pages, 5 figures, published versio

Electron Removal Self Energy and its application to Ca2CuO2Cl2

We propose using the self energy defined for the electron removal Green's function. Starting from the electron removal Green's function, we obtained expressions for the removal self energy Sigma^ER (k,omega) that are applicable for non-quasiparticle photoemission spectral functions from a single band system. Our method does not assume momentum independence and produces the self energy in the full k-omega space. The method is applied to the angle resolved photoemission from Ca_2CuO_2Cl_2 and the result is found to be compatible with the self energy value from the peak width of sharp features. The self energy is found to be only weakly k-dependent. In addition, the Im Sigma shows a maximum at around 1 eV where the high energy kink is located.Comment: 5 pages, 3 figure

Quasi-particle scattering and protected nature of topological states in a parent topological insulator Bi2_2Se3_3

We report on angle resolved photoemission spectroscopic studies on a parent topological insulator (TI), Bi$_2$Se$_3$. The line width of the spectral function (inverse of the quasi-particle lifetime) of the topological metallic (TM) states shows an anomalous behavior. This behavior can be reasonably accounted for by assuming decay of the quasi-particles predominantly into bulk electronic states through electron-electron interaction and defect scattering. Studies on aged surfaces reveal that topological metallic states are very much unaffected by the potentials created by adsorbed atoms or molecules on the surface, indicating that topological states could be indeed protected against weak perturbations.Comment: accepted for publication in Phys. Rev. B(R

K*{\Lambda}(1116) photoproduction and nucleon resonances

In this presentation, we report our recent studies on the $K^*\Lambda(1116)$ photoproduction off the proton target, using the tree-level Born approximation, via the effective Lagrangian approach. In addition, we include the nine (three- or four-star confirmed) nucleon resonances below the threshold $\sqrt{s}_\mathrm{th}\approx2008$ MeV, to interpret the discrepancy between the experiment and previous theoretical studies, in the vicinity of the threshold region. From the numerical studies, we observe that the $S_{11}(1535)$ and $S_{11}(1650)$ play an important role for the cross-section enhancement near the $\sqrt{s}_\mathrm{th}$. It also turns out that, in order to reproduce the data, we have the vector coupling constants $g_{K^*S_{11}(1535)\Lambda}=(7.0\sim9.0)$ and $g_{K^*S_{11}(1650)\Lambda}=(5.0\sim6.0)$.Comment: 2 pages, 2 figures, talk given at International Conference on the structure of baryons, BARYONS'10, Dec. 7-11, 2010, Osaka, Japa

SBE-type metal-substituted aluminophosphates: detemplation and coordination chemistry

The detemplation process in Me-SBE (Me = Co^2+, Mg^2+, and Mn^2+) aluminophosphates was studied to elucidate materials stability and framework characteristics. In addition, the hydrothermal synthesis conditions were optimized to obtain materials with minimal phase impurities. This was accomplished by means of decreasing reaction temperature and increasing aging periods. Scanning electron microscopy analysis of the Mg- and Mn-SBE as-synthesized samples revealed square plates with truncated corner morphologies grown in aggregated fashion and contrasting with the previously reported hexagonal platelike morphology of Co-SBE. Cautious detemplation in vacuum, using an evacuation rate of 10 mmHg/s and a temperature of 648 K, resulted in surface areas of about 700, 500, and 130 m^2/g for Mg-, Co-, and Mn-SBE, respectively. Thermal gravimetric analysis and in situ high-temperature powder X-ray diffraction analyses indicate the frameworks for all of the SBE variants experienced collapse upon treatment with helium at temperatures above 700 K and subsequently formed an aluminophosphate trydimite dense phase. Detemplation in air at all times resulted in framework destruction during detemplation. In situ differential scanning calorimetry−powder X-ray diffraction data showed that the SBE frameworks experience breathing modes related to specific endothermic and exothermic scenarios during air treatment. Decomposition and elimination of the organic template during vacuum treatment was verified by Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy revealed that most of the Co atoms in vacuum-treated samples are in tetrahedral coordination, while the Mn atoms exhibit various coordination states. Ultraviolet-visible, electron paramagnetic resonance, and magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy corroborated the latter result in addition to providing evidence for the formation of Mn extra framework species. ^(27)Al MAS NMR spectra for vacuum-detemplated Mg-SBE samples prior to and after dehydration confirmed the reversible formation of aluminum octahedral sites. This, however, did not affect the porous nature of detemplated Mg-SBE samples as these are capable of adsorbing 19 water molecules per super cage at 298 K

High resolution angle resolved photoemission studies on quasi-particle dynamics in graphite

We obtained the spectral function of the graphite H point using high resolution angle resolved photoelectron spectroscopy (ARPES). The extracted width of the spectral function (inverse of the photo-hole lifetime) near the H point is approximately proportional to the energy as expected from the linearly increasing density of states (DOS) near the Fermi energy. This is well accounted by our electron-phonon coupling theory considering the peculiar electronic DOS near the Fermi level. And we also investigated the temperature dependence of the peak widths both experimentally and theoretically. The upper bound for the electron-phonon coupling parameter is ~0.23, nearly the same value as previously reported at the K point. Our analysis of temperature dependent ARPES data at K shows that the energy of phonon mode of graphite has much higher energy scale than 125K which is dominant in electron-phonon coupling.Comment: 9 pages, 8 figures, accepted for publication in Phys. Rev.